Quantitative assessment of parameters that affect strength development in alkali activated fly ash binders

The influence of activator composition (pH, modulus), activator to fly ash ratio, (L/S)_vol, and curing on strength development of alkali activated fly ash (AAFA) mortars is investigated. A statistical analysis is performed to evaluate the significance of these parameters and to develop a preliminary regression model for predicting the 1-day strength. The results show that to achieve high strengths, activators with very high pH (≥15.0) or high pH and moderate modulus (pH ≥ 14.75, n ≥ 0.75) are needed. Such activators have high viscosity and lead to low workability. AAFA strength does not monotonically increase with reducing (L/S)_vol, but is maximum at intermediate (L/S)_vol.