Experimental Study On Mechanical Properties And Durability Of Basalt Fiber Aeolian Sand Concrete Under Salt-frozen Environment

Concrete demand surge,the original rich river sand resources are facing a shortage,gradually unable to meet the needs of today,s infrastructure.There are abundant aeolian sand resources in the northwest of China,which have caused great damage to the local ecological environment.Aeolian sand concrete(ASC)is prepared by replacing common river sand with eolian sand.It has great significance in economy,ecological environment and sustainable development.As a new kind of environmental protection green concrete material,a series of problems have been exposed in its application.Aeolian sand can only replace engineering sand within a certain range,and have similar properties with ordinary concrete,such as easy cracking and shrinkage,poor toughness,frost resistance and chloride ion resistance,etc.making it difficult to be used in practical construction.In order to improve the coagulation performance of aeolian sand,the continuous basalt fiber(BF)with high elastic modulus,high tensile strength and good durability is added to solve the above problems,and the improvement of ASC has certain practical application value.Aeolian sand through the mixing quality such as river sand instead of ordinary concrete(replacement rate was 10%,20%,30%)preparation of ASC,the BF by volume fraction(0,0.05%,0.10%,0.15%,0.20%)join the ASC,research on cube compressive strength,flexural strength,splitting tensile strength,stress-strain curve relationship,salt resistance and cold resistance to chlorine ion corrosion,the influence of and through the analysis of scanning electronic microscope morphology.The results are as follows:ASC is prepared by replacing part of river sand with aeolian sand,and its compressive strength,splitting tensile strength and flexural strength can meet the requirements.The addition of fiber in ASC significantly increased the splitting tensile strength and flexural strength,while the increase of the compressive strength was not obvious.The aeolian sand plays a filling role,which makes the cement stone and the interface transition zone closer.Proper addition of BF can improve the microstructure of ASC,and the integrity and compactness of basalt fiber eolian sand concrete(BF-ASC)can be enhanced through the bite and friction between the fiber and eolian sand cement foundation stone.The ascending section of BF-ASC uniaxial full curve is similar to ordinary ASC.When fiber is added,the descending curve becomes smoother,the stress at convergence pointincreases,and the ductility increases.With the increase of fiber content,the compressive strength and elastic modulus of prism first increase and then decrease.The peak strain shows an upward trend.Finally,the constitutive equation of BF-ASC stress-strain curve is obtained by fitting.In the early stage of salt-freezing,the mass loss rate and the relative dynamic elastic modulus of ASC and BF-ASC grew slowly,and the growth rate accelerated with the increase of the number of times of salt-freezing.The addition of BF improves the resistance of ASC to salt-freezing denudation and reduces the mass loss in repeated salt-freezing cycles.The addition of BF can effectively resist chloride ion erosion,but the crack resistance of high-content fiber cannot offset the pore increase caused by its agglomeration effect,which will accelerate the diffusion rate.The damage of salt-freeze aggravated the diffusion property of chloride ions,especially the surface layer chloride ions.The deeper the degree of salt-freezing,the higher the free chloride ion content in the same erosion depth.The number of salt-freeze cycles was positively correlated with the diffusion coefficient of chloride ions.