Nicolas Roussel graduated from Ecole Normale Supérieure in 1998 and is now in charge of the research activities dealing with rheology and processing of construction materials at the Navier Laboratory, FRANCE. He is the founding editor of the RILEM technical letters journal and president of the RILEM association. He has received in 2007 the Robert L'Hermite award for his work on rheology of fresh concrete. With a Thompson Reuters H-index of 54 and more than 8.000 citations, he is the author or co-author of around 130 papers in scientific journals such as Cement and Concrete Research, Physical Review letters or Journal of Non-Newtonian Fluid Mechanics. His research focus spreads from concrete rheology and rheometry to the understanding of construction processing technologies.
Rheology and packing properties of cement-based materials
Rheology of cement-based materials is reported to scale with various interparticle forces such as attractive colloidal forces or interparticle viscous lubrication forces. By playing on some organic molecules’ dosage and affinity for the cement grains surface, it was shown to be possible to specifically tune these forces and tailor the material fresh properties to the process. Rheology, however, also strongly depends on the packing properties of the suspending particles. As these properties do not change much for most standard Portland cements, this effect has often been considered as a secondary feature. However, substituting clinker by various alternative powders, including particles with very specific morphologies such as calcined clays, is bringing these aspects to the forefront of today’s research. This lecture will first cover the basics about packing properties, morphology and polydispersity. In a second part, we will discuss the tools allowing for some packing properties assessment and the existing artifacts. Finally, we will showcase the string role potentially played by the ettringite nucleation that follows the contact between cement and water and extrapolate on its consequences for blended cements.