Intrinsic viscoelasticity of C-S-H assessed from basic creep of cement pastes

This paper investigates the fundamental mechanisms behind the effect of supplementary cementitious materials (SCMs) on the basic creep behavior of cement pastes. The intrinsic creep properties of the C-S-H gel are assessed based on measurements of uniaxial compressive basic creep of cement pastes with different water-to-cement ratio (w/c), prepared either with pure cement or cement blended with fly ash or quartz. The viscoelastic response of the C-S-H was back-calculated from the macroscopic experimental creep results with Finite Element Method (FEM) homogenization. The numerical simulations show that the intrinsic viscoelastic behavior of the C-S-H gel follows a similar trend in different systems, independent of their w/c (in the range 0.35-0.63) and the binder used. The differences in the magnitude of the creep at the macroscopic scale in different cement-based systems appear to depend mainly on the volumetric fractions of the solid phases and on the porosity of the cement pastes.