Effect of nickel slag on the basic tensile creep of alkali-activated slag/nickel slag mortars

Abstract

Alkali-activated slag (AAS) is used as a green cementitious material with high strength and good durability, while the cracking damage due to high shrinkage limits the application of AAS in engineering project. The tensile stresses due to shrinkage can easily lead to the cracking of structures, while basic tensile creep can relax part of the tensile stresses and reduce the cracking risk. This study aims to investigate the effect of nickel slag (NS) on the basic tensile creep of alkali-activated slag/nickel slag mortars (ASNms). NS content refers to the weight ratio of NS to the summation of slag and NS. The properties of ASNms, including microstructure, hydration heat, internal relative humidity, mechanical properties, autogenous shrinkage and basic tensile creep, are studied. Results show that the mechanical properties of ASNms decrease with the increase in NS content. By reducing the hydration degree, the incorporation of NS decreases the amount of calcium aluminosilicate hydrate (C-(A-)SH) of ASNms, and the internal relative humidity and nominal crystal-binder ratio of ASNms are increased. As a result, the autogenous shrinkage of ASNms was significantly mitigated by incorporating NS. Autogenous shrinkage is the driving force of tensile creep. With the increase in NS content, the Na+ content absorbed by C-(A-)SH decrease, and therefore reduces the basic tensile creep of ASNms.