Here - Institute for Building Materials - ETH Zürich

11:20 – 12:30 POSTER SESSION12:30 Lunch14:00 Excursion to Cardada-Cimetta + social dinner (traditional Tessinrestaurant)THURSDAY 16Day 4 th – Gelation and agglomeration across length-scalesChair: Emanuela Del Gado (ETHZ)08:00 Alain Baronnet, Université de Marseille – Structure, texture, compositionand growth mechanism of calcium silicate hydrate (C-S-H) seen by TEM atthe nanoscale08:30 Jorge Dolado, TECNALIA – A simple textural nucleation and growth modelfor describing cementitious C-S-H formation09:00 Christophe Labbez, Université de Bourgogne –Mesoscopic simulations ofclay gels: a step toward models of C-S-H gels?09:30 Luc Nicoleau, Basf (contributed) –Oriented aggregation of C-S-H bypolymers09:50 Barbara Capone, University of Vienna (contributed) – Hierarchical selfassemblyof thelechelic star polymers: from soft patchy particles todiamond crystals10:10 BreakChair: Henri van Damme (ESPCI ParisTech)10:40 Ratan Mishra, ETHZ (contributed) – Effect of organic modifiers in theagglomeration of Tricalcium Silicate11:00 Jean-Baptiste d’Espinose, ESPCI– What is geopolymerization? A combinedchemical (NMR), structural (SAXS) and rheological study11:30 Final Discussion round12:30 Prize to young scientist presentationAfternoon excursion : Val Verzasca, 3h hike for those who stay.6

INVITEDLECTURESSOFTCEM 20127

Mesoscopic models for flow in amorphous solidsJean-Louis BarratLIPhy, Université Joseph Fourier Grenoble 1,UMR 5588 et CNRS, F-38402, Saint Martin d'Hères, FranceI will describe the microscopic simulation tools and the mesoscopic models that haverecently contributed to our understanding of the plasticity mechanisms in amorphoussystems. Molecular dynamics and quasistatic simulations have resulted in a clearmicroscopic understanding of the elementary mechanisms at the atomic level. Thisinformation can, in principle, be used as an input for coarse grained lattice modelsthat go beyond mean field descriptions such as STZ or SGR. Some results obtainedwith this type of models will be presented.Validity of Nucleation and Growth equations applied tocementsShashank BishnoiDepartment of Civil Engineering, Indian Institute of Technology DelhiHauz Khas, New Delhi 110 016, IndiaNucleation and growth is now widely accepted to control most of the first 24 hours ofhydration kinetics of alite. Although microstructural models are the most reliablemeans to model nucleation and growth processes, due to their computational costs,several simplified equations such as the Avrami equation and the Cahn equation areoften used to study the hydration of cements. However, this has been criticised sincethese equations have been derived for systems that differ significantly from cement.This talk examines the effect of the differences between the nucleation and growthmodels and cement hydration on their applicability to cement systems. It is seen thatalthough the models can be easily adapted to some of the differences such as multiphasegrowth and various shapes of products, the effect of the nucleation and growthof products on the surface of poly-disperse cement particles cannot be easilysimplified. Results from fitting these equations to cementitious systems can,therefore, be misleading.9

A simple textural nucleation and growth model for describing cementitiousC-S-H formationRaquel González-Teresa 1 , J. C. Gimel 2 , Jorge S. Dolado 11 TECNALIA . 2 CNRS-Université du MaineUnderstanding the kinetic mechanisms governingthe C-S-H precipitation is of great practicalrelevance to control the strength evolution ofconcrete. Traditionally the C-S-H formation hasbeen described by the well known Avramiequation [1,2,3]. While this nucleation and growthequation successes in describing the early growthrates (acceleration period), it fails to capture thepost-peak values found in calorimetricmeasurements (deceleration period). Thisdiscrepancy is usually attributed to the fact that C-S-H nucleation is known to occurs on the surfacesof the cement grains or C3S particles rather thanrandomly distributed in the bulk, as implicitlyassumed in the Avrami model. As pointed out byThomas [4], a better physical analogy to cementhydration can be made by using a slightly modifiedform of the boundary nucleation (BN) modeldeveloped by Cahn [5], where nuclei form only onplanar boundaries that are randomly oriented anddistributed within the volume. Likewise otherimprovements to the Avrami and Cahn solutionshave been proposed so far, to account for finitevolume effects [6] or impenetrable boundaries [7].A recent work [8] has reviewed the existingboundary nucleation models and has suggested thathydration should be described using models inwhich growth is confined within the capillarypores and the growth is dendritic.Here, and based on a simple Monte Carlocomputational scheme, we have generalized theAvrami and BN models to deal with texturalgrowing surfaces and accommodate the intrinsicnanoparticulate nature of the C-S-H gel. Inessence, the textural surfaces decorated with C-S-H nanoparticles offer an additional degree offreedom for continuing the phase conversion afterthe impingement of adjacent growing C-S-Hclusters. Interestingly, this new computationalscheme suffices to capture the experimentalcalorimetric profiles in the deceleration regime andsupports previous findings [9] which casted ashadow over the “diffusive” nature of thedeceleration regime…1W. A. Johnson and R. F. Mehl; 1939;Transactions of the Americal Institute of Miningand Metallurgy; 135:416-458.2M. Avrami; 1939; Journal of Chemical Physics;7:1103-1112.3A. Kolmogorov; 1937; Bulletin of the Academy ofSciences of the USSR; 3:355-359.4J. J.. Thomas et al.; 2007; Journal of theAmerican Ceramic Society; 90:3282-3288.5J. W. Cahn.; 1956; Acta Metallurgica; 4:449-459.6B. A. Berg and S. Dubey.; 2008; Physical ReviewLetters; 100:165702-1657057E. Villa and P. R. Rios; 2010; Acta Materialia;58:2752-2768.8G. W. Scherer.; 2012; Cement and ConcreteResearch; 42: 1252-:12609S. Bishnoi and K. Scrivener.; 2009; Cement andConcrete Research; 39:849-860.REFERENCES:12

Topological Excitations in Liquids and GlassesT. Egami, T. IwashitaUniversity of Tennessee, Knoxville, TN, USA, andOak Ridge National Laboratory, Oak Ridge, TN, USA.INTRODUCTION: The dynamics of a liquid isdescribed usually by the hydrodynamic theories withnon-linear extension, such as the mode-couplingtheory. Much less attention has been paid to theatomic level dynamics, because it has been believedthat the atomic motion in a liquid was so random thatdetails of the atomic motion were irrelevant to thephysics of liquid flow. Through molecular dynamicssimulation, however, we show that the dynamics of aliquid and glass is directly connected to the localatomic dynamics in the form of topologicalexcitations.METHODS: Molecular dynamics (MD) simulationswere carried out for various model liquids and glasses.To characterize the macroscopic dynamics wedetermined the Maxwell relaxation time, τ M = η/G ∞ ,where η is the viscosity of the system, calculatedthrough the Green-Kubo formula, and G ∞ is theinstantaneous shear modulus, and compared it withvarious atomic level relaxation times.RESULTS: We found that at temperatures muchabove the glass transition temperature, T g , the α-relaxation time, τ α , determined from the self-part ofthe intermediate scattering function at the first peak ofS(Q), is significantly longer than the Maxwellrelaxation time, as shown in Fig. 1. The average bondlifetime, τ B , is even longer. On the other hand therelaxation time of local topology, τ LT , defined as thetime to lose or gain just ONE nearest neighbour [1], isnearly equal to the Maxwell relaxation time as shownin Figs. 1 and 2, above the crossover temperature, T A .But the ratio τ M /τ LT increases below T A . Figures showonly the results for model liquid iron, but simulationsfor the Kob-Andersen model and the model ofZr 50 Cu 40 Al 10 interacting with the EAM potential gavevery similar results, suggesting that this relationshipmay be universal.DISCUSSION & CONCLUSIONS: This resultsuggests that the local topological excitation to changethe network of atomic connectivity is the elementaryexcitation in the liquid state. They are independentfrom each other above T A , but below T A they screeneach other, resulting in the increase in the τ M /τ LT ratio.This observation opens up the possibility to describethe atomistic processes of complex liquid dynamics interms of the topological excitations and the interactionamong them, thus creating a field theory ofmicroscopic excitations in the liquid. We also discussthe atomic dynamics in the stress driven liquid state atlow temperatures [1,2].Fig. 1: Temperature dependence of variousrelaxation times for model liquid iron. The α-relaxation time is defined in three different ways.Fig. 2: The ratio of the Maxwell relaxation time overthe relaxation time of local topology.REFERENCES: 1 T. Iwashita and T. Egami; 2012;Phys. Rev. Lett.; 108:196001.2 P. Guan, M.-W. Chen and T. Egami; 2010; Phys.Rev. Lett.; 104:205701.ACKNOWLEDGEMENTS: This work wassupported by the U.S. Department of Energy, Officeof Basic Energy Sciences, Materials Science andEngineering Division.14

What is geopolymerization? A combined chemical (NMR),structural (SAXS) and rheological study.Jean.-Baptiste d'Espinose de Lacaillerie, Arnaud BourlonSoft Matter Science and Engineering, ESPCI ParisTech,UMR 7615 UPMC-CNRS-ESPCI, 10 rue Vauquelin 75005 Paris, FranceAurélie Favier, Guillaume Habert and Nicolas Roussel.Université Paris-Est, IFSTTAR, 58 bd Lefebvre, 75732 Paris cedex 15,France.Geopolymers are amorphous silica-aluminates binders which are the products of thereaction of metakaolin or fly ashes with an alkali silicate solution. There is a growingbody of literature on geopolymers, mainly driven by the search for non Ca-basedmineral addition, or even substitution, to Portland cement. However, there is asignificant lack of understanding of what exactly is the geopolymerization process.Shortly put, in contrast to Portland cement hardening, we still do not know what arethe chemical and physical processes that lead from a viscous aluminosilicatesuspension to a solid geopolymer material.A comparison of the evolution of the local chemical speciation and structure duringgeopolymerization by NMR and SAXS with the evolution of the bulk rheologicalproperties of the paste reveals that the process, while kinetically controlled by thealuminum dissolution, is clearly heterogeneous. The development of local overconcentrations in aluminum between the particles appears essential to thedevelopment of the paste modulus, and, hence, the formation of a geopolymer.Chemical admixtures: From dark arts to molecular designRobert J. FlattETHZ, D-BAUG, Physical Chemistry of Building Materials,Schafmattstrasse 6, Zürich CH-8093, SwitzerlandChemical admixtures play a central role in concrete technology. They enter thebroader range of products that can be classified as “chemical spices” in that smallamounts induce large effects. This offers a rather unique possibility of improvingmaterials already used for larger volume applications, but at a low cost.In particular they have a big role to play by facilitating the replacement of the highenergycompound in concrete (the clinker in cement) by alternative materials. Indeed,such replacements typically lead to a reduction in strength and one way tocompensate it is to formulate concrete with a lower water content. However, this hasa negative impact on rheology that dispersants can counteract. It is also possible toenhance the early strength development using accelerators and without changing thewater content.Such solutions are already used, but they are being met with increasing demands andexpectations. This has various implications as:15

1. Admixtures will be used more and more in combination in order to deliverthe expected performances. For this, interactions among these admixtures will have tobe mastered in blended cements.2. Systems are being pushed to their limits so that new problems appear. Forexample, the packing fraction of solids approaches its maximum so that dispersionalone is no more sufficient to recover the desired rheological properties.3. Secondary effects of admixtures must be eliminated as for example theretardation by some dispersants.The challenges brought along by the above examples can be summarised by the termof “mastering complexity”. In this context the notion of multiple interactions plays acrucial role whether in adsorption, dissolution, nucleation or growth. In all cases,knowledge relating to the molecular structure of chemical admixtures will be crucial,so as the chemical understanding of blended cement reactivity. This argument will bedeveloped and illustrated using the case of the competition between sulphates andpolycarboxylates.Paving the narrow path to sustainable constructionGuillaume HabertInstitute for construction and infrastructure managementETH Zurich, 8092 Zurich, Switzerland.Among all human activities, the building sector has one of the largest environmentalimpacts. It accounts for two-fifths of the raw stone, gravel and sand consumption aswell as one-fourth of virgin wood. It is also accountable for 40 % of total energy and20 % of annual water consumption and it is a major waste producer as buildingconstruction and civil engineering works produce 40% of all waste. With such a greatcontribution, the construction industry has a major role to play in the promotion of asustainable society. To do so, it is fundamental to accurately assess environmentalimpacts and clarify which particular aspect of the construction has to be improved. Inthis presentation, the identification of the relevant parameters that influence theenvironmental impacts of buildings and infrastructures at the international, nationaland regional levels allows to highlight the fact that the key factor in sustainableconstruction is the use of an appropriate structural material. Actually, fired claybricks, steel and concrete are the only materials where an adequacy between theexpected service life of the structure and their own durability is so pregnant.Furthermore their dependence to high temperature processes is sensitive from aresilience point of view. But the implementation of identified improvement potentialsis different for developed and developing countries as well as for buildings andinfrastructures.In developed countries, as population and economic growth are moderate, technologyimprovement can be effective. This is specifically the case for the heating of housingdue to the important stock of poorly insulated houses. Furthermore, the production ofinsulation materials isn’t costly, from an economic or environmental point of view,and should therefore facilitate renovating existing buildings. For new buildings whichhave very low heating costs, the environmental impacts of the construction materialsare not negligible and can represent up to 50% of the greenhouse gas emitted duringthe life cycle of the building; and among them, structural materials often account fornearly half of the impacts. We therefore have to make an effort to develop structuralmaterials with a low environmental impact and current studies show that the16

improvement potentials allow for a reduction by a factor 4 of greenhouse gasemission if a breakthrough in technology is done. In the case of infrastructures, trafficproduces most of the environmental impacts compared to construction andmaintenance of the structure. Civil engineers should therefore focus on technologiesthat could save execution time in order to reduce traffic increasing because ofdeviations or traffic jams during road works.In developing countries, the population (P) and economic (A) growth do not allowenvisioning a reduction on the total environmental impact (I), while only improvingthe technological parameter (T) of the I=PAT equation. However, it is cruciallyneeded to implement the best available technology or even to develop appropriatetechnologies in order that these countries do not follow the trend of developedcountries. But appropriate technology with Schumacher’s classic idea of “small isbeautiful”: a development that is simple, low cost, using local materials should alsobe combined with the question of using appropriate materials for buildings andinfrastructures built in fast growing cities.As a conclusion, the concept of sustainable construction has led to intense activity incivil engineering research institutes. The research on new materials has encouragedthe re-examination of past chemistry and structural concepts that had been longabandoned. Not only have new materials been developed, but taking sustainabilityinto account has pushed industries to reconsider fundamental knowledge, to betterunderstand cement physics and chemistry, in order to optimise mixes. One finalquestion which remains open is how to implement them on the field? What is theappropriate policy?Coupling nano and meso-scale structure of cement paste:A key to the mechanisms that control propertiesHamlin JenningsConcrete Sustainability HubMassachusetts Institute of TechnologyUSAThe structure of cement paste is examined between 5 – 50 nanometers, which forcement paste is the meso-scale where mechanisms of creep and shrinkage operate.Experimental techniques such as water (and nitrogen) sorption isotherms and smallangle neutron scattering provide information on both the solid particles and thestructure of the gel pores. Ongoing molecular modeling and simulations are providingnew interpretations of experimental results and are being directed towardsunderstanding the mechanisms of irreversible deformation. New questions are beingformulated. For example, the properties of water in tiny confined spaces, particularlyits viscosity, may hold the key to understanding the complex nonlinear coupling ofthe influences of applied stress, drying and changes in temperature on plasticdeformation, known as the Pickett effect, a phenomenon that is also observed in othercolloidal systems.17

