Study On Physical And Mechanical Properties Of Steel Fiber Reinforced High Content Fly Ash SCC

The Self-Compacting Concrete?SCC?is a kind of green high-performance concrete,which has the characteristics of high fluidity,uniformity and stability.When pouring,SCC can flow by self weight and fill the formwork space.It is widely used because of its good workability.Compared with ordinary concrete of the same strength grade,the SCC has the disadvantages of low water binder ratio,high sand ratio,large amount of cement and admixture,resulting in high hydration heat,large shrinkage and high cost.Using fly ash and steel fiber to modify SCC,on the one hand,the physical and mechanical properties and economy of SCC can be improved,on the other hand,the deformation performance and toughness of SCC can be improved,and in line with the development concept of green building materials.According to the technical code for the application of self compacting concrete,the slump expansion,T₅₀₀00 and J-ring expansion are taken as the performance test indexes in this project.This paper prepared C40 grade the high content fly ash SCC?FA-SCC?,steel fiber reinforced SCC?SF-SCC?and steel fiber reinforced high content fly ash SCC?SFFA-SCC?,studied the influence of fly ash content and steel fiber volume fraction on the workability,drying shrinkage properties,basic mechanical properties and axial compression deformation properties of three SCC,analyzed the mechanism of action.The main research results are as follows:?1?Study on the change rule of each series of SCC workability with fly ash content and steel fiber volume fraction.With the increase of fly ash content,the fluidity and fillying ability of FA-SCC decreased of first and the increased.With the increase of fly ash content,the gap passing ability was not significant,and the segregation resistance met the specification requirements.The fluidity,filling ability and gap trafficability of SF-SCC was decreased with the increase of steel fiber volume fraction,and the segregation resistance ability increased gradually.The workability of SFFA-SCC was decreased with the increase of steel fiber volume fraction and was improved with the increase of fly ash content.?2?Study on the drying shrinkage properties of FA-SCC,SF-SCC and SFFA-SCC.The early dry shrinkage of the three kinds of SCC was obvious,and the later one was decreased.When the content of fly ash was 40%and 50%,the dry shrinkage of FA-SCC was higher than that of SCC.When the content of fly ash was 60%and 70%,the dry shrinkage was reduced.The change of steel fiber volume fraction had a certain inhibition on the dry shrinkage of SCC.?3?Study on the basic mechanical properties and axial deformation properties of FA-SCC,SF-SCC and SFFA-SCC.With the increase of fly ash content,the compressive strength and elastic modulus of FA-SCC increased first and the decreased,and the flexural-tensile strength decreased obviously.When fly ash replaces part of cement,the strain energy and relative toughness under SCC axial compression was improved.The strain energy and relative toughness of FA-SCC were increased by 99%and 128%respectively when the content of fly ash was 50%.The influence of steel fiber on the compressive strength of SF-SCC was not obvious,but the flexural-tensile strength and axial compression deformation performance were improved significantly.When the volume fraction of steel fiber was 1.00%,the splitting tensile strength,flexural strength,strain energy and relative toughness of SF-SCC were increased by 61%,29%,83%and 40%respectively,and the elastic modulus was the smallest when the volume fraction of steel fiber was 0.50%.The compressive strength and modulus of elasticity of SFFA-SCC were reduced obviously by replacing part of cement with fly ash.The influence of steel fiber on the compressive strength of SFFA-SCC was not obvious,but the flexural-tensile strength of SFFA-SCC was improved significantly.The modulus of elasticity basically increased first and then decreased with the increase of steel fiber volume fraction.When the content of fly ash was 40%and 50%,the strain energy and relative toughness of SFFA-SCC were improved significantly,and the strain energy and relative toughness increased first and then decreased with the increase of steel fiber volume fraction.When the content of fly ash was 60%and 70%,the improvement effect of the strain energy and relative toughness of SFFA-SCC was not obvious.