Studying the Effect of the Amount of Source Materials and Water to Binder Ratio on Chloride Ions Ingress in Alkali-Activated Slag Concretes

Due to the high amount of CO2 emission through the production of cement and great energy consumption in the cement industry, one of the most important issues in concrete technology is to find out an appropriate replacement for Portland cement. Alkali activated materials are the new approach for solving this problem. In fact, alkali activated concrete consists of an inorganic structure containing two parts: Source material and alkaline activator liquid. In this study, the effect of the amount of source material and water to binder ratio on chloride ions ingress was evaluated. For this purpose, 5 mix designs were used to make alkali activated slag concretes and for activating slag, 6 molar potassium hydroxide and sodium silicate solutions were employed as alkaline activator liquid. Additionally, one mix design was dedicated to ordinary Portland cement concrete for the sake of comparison.
The properties of AAS concretes were examined by means of slump loss, measurement of compressive strength at the ages of 1 to 180 days and capillary water absorption test at 7, 28 and 90 days. Furthermore, chloride ions penetration was measured through electrical resistivity test, rapid chloride migration test (RCMT) and resistance against chloride ions diffusion test according to NT Build 443. The results indicated that the performance of water to binder ratio and also the amounts of source material were comparable to that of ordinary Portland cement concretes. Additionally, alkali activated slag concretes had higher compressive strength and also superior durability against chloride ions penetration compared to OPC concretes