الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
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’s 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 MK
based geopolymer (MK-GP) mortar by 5%,10%,20%, 40% and 60% and the
samples were cured at ambient air condition (23 ± 2 °C) as well as at 60 °C heatcuring for 24 hours after casting. The fresh properties; (Setting time, flowabilityand flowability loss), mechanical characteristics; (compressive and splitting tensile strength), Water transport properties have been evaluated in terms of water absorption by capillary action (sorptivity) and water absorption by total immersion. Durability related characteristics in terms of change in weight and
compressive strength degradation were investigated after 10 weeks exposure to
extreme aggressive chemical solution (10% MgSO4, H2SO4 (pH=3) and 10%
NaCl) of hybrid cement at different curing ages were investigated. Furthermore, the samples were characterized through X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with energy dispersive X-ray (EDS) spectroscopy to identify their microstructure characteristics. The results were compared with conventional OPC mortar as well as MK-GP mortar. The results demonstrated that both fresh and mechanical properties of MK-GP 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) excelled those of conventional OPC mortar at 28 days of age in ambient air curing condition. These results are confirmed from microstructure analyses and attributed the
improved mechanical characteristics to the formation of more densified CSH,
CASH, NASH gels. In short, hybrid 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. The results reveal that, the inclusion of OPC up to 20% in MK-GPM slightly increases water transport under both curing
conditions. Although, MK-GPM shows better durability when exposed to
aggressive environmental attacks, incorporating cement up to 20% demonstrates superior durability performance than OPC mortar under same curing condition. Heat curing improves the microstructure and consequently durability characteristics of MK-GPM than ambient curing.