Experimental Study On Effect Of Chloride Salt Erosion On Properties Of Fiber Self-compacting Concrete

Self-compacting concrete has the advantages of good work performance and no need for external vibration,and it has been widely welcomed in engineering in recent years.A large amount of self-compacting concrete cementing material will lead to poor segregation resistance,poor ductility,poor tensile properties,and easy shrinkage and cracking in the early stage.Adding fibers can better improve the shrinkage phenomenon and tensile properties,and hybrid fibers can achieve a better overall effect;fibers will change the internal microstructure of the concrete and affect the durability.Chloride corrosion is an important topic of concrete durability.At present,there is relatively little research on the resistance of fiber self-compacting concrete to chloride salt corrosion.Based on previous studies,polypropylene fibers and steel fibers were selected as added fibers,and the fiber self-compacting concrete was tested for performance,compressive strength,split tensile,and flexural tests.Effect of compressive puckin g strength.The effects of soaking time,fiber types,and carbonization on the resistance to corrosion by chloride salts of self-compacting concrete were studied through carbonization test,chlorine salt immersion test,and micro-test on fiber concrete.(1)A total of 16 groups of 0.1%,0.15%,and 0.2%polypropylene fiber self-compacting concrete,0.2%,0.4%,and 0.6%of steel fiber concrete and two kinds of mixed self-compacting concrete Slump test,J-ring test and V-shaped funnel test.It is found that in addition to SF60PP00,the other groups of concrete meet the requirements of self-compacting concrete for work performance.(2)The results of compression and tensile test of fiber-reinforced concrete show that polypropylene fiber and steel fiber have better effects on improving the tensile strength,but the effect of improving the compressive strength and flexural strength is not obvious.Among them,the steel fiber has a compressive strength on self-compacting concrete.The effect of increasing strength and tensile strength is stronger.Hybrid fibers can significantly increase the tensile strength,and have positive and negative effects on the compressive strength and flexural strength of self-compacting concrete.When the steel fiber content is 0.6%and polypropylene fiber content is 0.15%,the tensile strength reaches a maximum of 5.31 MPa.(3)The results of compression and tensile test of fiber-reinforced concrete show that polypropylene fiber and steel fiber have better effects on improving the tensile strength,but the effect of improving the compressive strength and flexural strength is not obvious.Among them,the steel fiber has a compressive strength on self-compacting concrete The effect of increasing strength and tensile strength is stronger.Hybrid fibers can significantly increase the tensile strength,and have positive and negative effects on the compressive strength and flexural strength of self-compacting concrete.When the steel fiber content is 0.6%and polypropylene fiber content is 0.15%,the tensile strength reaches a maximum of 5.31 MPa.(4)After quick carbonization of ordinary self-compacting concrete and fiber self-compacting concrete,chlorine salt soaking is performed.The test results show that carbonization can improve the resistance to chloride salt erosion of self-compacting concrete,increase the tensile strength of self-compacting concrete under the combined action of carbonization and chloride salt,and reduce the free chloride ion content and diffusion coefficient of self-compacting concrete.(5)The SEM test and XRD phase analysis showed that chloride salt soaking and carbonization can change the internal microstructure and phase composition of concrete.In the case of chloride salt soaking,chloride ion and concrete hydration products form Friedel salt,which fills the pores inside the concrete.The carbonization reaction reduces the formation of Friedel salts.At the same time,the formation of CaCO3 from CO2 and Ca(OH)2 can attach to the hydration products,compact the internal structure,and improve the concrete's resistance to chloride attack.Figure 40 table 13 reference 78...