Influence of PEA on Volume Stability of Cement-Based Grouting Materials and Its Mechanism

Traditional expansive agents often fail to address early-stage cracking issues of grouting. A plastic expansive agent (PEA) can generate evenly distributed and closely packed microbubbles in the cement-basted grouting materials during the grout's setting process to cause volume expansion. However, its expansion mechanism is still unclear, and this restricts its practical application in engineering. Thus, the effects of PEA on the volume stability of grouting were evaluated in this research, and its mechanism was analyzed by setting time, pH, compressive strength, and bubble spacing coefficient. The results indicated that an increase in PEA content enhanced the volume expansion rate of the grout, while the bubble spacing coefficient gradually decreased and air contents increased. However, it was not advisable to blindly increase its contents. A higher content could lead to a less dense pore structure and a decrease in compressive strength. Therefore, the optimal content for PEA was approximately between 0.04% and 0.06%. Additionally, the expansion process of PEA was related to cement hydration. Therefore, by adjusting the mixture proportion, its expansion process could be designed to exhibit microexpansion properties.