Mechanical Properties Of GO-fly Ash-steel Fiber Concrete And Freeze-thaw Cycle Test

As a new type of nanomaterial in the 21 st century,GO has a large specific surface area and is easy to disperse in water.It has been widely used in the field of materials research.This paper mainly studies the mechanical properties and durability of steel fiber reinforced concrete(SFRC)mixed with go-fly ash,single blended with GO,single blended with steel fiber reinforced concrete(SFRC)and ordinary concrete.In the test,there are 18 mixture ratios of concrete,among which 12 are designed mixed with go-fly ash and steel fiber concrete.The amount of fly ash in concrete accounts for 15%,30% and 45% of cement content respectively,and the amount of GO accounts for 0.01%,0.03%,0.05% and 0.07% of sand content respectively.In the single-mixed GO concrete,the proportion of GO content is consistent with that of the compound concrete,and a total of 4 mixing ratios are designed for the single-mixed GO concrete.The control group consisted of ordinary concrete and steel fiber reinforced concrete.The compressive test,splitting tensile test,freeze-thaw cycle test and CT scan analysis test were carried out on the concrete specimen cube.The compressive strength and splitting tensile strength of 7-day,14-day and 28-day concrete specimens were studied.Different times of freeze-thaw cycle tests were carried out on concrete specimens with different proportions to observe the appearance changes of specimens,test the mass loss rate,strength loss and relative dynamic elastic modulus of concrete specimens.Nondestructive testing of the specimens was performed using industrial CT to analyze the effect of GO on the porosity of concrete.The test results show that:(1)The single addition of GO significantly improved the early mechanical properties of concrete,and the compressive strength of the 7-day concrete cube increased by 33.15% to the maximum.When the fly ash content is 30%,the compressive strength of compound concrete is better.On the whole,the compressive strength of concrete is in descending order from large to small: single mixed GO concrete,ordinary concrete,steel fiber concrete,mixed go-fly ash-steel fiber concrete.(2)GO has a good enhancement effect on the splitting tensile strength of concrete,while fly ash has a reducing effect on the splitting tensile strength of concrete.(3)Single GO plays a great role in freezing-thawing resistance of concrete.When single GO is 0.03%,concrete has the best freezing-thawing resistance effect.When GO is added,concrete is denser than ordinary concrete,and when fly ash content is 45%,it is not good for concrete to resist freezing-thawing cycle.(4)The compressive strength of concrete is related to the porosity in concrete to some extent.The lower the porosity is,the better the compressive strength and splitting tensile strength are and the stronger the freeze-thaw resistance is.The mechanical properties and freeze-thaw cycle test of go-fly-ash steel fiber concrete were studied and analyzed,which provided certain basis and reference for engineering application.