ALKALI SILICA REACTION OF RECYCLED GLASS AGGREGATE MORTAR USING FLY ASH UNDER STEAM CURING

Utilization of recycled glass as fine and coarse aggregates in concrete materials can give significant economical and environmental benefits, especially in the case of developing countries. However, alkali-silica reaction (ASR) will be a serious problem when the recycled glass is used as concrete aggregates. This paper shows an investigation of the alkali-silica reaction of glass sand mortar under steam curing. The test for ASR expansion follows ASTM C1567. Type F fly ash (FA) is used together with Ordinary Portland cement (OPC) mixing with mixed color glass sand. FA contents are of 20%, 30%, 40% and 50% as OPC replacement. Steam curing accelerating FA reaction is used to contribute to the mitigation of ASR by strength improvement of the mortar. Under steam curing, the results show that the recommended contents of FA to use are of 20% to 30% to ensure expansion lower than the threshold of ASTM. Moreover, steam curing increases the expansion of the glass sand mortar in compared to the moist curing, and expansion crack appears at the interface between glass sand and cementitious matrix, not in the glass sand. In comparison with glass sand mortar under moist curing, expansion of glass sand mortar using fly ash under steam curing is contributed primarily by: (1) delayed ettringite formation, (2) reducing ion transportation, (3) increasing tensile strength of fly ash glass sand mortar and (4) reducing glass sand dissolution rate in rich alkalinity solution.