Synergistic effects of ettringite-based expansive agent and polypropylene fiber on early-age anti-shrinkage and anti-cracking properties of mortars

Effects of the ettringite-based expansive agent (EA) and polypropylene (PP) fiber on early-age anti-shrinkage and anti-cracking behaviors of mortar are comprehensively investigated in this paper. Combined with mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) analyses, its mechanism of the combination of EA and PP fiber on shrinkage and cracking restriction behavior of mortars is also proposed. The results indicate that the drying shrinkage resistance and cracking resistance behavior of the specimens with the combination of EA and PP fiber, are better than those of the specimens with single EA and PP fiber, while their residual expansion strain in autogenous shrinkage is lower than that of the specimens with single EA. The results of MIP and SEM analyses confirm that the formation of self-compressive stress generated by reinforcing effects of PP fiber and well three-dimensional network structure of ettringite distribution during expansion stage will partly offset the shrinkage force during shrinkage stage. Therefore, the combination of EA and PP fiber is prone to create a non-cracking shrinkage-compensating concrete in real construction.