The Influence of Expansive Agent on the Time-Dependent Deformation Characteristics of CA Mortar

To maintain the volume stability of the cement asphalt (CA) mortar for key elastic cushion layers in modular track systems, the effects of different types of expansive agents, their dosages, and curing humidity on the time-dependent deformation characteristics of the CA mortar were investigated. The results show that when aluminum powder is used as the expansive agent, the CA mortar expands within 0 to 12 hours and then shrinks after 16 hours, with the dosage of aluminum powder having little effect on the deformation after hardening. The U-shaped expansive agent has a minor compensating effect on the shrinkage of the CA mortar within 12 hours, but it causes significant expansion after 20 hours, with a high expansion rate at 7 days followed by shrinkage. The shrinkage rate decreases with an increase in the dosage of the expansive agent. The CA mortar with a mixture of aluminum powder and U-shaped expansive agents reaches an expansion rate at 7 days, followed by shrinkage, with the shrinkage rate decreasing with higher curing humidity, ranging between 0.035‰ and 0.100‰. The M-type expansive agent can significantly reduce the post-hardening shrinkage of the CA mortar, with the shrinkage rate decreasing by over 0.16‰ at the 180-day age.