Comparative Study on Heat Evolution of Alkali-activated Slag: Early-stage Assessment Prior to Plastering

Alkali-activated slag has shown favorable properties such as fast setting, high early-age strength, and excellent durability, making it particularly suitable for applications that require fast setting for ambient condition. However, controlling heat evolution remains important as it affects early-age behavior, which is an essential preliminary consideration before being further developed for plastering applications. This study investigates the influence of sodium hydroxide (NaOH) molarity (6–14 M) and solid-to-liquid (S/L) ratios (0.6 and 1.4) on heat evolution and early-age properties of AAS. Heat evolution was monitored using heat flow calorimeter, and the AAS with the highest (10 M, S/L 0.6: 263.44 J/g) and lowest (14 M, S/L 1.4: 210.46 J/g) total cumulative heat were further assessed for density, compressive strength, morphology, and in-situ phase evolution. Results showed that S/L = 1.4, 14 M achieved the highest density (2.10 g/cm³) and compressive strength (40.25 MPa at 3 days). A key contribution of this study is the elucidation of the correlation between heat evolution and the early-age performance of alkali-activated slag, providing insight knowledge on evaluation of alkali-activated slag formulations with controlled heat evolution for potential use in plastering and surface protection applications.