Study On Basic Mechanical Properties And Durability Of Hybrid Fiber Fly Ash Reinforced Concrete

With the development of industry,fly ash has become one of the industrial wastes with large displacement in China.If it is not treated,it will not only occupy land resources,but also cause environmental pollution such as dust and sewage.At the same time,the production process of cement will discharge SO2,CO,CO2 and particulate matter into the atmosphere,resulting in air pollution.Incorporating mixed fiber and fly ash into concrete to form hybrid fiber fly ash concrete can not only solve the problem of utilization of fly ash,but also saving cement.The compressive strength and splitting tensile strength tests of basalt-polypropylene hybrid fiber concrete,basalt-polypropylene hybrid fiber concrete and basalt-polypropylene hybrid fiber fly ash concrete for 7d,14d,28d and 60d were earied out.At the same time,the carbonation tests for 3d 7d,14d and 28d and freeze-thaw cycles for 15,30,45 and 60 times were carried out.The results of basic mechanical properties test show that the early hydration reaction of hybrid fiber reinforced concrete is inhibited after the same amount of fly ash is substituted for cement,and the degree of inhibition is positively correlated with the amount of fly ash.Fly ash reduces the compressive strength of hybrid fiber reinforced concrete and the splitting tensile strength within 28 days,but when the fly ash content is less than 10%,the splitting tensile strength of mixed fiber concrete with age of 60d has different degrees of improvement.At 7d,the compressive strength and splitting tensile strength of hybrid fiber reinforced concrete with 10%fly ash were 0.6%and 4.5%lower than that of the reference concrete.At 28d,the compressive strength and splitting tensile strength were respectively higher.The benchmark concrete increased by 1.8%and 7.2%.The experimental results of tensile strength are fitted,and the empirical formula between the compressive strength of concrete and the content of fly ash at different ages is obtained.The formula has good prediction accuracy for the compressive strength of 28 d and 60 d.The results of carbonation performance test show that fly ash accelerates the carbonization rate of hybrid fiber concrete,and the carbonization rate is positively correlated with the amount of fly ash.When the amount of fly ash is changed from 10%to 20%,the carbonization rate of the hybrid fiber fly ash concrete is the most sensitive.When the fly ash content is less than 10%,the carbonization speed of the hybrid fiber fly ash concrete is lower than that of the reference concrete;when the fly ash content is above 20%,the carbonization speed of the hybrid fiber fly ash concrete is higher than that of the reference concrete.The results of freeze-thaw cycle test showed that after 60 freeze-thaw cycles,the loss rate of compressive strength of hybrid fiber concrete decreased by 3.4%compared with the reference concrete,and the mixed fiber fly ash concrete with fly ash content less than 30%The rate of compressive strength loss is substantially the same as that of the reference concrete.When fly ash content is less than 10%,the relative dynamic elastic modulus of hybrid fiber fly ash concrete is higher than that of reference concrete,and when fly ash content is more than 20%,the relative dynamic elastic modulus of hybrid fiber fly ash concrete is lower than that of reference concrete.Figure[38]Table[21]References[76]...