Experimental Research On Mechanical Performance Of Recycled Coarse Aggregate Concrete Strengthened By Mechanical Method

In recent years,with the aggravation of pollution and the shortage of resources,the recycled concrete in construction industry is developed and applied all over the world.On the one hand,The recycling of waste concrete can reduce the consumption of natural aggregate in construction industry.On the other hand,it can also reduce the deterioration of the ecological environment caused by wasted concrete and ensure the sustainable development of human society.Ordinary recycled concrete performance is poor,it is difficult to meet the requirements of the actual engineering,so it is necessary to strengthen the ordinary recycled coarse aggregate.Compared with other methods,the mechanical strengthening method is more effective,simpler and lower cost.In order to apply the mechanical strengthening recycled concrete to the practical engineering,it is necessary to know the stress-strain curve.However,there is no research on stress-strain curves of mechanically strengthened recycled coarse aggregate concrete at present,So it is great significance to fill the gap of recycled concrete research in this aspect.In order to obtain the complete stress-strain curve,we compared the advantages and disadvantages of various test methods by literature review,reference to the previous test experience and repeating testing.we found a method which is matching the laboratory conditions.The rigid auxiliary frame is customized,and the way of use test machine and auxiliary frame are summarized in the process of testing.Finally,the stress-strain curve can be measured steadily.In this project,the ordinary recycled coarse aggregate is treated by multiple mechanical strengthening.Study on the physical properties of natural aggregate,ordinary recycled coarse aggregate,once mechanical strengthening recycled coarse aggregate and twice mechanical strengthening recycled coarse aggregate.Such as particle size,apparent density,bulk density,water absorption rate,crushing index and so on.It is found that mechanical strengthening has a significant reduction effect on crushing index and water absorption of recycled coarse aggregate.The performance differences of natural concrete,ordinary recycled coarse aggregate concrete and mechanical reinforced recycled coarse aggregate concrete were studied with two water binder ratios of 0.5 and 0.35 and four kinds of substitution rates of 30%,50%,70% and 100% as variables.The uniaxial compression test of concrete is completed by electro-hydraulic servo pressure testing machine and rigid auxiliary frame.In the process of experiment,we can observe the whole process of specimens' force and deformation.After completion of the test,we summarized that the failure modes of different types of concrete specimens are vertical cracks,vertical oblique cracks,diagonal cracks,diagonal cracks and mid oblique cracks.We also obtained the stress-strain curves of different kinds of concrete specimens by processing the data.we summarized the effects of water binder ratio and substitution rate on curve characteristic parameters and curve shape by comparing the obtained curves.In order to establish the model of stress-strain curve in this article,We compare the full curve models proposed and used by scholars,and find the two section full curve model of Zhenhai Guo is most suitable for the curve fitting in this paper.Finally,the model is used for curve fitting and the parameter of fitting are compared.