Research Of Volumetric Stability And Other Properties Of High Flowing Concrete

With the rise of concrete pumping construction technology,high flowing concrete has been more and more widely used.However,compared with the ordinary concrete(slump of 30～70mm,sand rate of 28～35%),in order to meet the requirements of pumping workability of high flowing concrete,we have to use large sand rate(45%),small stones to prepare.In this way,it weakens the function of the aggregate as the volume stability of the skeleton,so the phenomenon of cracks and cracks often appear in the practical application of high flowing concrete.At present,there are few studies on the volumetric stability of high flowing concrete.In this paper,the volumetric stability and other properties of high flowing concrete are systematically studied through a large number of experiments.The experimental results of this paper have a good reference value for improving the application quality of high flowing concrete.(1)The volume shrinkage rate of high flowing concrete at each age is much higher than that of ordinary concrete.The shrinkage crack of high flowing concrete increases with the increase of sand ratio when the sand ratio is between 32%and 48%.The higher sand percentage than that of ordinary concrete is an important reason for the poor volume stability of mass fluidity.However,if the sand percentage is smaller,the high flowing concrete can not meet the workability and strength requirements.(2)Compared with ordinary concrete,the volume shrinkage cracking of high flowing concrete with particle size of 20mm,31.5mm and 40mm is more serious,and the volume shrinkage rate increases with the decrease of gravel particle size.Smaller particle size of gravel than that of ordinary mobile concrete is an important reason for the poor stability of large fluidity volume,but larger particle size of gravel leads to poor workability and low strength of large fluidity concrete.(3)The influence law of sand ratio on the volume stability of high flowing concrete can be analyzed from the average thickness of cement slurry coating.The relationship between the particle size of gravel and the volume stability of high mobility concrete can be analyzed from the relative coefficient K of mortar coating thickness.(4)Fly ash,stone powder and polyester fiber can improve the bulk stability of high flowing concrete,but they have different effects on workability and strength.It can be mixed in a certain proportion.The proportion of stone powder to replace fly ash should not exceed 40%,and polyester fiber incorporation amount of 1.2kg/m~3 is better.(5)The sulfate corrosion resistance and frost resistance of l high flowing concrete are worse than those of ordinary concrete.The sulfate corrosion resistance and frost resistance of high flowing concrete decrease with the increase of volume shrinkage.