Study On The Erosion Wear Of Concrete And Protective Material

Erosion is a material loss phenomenon or process in which loose particles of liquid orsolid impact surface of the material at a certain speed or angle. It is widely found inmachinery, metallurgy, energy, building materials, aviation, aerospace and many otherindustrial sectors, and has become one of the important reasons for material damage orequipment failure. The second double-track for Lanzhou-Xinjiang railway pass through thefive strong wind area, in which the wind power is strong and sustain for a long time annually.When the wind speed is greater than the limited speed, the windward side of bridge pier issubjected to the action of wind pressure and the impact of sand, inducing cement spalling andthe tiny crack of cement and aggregate interface quick extension, which accelerate injuries ofconcrete, such as carbonation, chlorine salt damage, freeze-thaw damage, thereby severelyreducing the durability of concrete structures. Therefore, the study of erosion of concrete andprotective material has obvious practical significance for protection of concrete structures inareas with a strong sandstorm.The erosion wear tests of concrete and protective material are carried out by sediment-airinjection method, which can simulate the gobi wind-sand flow environment and is a idealexperimental method compared with the wind tunnel test, because of low cost and simple andeasily controlling the experimental parameters. The effects of erosion velocity, erosion time,impacting angle and the flow rate of sand on the erosion rate of the sample are studied and theerosion rules and mechanisms of concrete and epoxy composites are discussed. The singleparticle erosion process of cement and epoxy are simulated by ANSYS-Dynamic software,which prove that the random vibration during the collision accelerates erosion damage ofmaterials.The experiment results of this dissertation are as follows:(1) The compressive strength of samples have influences on erosion rates, but not thedeciding factor. The erosion rates of samples have closed relationship with the structure ofsamples.(2) The relationship between the erosion rates of concrete, mortar and cement paste andwind-sand flow velocity is approximately linear. Slope of mortar specimen is the largest，andlowest for cement paste and in the middle for mortar. it is most serious erosion damage,theslope of cement is the smallest,erosion damage is the lightest,erosion of concrete specimencentered.(3) The erosion rates of Concrete, mortar and cement are highest at90°impact, andlowest at low impacting angle, which was consistent with traditional brittle material erosionlaws. (4) The cement and concrete erosion rate decrease when the flow rate of sand increases.However, the erosion rates of mortar firstly decrease and then increase. The erosion rate ofconcrete and cement decrease with erosion time and then attain stabilization, for mortar keepstabilization from the beginning.(5) With the increase of the amount of fly ash in concrete, the erosion rates of concretefirstly decrease and then rise. However, the erosion rate of concrete gradually decreased withthe extension of the curing time.(6) The relationship between the erosion rates of epoxy resin, glass fiber reinforced epoxycomposites and carbon fiber reinforced epoxy composites and wind-sand flow velocity isapproximately linear too.(7) The epoxy and its composites indicate semi ductile erosion behaviour, with peakerosion rate at45-60°impingement angle. But glass fiber reinforced epoxy composites tend tobrittle compared to carbon fiber reinforced epoxy composites, with peak erosion rate at60°impingement angle.(8) The erosion rate of epoxy and its composites is approximately1/5~1/20of the concreteand cement paste erosion rate at the same condition. Therefore, it is a ideal material forconcrete bridge pier protection under gobi wind-sand flow environment.(9) The single particle erosion processes of cement and epoxy are simulated by ANSYSsoftware. Results show that stress variation of collision course is random vibration. Withimpact velocity increasing, the maximum stress increases. As reducing the impact angle, themaximum stress reduce, and stress decay time becomes longer. The amplitude and frequencyof random vibration for cement stress curve is greater than the epoxy′s.