Optimization of ZnO2 nanoparticle content in binary blended concrete to enhance high strength concrete

Abstract

Abstract The mechanical properties of concrete containing ZnO2 nanoparticles which was cured in saturated limewater have been optimized. ZnO2 nanoparticles were added to concrete as nano-fillers. The specimens were cured in water and saturated limewater for 7, 28 and 90 days after casting and then their strength was evaluated by mechanical testing (compressive, split tensile and flexural strength tests). The results showed that replacement of Portland cement with ZnO2 nanoparticles up to 1.0 wt.% for the specimens cured in water and 2.0 wt.% for the specimens cured in saturated limewater produces concrete with the best strength. It has been shown that curing the specimens in saturated limewater for 28 days and then in water until 90 days, produces a stronger concrete than those cured only in saturated limewater for 90 days. Excess Ca(OH)2 crystals which form after 28 days, when the specimens are cured in limewater, do not contribute to strength enhancement as much as strengthening gel and hence, the mechanical properties of the specimens do not reach the highest level. On the other hand, curing the specimens in water after 28 days produces more strengthening gel and results in a concrete with higher strength. The addition of nanoparticles improves the pore structure of concretes, thus, the refined extent of the pore structure increases with decreasing nanoparticle content. The pore structure of concrete cured in saturated limewater is better than that of concrete cured in water.