Effects of high-temperature curing on hydration and microstructure of alkali-activated typical steel slag cementitious material

Hydration process, products, microstructure, and compressive strength of steel slag in alkaline environments at room and high temperature were investigated. Results show that high-temperature curing significantly promotes the early hydration, causing more products. The promoting effect of temperature becomes more apparent with higher activator content. The cumulative heat apparently increases by approximately twice at 6% alkali content. Increasing temperature has no effect on the types of products and hydration of inactive components. The products remain as Ca(OH)2 and C-(A)-S-H, but Ca/Si and Al/Si ratios significantly increase from 1.42 to 2.41 and from 0.14 to 0.21, respectively. High-temperature curing makes matrix denser, resulting in a substantial increase in the early strength. However, promoting effect on the strength diminishes over time. The growth rates of 28 d strength are only -1% and 4% at different alkali content. Moreover, alkali-activated steel slag material has great potential in the field of low-carbon cementitious materials.