Influential Mechanism Analysis of Modified Absorbent Polymer in Roller-Compacted Cementitious Materials

Roller-compacted concrete (RCC) in dam construction has become popular in most areas of Tibet. The service environment and incorporation of high fly ash in RCC make it a big challenge of attaining balance between excellent freezing–thaw resistance and high strength. It is reported that the modified absorptive polymer (MAP) presents excellent freezing–thaw resistance in RCC. However, the influential mechanism of MAP in RCC is not clear. In this study, the cementitious materials (RCC, fly ash blended pastes, and mortars) incorporated with MAP are utilized. Working and mechanical performances of RCC are studied. Hydration and microstructure of blended pastes are investigated by many experimental tests (hydration heat test, electrical resistivity test, differential thermogravimetric test, nuclear magnetic resonance test, and nanoindentation test). Rheological and drying shrinkage of mortar are analyzed. It is found that MAP has no significant effect on the Vc value, air content, and apparent density of RCC. The incorporation of 0.3% by weight MAP2 significantly increases the compressive strength of RCC by up to 28.7%, but the effect on the splitting tensile strength is negligible. The incorporation of MAP has little effect on the rate of hydration of blended pastes, amount of chemically bound water and calcium hydroxide (CH). The incorporation of MAP in the blended paste is helpful to increase the average chain length (ACL) of C─ S─ H and content of high-density C─ S─ H (HD C─ S─ H) gel, concurrently impeding the migration of Al. Water absorption and release behaviors of MAP strongly affect the fluidity, yield stress, plastic viscosity and drying shrinkage of the mortar.