Study On Mechanical Properties And Durability Of Basalt Fiber Fly Ash Concrete

Basalt fiber fly ash concrete is a new type of green composite building material with the advantages of high flexural strength,good crack resistance and high toughness.In order to further study the effects of fly ash admixture,basalt fiber admixture,basalt fiber length,and water reducing agent admixture on the performance law of basalt fiber fly ash concrete,this paper through the design of orthogonal experiment,carried out 7d,28 d of mechanical properties of the orthogonal experiment,the corrosion of seawater and seawater corrosion conditions of freezing and thawing orthogonal experiment research.The mechanism of the microstructure under different conditions was analyzed by scanning electron microscopy.The main research contents and conclusions are as follows:(1)Basalt fiber fly ash concrete after 7d curing,compressive and splitting tensile orthogonal test,the research results show that the basalt fiber length has the most significant effect on compressive strength,fiber length 24 mm reduces 20.29% compressive strength than 12mm;water reducing agent admixture has the most significant effect on splitting tensile strength,water reducing agent admixture 1.6% reduces 33.71% than 0.8%Splitting tensile strength;in terms of compressive strength and splitting tensile strength,the best matching ratio is A1B3C1D1 and A3B1C1D1.(2)Basalt fiber fly ash concrete was subjected to compressive,splitting tensile and flexural orthogonal tests after standard curing,and the results showed that the effect of fly ash admixture on compressive strength and splitting tensile strength was significant,and basalt fiber admixture had the highest degree of effect on flexural strength;fly ash admixture of 40% reduced compressive strength by 15.77% and splitting tensile strength by 7.81% compared with admixture of 20%;basalt fiber at 0.1% dosing reduces the flexural strength by 14.08% compared with 0.3% dosing;in terms of compressive strength,splitting tensile strength and flexural strength,the optimal ratio is A1B1C2D2,A1B3C2D1 and A1B1C3D2 respectively.(3)After 180 d of seawater corrosion,the orthogonal test of compressive strength,splitting tensile strength and bending strength of basalt fiber fly ash concrete was carried out.The results show that the content of fly ash has the most significant effect on the compressive strength,splitting tensile strength and bending strength;when the fly ash content is 40% to 20%,the compressive strength decreases by 14.94%;when the fly ash content is 40% to 30%,the splitting tensile strength decreases by 12.13%;when the fly ash content is 40% to 20%,the bending strength decreases by 27.57%;in terms of compressive strength,splitting tensile strength and bending strength,the optimal mix ratio is A1B1C2D1,A2B3C2D1 and A1B1C3D1.(4)After the freeze-thaw cycles of seawater corrosion of basalt fiber fly ash concrete,each group of tests as a whole showed that the more freeze-thaw cycles,the faster the relative dynamic elastic modulus decreased.At 150 freeze-thaw cycles,compressive and splitting tensile orthogonal tests were conducted,and the results showed that the most significant effect of fly ash admixture on compressive strength,fly ash admixture of 40%compared with 20% reduces the compressive strength by 26.49%;the most significant effect of water-reducing agent admixture on splitting tensile strength,water-reducing agent admixture of 1.6% reduces the splitting tensile strength by 26.64% compared with 0.8%;in terms of compressive strength and splitting tensile strength,the best matching ratio is A1B1C2D1 and A1B1C2D1.(5)Multiple linear regression analysis of the orthogonal test results of each group can get the prediction model of mechanical properties of basalt fiber fly ash concrete,according to which the mechanical properties of basalt fiber fly ash concrete under different conditions can be predicted.(6)The scanning electron microscopy of basalt fiber fly ash concrete and the microstructure of the specimen showed that the basalt fiber plays a restraining role on the surrounding concrete and inhibits the crack generation;the easier the longer the basalt fiber internal residual pore space,after freezing and thawing cycle can seriously reduce the mechanical properties of concrete;the tiny spherical particles of fly ash can effectively fill the residual pores in concrete and enhance the corrosion resistance and freeze-thaw resistance of concrete.