Study On Salt Corrosion Resistance Of Polyvinyl Alcohol Fiber Concrete Under Saline Soil Environment In Aksu Area

In southern Xinjiang,the natural environment is harsh,the temperature difference between day and night is large,and the saline soil is widely distributed.As a result,many local concrete buildings,bridges,urban roads and other concrete projects suffer from multiple deterioration factors such as saline soil erosion,dry-wet cycles,and freeze-thaw cycles all year round.The coupling effect causes different degrees of corrosion and damage to the structure.The maintenance and reinforcement caused by this consumes a lot of financial and material resources,which seriously restricts the rapid development of the local economy and society.In this paper,combined with the climate environment and soil characteristics of the Aksu area in southern Xinjiang,6 kinds of polyvinyl alcohol fibers（PVA fibers）with different volume dosages（0.0%,0.1%,0.2%,0.3%,0.4%,0.5%）were developed.Comparative test of cube compressive strength,Flexural strength and splitting Tensile strength of Concrete at 3d,7d and 28d age respectively.At the same time,four kinds of PVA fiber reinforced concrete specimens with different volume contents（0.0%,0.1%,0.2%,0.3%）were carried out under the coupling action of different concentrations of complex salt solution（Na₂SO₄+Na CL）erosion,drying-wetting cycle and freeze-thaw cycle Corrosion deterioration test,and SEM,XRD and EDS were used to analyze the microstructure characteristics of PVA fiber concrete during the test process,and to explore the influence of PVA fiber content on the basic mechanical properties and salt corrosion resistance of concrete in the extremely arid saline soil environment in southern Xinjiang.,to provide reference and reference for the practical engineering application of PVA fiber reinforced concrete in southern Xinjiang.The conclusions of this study are as follows:（1）The experimental results of mechanical properties show that the addition of PVA fibers will reduce the cubic compressive Strength of concrete,and the greater the dosage,the greater the reduction.The ratios are1.4%,2.5%,7.9%,9.8%,and 15.3%in sequence;however,the flexural strength and splitting tensile strength of concrete can be significantly improved when PVA fibers are added,and the optimum fiber content is 0.3%.,compared with the PVA-0.0%specimen,the f Lexural strength and splitting tensile strength of the specimen were increased by 3.9%and 22.17%,respectively.（2）The durability test results show that the incorporation of PVA fibers can significantly improve the salt corrosion resistance and salt-freezing resistance of concrete.With the increase of solution concentration,the relative dynamic elastic modulus and mass loss rate of the specimen with a fiber content of 0.3%fluctuated the smallest.The denudation degree of the surface mortar of the specimen is the lightest,and its macroscopic durability performance is the most stable.（3）According to SEM scanning electron microscope image analysis,PVA fibers can effectively improve the internal structure of concrete,and the bridging effect of fibers enhances the tie-up ability between internal cracks in concrete,inhibits the expansion of micro-cracks,and reduces the generation of pores.The brittle failure of the PVA fiber reinforced concrete specimen was transformed into a ductile failure;it can be seen from the EDS energy spectrum and XRD diffraction analysis that under the erosion of the composite salt solution,the PVA fiber reinforced concrete undergoes physical salt crystallization corrosion and chemical corrosion damage,and the products are mainly ettringite（AFt）and gypsum,the incorporation of PVA fibers reduces the generation of corrosion products in the later stage of erosion,ensures the integrity of the concrete matrix,and enhances the salt corrosion resistance of concrete.