Ambient temperature effects on hydration kinetics and performance mechanisms of SAP-modified cement paste

Abstract This study investigates temperature-dependent hydration mechanisms of superabsorbent polymer (SAP)-modified cement paste. SAP dynamically regulates cement hydration via reversible, temperature-sensitive water absorption and release. At 40°C, the hydration induction period vanishes; hydration rate rises over 50% compared with 20°C curing, yet SAP still delays early hydration, confirming ambient temperature governs early hydration kinetics. SAP improves 7-28 d late-stage hydration at all tested temperatures, with optimal efficacy at 20°C. It redistributes pore water by converting free water to capillary and gel water without altering total mixing water, maintaining hydration product types while enhancing crystallinity. SAP also inhibits detrimental preferential growth of calcium hydroxide along the (001) plane to stabilize concrete microstructure and durability. These results support targeted SAP design for pavement concrete across diverse climates and reduce gaps between laboratory and field curing conditions.