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Investigations on Aggregate Reactivity in Geopolymer Concrete
Abstract The potential reactivity of sandstone/siliceous aggregates in geopolymer concrete based on fly ash/GGBS composite mixes was assessed in terms of alkali-silica reaction. The mortar bars made as per ASTM C1260 were exposed to 1 M NaOH at 80 °C up to 90 days. The exposed samples were examined for their expansion and petrography. It was observed that the samples expanded less than the threshold of 0.1% at the end of 16 days exposure while its OPC counterpart failed by exceeding the limit. At 90 days, the geopolymer mortars containing composite mixes had expansion in the range of 0.31–0.56% as compared to 0.12% for fly ash-based geopolymers. Evidence of crystalline zeolites, sodium calcium silicate gel and cracks observed under FESEM after 90 days could be responsible for higher expansion. Reduction in alkalinity of solution/dissolved silica from aggregate after 24 h exposure in 1 N NaOH solution indicated innocuous nature of aggregates contrary to the expansion results. It was noted that geopolymer concrete made with high GGBS content exhibited prominent ASR product. It was concluded that siliceous aggregates had less ASR than the sandstone aggregate.
Investigations on Aggregate Reactivity in Geopolymer Concrete
Abstract The potential reactivity of sandstone/siliceous aggregates in geopolymer concrete based on fly ash/GGBS composite mixes was assessed in terms of alkali-silica reaction. The mortar bars made as per ASTM C1260 were exposed to 1 M NaOH at 80 °C up to 90 days. The exposed samples were examined for their expansion and petrography. It was observed that the samples expanded less than the threshold of 0.1% at the end of 16 days exposure while its OPC counterpart failed by exceeding the limit. At 90 days, the geopolymer mortars containing composite mixes had expansion in the range of 0.31–0.56% as compared to 0.12% for fly ash-based geopolymers. Evidence of crystalline zeolites, sodium calcium silicate gel and cracks observed under FESEM after 90 days could be responsible for higher expansion. Reduction in alkalinity of solution/dissolved silica from aggregate after 24 h exposure in 1 N NaOH solution indicated innocuous nature of aggregates contrary to the expansion results. It was noted that geopolymer concrete made with high GGBS content exhibited prominent ASR product. It was concluded that siliceous aggregates had less ASR than the sandstone aggregate.
Investigations on Aggregate Reactivity in Geopolymer Concrete
Singh, B. (author) / Ishwarya, G. (author)
2018-08-02
10 pages
Article/Chapter (Book)
Electronic Resource
English
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