Formation of shlykovite and ASR-P1 in concrete under accelerated alkali-silica reaction at 60 and 80 °C

Three types of alkali-silica reaction (ASR) products, i.e., crystalline K-shlykovite, Na-shlykovite and nano-crystalline ASR-P1, have recently been synthesized at 80 °C. It is critical to verify the formation of these ASR products in concrete in order to transfer the knowledge of ASR gained from the synthesized products to the ones formed in field concrete. Therefore, ASR products formed in concrete exposed to KOH, NaOH or mixture of KOH/NaOH solution at 60 and 80 °C are analyzed using Raman spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The results show that at temperature between 60 and 80 °C K-shlykovite and ASR-P1 are formed in concrete exposed to KOH or a mixture of KOH/NaOH solution, whereas Na-shlykovite is formed in concrete exposed to NaOH solution. Moreover, K-shlykovite and Na-shlykovite do not co-precipitate in the same concrete, not even in the concrete exposed to the mixture of KOH/NaOH solution.