Research For Mechanical Performance Of Reinforced RAC Large Eccentric Compressive Columns Under Load Coupled With Chloride Environment

The application of RAC(recycled aggregate concrete)helps to promote the sustainable development of the civil industry,reinforced concrete columns have great influence on structural safety,it is significant to study the mechanical performance of reinforced RAC columns.However,the coastline of our country is very long.and the structure of the coastal area is not only loaded.,but also eroded by the marine environment dominated by chloride ion.In order to make RAC more widely used in practical engineering,the mechanical performance of reinforced RAC large eccentric compressive columns under load coupled with chloride environment is studied in this paper.The main research contents and results are as follows:1.Five factors are taken into account,the replacement rate of recycled coarse aggregate,strengthening treatment method of recycled coarse aggregate,proportion of nano-Silica,loading size and corrosion rate of steel,this paper is to design and fabricate 15 reinforced RAC large eccentric compressive columns,with the size of 180mm×180mm×1100mm,including control group.Imposing sustained load by mechanical force loading method,using surface coating method with external current to achieve accelerating corrosion of reinforcing steel bar,they are combined to simulate the environment of load coupled with chloride environment.After the corrosion,the rust expansion cracks of the component is depicted,then the bearing capacity test is carried out on the test machine to study the influence of various factors on the stiffness,bearing capacity,ductility,failure characteristics and strain development of components.And the actual corrosion rate of steel is measured after breaking the components.2.The results of corrosion test show that the number of rust expansion cracks and the actual corrosion rate of longitudinal steel increase with the increase of the replacement rate and loading size.With the increase of corrosion rate,the number and maximum width of rust expansion cracks are obviously increased,especially when the theoretical corrosion rate reaches 12%,the rust expansion cracks are serious.3.The results of bearing capacity test show that the stiffness.,bearing capacity and ductility decrease with the increase of replacement rate,but the change regulations with loading size are different.When the corrosion rate is more than 3%,the stiffness,bearing capacity and ductility of the component decrease with the increase of corrosion rate,but when the corrosion rate is not more than 3%,the stiffness,bearing capacity and ductility of the component are equivalent to the non corrosion component.4.when the recycled coarse aggregate is carbonized or soaked by nano-Silica slurry,the extent of rust expansion cracks and the actual corrosion rate of steel decrease,and the lateral stiffness,bearing capacity and ductility of the component are improved,and the modified effect of nano-Silica slurry soaking is slightly better than that of carbonization treatment.5.Nano-Silica mixing method is applied to study its effect of the improvement on the performance of RAC columns,the dosages are 0.5%.1.0%and 1.5%respectively.The results show that the three kinds of mixing can improve the rust expansion cracks of the components,reduce the actual corrosion rate of the steel,improve the lateral stiffness,bearing capacity and ductility of components,and the modified effect of the 1%dosages is the best,followed by 0.5%dosages.The 1.0%nano-Silica mixing method and the method of nano-Silica slurry soaking recycled coarse aggregate are used for comparison,the modified effect of the former is better than the latter.When making equal amount of concrete,the cost of nano-Silica produced by the former is only 41%of the latter.6.Observe the failure characteristics and strain development of components during the bearing capacity test.The results show that the overall failure characteristics of each component aer similar,and all of them belong to the ductile failure.The strain distribution of concrete satisfies the plane section assumption.The test results of bearing capacity are in good agreement with the calculation model of the bearing capacity of the corroded reinforced concrete large eccentric compressive column,and the theoretical values are partial to safety.