Mesoscopic simulations of clay gels:A step towards models of C-S-H gels ?Christophe LabbezLaboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universitéde Bourgogne F-21078 Dijon, FranceIt is generally appreciated that the interactions of colloidal particles depend stronglyon the heterogeneities in the distribution of the surface charges as well as on theanisotropy in their shape. As an example, dispersions of plate-like particles such asclays and calcium silicate hydrate (C-S-H) undergo a sol/gel transition at low volumefractions, which are typically one order of magnitude lower than those of ordinarycharged spherical particles, e.g. latex, silica. Surprisingly, few theoretical studies dealwith such a problem. This presentation will describe a Monte Carlo investigation ofthe gelation of a model clay dispersion in 1-1 salt solutions varying the particlevolume fraction, ionic strength as well as the charge heterogeneity in the canonicalensemble 1 . Overall, the simulation results provide fundamental insights into themechanisms of the recent fluid/gel phase separation observed in Laponitesuspensions 2 and sol/gel transition of Na-Montmorillonite suspensions at low pH 3 .Finally, we will discuss at some length the strategy used as well as its limitations inthe context of highly coupled systems, e.g. highly charged C-S-H nanoplatelets incalcium salt solutions and cement paste -mixture of C-S-H and aluminates.1. M. Delhorme, B. Jönsson, C. Labbez, Soft Matter, 2012,DOI:10.1039/C2SM25731A2. B. Ruzicka, E. Zaccarelli, L. Zulian, R. Angelini, M. Sztucki, A. Moussaid, T.Narayanan and F. Sciortino, Nature Mat., 2011, 10, 56–60.3. A. Shalkevich, A. Stradner, S. K. Bhat, F. Muller and P. Schurtenberger,Langmuir, 2007, 23, 3570–3580.19

Intermittent dynamics of confined fluids, first passage statistics and diffusionprocess in colloidal and porous media.P. Levitz 11 PECSA, University Pierre et Marie Curie- CNRS, Paris FranceINTRODUCTION: Porous materials,concentrated colloidal suspensions are example ofconfining systems developing large specificsurface, presenting a rich variety of shapes andexhibiting complex and irregular morphologies ona large length scale. Such a confinement stronglyinfluences the molecular dynamics of embeddedfluids and the diffusive motion of particlesentrapped inside these materials. The particletrajectory can be described as an alternatesuccession of surface adsorption steps andconfining bulk relocations. The full transportprocess appears as an intermittent dynamics. Thisquestion related to a first passage problem isdiscussed in this presentationSPECTRAL ANALYSIS OF THEINTERMITTENT DYNAMICS: The timedependence of the intermittent dynamics of aconfined fluid near a pore interface can beanalysed using the density probability distribution(p.d.f.) of the time either spend in the bulk before areadsorption on the surface or characterizing theway that an adsorbed molecules is released in thebulk [1,2]. These two p.d.f. reflect two firstpassage statistics, one for the surface adsorptionthe other for the bulk relocation. A spectralanalysis of this dynamics is discussed for severalinterfacial geometries [1-3]. Direct comparisonswith recent molecular dynamics simulationsperformed for confined liquid water inside variouspore shapes are discussed [4].PROBING INTERMITTENT DYNAMICS:The Nuclear Magnetic Relaxation Dispersiontechnique (NMRD) is an effective experimentalmethod to follow an intermittent dynamics near aninterface. Under some general conditions ofrelaxation [1]; the related spin-lattice relaxationrate R 1 (ω) provides a direct evaluation of thespectral density of the intermittent dynamics. Inthis part, we will present several experimentalstudies of the water intermittent dynamics, usingNMRD. Various colloidal and/or porous interfaceswill be dicussed (plaster pastes [5], flat colloidalclay particles [1], long and stiff nanometric strands[3]) with a special emphasis on the fluid-surfaceinteraction ( “nano-wettability” [5]).DISCUSSION & CONCLUSIONS: The formeranalysis of the intermittent dynamics provides asimple description of the local exploration of aninterfacial medium by a particle and/or a molecule.This coarse grained description allows to quantifythe influence of the “local” confining geometryand also to estimate the degree of interactionduring the adsorption step. On larger length scale,real interfacial media such as pore networks orconcentrated colloidal suspensions generallyexhibit a complex interfacial geometry. Atraditional way to follow the geometrical upscalingis to look first at the pore scale, second, at a porenetwork, etc… Iteration of the intermittent processat these different levels of organization can bepursued using First Passage Time statistics.Finally, another important aspect of theintermittent dynamics is related to its efficiency tooptimize the research of a surface target [6], whichputs forward a general mechanism of enhancementand regulation of chemical reactivity. We willemphasis these two topics and comment somepreliminary results.REFERENCES:1 P. Levitz; 2005; J. Phys.Condens. Matt. 17: S4059 2 P. Levitz, D. S.Grebenkov, M. Zinsmeister, K. Kolwankar; B.Sapoval, 2006; Phys. Rev. Lett. 96: 180601 3 P.Levitz, M. Zinsmeister, P. Davidson, D.Constantin, and O. Poncelet; 2008; Phys. Rev. E78: 030102 (R) 4 P. A. Bonnaud, B. Coasne and R.J.-M. Pellenq, J. 2010, Phys. Condens.Mat., 22:284110 5 J-P Korb and P Levitz;2008; Magnetic Resonance in Porous Media. 1081;55-58 6 O. Bénichou, D. Grebenkov, P. Levitz, C.Loverdo and R. Voituriez; 2010; PRL 105:150606ACKNOWLEDGEMENTS: This work wasperformed in several collaborations with M.Zinsmeister, J-P Korb, D. Grebenkov, O.Benichou, M Han, M. Fleury, P. Bonnaud, P.-A.Cazade, R. J.-M. Pellenq 2,3 , and B. Coasne. Manythanks to all of them.20

Diffusion in soft particle suspensions near jammingCraig E. MaloneyCivil & Environmental EngineeringCarnegie Mellon UniversityPittsburgh, PA 15213-3890, USASuspensions of soft particles exhibit a remarkable bifurcation at the random closepacking volume fraction, [1]. There is a yield stress above but not below. Weperform numerical simulations of soft-particle suspensions under shear near . Wefind that above at sufficiently low shearing rates, the effective diffusion constant,, scales with length of the simulation cell in the flow-gradient direction, . Thisis in agreement with the size-dependent diffusion constant observed in lowtemperatureLennard-Jones glasses. Furthermore, the value of can beunderstood in terms of organized lines of slip and is independent of the form of therepulsive interactions between the particles and the precise way in which the viscousdrag of the suspending fluid is modeled in the particle-scale simulations.[1] Microfluidic Rheology of Soft Colloids above and below Jamming. K. N.Nordstrom, E. Verneuil, P. E. Arratia, A. Basu, Z. Zhang, A. G. Yodh, J. P. Gollub,and D. J. Durian. Phys. Rev. Lett. 105, 175701 (2010)How do yield stress materials start to flow?Sébastien MannevilleUniversité de Lyon, Laboratoire de Physique, École Normale Supérieure de Lyon,CNRS UMR 5672 - 46 Allée d'Italie, 69364, Lyon cedex 07, FranceInstitut Universitaire de France, FranceYield stress materials are viscoelastic solids at rest but behave as viscous liquidswhen stressed above their yield stress. In soft jammed systems, yielding can be seenas an instance of an unjamming transition driven by the shear stress. The question ofwhether this shear-induced fluidization displays universal features, in a way similar tojamming driven by temperature or by volume fraction, has triggered much researcheffort in the recent years. Experimentally, difficulties arise from the need to measuredeformations and flows close to yielding at vanishingly small shear rates withsufficient spatial and temporal resolutions.In this talk, I will first review the current state of research on the steady state reachedby a soft glassy system above yielding. It is now established that some "simple"materials undergo a continuous yielding transition characterized by homogeneousflows while others display flow heterogeneities, e.g. shear bands, at steady state. Iwill then concentrate on the spatiotemporal fluidization dynamics of a "simple" yieldstress material, namely a carbopol microgel, that presents negligible aging andthixotropy. Through long experiments combining standard rheology and ultrasonic21

velocimetry under imposed strain or stress, I will show that the material firstundergoes a transient regime characterized by (i) a short-time creep regimereminiscent of Andrade creep in elastic solids and (ii) a long-lasting shear bandingregime that progressively gives way to homogeneous flow. The duration of the shearbandingregime decreases as power laws of the applied shear rate and of the appliedviscous stress. These power laws nicely combine to recover the Herschel-Bulkley lawcharacteristic of the steady-state rheology of our microgel. Time permitting, I willbriefly address the case of other yield stress materials, showing that the abovefluidization scenario is probably not universal.Computational Modeling of Suspensions: Application toCement Based MaterialsNicos MartysNational Institute of Standards and Technology,100 Bureau Drive, Stop 8615, Gaithersburg, MD 20899-8615, USAAs concrete is one of the most widely used building materials, it behooves us improveits performance while minimizing its environmental impact. Optimizing andcontrolling its flow and placement is important for quality control of performance,architectural complexity and reduced costs. However, concrete poses a greatchallenge to the rheological sciences in regards to both modeling and measurement.This is largely due to its random and complex composite nature, where solidinclusions have wide size and shape distributions, and the dynamically changingrheological properties of the cement matrix. So-called "greener" concretes, whichtypically involve replacing cement with other materials that are largely industrial byproductslike fly ash and slag, can have rheological properties that are stronglyaffected by these additions. Indeed, even ignoring hydration of the cement paste, thenon-Newtonian nature of the binding matrix creates significant challenges for propercharacterization and modeling of concrete's rheological properties.In this presentation I will briefly describe an approach for modeling suspensions thataccounts for the shear rate dependence of the matrix fluid's viscosity, which will beapplied to cement-based materials. I will then illustrate its application in a variety offlow scenarios with the goal of stimulating discussion on its utility for addressingchallenges in the rheological sciences of concrete. Examples include: Modeling offlow in a vane rheometer, transmission of stress in suspensions, modeling theinfluence of fly ash on cement paste rheology, universal scaling of viscosity, multiscalingmodeling as a tool to predict concrete viscosity, insights into yield stress andthe onset of flow.22

Challenges and Innovation in the Cement IndustryMichael RomerHolcim Group Support Ltd, SwitzerlandThe world population is projected to grow by more than one third to 9.3bn by 2050.In addition, the population growth is more intense in urban areas than in rural areasleading also to growth of megacities in size and number. Concrete will continue toplay a crucial role to serve theincreasing demands of societies around the world. Dueto its energy and material intensity, our industry is confronted with various challengesto increase the sustainability of cement and concrete, which also asks for moreinnovative solutions and will cause higher investments into R&D.A main challenge of our industry is to improve the resource efficiency of ourproducts and processes. The use of alternative fuels and resources for clinker andcement production will foster the incorporation of more by-products and wastes fromother industries. In parallel, the built environment needs to be maintained andrenewed and offers itself a new source of materials and the opportunity to better closethe loop in construction materials.Considering life cycle analysis for building materials, we see CO2 as being the singlebiggest influencing factor in weight to assess environmental impacts. In concrete aswell as cement the most important factor to reduce CO2 is the amount of clinker use.Other constituents such as water and aggregates add little to the overall balance.Clinker can be reduced mainly by introducing alternative components such as mineralcomponents (or supplementary cementitious materials) and improving performancewith additives and admixtures. The use of mineral components to reduce CO2footprint is challenged by the various and developing CO2 regulations around theworld and especially by the current discussions on the allocation of the CO2 toindustrial mineral components such as slag or fly ash.With the Holcim cement portfolio, the proportion of pure Ordinary Portland Cementdeclined from 56% in 1995 to 23% in 2011.To keep the specific CO2 emission ofcement low while serving larger cement demands, the amount and variety of mineralcomponents used in cement needs to grow in the future. At the same time the productdesign of low clinker cements must be carefully customized for the given applicationneeds. Trends in construction ask for faster construction processes and high risestructures, longer service live and better life service cost as well as more “green”products and solutions. To overcome the intrinsic properties of less reactive mineralcomponent, it is required to better understand the fundamentals of hydration reactionsof an increasing number of potential constituents and systems with growingcomplexity. Coordinated and pre-competitive research in this area and also in regardto polymer interaction plays a crucial role for the future optimization potential incement application.Today, several alternative binder systems are under development. Key drivers are theuse of non-traditional materials (e.g. Magnesium oxides instead of Calcium oxides)with different processes (e.g. ‘cold’ activation of geopolymers) to reduce CO2emissions. A variety of initiatives on alternative low carbon cement research areknown. Several approaches are pursued in parallel but there is very low likelihood,that one solution will replace the current Portland cement markets. It is more likelythat several solutions will make it to commercialization and full size application. Keybarrier for such new binder systems to take a relevant share of the cement market ismainly the limited and local amount of alternative raw-material available.Nevertheless, it is important to innovate both, in the traditional systems as well as in26

novel alternative binder systems. However, it will take a long time until clinker basedbinders will see some substitution by these new binder systems.Building materials today are responsible for around 10% of the environmentalfootprint of an average European building. As the environmental footprint during theusage phase in buildings gets continuously improved (e.g. Minergie buildings inSwitzerland), the relative environmental impact of building materials will increaseand should therefore weight more in future green building certification schemes.Standardization is another important aspect to be considered when developinginnovative cement products. On the one side, it should allow future opportunities fornew products in the market. On the other side, it must assure the quality of theproducts to guarantee the requirements and benefits of the customers. Most recentdevelopments in standardization focus on limestone addition up to 15% in ASTM andon new ternary blend cements (CEM X) in Europe. Setting up new standards andobtaining certifications alone are not sufficient to promote innovative cements.Convincing specifiers, engineers, designers and final users with the evidences oflong-term performance and benefits of the new products needs to facilitate theproduct introduction into the markets.27

