Understanding the shrinkage behaviour of alkali-activated slag binders modified by the superabsorbent polymer

Superabsorbent polymers (SAPs) have gained attention as internal curing agents in alkali-activated slags (AAS). The absorption-desorption kinetics of SAPs in AAS pastes were monitored using X-ray computed tomography. This study examines the influence of Angular covalently crosslinked sodium polyacrylate SAPs on AAS's reaction kinetics, pore structure, and microstructure f AAS. Meanwhile, autogenous, total drying shrinkage and contin-uous monitoring of internal relative humidity changes were performed. The results showed that the SAPs' desorption kinetics is crucial in influencing the efficiency to counteract the shrinkage. SAPs significantly miti-gated the autogenous and total drying shrinkage up to 90% and 30%, respectively. The incorporation of the ideal content of SAPs significantly compensated for the impact of the w/b ratio AAS properties. The optimum SAPs dosage was found to be 0.6 %, which enhanced the ability to control IC water, yielding better performance in terms of shrinkage, assisting the hydration degree, and enhancing the surface quality and anti-permeability. No reaction products were detected inside the voids of SAP, and the agglomeration of SAP was observed. However, care should be taken when incorporating a high content of SAP (i.e. > 0.6 %), which can adversely affect the properties of AAS. This work confirms that IC of AAS using SAPs is a powerful mitigating strategy, particularly when traditional curing is insufficient.