Effect of microwave curing as compared with conventional regimes on the performance of alkali activated slag pastes

Increasing the rate of strength development can greatly facilitates and accelerates numerous essential procedures in the construction field. Rapid strength development in alkali-activated materials composites could be reached by various techniques. In recent era, alternative techniques for accelerated heating, and curing have been investigated for cementious composites. The microwave heating is one of those methods, which is the main concern in the proposed research. As for the alkali-activated materials concrete, it has not been yet extensively studied, the aim of the conducted research program was to investigate the microwave curing effect on the compressive strength, and microstructure of alkali-activated slag pastes as compared with other curing regimes; air, water, and conventional heating. The experimental results revealed that, microwave curing is beneficial for achieving high early strengths over all of the other curing regimes studied, furthermore, the heat curing time of application was significantly shortened by the microwave radiation. Results demonstrated that microwave energy increased the dissolution of slag in the alkaline media. Widespread formations of the hydration gels were identified in the microscopic analyses. This led to a denser, well compacted, and stronger matrix resulting in higher compressive strength gain compared to those pastes cured under air, water, and conventional heating regimes. The microwave significantly accelerated the activation, so it can reach around 90% of its 28 days strength at the first 7 days. (C) 2019 Elsevier Ltd. All rights reserved.