Carbonation Performance and Characterization of Alkali-Activated Cementitious Materials Incorporating Superabsorbent Polymers

To effectively mitigate the early-age shrinkage and cracking of alkali-activated cementitious materials (AAMs), superabsorbent polymers (SAPs) were adopted in this study to absorb and store water in the mixture, which is continuously released during the setting and hardening process. This approach prolongs the setting and hardening process of AAM, improves the stability of its microstructure, and reduces crack formation. Meanwhile, the influence mechanism of CO2 curing on the strength of SAP-modified AAM was investigated. Through mechanical strength testing, X-ray diffraction (XRD), thermogravimetric analysis (TGA), heat release measurement during setting and hardening, and pore size distribution testing of specimens with different mix proportions and curing conditions, effective methods to improve the mechanical strength and microstructural development of AAM were explored. The results show that CO2 curing can significantly enhance the early-age strength of AAM, promote the formation of carbonation products, and optimize the pore structure of AAM at the micro-level. An appropriate amount of SAP can prolong the setting and hardening process of AAM and improve the degree of its setting and hardening; however, excessive SAP reduces the concentration of alkaline solution in the mixture matrix, increasing resistance to the setting and hardening of AAM.