compatibility of ultra high performance concrete as repair material

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AbstractThe rehabilitation of concrete structures, especially concrete bridge decks, is a majorchallenge for transportation agencies in the United States. Often, the most appropriatestrategy to preserve or rehabilitate these structures is to provide some form of a protectivecoating or barrier. These surface treatments have typically been some form of polymer,asphalt, or low-permeability concrete, but the application of UHPC has shown promisefor this application mainly due to its negligible permeability, but also as a result of itsexcellent mechanical properties, self-consolidating nature, rapid gain strength, andminimal creep and shrinkage characteristics. However, for widespread acceptance,durability and performance of the composite system must be fully understood,specifically the bond between UHPC and NSC often used in bridge decks. It is essentialthat the bond offers enough strength to resist the stress due to mechanical loading orthermal effects, while also maintaining an extended service-life performance.This report attempts to assess the bond strength between UHPC and NSC under differentloading configurations. Different variables, such as roughness degree of the concretesubstrates, age of bond, exposure to freeze-thaw cycles and wetting conditions of theconcrete substrate, were included in this study. The combination of splitting tensile testwith 0, 300, 600 and 900 freeze-thaw cycles was carried out to assess the bondperformance under severe ambient conditions. The slant-shear test was utilized withdifferent interface angles to provide a wide understanding of the bond performance underdifferent combinations of compression and shear stresses. The pull-off test is the mostaccepted method to evaluate the bond strength in the field. This test which studies thedirect tensile strength of the bond, the most severe loading condition, was used to providedata that can be correlated with the other tests that only can be used in the laboratory.The experimental program showed that the bond performance between UHPC and NSCis successful, as the strength regardless the different degree of roughness of the concretesubstrate, the age of the composite specimens, the exposure to freeze-thaw cycles and thedifferent loading configurations, is greater than that of concrete substrate and largelysatisfies with ACI 546.3R-06.xii
1 Introduction and MotivationCurrently, civil engineers have to face a new issue in the concrete industry: the increasingneed for rehabilitation of many concrete structures that were constructed in the secondpart of the last century. Thus far, most of the efforts of the engineers were addressed todesign new infrastructures. However, after the construction boom in developed countriesover the last few decades, the repair of structures is becoming increasingly necessary.The latter represents an important environmental concern: if we are able to designsuccessful repairs, the material and cost saving can represent a significant achievementfor the sustainability of the concrete industry, increasing the service live of the existingconcrete structures with the lowest consumption of material. The experimental resultsshow that UHPC would have an excellent performance under severe environmentalconditions due to its negligible permeability. This makes UHPC have almost nopenetration of chlorides and sulphides. Further, its high abrasion and freeze-thawresistances make this material suitable as overlay that protects the rest of the structurefrom extreme environmental conditions. Nonetheless, for widespread use of UHPC asrepair material, the bond between UHPC and Normal Strength Concrete (NSC) needs tobe assessed. It is essential that the bond offers enough strength to resist the stress due tomechanical loading or thermal effects, while also maintaining an extended service-lifeperformance.1.1 ScopeThe major objective of this project is to study the potential use of UHPC as repairmaterial of concrete structures. The main goals of this research are outlined below:• To study the bond strength between UHPC and NSC under different loadingconditions, such as indirect tension, shear-compression and direct tension.• To evaluate the influence of the freeze-thaw cycles on the bond strength.• To assess the effect of the different degrees of roughness of the substrate on thebond strength.1
Page 1 and 2: COMPATIBILITY OF ULTRA HIGH PERFORM
Page 3 and 4: Table of ContentsList of Figures ..
Page 5 and 6: 4.3.2 Discussion ..................
Page 7 and 8: Figure 3.14 CSP index .............
Page 9 and 10: Table 4.7 Summary of indirect tensi
Page 11: List of AbbreviationsACI.AFtASTM.CO
Page 15: 2 Background and Literature ReviewT
Page 18 and 19: spaces and to decrease the amount o
Page 20 and 21: water/binder=constantChoose steel f
Page 22 and 23: UHPC formulations and provides a se
Page 24 and 25: Table 2.3Comparison of UHPC materia
Page 26 and 27: esults obtained in this project wer
Page 28 and 29: 2.1.3.4 Environmental Impact of UHP
Page 30 and 31: 1997). Emmons and Vaysburd (1996) d
Page 32 and 33: e) ConstructabilityIt is recommenda
Page 34 and 35: Table 2.5, continuedCementitious ma
Page 36 and 37: • Rehabilitation of a bridge pier
Page 38 and 39: UHPC is a cost-effective solution i
Page 40 and 41: apparatus will measure the shear st
Page 42 and 43: substrate while the scarifying meth
Page 44 and 45: such test configuration, this upper
Page 46 and 47: From the equilibrium of forces of F
Page 48 and 49: The first layer, also called penetr
Page 50 and 51: 3 MethodologyThis report aims to st
Page 52 and 53: f sp = 2 ∗ PA ∗ π in psi Equat
Page 54 and 55: that the bond interface, in this lo
Page 56 and 57: Ductal® premix is typically compri
Page 58 and 59: associated test results (temperatur
Page 60 and 61: Figure 3.2 Detail of splitting tens
Page 62 and 63:
3.3.3 Pull-off testPull off test wa
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(a) Chipped surface, slightlybrushe
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(a) Molds to cast slant shearspecim
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Timber moulds were used to cast the
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macrotexture depth was measured in
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As shown in the above tables, the m
Page 74 and 75:
(a) Concrete substrate under water
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used, as shown in Figure 3.17. A fa
Page 78 and 79:
Equation 2.2 and Equation 2.3 were
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(a) Steel disks glued to the UHPC s
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value to the lowest one in the foll
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Transversal frequency (Hz)255025002
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115113Relative Dynamic Modulus (%)1
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Only those specimens with a grooved
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Table 4.6, continued.MeanMeanCOV,st
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concrete or bond/concrete while for
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surface treatment applied. In contr
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Table 4.8Summary of slant-shear tes
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(a) B(C): Bond due to concrete fail
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3143Bond Capacity, (psi)30002500200
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The different failure modes obtaine
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failures occurred in the concrete s
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property of the concrete has higher
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5.1.1 Combination of Splitting Tens
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5.1.4 Overall performancea. For thi
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mismatch and load eccentricity. Tho
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6 ReferenceAbu-Tair, A. I., Rigden,
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Climaco, J. C. T. S., and Regan, P.
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Graybeal, B., and Tanesi, J. (2007)
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Misson, D. (2008). "Influence of Cu
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Silfwerbrand, J. (1990). "Improving
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7 Appendix: NSC mix designsTable 7.
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Table 7.33rd mix for the splitting
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Table 7.51st mix for the splitting
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Table 7.73rd mix for the splitting
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Figure 8.2 Concrete retarder inform
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Table 9.1, continued.BrBr w/oBr 300
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Table 9.2, continued.TrialBrushed 6
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10 Appendix: Splitting tensile pris
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Table 10.1, continued.128
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Table 10.2Splitting monolithic NSC
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11 Appendix: Slant-shear specimens
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PortionNumberof 1figures/tables/ill
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Figure 2.5Miguel Angel Carbonell Mu
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Miguel Angel Carbonell Munoz Mon, M
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Miguel - not sure what you need fro
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End Page 1235Type of UsePortionNumb
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Type of UseIntended publisher of ot
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