Effect of calcium carbonate whiskers on the setting behavior, autogenous shrinkage, drying shrinkage, and micro-structure of cement paste

Improving the volume stability of cement paste is crucial for designing high-strength and high-durability cementitious materials. Therefore, this study proposes a novel approach using calcium carbonate whiskers (CW) with high aspect ratio and high modulus to control the autogenous shrinkage and drying shrinkage of cement paste, and reveals its regulation mechanism through microscopic experiments. The results showed that the addition of 3 vol.% CW in cement paste had the most significant effect on reducing autogenous shrinkage and drying shrinkage, which were reduced by 33.2% and 19.8%, respectively. One is that CW has a retarding effect, which reduced shrinkage cracking due to rapid hydration. Secondly, the water-locking effect of CW slowed down the rapid evaporation of water, thus reducing the mechanical stress in the capillary pores due to water loss, and at the same time reducing the low mass loss. In addition, CW constrained the shrinkage and deformation of capillary pores due to water loss by crossing the capillary pores, and CW also formed a three-dimensional network structure in the microstructure, which increased the overall volume stability of the paste. It is worth that CW as a micron-sized fiber also bridged microcracks due to shrinkage, exhibiting the reinforcement effect of CW.