Jamming and void space in sphere packingsSrikanth SastryTIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony,Narsingi, Hyderabad 500075The formation of amorphous solids possessing mechanical rigidity and the nature ofthe transition from fluid to structurally arrested solid states is of interest in a widevariety of systems, from glass forming liquids, granular material, polymers, and manyother soft materials. Jamming in granular materials has been analyzed in a variety ofways, both comparing it with and contrasting it from the glass transition in molecularliquids. One of the key mysteries in understanding jamming and other structural arresttransitions is the nature of the structural change involved. In this talk, I will presentsome recent work on understanding the nature of the jamming transition, using as amodel system packings of frictionless hard spheres. In particular, the characterizationof void space using cavity and free volume distributions, and a striking signature ofjamming that arises in such characterization, will be described. Preliminary results onsimilar distributions for models of wet granular matter will also be discussed.Deformation of colloidal glassesPeter SchallInstitute of Physics, University of Amsterdam,Amsterdam, The NetherlandsSoft glasses such as suspensions and pastes show remarkable mechanical properties:they can be rigid when confined at high density or interaction potential, but can bemade to flow under applied stress. This transition from rigidity to flow is central to awide range of phenomena in geology, biology, and material physics, and importantfor designing products such as cement.We investigate the role of microscopic correlations in this transition: by tracking themotion of individual particles in a colloidal model system, we visualize fluctuationsof strain and non-affine displacements. At the transition from rigidity to flow, shear isneither macroscopically uniform nor strongly localized: We observe system-spanningstrain correlations that reveal a novel form of mechanical criticality at the onset offlow. These correlations are isotropic when temperature dominates over the appliedstress, and become anisotropic when the applied stress dominates, ultimately leadingto flow localization and flow instabilities. While our model system allows directimaging of these critical strain fluctuations, we expect very similar mechanisms tohold for other soft materials as well as atomic and molecular amorphous materials.28

Interfacial rheology and particle laden interfacesJan VermantDepartment of Chemical Engineering,K.U. Leuven, BelgiumSeveral high interface systems, such as foams or emulsions, derive their functionfrom the fact that surface active molecules and particles collect at fluid interfaces andrender them non-linear in their response to flow and deformation. When this occurs,the interfaces acquire a complex microstructure that must be interrogated. Interfacialrheological material properties must be measured to appreciate their role incontrolling the stability of the interfaces. Particularly particles display a intriguingability to stabilise foams and emulsions. In such systems complex interfacialmicrostructure leads to rheological complexity. Interfacial rheologicalcharacterization relies on the development of tools with the sensitivity to respond tosmall surface stresses in a way that isolates them from bulk stresses. In this work wewill first discuss how proper rheological material functions for interfaces can bemeasured, in shear, extension and dilation. subsequently we will study some classesof 2D suspensions and their intriguing rheological properties. Their role in complexmulti structured materials will be discussed.Colloidal gels and glassesDavid A. WeitzDepartment of Physics and SEAS, Harvard University,Cambridge, Massachusetts 02138, USAThis talk will present a summary of the properties of colloidal particles as a functionof both their volume fraction and their interaction energies. At high volume fractions,colloidal particles can form a glassy state, where structural relaxations becomeextremely slow so they system is solid like over measurable time scales. A solid-likestate is also achieved at lower volume fractions when an attractive interaction isintroduced. The overall behavior can be described by means of a phase diagram thatseparates solid- and liquid-like states as a function of interaction energy and volumefraction.30

Required Subjects for the Study of Concrete RheologyK.Yamada 1 , Y.Yamada 21 Taiheiyo Consultant, Chiba, Japan (Taiheiyo Cement Group). 2 University of the Ryukyus.INTRODUCTION: The goal of fluidity study isthe estimation of concrete workability, e.g.comprehensive properties such as easiness ofhandling at various w/c, passability and blockingbehaviors between high-density reinforcementsrequired from seismic reinforcement, segregationsto form rock pockets and breeding and so on.However, because of the lack of overall vision ofstudies, there has been limitations. For example,simple paste flow or flow curve tests under specificconditions were index for the study of workingmechanism of superplasticizers (SP). Despite ofthe existence of their stress history dependence, ithas been difficult to carry out time consumingmeasurements for the study discussing hugenumber of material character’s effects. This is abig frustration not to be able to consider shear rateand time dependence of deformation. Here, aconcept of description of non-linear rheology ofcement system is outlined.Table 1. Affecting factors on concrete rheology.Mat./ FactorSolid phaseCementMix prop.MixingTemp.DispersantCharacteristicsParticle size distribution, shapeReactivity, hydrates comp., SSA, solutioncomp., water consumption by hydrationw/c, water content, finesMixing efficiency, adding orderHydration, rheology of liquid phase, interparticle potentialAdsorption equil./ absorption, dispersionmechanism, hydrationAFFECTING FACTORS: Affecting factors onconcrete rheology are summarized in Table 1. It isdifficult to keep reproducibility of experimentswithout appropriate description of them at least 1 .Even from studies based on simple flow tests by K.Yamada, it has become clear that various materialfactors of cement and SP can be attributed tosurface area of solids including hydrates such asettringite formation and SP adsorption equilibriumcontrolled by solution chemistry. Completely samecement in chemical composition or even in mineralcomposition can behave differently depending ofslight weathering or SP additions. SP can affect thecement hydration also.RHEOLOGY MODEL: Beyond understanding ofthe interaction between cement and SP, a modeldescribing paste rheology has been required. Y.Yamada proposed a model considering volumetricratio of solid phase of cement particles and theirflocculation, i.e. the viscosity equation of modifiedRoscoe’s equation. This model can be applied notonly for paste but also for mortar and concrete. Itwill be possible to estimate workability of concretebased on this model in future. One example ofslump simulation is shown in Fig. 1.Height (cm)Target slump= 12 cmSpread(cm)Height(cm)Target slump= 21 cmSpread (cm)Fig. 1: Simulated slump shape by FEM based onnon-linear rheology parameters consideringdeflocculation and flocculation processes.Y. Yamada’s model considers dispersoid anddisperse medium in paste, mortar and concrete,respectively, and mix proportion is taken intoaccount. Concrete modifies its fluidity dependingon its movement state caused by non-linearrheology character of paste in concrete where itsinternal structure changes by various reasons.Considering what happens in this paste, solid phase(cement particles) is in one flocculated state andthe inter-particles interaction causing flocculationvaries by various conditions, e.g. w/c changesinter-particle distances, SP modifies inter-particlesinteraction force, kinds of cement and thoseactivities modify the volume and kind of solidphase and specific surface area (SSA), andhydration increases solid phase volume and SSAaffecting SP performance.Flocculated particles act as larger particles andcontain water that cannot act as disperse medium.Flocculation state changes by external force and itsacting time and this causes hysteresis in fluidity.This hysteresis can be described by parallelprogress of deflocculation and flocculation. Basedon this theory on flocculation state, paste rheologybecomes possible to describe. In mortar orconcrete, aggregate is assumed as dispersoid.REFERENCES: 1 K. Yamada; 2011; Cem ConcrRes; 41:793-798.31

Creep and Strain-Rate Effects in Cement AgingSidney YipMassachusetts Institute of Technology,Cambridge, 02139 Massachusetts,USAWe propose to discuss the rheological deformation of cement hydration product C-S-H over time periods where significant structural evolutions are occurring on the nanoto-mesoscales. In analogy to a recent result elucidating the origin of strain-rateeffects on the flow stress in simple metals, we ask whether similar concepts could beapplied to quantify our understanding of creep mechanisms in cementitious materials.32

ORALCONTRIBUTIONSSOFTCEM 201233

BEHAVIOR OF CONFINED WATER IN POROUS C-S-HP. A. Bonnaud 1 , Q. Ji 1 , B. Coasne 2 , R. J.-M. Pellenq, K. J. Van Vliet 31 Department of Materials Science & Engineering and Department of Civil &Environmental Engineering, Massachusetts Institute of Technology, 77Massachusetts Ave., Cambridge, MA, USA.2Institut Charles Gerhardt Montpellier, CNRS UMR 5253, ENSCM, 8 rue de l’EcoleNormale, 34296 Montpellier Cedex 05, France.3 Centre Interdisciplinaire de Nanoscience de Marseille, Aix-Marseille Université,UPR 3118 CNRS, Campus de Luminy – case 913, 13288 Marseille cedex 9, FranceINTRODUCTION: To improve the durability ofconcrete under extreme conditions, it isparticularly important to understand damagemechanisms within the cement paste that bindsaggregates. The multiscale porosity inherent tocementitious materials implies that water may bepresent as liquid, solid, and/or gas depending onthe thermodynamic conditions (temperature,pressure, ion concentration). It is thus appreciatedthat water may be both the source and the mediumcausing damage in cement paste. Here,computational simulations are particularlyadvantageous because water properties innanoscale pores (≤1 nm) are challenging to accessexperimentally.METHODS: Our study is based on the calciumsilicate hydrate phase 1 (C-S-H), the primarybinding constituent in cement paste. We employsemi-Grand Canonical Monte Carlo techniques toconsider how the water content within and betweennanoscale C-S-H volumes or “grains” changes as afunction of the relative humidity (% RH) at anambient temperature of 27°C. To relate the effectof the water content in the cement paste on thecohesion, we computed pressures due to the fluid(water and calcium ions) in the direction normal tothe grain surface. Negative pressure indicatescohesion, and positive pressure indicates repulsion.Two situations are considered: (i) inside a C-S-Hgrain and (ii) between two C-S-H grains separatedby varying distances up to 1 nm, reflecting theclose proximity of such grains within cementpaste.RESULTS: We found that calcium ions areresponsible for the overall cohesion in thesematerials (giving rise to a negative pressure).However, the role of water in reducing orreinforcing this intergranular and intragranularcohesion depended on separation distance betweenC-S-H grains. The reduced cohesion at separationdistances < 5 Å and increased intergranularcohesion at intermediate distances of 5-10 Å wereboth amplified with increasing %RH (fig. 1).CONCLUSIONS: These findings give for the firsttime an atomistic picture of the confined fluid andits induced pressure effects on the solid structure inthe lowest porosities of cement at ambienttemperature and 100% RH. It is a first step tounderstand cement paste damage processes inmore extreme conditions as high/low temperatures,high pressures, and/or various ionic concentrations.Fig. 1: Pressures applied by the fluid (water (H 2 O)and calcium ions (C w )) in the direction normal tothe grain surface as a function of the distancebetween the C-S-H grains at 100% RH. The blackcurve is the total pressure. The contribution ofwater to the pressure is indicated with blue filledcircles. The contribution of the calcium ions isindicated with red filled squares.REFERENCES: 1 R. J.-M. Pellenq, A. Kushima,R. Shahsavari, K. J. Van Vliet, M. J. Buehler, S.Yip, and F.-J. Ulm; 2009; PNAS; 106 (38):16102.ACKNOWLEDGEMENTS: This work wassponsored by the U.S. Department of HomelandSecurity, Science and Technology Directorate,Infrastructure Protection and Disaster ManagementDivision: Ms. Mila Kennett, Program Manager.The research was performed under the direction ofDr. Beverly P. DiPaolo, Engineer Research andDevelopment Center (ERDC), U.S. Army Corps ofEngineers. We acknowledge funding from the MITConcrete Sustainability Hub, supported by thePortland Cement Association and National ReadyMix Concrete Association.34

