Study On Bond Property Of Fly Ash Concrete And Steel Bar After High Temperature

The bonding performance of steel bar and reinforced concrete had a great influence on the overall structure when reinforced concrete structure experienced fire. As a kind of concrete admixture, fly ash has effect on the mechanical properties of concrete and reinforcing steel bar and the bonding performance of fly ash concrete.In this paper, the bonding performance of fly ash concrete and the steel after high temperature under the monotonic load was researched, the main contents were presented as follows:Test was carried out to study fly ash concrete after high temperature compressive strength and splitting tensile strength, analyzes the factors such as the hot temperature, cooling way, the dosage of fly ash on the concrete compressive strength and splitting tensile strength of fly ash. The results show that the change rules of fly ash concrete compressive strength and splitting tensile strength have some variation. When T ≤350℃ compressive strength rise with temperature rising and T > 350℃ compressive strength falls with temperature rising; Water spray cooling weaken the strength of fly ash concrete after high temperature; The dosage of fly ash fly ash concrete after high temperature impact is not big.Studied on the compressive strength and the splitting tensile strength of fly ash concrete of early age after high temperature and compared with the benchmark concrete. The results show that the fly ash is not conducive to the development of the strength of fly ash concrete of early age(less than 28d), but the curing age greater than 28 d, the compressive strength of fly ash concrete developed rapidly and 20% dosage of fly ash concrete have the highest strength of concrete.The compressive strength about 20% dosage of fly ash concrete after high temperature and standing were studied, analyzes the factors such as high temperature, high temperature age, cooling ways on the compressive strength of fly ash concrete. The results show that the concrete contains fly ash later to resist the ability of the temperature damage;the effect of high temperature ages on natural cooling and water cooling specimens have some variation, the compressive strength of the specimens heatedat 28 th day and stand to 90 th achieves maximum; Spray cooling is conducive to the development of the strength of early age of fly ash concrete after high temperature.The bonding performance of the steel and fly ash concrete after high temperature under the monotonic load was researched, analyzes the hot temperature, cooling way, with or without stirrups and the time for standing and other factors on the ultimate bond stress and the ultimate bond displacement of fly ash concrete between steel bar. The results show that the ultimate bond stress of steel bars and fly ash concrete with high temperature and its temperature changing law is similar to the strength of fly ash concrete with the development of the high temperature; Spray cooling reduce the ultimate bond stress between fly ash concrete and steel bar but ultimate displacement increases; the stirrup improve the bonding performance between the fly ash concrete and reinforcing steel bar; the fly ash concrete heated at 28 th and standing to 90 th has the supreme ultimate bond stress recovery degree, its ultimate bond stress reach maximum and its ultimate bond displacement reach minimum.Finally, SEM analysis was carried out on the fly ash concrete specimens after high temperature and XRF analysis of fly ash concrete are analyzed from the microscopic view of high temperature on mechanical properties and the effect on the properties of fly ash concrete and reinforcing steel bar binding mechanism.