Effect of binder and activator composition on the characteristics of alkali-activated slag-based concrete

Alkali Activated Slag Concrete (AASC) has been a sustained research activity over the past two decades. Its promising characteristics and being environmentally friendly compared to Ordinary Portland Cement made AASC of exceptional interest. However, there is still no firm mix design, for the AASC, that can provide desirable fresh and hardened properties based on the composition of the binder and activator. This research specifically aims to investigate the affecting parameters on the slump and compressive strength of alkali-activated slag/lime-based concrete and provide a better understanding of the potential reasons for these characteristics. The experimental program consisted of two stages; the first stage studied the effect of different binder and activator compositions, and the second stage studied the water-to-binder ratio and binder content effects on the slump and compressive strength of alkali-activated slag/lime-based concrete. The binder and activator compositions were defined through two main parameters, the hybrid factor (HF = CaO/Si₂O + Al₂O₃) and the solution modulus (Ms = SiO₂/Na₂O). The compressive strength, initial slump, and slump loss were measured to evaluate the different mixes and specify the optimum range of compositions. Based on the studied parameters, the effective range to achieve desirable slump and concrete compressive strength is from HF 0.6 up to 0.8 at Ms 1.5, this would achieve a compressive strength of more than 30 MPa and a slump of 100 mm after 90 min.