Abstracts Book - IMRC 2018

• SE2-O025
MULTI SPECKLE DWS ANALYSIS: APPLICATION TO PORTLAND
CEMENT SUSPENSIONS
O. Ojeda Farías 1 , P. Hebráud 2 , J. M. Mendoza Rangel 1 , D. Lootens 3 , M. Liard 3
1 Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Mexico. 2 Université de
Strasbourg, IPCMS/CNRS, France. 3 Sika Technology AG, Central Research, Switzerland.
The Portland cement pastes are constituted two interacting phases: solid and
reactive with the binder and liquid with the water and its admixtures, starting a
hydration process at the first instant of their contact, transforming a paste to a
hard-solid material. The interaction promoting the ion dissolution, saturation
and precipitation are occurring the mixing, starting with a dormant period where
the system is workable until the ions precipitation acceleration initiates the
suspension setting. The aim of this research is to understand the dynamic of the
concentrated suspensions constituted or the Portland cement particles and thus
the mixing to the hardening. The multi speckle diffusing wave spectroscopy (MS-
DWS) is used to measure the mobility of cement particles on the micro scale
during the entire hydration process. The technic is measuring the laser light
backscattering through the cement paste with a high-resolution camera.
Suspensions are placed in a 1 mm thick cell and illuminated with the laser, to
record the evolution of the speckle image. A sub micrometer particle tracking
measurements motion of all individual particle is then obtained. White portland
cement (WPC) suspensions with a water to cement ratio ranging 0.25 to 0.46 and
with the fine tuning of the interparticle interaction with the addition of high
range water reducing admixture (HRWRA) ranging a concentration 0.04% to
0.360% have been prepared to study the impact of the particles density and
interaction on the individual particles mobility. The correlation between two
images obtained by averaging the intensity fluctuations over the entire image is
used to determinate the decay time and as a consequence the mobility of the
particles. The preliminary results show a decay time plots in agreement with the
intensity correlation function g 2 as well as an acceleration of the decay time over
time.
Keywords: DWS, cement, light scattering
Presenting authors email: omar_2355@hotmail.com