Enhancing the performance of alkali-activated slag using KH-550 as a multi-functional admixture

This study proposes using KH-550 as a multifunctional admixture for improving the performance of alkali-activated slag (AAS). The hydrolysis products of KH-550 were characterized, and the influence of KH-550 on the fresh properties, hydration kinetics, pore structure, capillary water absorption, hydration products, compressive strength and micro-mechanical properties of AAS were investigated. The results showed that the addition of KH-550 improved the fresh properties of AAS. By adding 2.5 % KH-550, the initial and final setting time of AAS were prolonged by 105.1 % and 60.3 %, respectively, and the fluidity was increased by 10.26 %. The analysis of hydration kinetics showed that although the added KH-550 retarded the AAS hydration at early ages, the nucleation effect of KH-550 nanoparticles accelerated the hydration of AAS at later ages. Moreover, the addition of KH-550 improved the pore structure of the mortars, resulting in a denser microstructure of AAS, which was beneficial for capillary water absorption and compressive strength of AAS. Consequently, the capillary water absorption was reduced by 1.7—11.5 %, and the 28 d compressive strength was increased by 4.8—34.3 %.