The influence of water-to-cement ratio and superabsorbent polymers (SAPs) on solid-like behaviors of fresh cement pastes

摘要

Solid-like behaviors of fresh cement pastes are gaining increased attention with the emergence of 3D concrete printing. It is known that the fresh cement paste exhibits a "two-step yielding" in the solid regime. This study aims to achieve a more comprehensive understanding of "two-step yielding" behavior of the cement pastes with different water-to-cement ratios and with the addition of SAPs. The influence of water-to-cement ratio and SAPs on the solid-like behaviors of cement pastes were investigated by the constant shear rate test using a rotational rheometer. The results demonstrate that changes in the solid-like properties of the fresh cement pastes, such as static yield stress, critical strain, elastic limit, and tangent modulus, do not necessarily follow the same pattern since different aspects of solid-like properties can be attributed to the different particle interactions among cement systems. The results further emphasize that, for a better understanding of the influence of the mixture design parameter on the shape stability of 3D printed concrete, it is necessary to determine its impact on all aspects of solid-like behaviors, from pure elasticity to elasto-viscoplasticity, other than the static yield stress alone. (C) 2020 Published by Elsevier Ltd.