Advances in understanding the rheological behaviour of cement pastes

This study focuses on the origins of different strains in the cement pastes that condition the viscoelastic properties and the structural build-up/thixotropy. Owing to the complexity of demonstrating the contribution of the nucleation of hydrates during the induction period of cement hydration, different chemically inert mineral suspensions with different granular properties (fineness, shape and particle size) are tested. The effect of the solid volume fraction and time on the different strains is also investigated. The results reveal that all of the suspensions studied display a critical strain of the same order of magnitude, and this critical strain does not change over time in the case of cement pastes. So the critical strain cannot be associated only with the nucleation of hydrates (C–S–H bridges) at the contact points between particles, as reported in the literature. The nucleation and increase of hydration products just increase the surface contact between particles, resulting in rigidification of the particles network characterised by an increase of the storage modulus after the formation of a colloidal network.