Effect of Mineral Admixtures on Early Shrinkage and Cracking Properties of High Strength Machine-made Sand Concrete
Aiming at the problem of severe early shrinkage and cracking of concrete pumped with low water-binder ratio and high strength sand,which is easy to cause a sharp decline in the durability of buildings,the effects of fly ash,mineral powder and silica fume on the working performance,mechanical properties,early shrinkage and cracking properties of concrete under single,double and triple mixing were studied through experiments.The behavior of early shrinkage cracking was analyzed by low field nuclear magnetic resonance(NMR)through pore structure.The results show that the addition of fly ash and mineral powder can improve the working performance of concrete,but the addition of silica fume can reduce the working performance of concrete.The addition of mineral admixture has a great influence on the early strength of concrete,and with the extension of curing age,the late strength increases with the increase of hydration degree.When fly ash,mineral powder and silica fume are mixed,the high strength machine-made sand concrete has the smallest early shrinkage rate and cracking area.The addition of mineral admixtures can reduce the internal porosity of concrete,increase the internal density of concrete,and reduce the early shrinkage cracking.
concretemineral admixturemachine made sandmechanical propertiesearly contractionearly cracking