Alkali silica reaction of waste glass aggregate in alkali activated fly ash and GGBFS mortars

Abstract

This paper evaluates the alkali silica reaction (ASR) susceptibility of waste glass aggregate in alkali activated fly ash and ground granulated blast furnace slag (GGBFS) mortars as compared to that in ordinary Portland cement (OPC) mortars. In accelerated mortar bar tests, glass fine aggregate showed much lower expansions in alkali activated fly ash and GGBFS blended mortars than in OPC mortars or alkali activated neat fly ash or GGBFS mortars. Glass aggregate was classified as non-reactive with alkali activated fly ash and GGBFS blends according to 10-day and 21-day expansion limits of the Australian Standard. Microstructural studies revealed that glass aggregate produced typical ASR products in OPC mortars and alkali activated neat GGBFS mortars due to the presence of high calcium. However, alkali activated fly ash and GGBFS blended mortars produced reaction products of low Ca/Si and high Al/Si ratios that reduced the dissolution of reactive silica present in glass aggregate causing less expansions. The observed expansion of the alkali activated neat fly ash mortar is attributed to the analcime phase found in the X-Ray diffraction of this mortar.