Study On Corrosion And Deterioration Of Polypropylene Fiber Concrete In Saline Soil Environment In Southern Xinjiang

Salt erosion damage is one of the main reasons for the reduction of concrete durability.Concrete structures serving in southern Xinjiang are often damaged by extreme desert climates and saline soils,causing concrete to corrode and peel from the surface to the inside,and even corrosion of steel bars.,resulting in reduced structural durability and reduced bearing capacity.Incorporating polypropylene fiber(PP fiber for short)into concrete can effectively improve its mechanical properties and durability.With the improvement of construction technology,PP fiber concrete is more and more widely used in engineering practice.Therefore,it has important theoretical and engineering value to carry out the experimental research on the salt corrosion resistance of PP fiber reinforced concrete in the saline soil environment of southern Xinjiang.The main findings of this study are as follows:(1)The influence of PP fibers with different volume contents(0%,0.1%,0.2%,0.3%,0.4%,0.5%)on the basic mechanical properties of early-age concrete was tested and analyzed by SEM scanning electron microscope.The distribution characteristics of fibers in the specimen were studied,and the influence of fiber content on the early mechanical properties of concrete was studied.The test results show that the optimal dosage of PP fiber to improve the compressive strength of concrete cubes at early age is 0.2%,which is 38.82% higher than the corresponding strength of specimens with a dosage of 0%.The optimum dosage of strength and flexural strength are both 0.3%,which are 30% and 18% higher than the corresponding strength of the specimen with 0% dosage,respectively.(2)By carrying out PP fiber concrete composite salt erosion-dry-wet cycle tests with different volume dosages(0%,0.1%,0.2%,0.3%),the fiber dosage,compound salt solution concentration,and dry-wet cycle times are The main factors were investigated,and the changes of the apparent morphology,mass loss and dynamic elastic modulus of PP fiber reinforced concrete specimens under the action of salt erosion-dry-wet were analyzed.The test results show that the addition of PP fiber makes the mass loss rate and the relative dynamic elastic modulus decrease rate of the concrete specimen after the composite salt corrosion test slow down,and the PP fiber concrete specimen is resistant to salt corrosion under the four volume dosages.The dosages from strong to weak are as follows: 0.2%>0.3%>0.1%>0%.(3)By carrying out PP fiber concrete composite salt erosion-freeze-thaw cycle tests with different volume dosages(0%,0.1%,0.2%,0.3%),the fiber dosage,composite salt solution concentration,and freeze-thaw cycle times are The main factors were investigated,and the changes of the apparent morphology,mass loss and dynamic elastic modulus of PP fiber reinforced concrete specimens under the action of salt erosion-freeze-thaw cycles were analyzed.The test results show that the addition of PP fiber can effectively reduce the decline rate of the mass and dynamic elastic modulus of concrete specimens after salt freezing.The dosage from weakest to weaker is: 0.2%>0.3%>0.1%>0%.(4)Using SEM scanning electron microscope,EDS energy spectrum and XRD diffraction and other microscopic and mineral composition testing techniques,the microstructure and corrosion product composition of PP fiber concrete specimens after the salt corrosion test were analyzed.The test results show that: the incorporation of PP fiber The compactness of the interior of the concrete is improved,and the compactness of the specimen with a volume content of 0.2% is the best;with the increase of the concentration of the compound salt solution,the corrosive products generated gradually increase,resulting in the damage from the surface to the inside of the concrete.