| Corrosion of steel bars in concrete not only causes huge economic losses,but also is one of the main influencing factors for the change of residual bearing capacity and service life of reinforced concrete structures.Nowadays,mineral admixtures have better environmental protection functions.The advantages of economic saving and improvement of concrete characteristics have been widely applied in the fields of ports and offshore structures.In this paper,the rusted steel bars in fly ash concrete and ordinary concrete are taken as research objects,and different types(light round bars and threaded bars)and steel bars of different diameters(8mm,12 mm and 16mm)are considered,and the steel bars are designed to prevent the ends of the bars.The rusting method was carried out to accelerate the rust test,and the corresponding rusted steel test pieces were obtained.Based on this,the following work was carried out:(1)Three-dimensional scanning of corroded steel bars in fly ash concrete and ordinary concrete,and statistics and arrangement of pit parameters(depth D,lateral width W,longitudinal length L)of corroded steel bars.The test data show that the distribution of the remaining crosssectional area of corroded steel bars in fly ash concrete is relatively small compared to ordinary concrete,and the distribution is relatively uniform.The frequency of corrosion pit parameters on the surface of rusted steel bars in ordinary concrete is greater than that of fly ash concrete.As the degree of corrosion of steel bars deepens,the frequency of the depth of pits on the surface of rusted steel bars in ordinary concrete increases compared to fly ash concrete The amplitude is significant,and with the increase of the degree of corrosion,the frequency distribution of pit parameters of corroded steel bars in fly ash concrete and ordinary concrete gradually changes to an approximately normal distribution.(2)The axial tensile test of the steel bars after the derusting is completed.The test results show that when the degree of corrosion of the steel bars is low(the mass loss rate is less than 4%),the load displacement curve of the corroded steel bars is smaller than that of the original steel bars.And the yielding steps are obvious.With the deepening of the degree of corrosion(the mass loss rate is more than 4%),the load-displacement curves of the corroded steel bars in ordinary concrete and fly ash concrete have changed greatly,that is,the ultimate load and the yield load are obviously increased with the deepening of the corrosion.The reduction of the yielding step platform presents a shortening trend.For the same type of steel bars of the same diameter,the load-displacement curves of the corroded steel bars in ordinary concrete and fly ash concrete have certain differences,which are manifested in the ultimate load degradation rate of rusted light steel bars in ordinary concrete compared with fly ash concrete.The ultimate load of the corroded steel bar is degraded by 2.1%,that is,the bearing capacity of the corroded steel in the fly ash concrete decreases at a slower rate than the falling capacity of the corroded steel bar in ordinary concrete.(3)After observing and comparing the laws between mechanical properties degradation and maximum section corrosion rate of corroded steel in fly ash concrete and ordinary concrete,it was found that the main indexes of mechanical properties of corroded steel in fly ash concrete and ordinary concrete(There is a good linear law between nominal yield strength,nominal ultimate strength and elongation after fracture)and maximum corrosion rate.For the same type of steel bars,the degradation rate of mechanical properties of corroded steel bars in ordinary concrete is faster than that of corroded steel bars in fly ash concrete.The nominal ultimate strength degradation rate is the fastest,and the elongation after fracture is the second.The rate of degradation of yield strength is the slowest;for the same kind of concrete material,the degradation rate of mechanical properties of corrugated steel bars after rusting is much faster than that of reinforced bars,where the nominal ultimate strength and yield strength degrade at the highest speed,and the elongation at break is less.(4)The ANSYS finite element software is used for numerical simulation of the corroded steel bars based on the test data.The specific parameters of the ellipsoidal pit are discussed: the depth of the pit is 0.5 ? 2mm,the width of the pit is 1.5 ? 4.5mm and the length of the pit is 5 ? 20 mm.The effect on the corroded steel bar when changing within a range of 20 mm.It is found that as the depth of the corroded pit increases,the peak stress near the rust pit on the corroded steel bar increases greatly;as the lateral width of the corroded pit increases,the stress near the rusted pit The peak increase is small;with the increase of the longitudinal length of the pit,the stress peak near the rust pit on the surface of the rusted steel bar decreases.And with the increase of pit depth and lateral width,the stress concentration coefficient tends to increase.Among them,as the pit depth increases,the stress concentration coefficient increases the most;as the longitudinal length of the pit increases,the stress concentration coefficient decreases.Small trends.It shows that the depth of the surface corrosion pit has the most significant effect on the stress concentration after the steel bar is corroded,and the lateral width and longitudinal length of the corrosion pit have less effect. |
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