Influence of Different Curing Regimes on the Performance and Microstructure of Alkali-Activated Slag Concrete

This paper investigates the performance and microstructure of alkali-activated slag concrete (AASC) subjected to different 28-day curing regimes: air, intermittent water curing (7days in water followed by 21days in air), and continuous water curing. Three concrete mixes were prepared with fixed contents of slag, desert dune sand, and aggregate and activated by an alkaline solution consisting of sodium silicate and sodium hydroxide. The ratio of alkaline activator solution (AAS) to slag was varied between 0.45 and 0.55. Samples were tested to assess transport and mechanical properties. Test results showed that an AAS:slag ratio of 0.50 provided optimal performance. Intermittent water curing was found to be the most effective curing regime, resulting in a reduction in porosity and sorptivity, and an increase in bulk electrical resistivity, modulus of elasticity, and compressive strength. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to characterize the microstructure. Calcium alumino-silicate hydrate gel was highlighted as the main reaction product, while sodium alumino-silicate hydrate gel was only detected in air cured counterparts.