Verification of the mutually complementary effect of fly ash and clinker aggregate on the strength, heat of hydration, and alkali-silica reaction

Although fly ash, as used for supplementary cementitious material in Portland cement concrete, can reduce the heat of hydration and suppress the expansion caused by alkali-silica reaction (ASR), the early strength development of the concrete tends to be lower. On the other hand, it is known that the strength development can be improved using cement clinker as the aggregate for concrete (CL). However, there is a risk of ASR in using CL due to the alkali leaching from the CL. Therefore, the combined use of fly ash and CL may have a synergistic effect. Based on these considerations, we examined the effect of using fly ash and CL in combination on the internal temperature of mortar, strength development, and ASR. We demonstrate that the combined use of CL and fly ash results in good strength development as well as suppressing the internal temperature. In addition, when the binder was only ordinary Portland cement (OPC), the combination of CL and ASR reactive aggregate enabled reducing the expansion caused by ASR compared to the combination of limestone aggregate (LS) and ASR reactive aggregate. However, the higher the replacement ratio of fly ash for OPC, the lower its ASR suppression effect.