To reduce the emission of CO2, most countries are focusing on replacing the traditional OPC concretes by using other types of environmentally friendly binders. Metakaolin (MK)-based Geopolymer has proven to be one of the potential alternative materials to Portland Cement, not only due to its high strength and durability, but also because of its availability. However, geopolymer use as an alternative binder in concrete is limited by the fact that; its slow strength development under atmospheric condition and, higher cost. In this study hybrid cement was synthesized by partially replacing MK by Portland cement in (MKGP) mortar by 5%,10%,20% and 40% and the samples were cured at ambient air condition (23 ± 2 °C) as well as at 60 °C heat curing for 24 hours after casting. The fresh properties; (Setting time, flowability and flowability loss) and mechanical characteristics; (compressive and splitting tensile strength) of hybrid cement at dissimilar curing ages were investigated. These results were compared with conventional OPC mortar as well as MKGP mortar. The results demonstrated that both fresh and mechanical properties of MKGP mortar improve by replacing MK by 5% OPC. Moreover, not only the fresh properties of hybrid cement mortar were better than MK geopolymer mortar, but also the mechanical properties of hybrid cement (up to 40% OPC replacement) exceed those of conventional OPC mortar at 28 days of age in ambient air curing condition In short, hybrid
Al-Azhar University Civil Engineering Research Magazine (CERM)
Vol. (43 ) No . ( 3 ) July . 2021
655
cement based on metakaolin and OPC (95% MK and 5%OPC) can be conveniently used for casting in situ concrete under ambient air curing condition.