Microstructure, water permeability and micromechanical properties of alkali activated slag subjected to accelerated leaching

This study investigated the leaching resistance of alkali activated slag mortars (AAS) under immersion in a 6 M NH4NO3 solution for a duration of up to 28 days, taking into consideration the effect of water-to-binder (w/b) ratio. SEM-EDS analysis revealed decalcification, desodiumization, and dealumination in AASs during leaching, leading to changes in the microstructure and micro-mechanical properties of the materials. A combination of N2adsorption and MIP analysis demonstrated that there was a coarsening of the structure and an increase in porosity along the depth of degradation in the leached AAS. The predominant pore framework in the leached materials was found to be capillary pores. Furthermore, the elastic modulus and micro-hardness of AAS decreased after 28 days of leaching, as evidenced by micro-indentation. The water permeability of AASs exhibited an exponential rise with the increase in porosity, both before and after leaching, as a consequence of the changes in microstructure. Notably, the w/b ratio significantly influenced the leaching rate, microstructure, and water permeability of the AAS.