Surface-Modified Steel Fiber Concrete Preparation And Performance Study

Steel fibre reinforced concrete(SFRC)is a composite material composed of concrete and steel fibres.It exhibits excellent strength and durability which can also meet the requirements of various construction projects.It is widely used a high-performance building material at present.Steel fibres are easily dispersed in the concrete preparation process and work with aggregates to fill cracks and assume an essential role in supporting the structure.Traditional steel fibre reinforced concrete shows the problem of low utilization rate of steel fibre strength.When the steel fibre-reinforced concrete structure is damaged,the damage form is mostly the slip pullout of steel fibre,which causes the pullout load to be much smaller than the load corresponding to its tensile strength.At the same time,with the increasing application of steel fibre concrete in bridge engineering,road engineering,water conservancy engineering,the problem of corrosion of steel fibres in concrete has also became prominent.In the present work,a silane coupling agent was used to modify the surface of steel fibre.Mechanical performance test and corrosion resistance test was performed on the modified steel fibre.The main research contents and conclusions are as follows:(1)The modified solution was prepared with KH-550 and TEOS as the substrate.A dense organic silicon composite coating was prepared on the surface of steel fibre by the sol-gel method,which improved the weak layer between steel fibre and cement-based material.It improved the adhesion between them to achieve a better bonding effect.The fibre drawing test was carried out by controlling the relative proportion of silane coupling agent KH-550 and tetraethyl silicate TEOS in the modified solution as the control group.When the molar ratio of KH-550 and TEOS is 3:1,a protective coating with good surface morphology could obtain high flatness and strong adhesion.From the macroscopic point of view,the bonding properties of steel fibre and concrete interface are studied.The experimental results show that the effect of KH-550 and TEOS hybrid solution can significantly improve the surface roughness of steel fibre.When the ratio of KH-550 and TEOS is higher,the steel fibre drawing test results will be improved,but there will be a downward trend in the end.The coating obtained when the relative ratio is 3:1 has the most significant effect.(2)The compressive strength,splitting tensile strength and bending toughness of modified steel fibre-reinforced concrete increase with the amount of admixture,and the growth ratio of mechanical properties is roughly in the form of a convex curve when the amount of modified steel fibre admixture exceeds 1.5%,the mechanical properties of the increase is minimal,and the loss of work performance is more serious.The 1.5%admixture of modified steel fibre concrete in the case of retaining good work performance.All the mechanical properties are higher than those of ordinary steel fibre concrete at 2.0%admixture,which can be used in practical engineering applications to replace standard steel fibres with low-cost modified steel fibres,thus reducing the fibre admixture and achieving cost savings.Considering the workability,compressive strength,splitting tensile strength and bending toughness of modified steel fibre reinforced concrete,the recommended dose of modified steel fibre for construction is 1.5%.(3)To address the problem of poor corrosion resistance of steel fibre concrete,the effect of surface modification on the compressive strength,flexural strength and bending toughness of steel fibre concrete under different corrosive environments(NaCl solution,Na2SO4 solution and HCl solution)was investigated by accelerated corrosion tests in dry and wet cycles.The corrosion mechanism of modified steel fibre reinforced concrete was discussed by comparing it with the whole steel fibre group and modified steel fibre water in the same environment.The results show that when the corrosion time reaches 120 days,the surface rust of unmodified steel fibre is evident,and the mechanical properties are seriously lost.The influence degree of corrosion medium is HCl>Na2SO4>NaCl.The surface rust of modified steel fibre reinforced concrete is almost no,and the mechanical functional strength is maintained well in different corrosion environments.