Study On Salt Freezing Resistance Of Cement-limestone Powder-high Volume Fly Ash Green Concrete

Green concrete is such a kind of concrete in which mineral admixtures are added to replace cement in the process of concrete production.Green concrete realizes the greenization of concrete materials and achieves the purpose of energy conservation and emission reduction of concrete industry and effective environmental and ecological protection.At present,It is comment practice to replace part of cement to produce concrete with fly ash and limestone powder are used as admixtures.This practice not only reduce the amount of cement,increase the effective utilization of industrial by-products,fly ash and limestone powder,reduce environmental pollution,reduce concrete production cost,but also improve concrete working performance,and obtain good environmental,economic and social benefits.This paper simulates the soil environment and climate conditions in Da an area in the west of Jilin Province,and studies the working performance,physical and mechanical properties and salt frost resistance of cement-limestone powder-high volume fly ash green concrete from the material level.The main research work and conclusions of this paper are as follows:(1)Working performance of cement-limestone powder-High volume fly ash concrete.Adding fly ash and limestone powder can effectively improve the working performance of concrete.The slump of concrete mixture with 40%,50%and 60%fly ash replacing the same mass cement is 17%,23%and 28%higher than that of ordinary concrete;The slump of cement limestone powder high volume fly ash concrete with 5%,10%and 15%limestone powder and 40%fly ash is 22%,24%and 31%higher than that of ordinary concrete.(2)Mechanical performance of cement-limestone powder-High volume fly ash concrete.Adding fly ash and limestone powder can reduce the flexural and compressive strength of concrete.The cube compressive strength and prism flexural strength of fly ash concrete and cement limestone fly ash concrete are lower than those of ordinary concrete.The later strengths of fly ash concrete increases faster than that of ordinary concrete,and can reach with the strength of ordinary concrete.The flexure compressure ratios of concrete mixed with fly ash and limestone powder for 56 days is in the range of between 15%～20%,which are greater than those of ordinary concrete(15%).Adding fly ash and limestone powder can reduce the brittleness of concrete and improve the toughness of concrete.(3)Salt-freezing resistance durability of concrete.The greater the amount of fly ash and limestone powder replacing cement and the higher the concentration of salt solution,the more"steep"the quality change and relative dynamic elastic modulus of ordinary concrete,fly ash concrete and cement-limestone powder-high volume fly ash concrete with the number of salt-freezing cycles,and the more severe the salt corrosion freeze-thaw damage.The results of salt-freezing cycle under different concentrations of multi-salt solution show that the change of mass and relative dynamic elastic modulus of three kinds of concrete is a cubic function curve of y=Ax~3+Bx~2+C(x represents the number of salt-freezing cycle).