Effect of silicate modulus of water glass on the hydration of alkali-activated converter steel slag

Abstract

Converter steel slag, currently underutilized crystalline metallurgical residue, was investigated for use as a precursor for alkali activation. Water glass solution with various moduli (0.5, 1.0, 1.5 and 2.0) was used at the same Na2O dosage of 4% in order to investigate effect of modulus on hydration. Pure cement paste with the same ratio of water to binder was selected as the control sample. Results show that modulus has a significant impact on the hydration and mechanical strength development of alkali-activated steel slag. Similar to pure cement paste, alkali-activated steel slag paste has C–S–H gel and Ca(OH)2 as its main hydration products. However, alkali-activated steel slag pastes have lower hydration heat and fewer amounts of hydration products. Additional silicate has a retarding effect on the hydration of steel slag. Hydration heat, Ca(OH)2 contents and non-evaporable water contents reduce with increasing modulus. In addition, high silicate modulus fines the pore structure and improves compressive strength of the hardened paste.