Atomistic Simulations and Experimental study on the influence of silicates,sulphates and aluminates on the growth and morphology of Portlandite.S. Galmarini and P. BowenPowder Technology Laboratory, EPFL, Lausanne, Switzerland.INTRODUCTION: The morphology ofportlandite (Ca(OH) 2 ) in cementitious systemschanges depending on the composition (namelysulfate and aluminate content) of the cement.Since portlandite is the second most abundantphase in hydrated cement and thus an importantcomponent of concrete, the ability to understandand control these morphological changes wouldpotentially allow a better control of the propertiesof cementitious building materials. A betterunderstanding of the influence of silicates, sulfatesand aluminates on the growth and morphology ofportlandite is the aim of the present study. Thiswork uses both atomistic modeling (classicalmolecular dynamics) and an experimentalapproach using coprecipitation to try and link theatomistic knowledge with known effects in realcement systems.METHODS & RESULTS: As cementitioussystems are very complex and difficult tocharacterize, model precipitation systems wereused. As a point of reference the morphology ofportlandite particles precipitated from a purecalcium hydroxide solution by thermalprecipitation was studied. The particles in the pureCa – O – H system are facetted and relativelyequiaxed. This is in good agreement withtheoretical equilibrium morphology calculationsbased on classical molecular dynamics calculations(Fig.1).hinder the growth, aluminates hinder nucleation(low yield and larger particle sizes) and sulfatesstabilize the [00.1] facet of portlandite particles,leading to hexagonal platelet shaped particles. Tofurther understand the effect of these additives, theadsorption of the different species onto differentcrystallographic surfaces of portlandite was studiedwith classical molecular dynamics andmetadynamics. Adsorption energies have beenestimated for a series of different species identifiedto be the most abundant species for the silicatesystem from thermodynamic modeling, namely;Ca 2+ , OH - 2-, CaSiO 2 (OH) 2 and SiO 2 (OH) 2- 2 . Theadsorption energies of the silicate species areintermediate and show a certain amount of mobilityon the crystal surface (Fig. 2) supporting the effectsidentified from the experimental observations.Simulation work is currently concentrating onsulphate and aluminate species and thecoprecipitaion of mixed species (aluminates,sulphates, silicates) is being investigated.Fig. 2 Adsorption conformations of a calciumsilicate complex at the portlandite water interface– highlighting the possible growth modificationmechanism linked to their mobility on the surface(white = H, Red = O, Blue = Ca, Yellow = Si)Fig. 1: SEM image of portlandite particles producedby thermal precipitation in a pure Ca–O– H system(left) and theoretically calculated portlanditeequilibrium morphology in water (right)The influence of the addition of aluminates, sulfatesand silicates on the morphology of portlandite wasthen studied by a series of coprecipiationexperiments. The results indicate that silicatesACKNOWLEDGEMENTS: The Nanocemconsortium is gratefully acknowledged forfinancial support, Prof. S. Parker for illuminatingdiscussions, A. Aimable, N. Ruffray,T. Safaei andA. Kiani, for much of the experimental work, M.Stuer for the SEM.35

Hierarchical self-assembling of thelechelic star polymers: from soft patchyparticles to diamond crystalsB. Capone 1 , F. Lo Verso 2 , C. N. Likos 1 , R. Blaak 11Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria2Institut für Physik, Johannes-Gutenberg-Universität Mainz, D-55099 Mainz, Germany.The production of self-assembling material, relieson building blocks simple enough to be reliablyproduced on a large scale. We propose di-blockcopolymer (telechelic) polymer stars as a verysimple and extremely tunable system that is able tohierarcically self assemble first into soft patchyparticles and then into complicated crystallinestructures as the diamond crystal. It will be shownthat the self aggregating patchy behavior can befully controlled by two parameters, which are thenumber of arms per star and the percentage ofattractive monomeric units in the tail of each of thearms. The low density conformational ”phase”diagram is extracted, both computationally andtheoretically, as a function of these parameters. Forlow densities the stars preserve their selfassembled structure and interact with one anotheras extremely flexible patchy particles. Onincreasing the density, they form percolatinggellike networks, and, for sufficiently highdensities, they are capable to sustain crystallinestructures. In particular we will demonstrate thatthese soft flexible patchy particles can assembleinto a mechanically stable diamond crystal, whichhas not been achieved so far at finite temperatureswith other models. Moreover our work provides anexplanation to experimental findings in [8, 9],where telechelic star polymer solutions were foundto crystallize into a diamond lattice for suitablevalues of number of arms and percentage ofattractive monomers.Fig. 1: A percolating gel formed by telechelic starpolymers with f = 5 arms and 60% of attractivemonomers per arm.Fig. 2: A mechanically stable diamond latticeformed by telechelic star polymers with 10 armsand 60% of attractive monomers.36

Activated drying of hydrophobic nanopores and the line tension of waterL. Guillemot 1 , T. BIben 1 , A. Galarneau 2 , G. Vigier 3 , E. Charlaix 41 Université Lyon 1, Villeurbanne, France 2 ENSCM, Montpellier, France, 3 INSA de Lyon, Lyon,France, 4 Université Joseph Fourier, Grenoble, France.INTRODUCTION: Micelle-templated-silicas(MTS) provide an ideal nano-scale laboratory tostudy the properties of water confined in quasi 1Dcylinders of monodisperse radius. Native MTShave been used to study the phase diagram ofwater and its dense state under hydrophilic confinement,whereas silane-grafted MCM-41 allowsus to study water confined between hydrophobicwalls [1]. We report here first investigations of thedrying dynamics of hydrophobic nanopores using avariety of MTS.METHODS: The pressure-volume(P-V) isothermsof water in the hydrophobic pores are measuredusing an instrumented, deformable cell filled withdegassed water and grafted MTS. The intrusionand extrusion pressure of water into and from thepores are measured as a function of the intrusionand extrusion time.The critical nucleation volumes measured from theslope of the log-growth of P ext are in impressiveagreement with a classical theory [1] without anyadjustable parameter.Fig. 1: A traction machine (left) drives the volumeof the cell (center) at a constant rate. The isothermP(V) are recorded (bottom). Water enters the poresat the pressure P int and empties them at pressureP ext . The intrusion and extrusion times aremeasured on the P-V curves.RESULTS: While the intrusion pressure dependsonly weakly on intrusion rate, we find that theextrusion pressure has a robust logarithmic dynamicsover more than 3 decades in time. Thisdemonstrates an activated dynamics for the drying,triggered by the nucleation of a vapor bubble ofcritical volume V cP ext = (k B T/ V c ) ln (t ext /t o ) + P° ext (T) (1)Fig. 2: Top: extrusion pressure as a function ofextrusion time in hydrophobic MCM-41. Bottom:the critical nucleus volume measured from theslope. The coloured rectangles correspond to theclassical theory of nucleation in a cylinder.However the classical theory overestimates utterlythe energy barrier and predicts negative extrusionpressures. We show that the critical bubble energyis indeed dramatically lowered by a negative linetension of water on the hydrophobic wall. Theextrusion pressure provides a measurement of thisline tension with a much higher precision thatcurrently available methods. We find values lyingbetween -25 to -35 pN in a variety of silane-graftedMTS. This negative line tension favors theformation of nanosize bubbles and explain the easydrying of hydrophobic surfaces.REFERENCES: 1 B. Lefevre et al; 204; J. Chem.Phys. 120:4927-493837

Inherent Structures Deformations Detect Long-Range Correlations inSupercooled LiquidsM.Mosayebi 1 , E.Del. Gado 1 , P. Ilg 1 , H.C.Ottinger 11 ETH Zürich, Zürich, SwitzerlandINTRODUCTION: One of the most puzzlingfeatures of the supercooled regime and the glasstransition is the apparent lack of structural changesunderlying the dramatic slowing down of thedynamics. Recently, some progress has beenachieved in relating dynamical properties toinherent structures, which are the local minima ofthe collective potential energy [1].We have found striking similarities in the onset ofcooperative behaviour in dynamics and in the nonaffinepart of the inherent structure response toexternal deformations [2]. That approach wasmotivated by a recent theory [3] based on a generalframework of non-equilibrium thermodynamics.This thermodynamic treatment suggests that thereversible part of glassy dynamics changesconsiderably when approaching the glass transition.Above the glass transition, the particles can followan imposed deformation more or less freely,whereas closer to the glass transition the particlemovement becomes a hopping-like transitionbetween different basins of attraction of theunderlying inherent structures [1].METHODS: We study numerically wellestablishedmodel glass formers, in particularbinary Lennard-Jones and binary soft spheresystems consisting of N particles (N varies between2000 and 64000) from the high temperature liquiddown to the supercooled regime. From thermal,equilibrated particle configurations, we preparecorresponding inherent structures by minimizingthe potential energy with conjugate gradientmethods. We also apply instantaneous, affine sheardeformations to each thermal configuration and findthe closest inherent structure corresponding to thedeformed state. The difference between bothinherent structures – subtracting the affine part - isthe nonaffine displacement field.RESULTS: The distance between two inherentstructures - that are related via shear deformation ofrather small amplitude - sharply decreases withdecreasing temperature below the onset temperatureof the landscape-dominated regime. Furthermore,we observe a crossover between two regimes that isalso present in a qualitative change of the nonaffinedisplacement distribution from an exponential to apower-law shape. The exponent of the latter can beexplained by elasticity arguments. Qualitatively, wefind similar correlations of the nonaffinedisplacement field as experiments on correlatedmotions in colloids. Quantitatively, the staticcorrelation length extracted from nonaffinedisplacements of inherent structures is growingstronger than the dynamical one [4].Fig. 1: Nonaffine displacements for one sample ofthe binary Lennard-Jones system at high (left) andlow (right panel) temperature. Homogeneous sheardeformation of amplitude 10 -4 was applied. Forclarity, only particles near one face of the threedimensionalsimulation cell are shown.DISCUSSION & CONCLUSIONS: Here, wehave shown by extensive molecular simulations thatcorrelations in neighbouring inherent structures arequite reminiscent of cooperatively rearrangingregions that are observed in the system's dynamics[4]. Due to the absence of thermal fluctuations, ourmethod provides a very sensitive and efficient toolto investigate such correlated regions in great detail.REFERENCES:1 A. Heuer; 2008; J. Phys.:Condens. Matter; 20:373101. 2 E. Del Gado, P. Ilg,M. Kröger, H.C. Öttinger; 2008; Phys. Rev. Lett;101:095501. 3 H.C. Öttinger; 2006; Phys. Rev. E74:095501. 4 M. Mosayebi, E. Del Gado, P. Ilg,H.C. Öttinger; 2010; Phys. Rev. Lett; 104:205704.ACKNOWLEDGEMENTS: We gratefullyacknowledge stimulating discussions with LudovicBerthier, Andrea Cavagna, Walter Kob, SrikanthSastry, Anne Tanguy and Asaph Widmer-Cooper.38

Controlling building materials microstructure through the mixing stepHélène Lombois-BurgerLafarge – LCR (France)Mixing is a key step for the production of cement pastes or concretes. Indeed, eventhough very short this stage has a major influence on the quality of the microstructureof the mix and thus on the materials performances. Its impact extends on the wholematerial’s service life, from the rheology to the mechanical strength and even thedurability. These microstructural characteristics due to the mixing are the result of acomplex interplay between process and mix design parameters.Using several techniques to monitor the mixing extent in terms of homogenization,de-agglomeration of the fine particles, prevailing inter-particle forces, allows:(i) To unveil mixing mechanisms, and demonstrate the role of both processparameters (sequence for the introduction of the components, mixingtime/speed/energy, volume effects, etc) and mix design ones such as coarse aggregateproportion for instance. Mixing optimization consists then in obtaining the bestmicrostructure while shortening the process duration and required energy.(ii) To monitor mix design levers such as packing effects, water content, competitionbetween admixtures, etc39

Reactive Force Field Molecular Dynamics of the C-S-H Gel: Confined WaterDissociation and Impact on the Substrate PropertiesH.Manzano 1 , S.Moeini 2 , F.Marinelli 3 , A.C.T. van Duin 4 , F-J. Ulm 2 , R.J-M.Pellenq 2,51 Basque Country University UPV/EHU, Spain. 2 Concrete Sustainability Hub, MIT, USA.3Physique des Interactions Ioniques et Moléculaires, Université de Provence, France.4 Department of Mechanical and Nuclear Engineering, Pennsylvania State University, USA.5 Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, France.INTRODUCTION: The C-S-H gel is the mainconstituent of cement, up to the 70% of the finalmaterial. It is the phase which gives cohesion tothe material, and main responsible for cement'sstrength. The C-S-H gel can be broadly defined asa disordered material composed of short silicatechains held together by calcium oxide regions,forming clay-like layers, with water trapped insidethe structure [1]. However, the real structure is notwell determined, due to the difficulties to obtainexperimental quantitative data. Based on previousdescriptions and using atomistic simulation, amodel for the C-S-H gel was constructed byPellenq et al [2]. In this work, we take that modelas starting point, introducing a new degree offreedom using reactive force field moleculardynamics (rMD): the chemical reactions. We trackthe reactions taking place in the system, and studyhow they affect to the structure and properties ofthe C-S-H gel [3].METHODS: We have performed rMD in the C-S-H gel after parameterizing the calcium interactions(Ca−O−H) [4] within the ReaxFF reactive forcefield, and integrate them with the previouslydeveloped Si −O−H set [5]. The trajectoryintegration was done using a Verlet algorithm,with a time step of 0.25 fs. The simulations werecarried out for 4.5 ns in the NPT ensemble (T =298 K, P = 1 atm) with a Nosé-Hoover thermostatand coupling constant of 100 fs, averaging theproperties during the last 250 ps.RESULTS: 40% of the initial water present in C-S-H gel pore space dissociates in less than 250 psto form Ca−OH and Si−OH group . All the waterreacts in the NBO atoms of the silicate chainsforming silanol groups, while none of the siloxaneoxygen atoms reacts. The water dissociationreactions do not affect much the short-range orderand elastic properties of C-S-H gel, yet there is agreater impact on its strength. The maximum stressreached under a shear deformation increases afterwater dissociation from 2 GPa to 3.25 GPa, takingplace at 8% and 14% strain respectively.Fig. 1: (a) Graphic representation of the C-S-Hgel atomic structure. In purple the SiO 4 tetrahedra,+in orange the Ca 2 ions, and the water moleculesas red and white sticks. (b) Distribution of thewater molecules in the C-S-H gel beforedissociation and (c) after dissociation.DISCUSSION & CONCLUSIONS: Beforedissociation, the water molecules between layersact as a lubricant allowing the sliding betweenadjacent clay-like layers. After dissociation, thesmall rearrangements of the structure traps part ofthe water in small close pores. Those moleculespresent an ice-like behavior (characterized by thenonexistent diffusivity of the molecules and astrong interaction with the substrate) and hence donot contribute to the relaxation: they are stronglybonded structural water, leading to an increase ofthe C-S-H shear strength.REFERENCES: 1 H. F. Taylor, CementChemistry; 1997; Thomas Telford Publishing. 2 R.J. M. Pellenq et al., Proc. Natl. Acad. Sci. USA2009; 106; 16102. 3 H. Manzano et al., J. Am.Chem. Soc; 2012; 10.1021/ja209152n. 4 H.Manzano et al., Langmuir; 2012; under review. 5 J.C. Fogarty et al., J. Chem. Phys; 2010; 132, 10.ACKNOWLEDGEMENTS: H.M. acknowledgesthe postdoctoral grant received by the Department ofEducation, Science and Universities of the BasqueCountry Government.40

