Effect of Ca/Si and Si/Al Ratios on the Mechanical Properties of One-Part Alkali-Activated Nickel Slag Binder

Abstract

This study investigates the compressive and flexural strengths of one-part alkali-activated nickel slag binder (AANSB) with different Ca/Si and Si/Al ratios in the precursor. The compressive and flexural strengths were optimized at Ca/Si and Si/Al ratios of 0.39 and 5.0, respectively. When the Ca/Si ratio is too low or the Si/Al ratio is too high, SiO2 is formed, which does not partake in one-part AANSB hydration. Meanwhile, if the Ca/Si ratio is too high or the Si/Al ratio is too low, the excess Ca and Al forms Ca(OH)2 or Al(OH)3 crystals that hinder the polymerization reaction of the geopolymer gelling system, reduce the hydration degree, increase the porosity and incidence of internal micro-cracks, and limit the strength development.

Keywords: One-part alkali-activated binder, Nickel slag, Ca/Si ratio, Si/Al ratio, Mechanical properties