Alkali-silica reaction resistance versus susceptibility of geopolymer binders

^1* Department of Civil Engineering, Nelson Mandela University, South Africa
² Department of Engineering Sciences, University of the Free State, South Africa

^* Corresponding author: stephen.ekolu@mandela.ac.za

Abstract

Alkali–silica reaction (ASR) is a deterioration chemical process that causes expansion along with cracking of cement paste and aggregate particles, resulting in concrete degradation. Numerous factors influence ASR including aggregate reactivity, cement alkali content and moisture availability. Due to the high alkali content of the activator, the risk of ASR could be anticipated to be greater in geopolymer concrete than in Portland cement concrete. This article reviewed the susceptibility or resistance of geopolymer binders to ASR deterioration, based on published data in the literature. Generally, the vulnerability of geopolymer binders to ASR expansion is influenced by two factors comprising, the chemical composition of the aluminosilicate precursor and the alkaline activator solution characteristics. It is evident that low-calcium geopolymer binder systems exhibit very much lower ASR expansion than high-calcium geopolymer binders. Moreover, ASR expansion increases with increase in the alkali (M₂O with M = Na, K) concentration of the geopolymer binder mixture and declines as the silicate modulus rises SiO₂/M₂O. Calcium-rich geopolymer binders have a higher risk that may exhibit ASR attack, owing to the formation of the more expansive sodium-calcium-ASR gel.