NANO-STRUCTURE AND -MECHANICS OF CEMENT:POLYDISPERSE COLLOIDAL PACKINGE. Masoero 1 , E. Del Gado 2 , R.J.-M. Pellenq 1 , F.-J. Ulm 1 , S. Yip 11 Massachusetts Institute of Technology, Cambridge, U.S.A.2 ETH Zürich, Zürich, Switzerland.Cement setting and cohesion are governed by the precipitation and growth ofcalcium-silicate-hydrate (C-S-H), through a complex evolution of microstructure. Acolloidal model to describe nucleation, packing, and rigidity of C-S-H aggregates isproposed [1]. Polydispersity and particle size dependent cohesion strength combine toproduce a spectrum of packing fractions and of corresponding elastic properties thatcan be tested against small angle neutron scattering and nanoindentation experiments.Implications regarding plastic deformations and reconciling current structuralcharacterizations are discussed.Fig. 1:Elastic indentation modulus M vs. packing fractionφ. Νanoindentation experiment on a C-S-H sample from whitecement [2], and our simulation results with different polydispersityδ.[1] E. Masoero, E. Del Gado, R.J. Pellenq, F.J. Ulm and S. Yip, "Nano-structure and–mechanics of cement: Polydisperse colloidal packing", preprint (2012)[2] R. Pellenq et al.; 2009; PNAS; 106:16102-16107.41

Oriented aggregation of C-S-H by polymers.L. Nicoleau 1 , T. Gaedt 1 , O.Paris 2 , L.Chitu 3 , G.A. Maier, 31 BASF CC GMB Trostberg, Germany. 2 Montanuniversität Leoben, Austria.3 Materials Center Leoben Forschung, Leoben, Austria.INTRODUCTION: The synthesis of welldispersedC-S-H suspensions is a major challengefor BASF as it has demonstrated the revival of theseeding technology in cement with the purpose ofhydration acceleration. Polymer stabilized C-S-Hsuspensions form viscoelastic gels at remarkablylow volume fractions such as 1.4%, meaning thatthe self-organization of particles is important. Thepresent work studied the link between theorganization of C-S-H platelets and the efficiencyas cement hydration accelerator.RESULTS: The size of the primary C-S-Hparticles which are the constituents of the gel hasbeen determined using various methods such asTEM, Analytical Ultracentrifugation and USAXS.It turns out that C-S-H nanoparticles can bedescribed as platelets with a height of 1-2 nm and adiameter of 30-80 nm. Obviously, the particlesshow strong interactions and form superstructuresin suspension which finally result in gel formation.Importantly, there is no clear-cut correlationbetween particle size and cement hydrationefficiency.A large effort has been put into the elucidationof the structure of the C-S-H aggregates which isresponsible for the efficiency or inefficiency of C-S-H suspensions as accelerators. Methods likeanalytical ultracentrifugation and TEM gave firstinsights into the development of C-S-H aggregates.However, it became clear that a quantitativeevaluation of C-S-H aggregate morphology wasonly possible with scattering methods such asUSAXS. Experiments were performed at thesynchrotron facility of the ESRF in Grenoble incollaboration with the University of Leoben. Amass fractal model was developed which yieldedgood fits of the USAXS curves of stabilized C-S-Hsuspensions. The self-similarity of aggregatestructures was already revealed by TEM (Fig.1).The most important parameters extracted from themodel are the diameter D of the C-S-H platelets, ζthe cut-off size of the fractal structure and d thefractal dimension of the C-S-H aggregates. A goodcorrelation was obtained between the cementhydration acceleration and the fractal dimension dat constant fractal aggregate size. The main reasonfor this behavior lies in the availability of active C-S-H surfaces. Large C-S-H aggregates with a lowfractal dimension have a very “open”, i.e.accessible, structure which is ideal for cementhydration. In other words, the packing density ofthe C-S-H clusters has to be low to obtain efficientC-S-H suspensions.Finally, we identified three model polymerswhich yield characteristically different C-S-Haggregate structures. Polymer A as stabilizer giveschain-like C-S-H aggregates. Polymer B givesmainly isolated C-S-H particles which collapseinto an inefficient and dense clump of platelets.Polymer C yields a more 2-dimensional, plate-likeaggregate structure which gives at the end thehighest degree of “openness” which goes hand inhand with very good accelerator performance.Fig. 1: TEM picture of a 7 w % CSH suspension. AFractal image analysis results in a fractaldimension close to 1,8 and a self-similarity overtwo orders of magnitude.CONCLUSIONS: The use of polyelectrolytes isprerequisite in numerous systems in which thestabilization and/or the dispersion of smallparticles is desired. C-S-H does not depart fromthis and the achievement of colloidal suspensionsof C-S-H is only possible by the addition ofpolymers. The polymer stabilization leads to C-S-H fractal structures as it has been observed in othersystems.43

Colloidal gels under shearN. Koumakis, G. PetekidisIESL-FORTH and University of Crete,GreeceThe structural and rheological properties of colloidal gels are examined duringsteady state shear flow as well as after cessation using rheology, confocalmicroscopy and Brownian Dynamics simulations. Experimentally, the gelsconsist of model hard sphere particle dispersions of φ=0.44 with the addition ofnon-adsorbing linear chains, while BD simulations are conducted for hard sphereswith the superposition of an Asakura-Osawa potential for depletion attractions.Structural analysis shows that variation of the applied shear rate produces strongchanges in the structure of the gels both when under shear and during gelreformation at cessation. Larger rates are characterized by disperse particles andthe total breakage of structures at rest, which after cessation evolve with time intostrong solids with relatively homogeneous structures. However, smaller ratesshow large inhomogeneous structures under flow, which do not evolve aftercessation and additionally exhibit reduced elasticity and as such are weakersolids. Thus by tuning the way a gel is sheared, one may vary the final strengthand structure of the resulting gel.Work in collaboration with R. Besseling, W. C. K. Poon and J. F. Brady.44

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Microstructure of cement pastes with and without chemical admixturesM.Bellotto1 Bozzetto Group, Filago (Bg), Italy.1INTRODUCTION: In order to understand themacroscopic properties of materials it is necessaryto characterize the different levels of structurepresent and their relationship to a macroscopicproperty. Cement paste undergoes a process ofstructure formation since the very early mixingwith water, which macroscopically goes under theterms of stiffening and setting and which is drivenat the molecular level by the hydroxylation of thecement particles’ surface. At the mesoscale thisphenomenon is driven by the attractive forces withdevelop among the particles and which lead toweak aggregation.METHODS: Cement paste develops viscoelasticproperties immediately after mixing with water. Itflows under shear, with marked shear thinningproperties and forms an attractive gel at rest withelastic properties which develop rapidly over time.Rheological measurements are used tocharacterize the nature of the interactions and themicrostructure of cement paste both as such and inthe presence of dispersing “superplasticizing”chemical admixtures. The measurement areperformed either under macroscopic shear, i.e.flow curves, and in small amplitude oscillationmode within the linear viscoelastic regime.Different cements have been used, either a CEM IPortland cement or different limestone and slagCEM II and CEM III composite cements. Twodifferent classes of superplasticizers have beenused, poly-carboxylic-ethers (PCE) andphosphonic polymers (Ph).RESULTS: The shear thinning behaviour ofcement paste is due to the breakup of the weakaggregates in the hydrodynamic shear field [1]. Assuch it describes the strength of the interparticlebonds within the aggregates, and how theinteraction energy is modified by the presence ofdispersing agents. In Figure 1 it is reported theobserved decrease of the characteristic shear stressfor cluster breackup, τ * , on increasing the amountof the two classes of suplrplasticizers. Theviscosity vs. shear rate data are interpreted asaggregate dimension vs. shear stress, leading theway to a physical interpretation of the differentshear thinning behaviours observed with thedifferent superplasticizers. The aggregates areeither compressed and fractured by thehydrodynamic field, and acquire a densearrangement characterized by a fractal dimensionclose to 3.Fig. 1: Decrease of interparticle attractive forceon increasing the dosage of dispersingadmixture.The small amplitude oscillation measurementsprobe the elastic properties of the gel which formsat rest. The storage modulus G’ and the lossmodulus G” are measured, and they are linked tothe number density of the elastic links formingamong the particles [2].DISCUSSION & CONCLUSIONS: Thisapproach is powerful, yet entirelyphenomenological and difficult to reconcile withdifferent microstructural descriptions. For thisreason we are trying to describe the systemevolution through the determination of thetransition state pathway via atomistic simulation.As a first step we have measured the creepresponse of silica suspensions, before and aftercoagulation, and we have derived the retardationspectra which give indication of the time scales ofthe relaxation phenomena and thus of thetransition state barriers around each local freeenergy minimum.REFERENCES: 1 P.Snabre and P.Mills; 1996;J.Phys.III France; 6:1811-1834. 2 A.A.Potanin, R.De Rooij, D. Van den Ende and J.Mellema; 1995;J.Chem.Phys.; 102:5845-5853.46

TEMPERATURE EFFECT ON FLY ASH BLENDED CEMENTMICROSTRCTURE DEVELOPMENTM.Ben Haha 1,3 , K.De Weerdt 2 , B.Lothenbach 31 HeidelbergCement Technology Center, Leimen, Germany. 2 SINTEF Building and Infrastructure,Trondheim,Norway. 3 Empa, Dübendorf, Switzerland.INTRODUCTION: The development of themicrostructure, the hydrates assemblage and themechanical properties of hydrated ordinaryPortland cement (OPC) pastes and concrete aregreatly influenced by the curing temperature [1].Increasing the curing temperature is initiallybeneficial for strength development, but it isdetrimental for the later age properties due to itseffect on the development of the microstructure.Fly ash blended cements; on the other hand, reactdifferently to increasing the curing temperature.The dissolution of the FA is accelerated by raisingthe curing temperature albeit over a longer timespan than the OPC. A quantitative multi-methodapproach is adopted in this study to investigate theeffect of temperature on composite cementhydration.METHODS: Ordinary Portland clinker, naturalgypsum, class F siliceous fly ash (FA) andlimestone (L) powder were used for this study. TheFA has a glass content of 65%, and the L powdercontains 81% CaCO 3 . The hydration of two plainOPCs and three different fly ash blended cementswith a replacement level of OPC up to 35 % atthree different curing temperatures 5, 20 and 40°Cwas monitored up to 180 days. The compressiveand flexural strength were tested on mortar prisms.Cement paste samples were prepared with water tobinder ratio of 0.5 and stored in sealed plasticvessels at curing temperature of 5, 20 and 40°C.The amount of bound water (H) and calciumhydroxide (CH) are determined by TGA. Thecrystalline anhydrous and hydrous phases wereidentified, and if possible quantified applyingXRD combined with Rietveld analysis. Thedegree of hydration of OPC and FA as well as thecoarse porosity were determined usingcombination of methods incl. SEM image analysis[2-4].RESULTS: Increasing the curing temperaturesaccelerates the FA reaction as shown in Fig. 1.However, the enhanced reactivity of FA withincreasing curing temperature takes place overlonger time span. The slow reaction of FA at 5°Cis mirrored by the impaired mechanical propertiesobserved for the FA containing blended cements atthis low temperature. For FA blended cements, thematrix development during the first days is mainlydue to the OPC reaction. However, even thoughFA does not react considerably during the firstdays, it does influence the microstructure due toits filler effect: the surface of the FA particlesserves as precipitation surface for the hydrationproducts, and the effective water-to-cement ratiois increased. No detrimental effect of increasingthe curing temperature was observed for thecompressive strength of FA composite cements. Atlater ages, the pozzolanic reaction products furtherfill the coarse porosity and thereby improve thecompressive strength.FA reacted (%)4035302520151050OPC-FA*-5°COPC-FA-5°COPC-FA-L-5°COPC-FA*-20°COPC-FA-20°COPC-FA-L-20°COPC-FA*-40°COPC-FA-40°COPC-FA-L-40°C0,1 1 10 100 1000Age (days)Fig. 1: FA reacted at the different temperaturesDISCUSSION & CONCLUSIONS: To reach thesame strength level, FA blended cement binds lesswater than OPC. Independent of the curingtemperature, the total amount of reacted OPC andFA correlates well with strength for the fly ashblended cements. This was not the case for plainOPC. The coarse porosity appears to be thedominating factor regarding the compressivestrength, independent of the curing temperature orwhether part of the OPC is replaced by FA and Lpowder or not.REFERENCES: 1 KO Kjellsen, RJ Detwiler 1992Cem Concr Res 22(1):112–1202KL Scrivener 2004 Cem Concr Compos26(8):935–9453 M. Ben Haha et al 2010. Cem Concr Res40(11):1620–16294 K. De Weerdt et al 2011. Cem Concr Res41(3):279–29147

