Properties And Rheology Of Self Compacting Concrette

Concrete is one of the most important building materials. The development of concrete’s technology can effectively promote the social progress. Concrete’s technology develop to High Performance Concrete and Green Concrete since the21st century, Self Compacting Concrete (SCC) which has the ability to avoid vibration, high flow ability and performance of anti-segregation, quickly became the focus of research both at home and abroad. But as SCC need high content of cement, leading the direct cost is high, which block the popularization and application of SCC.Fly ash part replace cement can reduce the cost of concrete, enhance the durability of concrete, make waste profitable, help protect the environment, achieve sustainable development. But when the volume of fly ash is high, concrete’s early strength will decrease, which impact the period of removing form, leading the construction period increase, then hinder the further application of high volume fly ash in concrete. How to improve the early strength of high volume fly ash concrete had become a hot research hotspot. Due to the early strength agent, accelerating agent may make negative effect on concrete’s later strength and durability, so some scholar use nano SiO2, Al2O3, to enhance concrete’s early strength, nano CaCO3as new nano material, which cost is far below nano-SiO2, Al2O3and is decreasing with the steady growth of its production. But its application in concrete is rare.The project studied on the effect of nano CaCO3on high volume fly-ash self compacting concrete(HFSCC)’s early strength; the effect of nano CaCO3on cement paste’s setting time; the effect of nano CaCO3on cement paste’s fluidity; the effect of nano CaCO3, fly ash on rheology of cement paste and mortar; the effect of nano CaCC>3on HFSCC’s work performance, mechanical property and microcosmic pore structure and research the mechanism of nano CaCO3.Research results show that:1) nano CaCO3can effectively reduce the setting time of cement paste;2) nano CaCO3can enhance the viscosity and yield stress of cement paste and mortar;3) HFSCC’s slump flow decrease with the dosage of nano CaCO3increase, T500increase with the dosage of nano CaCO3increase;4) nano CaCO3can effectively improve HFSCC’s early strength, when nano CaCO3content is1%, the1d compressive strength of HFSCC increased50%than the blank test group; HFSCC’s Id,7d and28d compressive strength increase with the dosage of nano CaCO3increase;5) nano CaCO3can effectively improve HFSCC’s micro pore structure; the pore size distribution become smaller, gel hole below10nm content increased, capillary pore over50rnn decrease.To sum up, nano CaCO3can effectively improve HFSCC’s early strength, effectively improve its work performance and micro pore structure, and has broad prospects in concrete’s application.