Geopolymers as sustainable alternates for portland cement in constructive concrete: systematic review

Abstract

This systematic review presenting fundamentals of geopolymer (GP) for concrete technology. Geopolymer formulated by activation of sustainable aluminosilicate binders (eco-friendly, available, cheap, sustainable natural raw materials fly ash and slag wastes). Geopolymer concrete decrease scarcity of global ordinary Portland cement and decrease energy 0.110 kWh per gram and CO2(g) emission (800 kg ton-1). Durability, mechanical strength, resistance to water and leaching improved via by TiO2 nanoparticles. Polycondensation yield and physicochemical characteristics of GP are monotonic functions of (binder's chemistry, alkali concentration& types, reinforcing fibers, Si to Al ratio, precursors firing, types of solid wastes, heating activation, types and curing conditions. Concrete quality is controlled by geopolymer (composition, additives, mechanical strength and compressive strength). Nano materials SiO2, Fe2O4 and Al2O3 improved (mechanical characteristics, microstructure, functionality, durability, mortar strength, slurry mobility, permeability, impact, and rheology) as well as decreasing shrinkage and micro cracks on aging. Fumed nano silica showed be added at small 0.5% wt. with 4% wt.% superplasticizer with low water:cement ratio.Appropriate curing and optimum 7% super plasticizer improved workability, flow and fluidity. Limestone (CaCO3) is an ideal filler increases tensile strength and flexural strength, however impact the thermal expansion coefficient. The obstacle is the scale up using CaCO3 in GP cement.