Dissolution kinetics and rate-control of alite and portland cement clinkerBisschop, J., and Kurlov, A.Institute for Building Materials, ETH-Zürich,Schafmattstr. 6, 8093 Zürich, SwitzerlandHydration of portland cement is a complex chemical process involvingdissolution and precipitation reactions. An understanding of what the ratecontrollingreactions in cement hydration are, will benefit cement hydrationmodeling and ultimately the development of improved concretes. In thiscontribution we address the topic of the type of dissolution rate control for alite(C3S), i.e., by aqueous diffusion or by surface reaction rate. This will partlydetermine if C3S dissolution has a potential to act as a rate-limiting step duringportland cement hydration.A new flow-through dissolution method has been developed for the purpose ofmeasuring dissolution rates of single- or multiphase cements. Dissolution rateswere measured from SEM-BSE images of sample cross-sections which has anumber of advantages over existing dissolution measurement techniques. Thecapability of the method is demonstrated by experiments on flat-groundembedded fragments of raw portland cement clinker and synthesized alite pelletsin deionised water. Dissolution rates increased with water flow velocity (0, 0.45,4.5, 16.4 m/s) and this shows that the alite/C3S dissolution rate was transport(diffusion) controlled under the studied conditions, at least at lower flow rates.This result is supported by preliminary predictions of a diffusion boundary layermodel for the laminar flow regime in our experiments.Widespread precipitation of hydrates occurred during dissolution of C3S inclinker. In the synthesized alite fibrous/sheet-like precipitates on the dissolutionfront were sometimes observed as a result of water penetrating the material alongcrack or grain boundary surfaces. The amount of precipitates generally decreasedwith increasing flow rate, but no evidence was found that the precipitationaffected the initial dissolution rate. Hydrate precipitation is an expectedphenomenon during diffusion-controlled dissolution. After one hour ofdissolution, the dissolution rate of alite became larger than the one of C3S inclinker. This showed that dissolution of the latter was no longer limited byaqueous diffusion, but became limited by transport through a layer of precipitatesand non-dissolved clinker components.48

Autogenous shrinkage in oil well cementsA. Blanc1,2 , P. Faure 1 , S. Le Roy-Delage 2 , T. Fen-Chong 11 UR Navier, Champs sur Marne, France. 2 Schlumberger EPS, Clamart, France.INTRODUCTION: The work presented hererelates to cementing in an oilfield background andspecifically focuses on the hydration of the cementpaste and the autogenous deformations that canoccur. During the cement hydration, theconsumption of water in the pores creates adepression that causes eventual shrinkage of thematerial, which is critical as the sealing role of thecement annulus may be lost, at greatenvironmental as well as production cost. Therange of temperature and pressure conditions towhich the cement paste is exposed is very large,going up to hundreds of degrees Celsius and barsdown hole. The access to water coming from therock formations is also an important parameter inthat it can compensate water consumption.METHODS: These effects have been included ina modelling work by Brice Lecampion forSchlumberger. He created an incremental model torelate the hydration of the cement toporomechanical stress and strain, depending onpressure and temperature as well as access towater. Here, we try to bring experimental results toback up these results, by investigating thehydration of early-age cement paste.We first use uniaxial creep tests to explore theevolution of mechanical properties after around 24hour of hydration. The samples are made with aclass G cement paste with a water to cement ratioof 0.45, and moulded as cylinders of 2 cmdiameter and 10 cm height. After 24 hours, theyare submitted to a constant vertical compressivestress and the deformations over time are measuredfor 72 hours. We tried first a stress of 5.1 MPa,then went down to 1.7 Mpa.We also used NMR measurements to get a closerscale point of view on the setting phase. Thestudies were performed on a 0.5 T imager (protonresonance at 20 MHz). This low magnetic fieldreduces the apparition of inhomogeneities,allowing to observe large samples (around 500g),which is well suited for this type of materials. Wemeasure both the overall signal variation and theT1 relaxation over time in a setting paste. In orderto have a better control on curing temperature andaccess to water, we also use a Minispec unit withtemperature control. The samples are muchsmaller, from 1 to 5 g, and we explored atemperature range from 5 to 60 degrees, with orwithout access to water for the cement paste.RESULTS: The creep tests results show a highdispersion, due to large variation of the elasticstrain. The long-time stress however is quitereproducible, especially with the lower value ofstress.Fig. 1: Creep results with two values of stressThe NMR measurement show a good correlationbetween the decrease of the total signal and thesimulated degree of hydrationFig. 2:Measured water consumption againstmodelled hydration degree during 14 daysDISCUSSION & CONCLUSIONS: We will nowapply these measurements methods to cementspastes with various curing temperatures and witheventual access to water. This includes creating awater circulation device that we plan to adapt tothe creep experiment.49

Molecular-Dynamics and Monte-Carlo Simulations of Water Dynamics in CementS.-H. P. Cachia 1 , J. S. Bhatt 1 , S. V. Churakov 2 , N. C. Howlett 1 , D. A. Faux 1 , P. J. McDonald 11 Department of Physics, University of Surrey Guildford Surrey GU2 7XH United Kingdom 2 Laboratory forWaste Management, Paul Scherrer Institute, 5232 Villigen-PSI, SwitzerlandINTRODUCTION:1 H Nuclear MagneticResonance (NMR) relaxometry has been used tocharacterise water dynamics in cement pastes onthree timescales: (i) nanosecond hopping of watermolecules across pore surfaces; (ii) microsecondresidency time for water molecules adsorbed atpore surfaces and (iii) millisecond exchange ofwater between C-S-H interlayer and gel pores. It isthe purpose of this work to seek to corroboratethese measurements using a combination ofMolecular-Dynamics (MD) and Monte-Carlo (MC)simulations. The MD is able to assess waterdynamics in nano-pores from the pico to nanosecond timescale in great detail. MC is required toextend this to longer length and timescale.METHODS: Atomic trajectories of water inconfined geometries have been obtained with MDand MC simulations. These are used to calculatethe nuclear dipole-dipole correlation functions:G * (t) = 1 (3cos 2 (! 2 ! ij)"1) / (r 3 ij(t)r 3 ij(0))where the sum is over all pairs of 1 H nuclei withseparation r ij (t) and θ is the angle between thisvector at time zero and t.The correlation functions are Fourier transformedto yield the spectral density function J(!) fromwhich the NMR spin-lattice and spin-spinrelaxation times, T 1 and T 2 respectively, arecalculated:1 = A J(!T1( 0)+ 4J(2! 0))1 = A 3J(0)+ 5J(!T2( 0)+ 2J(2! 0))where A is a constant characteristic of the materialand ! 0is the NMR frequency.RESULTS: MD simulations were performed forbulk water, water confined between (100)-facets ofSiO 2 , Tobermorite’s basal plane and other C-S-Hanalogues.Figure 1 shows a snapshot of an MD simulation ofwater confined between two planes of SiO 2 . Theplanar spacing is d = 3.1 nm. Simulations havebeen performed for separations as small as 1 nm.Water confined to a pore can be identified as“surface” or “bulk” dependent upon its initiallocation with respect to the SiO 2 . Figure 2 showsthe contribution to the correlation function arisingfrom bulk-bulk, surface-bulk and surface-surfaceinteractions from which the relaxation times arecalculated. There are significant differencesbetween the correlation functions of confinedwater and those for bulk water that give rise to thereduction in relaxation times. Further simulationshave followed the contribution of, for instance,surface paramagnetic impurity contributions andinter- and intra-water molecule contributions.Fig. 1: An MD snapshot of water confined between(100) SiO 2 facets. O-atoms are red, Si-atoms areyellow, H-atoms are white.Fig. 2: Total and partial G * (t) correlationfunctions. Black: total; Green: bulk-bulk; red:surface-bulk; blue: surface-surface.REFERENCES:1A. Abragam, The principle of nuclear magnetismOxford, (1961)2 Sholl, J. Phys. C. 7, 3378 (1974)3 Faux, et al, J. Phys. C. 19, 4115 (1986)ACKNOWLEDGEMENTS:This work is supported by the European UnionSeventh Framework Programme (FP7 / 2007-2013) under grant agreement 264448 and by theU.K. Engineering and Physical Sciences ResearchCouncil, grant number EP/H033343.50

Cooperative processes in restructuring gel networksJader Colombo and Emanuela Del GadoMicrostructure and Rheology, Institute for Building Materials,ETH Zurich, CH-8093 Zurich, SwitzerlandColloidal gel networks are disordered elastic solids that can form also via reversibleaggregation and even in extremely diluted particle suspensions. The possibility ofinternal restructuring underlies their smart mechanics and being able to design it atthe level of the nanoscale components would be ground-breaking for severaltechnological applications. This is challenging, especially because there is limitedunderstanding of how local breaking and recombination change the mesoscaleorganization of the network and the stress transmission through it.We have carried out a comparative study of restructuring and non-restructuring gelnetworks, by means of molecular dynamics. The networks arise from self-assembly ofcolloidal particles, whose effective interactions yields local rigidity necessary tomake thin network structures at low volume fractions mechanically stable. Thelocalization of particles in the network, akin to some extent to caging in denseglasses, appears to be determined only by the network topology and displays thesame features in restructuring and non-restructuring networks. Nevertheless, bondbreakinginduces cooperative processes that are not present in the non-restructuringnetworks and we are able to relate them to the presence of regions where bondbreakingis more likely to occur. Interestingly, such regions are not characterized bymore mobile particles: because the mesoscale organization of the network is notdisrupted by single bond-breaking events, such events can instead changesignificantly the mobility of regions further away.Spatial map of particle mobility.Spatial map of propensity to bond breaking.51

Consolidation of superplasticized pastesJ. Colombo, E. Del Gado, R. J. Flatt, and H. J. HerrmannInstitute for Building Materials,ETH Zurich, CH-8093 Zurich, SwitzerlandSuperplasticizing polymers can adsorb to the surface of (micro-sized) grains ofcement powder in water and, by screening inter-grain interactions, stabilize thesuspension against flocculation. By allowing the fresh material to become workablewith less water, superplasticizers can reduce the porosity of the hardened concrete:this greatly enhances the durability and also makes it possible to substitutesubstantial volumes of cement with industrial waste materials. Exploitation of thehuge potential of these admixtures is hindered by the limited understanding andcontrol of the adsorption process and of the mechanisms by which the screening ofthe inter-grain interactions changes the rheology of the paste.We propose a Discrete Element approach to investigate the microscopic mechanismsby which superplasticizers affect the rheology of flocculated cement pastes. Wemodel the systems as a suspension of micro-sized grains whose effective interactionscan be tuned to mimic different surface coverage by polymer adsorption. We willperform different rheological tests and investigate the microscopic processesdetermining the change of the rheological response upon changing admixture dosageand adsorption properties. Because of the large surface/volume ratio in these systems(i.e. cement paste, but also in many other cohesive micro-structured materialsrelevant for engineering applications), surface forces are extremely relevant andhence their physics appears as an intriguing combination of colloidal and granularphysics.Discrete element simulation of the compaction of acohesive granular material52

PROTON NMR RELAXOMETRY AS A PROBE FOR FOLLOWINGSETTING OF CEMENT MATERIALSP. Faure1 , B. Wang 1,2 , M. Thiery 2 , V. Baroghel-Bouny 21 Université Paris-Est, Laboratoire Navier (ENPC-IFSTTAR-CNRS), Champs sur Marne, France.2 Université Paris-Est, Département Matériaux (IFSTTAR), Paris, France.INTRODUCTION: 20-MHz proton nuclearmagnetic resonance T 1 relaxation has been used todetect cement materials hydration. NMRmeasurements were performed since casting to 3days, during setting.METHODS:NMR experiments were performed with verticalimaging spectrometer DBX 24/80 Bruker,operating at 0.5 T (20 MHz proton), equippedwith a birdcage radio-frequency coil with an innerdiameter of 20 cm (centimeter-size samples withnegligible edge effects). The mobility of watermolecules was assessed by an analysis of thelongitudinal relaxation time T 1 generated by anInversion Recovery sequence. The free waterevolution was investigated by using a simple onepulseacquisition sequence.Temperature evolution was monitored byembedding sensors at three different positionsinside the samplesThe setting process was monitored by a Vicatneedle equipped with four positions (an averagevalue was taken into account). The samples wereisolated in a water bath at a constant temperatureof 20 ± 0.01oC during measurement.A multi-kinetics hydration model based on thePowers’ theory was used to simulate the free watercontent during hydration. This model is based on adescription of the coupled hydration of eachclinker phase (C3S, C2S, C3A and C4AF). Thehydration kinetics is controlled by threeconsecutive steps: (1) dissolution of clinkerphases, (2) nucleation-growth of hydrationproducts, (3) reduction of the reaction rate due toion diffusion through C-S-H layer. The reactionrate for each clinker phase is thermo-activated(according to the Arrhenius law).MATERIALS:Cement pastes and mortars with different water-tocementratios made of grey or white OPC cementswere tested. The effects of some additions (sand,super-plasticizer) on the hydration kinetics werealso investigated.RESULTS:NMR measurements evolution exhibited theknown stages of the hydration process [1]. T 1 wassupposed associated to hardening and so calledmechanical setting and water content evolutioncorresponding to hydrations reactions is supposedto represent a chemical setting time. Conventionaltechniques (Vicat needle and temperaturemonitoring), as well as numerical simulations ofhydration, were complemented and validated theseNMR results.Fig. 1: Time derivative of T 1 value dT 1 /dt andNMR signal amplitude dI FID /dt for cement pastesmade of white OPC of w/c = 0.35 (WC35).DISCUSSION & CONCLUSIONS: Theevolution of T 1 relaxation time has been applied tomonitor the percolation of the solid network and ashas been shown as a relevant mechanical indicatorof setting. The NMR signal amplitude has beenassessed to monitor the global free water depletionduring hydration which has been used as anaccurate chemical indicator of the hydrationprocess from casting to more than 100 days.REFERENCES: 1 P. Faure, S. Rodts; 2008;Magn. Reson. Imaging, 26:1183-1196.ACKNOWLEDGEMENTS: This research isfunded by IFSTTAR Paris and Navier Laboratory.The authors acknowledge Jean-Daniel Simitambe(IFSTTAR) for Vicat needle test, Teddy Fen-Chong (Navier) for the utilization ofthermocouples to monitor temperature.53

