Developing Low-Cost Activators for Alkali-Activated Phosphorus Slag-Based Binders

Making use of low-cost alkali activators to produce suitable binders can play a key role in replacing portland cement by alkali-activated binders. The most effective and common activators are often based on sodium hydroxide and/or sodium silicate, which are relatively high in cost. In this study, attempts were made to develop suitable activators incorporating low-cost alkali and alkali earth metal-bearing salts for phosphorus slag. To fulfill this purpose, plain NaOH as a control activator as well as combinations of the control activator with Na2CO3 and also a combination of Na2CO3 and Ca(OH)2 at different proportions were used to activate ground phosphorus slag. To evaluate the cementing property and soundness of the resulting mixes, compressive strength and efflorescence severity data were employed, respectively. Two suitable cement mixes were then selected and their chemical bond structure and the rate of adiabatic heat release were characterized by means of Fourier transform infrared spectroscopy (FTIR) and adiabatic calorimetry data, respectively. Finally, cost assessment done on the corresponding low-cost activators of the selected cement mixes revealed significantly lower cost-to-compressive strength ratios compared to the conventional control activators.