Tensile Creep of Alkali-Activated Slag–Stainless Steel Slag Mortar: In-Depth Analysis of Effects and Mechanisms

Despite the excellent mechanical and environmental properties of alkali-activated materials, the susceptibility to early cracking significantly limits their widespread application in engineering. Tensile creep plays a key role in the early stages by relaxing shrinkage-induced tensile stresses and delaying the onset of cracking. Therefore, the effect of stainless steel slag (SS) on the tensile creep of alkali-activated slag-SS mortar (ASM) with SS contents of 0%, 10%, 20%, 30%, and 40% was investigated. SS content represents the mass ratio of SS to the sum of SS and slag. The mechanical properties, autogenous shrinkage, and tensile creep of ASM were studied. The results demonstrate that the tensile creep decreases with the increase of SS contents. Increasing the SS content reduced the hydration of ASM, leading to a lower amount of calcium-aluminum-silicate-hydrate (C─ A─ S─ H) gels, and consequently reduced autogenous shrinkage. Autogenous shrinkage is the primary driver of tensile creep. Furthermore, an increase in SS content resulted in a decrease in the amount of sodium ions adsorbed by the C─ A─ S─ H gel, which can limit the relative slip of the C─ A─ S─ H gel. Therefore, increasing the SS content decreases the tensile creep of ASM.