A ROBUST METHOD TO MEASURE FRICTION COEFFICIENTSBETWEEN MICROSPHERESN. Fernandez1 , L.Isa 1 , J. Cayer-Barrioz 2 , N.D. Spencer 11 LSST, ETH Zürich, Zürich, Switzerland2 LTDS - UMR 5513 CNRS, Ecole Centrale de Lyon, FranceINTRODUCTION: Therheological properties ofnon-Brownian suspensions at low shear rates, suchas yield stress or setting time, are linked with thefrictional properties of individual particles [1].Unfortunately,the frictional properties ofmicrospheres are not directly attainable usingconventional toolsand can only be measured usingcomplex procedures [2]. Here, we report a directand robust method to measure the frictioncoefficient between microspheres using LateralForce Microscopy (LFM) and we demonstrateresults for bare and brush-polymer-coated silicamicrospheres.METHODS: Friction measurementsare performedusing an AFM and exploiting both the torsion andthe flexion of the cantilever.A microsphere is glued onto a tipless siliconcantilever and used to map a densely packed layerof the same particles in an aqueous buffer medium.During the mapping, various normal loads andscanning velocities are applied and thecorrespondent torsion of the cantilever is recorded.Our results extendordinary AFM nanotribology tothe contact between two spheres and build on theprevious work of Butt and collaborators [3].Wedemonstrate that the complete friction law ofindividual particle pairscan be extracted fromthe average of the difference of the cantilevertorsion on the backward and forward tracksduring scanning.Using classical LFM calibrationprocedures and under specific theoreticalassumptions of the contact geometry,the frictioncoefficient (COF) between the two microspherescan be obtained in simple imaging mode anddepends only on two geometrical parameters:COF (A*Load) = B *½ image /Load(1)If the two particles have a similar radiusA = 1 -[2a 2 (α+1)] / [96 (α+1) + a 2 (α-1) ]B =(α+1) [1 –a 2 (α+1) / (96 (α+1) + a 2 (α-1)) ]where a is the size of the image divided by the tipparticle radius and α the thickness of thecantileverdivided by the tip particle radius.an image of lateral size equal to 80% of the particleradius, having a miscentering up to 50 %, and anuncertainty of the mapped particle diameter of +/-40%, the systematic error in the COF is < 5%. Thisvalue is remarkably small compared to other errorsfrom LFM measurements (e.g. cantilevercalibration errors).RESULTS: We measured the coefficient offriction between two silica particles in a salinebuffer solution at pH 7 obtaining values consistentwith the ones found for silica on silica contact.Moreover, the method also yields information ondependence of the friction coefficient on thesliding speed. The data also show a reduction ofthe friction coefficient when the particles arecoated with a polylysine-grafted-PEG combpolymer designed for lubrication.DISCUSSION & CONCLUSIONS: We reportfor the first time measurements of the friction lawbetween identical microspheres in a fluid using asimple and robust protocol that can be used forparticlesranging from hundreds of nanometres totensof microns, including polydisperse powdersused to model construction materials.This precise knowledge of the microscopicinteractions can help to understand and quantifythe role of the friction in dense suspensionrheology and wet soil mechanics.REFERENCES:[1] Huang& al., PRL, 94,028301 (2005)[2] Ling & al, Langmuir, 23, 8392-8399(2007)[3] Ecke& al. Rev. Sci. Instrum,72, 4164 (2001)This procedure shows an extreme robustnessagainstexperimental errors. Indeed it does notrequire precise centring of the image and issuitablefor polydisperse powders. For instance in54

A Pore-type Resolved Isotherm of Cement PasteA. Gajewicz, P. J. McDonaldDepartment of Physics, University of Surrey, Guildford, GU2 7XH, UKINTRODUCTION:1 H nuclear magnetic resonance (NMR) relaxationanalysis of water has been performed on whitecement paste during progressive drying andrewetting in a controlled relative humidityenvironment at room temperature.METHODS: NMR relaxation time analysis is anadvanced technique for non-destructivecharacterization of pore size distributions in porousmedia such as cement but requires knowledge ofthe “surface relaxivity” to calibrate the poresurface–to–volume ratio 1 . Recently an alternativemethod was proposed by McDonald et al 2 . Thisestimate of pore size distribution is based on theamplitudes of relaxation components as a functionof water content rather than on the relaxation time.This study extends and improves this approach.The NMR experiment was performed in twostages:• Solid echo pulse sequence to quantify the boundwater fraction• CPMG pulse sequence to separate intra-C-S-Hsheet, C-S-H gel and capillary pore water.RESULTS: Measurements were made on whitecement paste (w/c = 0.4) cured under water for 28days and then equilibrated to constant mass atreduced relative humidity.The NMR signal can be decomposed intorelaxation fractions corresponding to chemicallycombined water and water in C-S-H sheet, gel andcapillary pores. In this way a pore specificdesorption / adsorption isotherm can be generated.The data can be further analysed to reveal the poresizes. Loss of total signal intensity with mass islinear and implies an effective w/c = 0.424reflecting underwater curing – Figure 1 (left). Thecalculated mass fraction of Ca(OH) 2 is 24.5% inagreement with TGA, 23.4%.DISCUSSION & CONCLUSIONS: Thenormalized total signal intensity over one and ahalf cycles presents a normal gravimetric isothermloop, Figure 1 (right).Fig. 1: Left: The total signal plotted againstrelative water mass and humidity (circles) and decomposedinto a chemically combined fraction(open circles), and water within the C-S-H sheets(triangles), gel pores (squares) and capillary pores(open squares) for primary desorption. Right: Thenormalised total NMR signal intensity as afunction of humidity – first desorption (circles);adsorption (squares); second desorption(triangles). During desorption, decay of the gel pore watersignal proceeds faster than the total. The differenceis compensated mainly by an increase of the sheetporewater because an immobile residual surfacelayer is left. Changes in sheet pore water intensityare used to calculate the pore size.The best estimates for the sheet and gel porethickness from primary desorption based onamplitudes model are 1.6 and 3.7nm respectively.The latter is in good agreement with the valueobtained by the relaxation time model – 3.1nm.The agreement of the former is less good (0.95nm)as the underlying model of drying may be breakingdown.The gel pore size slightly increases uponrehydration of cement paste (4.1nm).REFERENCES:1 W. P. Halperin, J.-Y. Jehng, Y.-Q. Song, Magn.Reson. Imag. 12, 169 (1994)2 P. J. McDonald, V. Rodin, A. Valori, Cem. Conc. Res.40, 1656 (2010).ACKNOWLEDGEMENTS: The research leading tothese results has received funding from the EuropeanUnion Seventh Framework Programme (FP7 / 2007-2013) under grant agreement 26444855

Potential use of time domain reflectometry (TDR) for characterisation of thetemperature dependence of cement based materials’ moisture sorptionAlexander Michel a , Henryk A. Sobczuk b , Mette R. Geiker ca)Technical University of Denmark (DTU), Department of Civil Engineering, Kgs.Lyngby, Denmarkb)Department of Environmental Engineering, Lublin Univ. of Technology, Lublin,Polandc)Norwegian University of Science and Technology (NTNU), Department of StructuralEngineering, Trondheim, NorwayThe amount and state of moisture affects the engineering properties of cementbased materials. Although recognized, the influence of temperature on themoisture sorption is poorly investigated. Comparison of the obtained results withwater vapour sorption isotherms from the literature indicate that time domainreflectometry (TDR) can be used to determine the impact of temperature on thewater vapour sorption isotherm of cement based materials.In the present study sealed concrete with defined moisture contents was subjectedto varying temperatures and monitored by means of TDR. The high precision andstability of the TDR measurement technique allowed tracking of changes in thestate of the moisture in the specimens.56

Nonlinear Mesoscopic Elasticity and microstructural developments in cementbasedmaterials due micro-damage processesM. Griffa1 , P. Lura 1,2 , A. Leemann 2 , J. Neuenschwander 3 , M. Wyrzykowski 1 , P. Antonaci 4 , M.Scalerandi 51 Concrete and Construction Chemistry Laboratory, Swiss Federal Laboratories for Materials Science andTechnology (EMPA), Dübendorf, Switzerland.2 Institute for Building Materials, Swiss Federal Institute of Technology Zürich (ETHZ), Zürich, Switzerland.3Electronics/Metrology/Reliability Laboratory, Swiss Federal Laboratories for Materials Science andTechnology (EMPA), Dübendorf, Switzerland.4 Dept. of Structural, Geotechnical and Building Engineering, Torino Institute of Technology, Torino, Italy.5 Institute for Computational and Condensed Matter Physics, Torino Institute of Technology, Torino, Italy.INTRODUCTION: Several categories ofconsolidated granular materials, i.e., materialswhose structure can be described as made of grainsembedded in a binding matrix, exhibit peculiarstatic, quasi-static and dynamic mechanicalbehavior [1]. This includes (a) hysteresis in thequasi-static stress-strain constitutive relation, (b)dynamic nonlinear elastic responses well describedby the classical theory of nonlinear elasticity [2],e.g., harmonic and sub-harmonic generation,nonlinear wave mixing, nonlinear attenuation, butalso other types of dynamic nonlinear responsesthat cannot be interpreted and analyzed within theframework of the classical theory of nonlinearelasticity [1].Some examples of such materials are rocks [3],soils [4], cement-based materials like concrete [5].In addition, several other types of materials showsimilar nonlinear elastic effects upon microdamagedevelopment, e.g., micro-cracking due tomechanical loading [5,6], thermal shocks [7] orchemical degradation [8].We present results of a set of investigations aimingat the characterization of the micro-damaging andmicrostructure degradation in concrete. Theseinvestigations are focused on two main types ofdegradation processes: micro-cracking duetransitory thermal shocks and micro-cracking andaggregate corrosion due to the alkali-aggregatereaction.METHODS: The measurements have beenperformed at the Torino Institute of Technologyand et EMPA using a special type of NonlinearElastic Wave Spectroscopy [3] technique calledScaling Subtraction Method (SSM) [8] that relieson ultrasound pulse propagation at differentexcitation amplitudes.RESULTS:Fig. 1:SSM plot for a mortar sample subjectedto four thermal loading cycles (T0 = 23°C, T1=T2=120°C, T3=180°C). The increase of theSSM energy with the energy of the ultrasonicexcitation, thus with the amplitude of thepropagated (output) pulse, indicates an increasein the nonlinear elastic response due to microcracking.REFERENCES:1 R.A. Guyer; P.A. Johnson; 2009; NonlinearMesoscopic Elasticity, Wiley-VCH, Weinheim(Germany).2 L.D. Landau; E.M. Lifshitz; 2007; Theory ofElasticity, 3 rd edition, Butterworth Heinemann,Oxford (UK).3 R.A. Guyer; P.A. Johnson; 1999; Phys. Today52(4): 30-36.4 Z. Lu; 2007; Geophys. Res. Lett. 32: L14302.5 M. Bentahar; H. El Aqra; R. El Guerjouma; M.Griffa; M. Scalerandi; 2006; Phys. Rev. B 73:014116.6 M. Scalerandi et al.; 2008; Appl. Phys. Lett. 92:101912 ; C.L.E. Bruno et al.; 2009; Phys. Rev. B79: 064108.7 C. Payan et al.; 2007; J. Acoust. Soc. Amer. 121(4): EL125-EL130.8 F. Bouchaala et al.; 2011; Cem. Concr. Res. 41:557-559.57

A MESOSCOPIC MODEL FOR C-S-H HYDRATION AND SETTINGKaterina Ioannidou 1 , Emanuela Del Gado 11 ETH Zürich, Zürich, Switzerland.INTRODUCTION: Calcium-silicate-hydrate (C-S-H) is the primary hydration product of Portlandcement. It precipitates and solidifies into a nanoscalegel, which literally glues together thedifferent parts of cement and it is responsible forits mechanics [1-4]. To investigate the connectionbetween the evolution of the C-S-H gelmicrostructure and its rheological properties [5],we use a mesoscale model, whose fundamentalunits are nano-scale particles. Although thisapproach does not account for the atomistic detailsof the C-S-H these ultimately determine thecohesive effective interaction of the nano-particles[6]. We follow the nano-particles trajectories withMolecular Dynamics. A very important effect inthe evolution of the C-S-H gel is the continuoushydration reaction. To incorporate in our modelthe formation of new C-S-H hydrates, weintroduce Monte Carlo events of addition anddeletion [7]. The competition between effectiveinteractions and particle formation allowscooperative motions and rearrangements, whichlead to complex spatial configurations andrheological behavior.DISCUSSION & RESULTS: We present thesimulation results for two different interactionpotentials that would correspond to different limeconcentrations. We analyze the aggregationprocess for different precipitation parameters thatproduce different non-equilibrium structures anddynamics. Analyzing the trajectories of the MDsimulations, we characterize the microscopicstructure and dynamics of the gels in terms of theradial distribution function, the structure factor,the mean square displacement and theintermediate scattering function. Performing sheardeformation tests by means of non-equilibriumMD, we observe different solid-like behaviorsarising during far from equilibrium aggregation.Fig. 1: Microstructures of the mesoscale gelmodel for C-S-H, at density ρ=0.25 andtemperature T=0.3, for two different effectiveinteractions in equilibrium.REFERENCES:[1] A.J. Allen, J. J. Thomas, H.M. Jennings, Nat.Mater. 6, 311-316 (2007).[2] J.W. Bullard, H.M. Jennings, R.A. Livingston,A. Nonat, G.W. Scherer, J.S. Schweitzer, K.L.Scrivener, J.J. Thomas, Cem. and Concr. Res., 41,1208-1223 (2010).[3] C.Vernet, G. Cadoret, Les B.H.P.,charactéristiques, durabilité, applications,E.N.P.C. Press, Paris (1992). [4] A. Nonat, Cem. and Concr. Res., 34, 1521-1528 (2004).[5] D. Lootens, P. Hébraud, E. Lécolier, H. VanDamme, Oil Gas Sci. Tech. 59, 31-40 (2004).[6] R.J.-M. Pellenq, A. Kushima, R. Shahsavari,K.J. Van Vliet, M.J. Buehler, S. Yip, F.-J. Ulm,PNAS 106, 16102-16107 (2009).[7] E. Masoero, E. Del Gado, R.J. Pellenq, F.J.Ulm and S. Yip, "Nano-structure and –mechanicsof cement: Polydisperse colloidal packing",preprint (2012).58

