EFFECTS OF SODIUM OXIDE CONCENTRATION AND FLY ASH/SLAG RATIO ON MECHANICAL BEHAVIORS OF ALKALI-ACTIVATED FLY ASH/SLAG MORTARS
The main purpose of this study is to investigate the effects of sodium oxide concentration and fly ash/slag ratio on mechanical behaviors of alkali-activated fly ash/slag (AAFS) mortars. Sodium oxide (Na2O) concentrations of 4% and 6% by cementitious material weight and liquid sodium silicate with modulus ratio (mass ratio of SiO2 to Na2O) of 1 were prepared as activators and 10 AAFS mortars with various ratios of fly ash to slag and a control ordinary portland cement (OPC) mortar were cast. Three tests, compressive strength test, water absorption test, and drying shrinkage test, were conducted. Their performance was discussed and compared with reference OPC mortar. Test results show that the compressive strength and drying shrinkage are higher than that of OPC mortar. Both fly ash/slag ratio and the dosage of Na2O are two significant factors influencing the mechanical behaviors of AAFS mortars. The mechanical behaviors of AAFS mortars improved with an increase dosage of Na2O. Superior mechanical behaviors have been obtained in AAFS mortars with a fly ash/slag ratio of 50/50 alkali-activated by Na2O concentrations of 6%, than any other AAFS mortars.