Experimental Study On Salt Corrosion Damage Deterioration Of Polyvinyl Alcohol Fiber Concrete

Saline soil is widely distributed in Aksu region of Xinjiang,for many years,which leads to serious corrosion damage factors such as salt erosion and dry and wet cycles for many concrete buildings(structures)in this region.The service life of building is significantly shortened,which brings heavy economic burden to the healthy and rapid development of local economy and society.Therefore,combining with the climatic environment and salted soil characteristics in Aksu region,in this paper,the indoor salt corrosion-dry-wet cycle test and on-site exposure test of concrete with different amount of polyvinyl alcohol fiber(0%,0.1%,0.2%,0.3%)was carried out,and the early age cube compressive strength of polyvinyl alcohol fiber concrete under four volume admixture was compared and analyzed.The microstructure and mineral composition of corrosion products of concrete specimens during the test process was analyzed by using XRD,SEM and EDS microscopic and mineral test techniques,so as to reveal the salt damage inferior mechanism of polyvinyl alcohol fiber concrete.Moreover,in combination with accelerated test,and to provide reference for solving the salt corrosion problem of engineering structural concrete in this area.The main research contents and conclusions of this paper are as follows:(1)The experimental results of cube compressive strength in early age show that with the increase of admixture,the cube compressive strength of concrete specimens is not directly proportional to the increase of fiber admixture,however,it will reduce the cube compressive strength of concrete when the fiber admixture is too high.Besides,reasonable polyvinyl alcohol fiber admixture will improve the compressive strength of concrete,and unreasonable fiber admixture will decrease it instead.The optimum volume admixture of polyvinyl alcohol fiber is 0.2%,and compared with the reference concrete after 7 days and 28 days of curing,its compressive strength is increased by 6.2% and 6.9%,respectively.(2)The results of composite indoor salt corrosion-dry-wet cycle test and on-site exposure test show that the concrete specimens produce various degrees of corrosion damage under various test environments,but the adding of of fibers strengthens the salt corrosion resistance of concrete,of which the concrete specimens with 0.2% polyvinyl alcohol fiber volume admixture present the best durability performance in indoor test and on-site test,meanwhile,under the four volume additives,the salt corrosion resistance of polyvinyl alcohol fiber concrete ranks from large to small is 0.2% > 0.3% > 0.1% > 0%.(3)According to the analysis of XRD test results,it is found that the corrosion products of concrete samples in indoor test contain the generation of ettringite(AFt)and gypsum,and only ettringite(AFt)is generated in on-site test due to the short exposure time of samples;SEM and EDS analysis show that the needle-like ettringite in the corrosion products is mainly concentrated in the inherent pores of polyvinyl alcohol fiber concrete,which makes the concrete more dense and enhances its salt corrosion resistance,while some ettringite leads to microcracks in the concrete samples due to its own expansion and excessive accumulation.