1 H Nuclear Magnetic Resonance Pulsed Field Gradient Diffusometry Analysis ofWhite Cement PastesV. Rodin, S.Zamani, P.J. McDonaldDepartment of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.INTRODUCTION: We report1 H nuclearmagnetic resonance (NMR) pulsed field gradient(PFG) diffusometry measurements to the study ofwater dynamics and microstructure in whitecement pastes. These new experiments, whichextend previous work 1 , are made and interpreted inthe light of recent advances in the understanding ofporosity arising from 1 H NMR relaxation timeanalysis.METHODS: PFG diffusometry is a wellestablishedmethod for measuring the selfdiffusioncoefficient of small molecules in liquids.A short pulse of magnetic field gradient, g, ofduration δ is used to encode the spatial location ofmolecules through a rotational phase angle. A shorttime Δ later a second pulse of gradient applied inthe opposite sense is used to unwind this rotation.Any residual rotational phase is a direct measure ofmolecular displacement. Measurements are madeas a function of g, δ or Δ. Averaging over allmolecules in bulk liquid the measurement canyield the self diffusion coefficient D.In porous media, the molecular motion isrestricted. Hence, measurements of the apparentdiffusion coefficient as a function of g or δ and Δcan reveal information on the pore morphology.Hence, the alternate name for the method, NMR q-space microscopy 2 .Cements pose multiple challenges. First, the largemagnetic field gradient due to inhomogeneity ofmagnetic susceptibility can swamp appliedgradients making quantitative measurementdifficult. Second, cements have small pores so thatmean free paths are very limited. Thirdly, NMRrelaxation times are very short, limiting themaximum values of δ and Δ that can be applied.However, there are known routes to overcomingsome of these limitations 3 .RESULTS: The self-diffusion coefficientmeasured with a short Δ decreases rapidly duringthe early stages of hydration. Moreover, the waterfraction exhibiting this diffusion coefficientdecreases too. This is in line with relaxation timemeasurements that show increasing fractions ofwater either chemically bound into the structure orrestricted to increasingly confined poreenvironments.In more mature samples, the primary signal arisesfrom the small fraction of residual capillary water.We explore the Δ dependence of the diffusionencoded signal as a function of the gradientstrength. We show that, for accessible Δ up toabout 50 ms, the encoding is in the medium to longtime limit, whereby the molecules sample thewhole pore space during the measurement. Weanalyse the data in terms of different models ofrestricted diffusion and infer capillary pore sizes ofthe order of microns. This is larger than measuredby relaxometry. However, it is likely that as Δincreases and only accesses the more slowlyrelaxing molecules, so the experiment self-selects adiminishing reservoir fraction of larger pore sizeswithin the overall pore size distribution since poresize correlates with signal relaxation times T 1 andT 2 .log (I/I0)1.000.100.010 0.05 0.1 0.15β 2 ( rads/ µ m)2Fig. 1: Normalised echo intensity as a function ofβ 2 = (γδg) 2 /5, for a 54-day old white cement pastew/c=0.4. Δ=6 ms, where γ is the gyromagneticratio of 1 H . The solid line is the fit to the longtime limit model 2 and yields a pore size of 7.2 ±2.8 µm.REFERENCES:1 N. Nestle, P. Galvosas and J. Karger, Cem. Conc. Res.,37, 398-413, (2007).2 P. T. Callaghan, Translational Dynamics andMagnetic Resonance (Oxford University Press, 2011).3 R. Kimmich, NMR - Tomography, Diffusometry,Relaxometry (Springer, 1997), Germany.ACKNOWLEDGEMENTS: The authors wouldlike to thank U.K. Engineering and Physical SciencesResearch Council for financial support. (Grantnumber EP/H033343)59

Effect of size polydispersity for nanoparticle adsorption on liquid interfacesKonrad Schwenke and Emanuela Del GadoMicrostructure and Rheology, Institute for Building Materials,ETH Zurich, CH-8093 Zurich, SwitzerlandNanoparticles at liquid-liquid interfaces have stirred great interest as potentialbuilding blocks for the self-assembly of functional materials in 2 dimensions. Recentadvances in the synthesis of core-shell nanoparticles with a hard core and a soft shellof grafted polymer chains offer a new material for self-assembling structures atinterfaces [1].We present numerical data investigating the adsorption of polydisperse soft shellparticles towards the liquid interface. The nanoparticles are modeled via a repulsivepotential which allows partial overlap of particles and represents a good compromisebetween numerical simplicity and the aim to model the experimental system. Themotion of particles at the interface is simulated via Molecular Dynamics whereas weuse a Grand Canonical Monte Carlo scheme to model the process of adsorption anddesorption [2].It is elucidated how the kinetics of the adsorption process depends upon the influx ofparticles and the adsorption energy. We comment on the qualitative differences inthe adsorption characteristics for mono- and polydisperse size distributions ofparticles.References[1] L. Isa, E. Amstad, K. Schwenke, E. Del Gado, P. Ilg, M. Kröger and E.Reimhult, Soft Matter, 2011, 7, 7663-7675.[2] D. Frenkel and B. Smit, Understanding Molecular Simulation, Academic press,200260

Lattice Boltzmann Simulations of the Permeability and Capillary Adsorption ofCement Model MicrostructuresM. Zalzale 1 , P.J. McDonald 21 EPF Lausanne, Lausanne, Switzerland. 2 University of Surrey, Guildford, GU2 7XH UK.INTRODUCTION: In this work we assess thelattice Boltzmann (LB) method for solvingproblems of fluid dynamics in the context of modelcement microstructures. LB has several potentialadvantages over other numerical methods. First, itremoves the requirement to reduce themicrostructure to a network of connected cylindersso there is no inadvertent modification of the porenetworkand porosity in calculations of, forinstance, permeability. Second, it allows us toextend the modelling to the adsorption anddesorption of water liquid and vapour as a twophasefluid. In the LB approach it is not necessaryto specifically track the liquid / vapour interfacemaking it computationally efficient.METHODS: In this work, we use the LB methodto calculate the permeability and capillarycondensation part of the water adsorption /desorption isotherm in microstructures determinedusing the model µIC 1 . In both cases we use aD3Q19 LB network. For the calculation ofpermeability we used a single fluid LBimplementation with a multi-relaxation-timecollision operator 2 , forced flow and application ofDarcy’s law. For adsorption / desorption we used afree energy two-phase free energy model withsingle-relaxation-time operator 3 , with the networksurface held at successive constant relativehumidities.RESULTS: For the pressure-induced single-phaseflow the model captures the expected trends forpermeability as a function of porosity and degreeof hydration. However, the computed permeability(e.g. 10 -19 m 2 for w/c=0.4 and 10.5% capillaryporosity) is larger than expected from experiments(10 -20 -10 -21 m 2 ). Decreasing the minimum particlesize of the microstructure and increasing themagnification (voxels per particle), we increase thepore-structure complexity and LB better recoversthe hydrodynamics. Consequently, thepermeability decreases and tends closer toexperimental values, although the computationalrequirements increase prohibitively. Moreimportantly, however, the current model addressesonly the capillary porosity and does not address thegel porosity. Also, the model currently allowsunphysical “diagonal leaks”.Fig. 1: Water streamlines of a pressure-inducedflow (left) and the capillary desorption anddesorption isotherm (right) in a µICmicrostructure with a resolution (minimumparticle/pore size) of 1 µm.In multi-phase simulations of the adsorption anddesorption isotherm, hysteresis loops are generatedindicating the occurrence of capillarycondensation. However, the lack of breadth to thecapillary pore size distribution, and in particular tothe pore throat distribution, leads to an isothermwith a dramatic step at around 90% RH. Theabsence of the C-S-H intrinsic microstructure leadsto the false conclusion that the porosity is emptyby circa 80% RH.DISCUSSION & CONCLUSIONS: We believethat the LB method holds much promise for thestudy of water transport in cementitious materials.However, improvements should be made in termsof (1) computing efficiency to be able to computethe flow in highly-resolved microstructures; (2) theinclusion of gel porosity within the microstructuralmodel and LB simulations.REFERENCES:1S. Bishnoi & K.L. Scrivener; 2008; Cem ConcRes; 39:266-274.2 D. D’Humieres et al., 2002; Philos. T. R. Soc. A.;360:437-4513 A.J. Wagner & C.M. Pooley; 2007; Phys. Rev. E.;76:045702ACKNOWLEDGEMENTS: The researchleading to these results has received funding fromthe European Union Seventh FrameworkProgramme under grant agreement 264448. PJMthanks Nanocem and the UK Engineering andPhysical Sciences Research Council for financialsupport under grant number EP/H033343/1.61

List of Participants___________________________________________________________________OrganizersEmanuela Del Gado -- ETH Zurich, SwitzerlandPeter McDonald -- University of Surrey, UKRoland Pellenq -- CNRS-MIT, USAKaren Scrivener -- EPF Lausanne, Switzerland___________________________________________________________________Muhannad Abuhaikal – MIT, USAAlain Baronnet -- Université de Aix-Marseille, FranceLuis Baquerizo -- EPF Lausanne, SwitzerlandLaurent Barcelo -- Lafarge Canada, CanadaJean-Louis Barrat -- Université Joseph Fourier-Grenoble, FranceRobert Baumann -- Dow Europe, SwitzerlandMaurizio Bellotto -- Bozzetto Group, ItalyShashank Bishnoi -- IIT Delhi, IndiaJan Bisschop -- ETH Zurich, SwitzerlandAdrien Blanc -- Université Paris Est, FrancePatrick Bonnaud -- MIT, USAPaul Bowen -- EPF Lausanne, SwitzerlandSerge-Henri Cachia -- University of Surrey, UKBarbara Capone -- University of Vienna, AustriaAude Chabrelie -- Saint-Gobain Recherche, FranceElisabeth Charlaix -- Université Joseph Fourier – Grenoble, FranceJader Colombo -- ETH Zurich, SwitzerlandPhilippe Coussot -- Université Paris-Est, FranceJean-Baptiste d'Espinose -- ESPCI ParisTech, FranceMarjolein Dijkstra -- University of Utrecht, NetherlandsBelay Zeleke Dilnesa -- BASF Construction Chemicals, SwitzerlandJorge Dolado -- Tecnalia, SpainTakeshi Egami -- University of Tennessee, USAMichael Enders – Thyssenkrupp Polysius ,GermanyPamela Faure -- IFSTTAR - ENPC – CNRS, FranceNicolas Fernandez -- ETH Zurich, SwitzerlandRobert J. Flatt -- ETH Zurich, SwitzerlandAgata Gajewicz -- University of Surrey, UKEllis Gartner -- Lafarge Centre de Recherche, France63

Mette Geiker – NTNU, NorwayMichele Griffa – EMPA, SwitzerlandGuillaume Habert -- ETH Zurich, SwitzerlandChristoph Hesse -- BASF Construction Chemicals, GermanyPatrick Ilg -- ETH Zurich, SwitzerlandFunda Inceoglu -- Kalekim A.S., TurkeyAikaterini Ioannidou -- ETH Zurich, SwitzerlandHamlin Jennings -- MIT,USAPhilippe Jost – Sika, SwitzerlandPatrick Juilland -- Sika Technology, SwitzerlandChristophe Labbez -- Université de Bourgogne, FranceStefano Leoni -- Technical University Dresden, GermanyPierre Levitz -- UPMC Paris, FranceHelene Lombois-Burger -- Lafarge Centre de Recherche, FranceCraig Maloney -- Carnegie Mellon, USASébastien Manneville -- ENS Lyon, FranceHegoi Manzano -- University of the Basque Country, SpainDelphine Marchon -- ETH Zurich, SwitzerlandNicos Martys -- NIST, USANicola Marzari -- EPF Lausanne, SwitzerlandEnrico Masoero -- MIT, USAThomas Matschei -- Holcim, SwitzerlandRatan Mishra -- ETH Zurich, SwitzerlandPaulo Monteiro – Berkeley, USAMartin Mosquet – Lafarge, FranceArnaud Muller -- EPF Lausanne, SwitzerlandKatrina Newlands -- University of Aberdeen, UKLuc Nicoleau -- BASF Construction Chemicals, GermanyAndré Nonat -- CNRS -Université de Bourgogne, FranceGeorge Petekidis -- FORTH - University of Crete, GreeceVictor Rodin -- University of Surrey, SwitzerlandMichael Romer -- Holcim, SwitzerlandPrinya Sainamthip -- Siam Research and Innovation, ThailandManasit Sarigaphuti -- Siam Research and Innovation, ThailandSrikanth Sastry -- TIFR Hyderabad, IndiaPeter Schall -- University of Amsterdam, NetherlandsGeorge Scherer -- Princeton, USAKonrad Schwenke -- ETH Zurich, SwitzerlandDenise A. Silva -- W.R. Grace, USAJulius Strigac – Povazska cementaren a.s. Ladce, Slovakia64

Prannoy Suraneni -- ETH Zurich, SwitzerlandGulden Tombas -- Kalekim A.S., TurkeyHenri Van Damme -- ESPCI ParisTech– IFSTTAR, FranceAdri van Duin -- Penn State, USASurachai Vangrattanachai -- Siam Research and Innovation, ThailandJan Vermant -- KU Leuven, BelgiumDavid Weitz -- Harvard, USAKazuo Yamada -- Taiheiyo Consultant, JapanSidney Yip -- MIT, USAMohamad Zalzale -- EPF Lausanne, Switzerland65