Effect of incorporating hydrated lime on strength gain of high-volume fly ash lightweight concrete

High-volume fly ash concrete, HVFALC, may acquire popularity as durable, resource-efficient, and option of sustainability for different applications of concrete. The Pozzolanic reaction between fly ash, Ca(OH)2 and water is the cause of making high-volume fly ash concrete a promising sustainable material. The aim of this study is to enhance the rate of the Pozzolanic reaction by incorporating external source of hydrated lime in the mix by two approaches. The first is to replace 10% by weight of the cementitious materials with hydrated lime and second is to use a lime-saturated water, with a concentration of 3g/L, for mixing. Two high-volume fly ash concrete mixes, with 50 and 60 % replacement by weight of cement, were included in this study. The testing program included water absorption, dry density, compressive and splitting tensile strengths. The testing program was extended to the age of 120 days. The present results showed that both approaches have caused an increase, ranging between 10 and 24 %, in absorption values and a slight reduction, less than 3 %, in dry density values. Both approaches have caused a significant gain in compressive and splitting tensile strengths. Replacing 10 % by weight of the cementitious materials with hydrated lime caused better enhancement in compressive and splitting tensile strengths for all curing ages than using lime-saturated water in mixing. The former approach was more effective for mix FA60 than for FA50 and the higher fly ash content in the FA60 mixes could be the reason.