Experimental And Numerical Simulation Study On Curing Method Of Railway Concrete Bridge Pier

With the rapid development of our country railway industry,the number of railway concrete bridges under construction and to be constructed is increasing day by day.The temperature stress caused by the excessive internal surface temperature difference and the shrinkage stress caused by humidity consumption and diffusion of railway concrete piers make the surface of railway concrete piers prone to temperature and humidity cracks,which is important for the safety,reliability and durability of railway concrete piers.Railway concrete bridge piers have a complex temperature and humidity coupling field generated inside the structure under the combined effects of its own cement hydration heat,external environment temperature,humidity,and curing methods,resulting in difficulties in internal surface temperature difference the structure,maximum adiabatic temperature rise,and surface temperature.Therefore,it is particularly important to find a reasonable way of railway concrete maintenance to reduce the above-mentioned problems.In this paper,three curing methods of curing agent curing,geotextile curing,and curing film curing,were carried out on the concrete specimens.The macro-mechanical performance tests under two humidity conditions of RH=50% and RH=30% were tested,and different curing methods were tested.The influence of different curing methods on the hydration degree of concrete about the compressive strength,splitting tensile strength and elastic modulus of the concrete underneath combined with the chemical bound water test were explored.The test results show that the compressive strength and splitting tensile strength of the concrete specimens cured by the curing film curing are the best among the three curing methods,and the cement hydration is the most complete.The geotextile curing is the second.The strength and splitting tensile strength are the lowest at the concrete specimens cured by the curing agent compressively.At the same time,in order to simulate the actual state of railway concrete piers,all specimens were maintained in an upright manner.Research has shown that the concrete specimens under the geotextile curing method have a significant increase in humidity from top to bottom.The performance difference between the upper and lower parts of the specimen is obvious.The bottom part is better than the top specimen due to the higher relative humidity;the concrete specimen under the curing mode of curing agent and curing film is not significantly affected by the height.Secondly,through the COMSOL Multiphysics software,a three-dimensional solid finite element model of the railway concrete pier is established,and the internal temperature and humidity coupling field of the railway concrete pier is simulated.Comparing the first principal stress results of the pier temperature and humidity coupling under the four curing methods,it is found that the maximum tensile stress on the surface of the concrete pier under the curing film+ rubber-plastic board curing method is the smallest under the four curing methods.The next is the membrane,the curing agent is the largest,the geotextile is in the middle,and the concrete is the least likely to crack under the curing membrane + rubber-plastic board curing method,which is the best curing method for railway concrete piers.In order to study the effect of the difference on the initial curing time on the concrete piers,two modes were used to simulate the piers,which was the curing started after the concrete poured and at 7th day after the steel formwork was removed.It was found that under the same environmental conditions and curing methods,the surface tensile stress of concrete piers under the curing mode after the concrete poured was less than that of the concrete curing mode 7 days after the removal of the steel formwork under the four curing methods.Therefore,the piers should be cured in the first mode,and reasonable curing methods should be adopted as soon as possible.It will significantly reduce the maximum tensile stress on the surface of the railway concrete pier.Combined with the concrete test results and numerical simulation results,it can be seen that the curing film + rubber-plastic board curing method is the best curing method for railway concrete piers,because it not only has a thermal insulation effect on railway concrete piers,but has a good moisturizing effect.So it can provide a strong reference basis for the curing of railway concrete piers.