Investigation on the sodium silicate modulus-affected macroscopic and microscopic characteristics of alkali-activated slag concrete

This study systematically examines the effects of the modulus of Na₂SiO₃ on the compressive strength, hydration exothermic characteristics, pore structure, physical phase components, and microscopic morphology of slag concrete based on the fact that the modulus (m_SiO2/m_Na2O) of activated alkali has a significant impact on the properties of alkali-activated slag concrete (AASC). The results shown that as the modulus of Na₂SiO₃ increased, the compressive strength of alkali-activated slag concrete increased (11.31%-29.2%) and then dropped. The maximum compressive strength of AASC is found in AASC manufactured using Na₂SiO₃ with a modulus of 1.5. The cumulative heat release is greater for slag prepared with a modulus of 1, while the initial compressive strength is higher for slag prepared with a modulus of 2. In comparison to the AASC generated using Na2SiO3 with moduli of 1 and 2, the AASC prepared using Na2SiO3 with a modulus of 1.5 had the lowest porosity, a more optimized pore structure, the greatest C-(A)-S-H content, and the densest microstructure at the 28-day curing age, which is more conducive for the development of compressive strength of AASC.