Research On Dynamic Mechanical Properties Of Recycled Concrete Aggregate In Split Hopkinson Pressure Bar Experiment Test

The rapid development of civil engineering industry has produced a large amount of construction waste,the lack of recycling leads to serious environmental pollution and waste of resources.In order to realize reasonable cyclic utilization of construction waste,this paper handled the waste concrete and cleaned out the recycled coarse aggregate,reprocessed and prepared into recycled concrete.Building explosion accidents often happened in recent years,when the concrete structure was subjected to impact,it is prone to deform or even overall destroy and collapse,this will lead to all kinds of inestimable losses.So it is necessary to study the dynamic mechanical properties of recycled concrete under impact,and verify its application value in engineering practice.This paper adopts the research methods of experiment and numerical simulation,the dynamic mechanical properties of C30 and C40 strength classes of recycled concrete and ordinary concrete were tested by using Xi ’an university of science and technology rock dynamics laboratory 50mm rod diameter Hopkinson pressure bar device,and using ANSYS/LS-DYNA simulation software to simulate the dynamic impact process of concrete.The main contents and conclusions are as follows:(1)The compressive strength and failure modes of C40 strength grade ordinary concrete and recycled concrete were studied experimentally,experimental results showed that the failure modes of two concrete are similar,the static compressive strength of recycled concrete is slightly lower,the main failure form of the two concrete is the damage of cement mortar.(2)The dynamic mechanical properties of recycled concrete with two strength grades of C30 and C40 were tested under impact pressure of 0.1～0.5MPa,It is found that the dynamic compressive strength curves,stress-strain relations and waveform diagrams of recycled concrete under different strength grades are basically the same.The dynamic compressive strength increases with the increase of impact pressure,the dynamic elastic modulus decreases gradually,the higher the strength of concrete,the greater the dynamic compressive strength and dynamic elastic modulus,the smaller the waveform oscillation.(3)The dynamic characteristics of ordinary concrete under the same strength and impact pressure as recycled concrete were contrastively tested,it is found that the dynamic compressive strength curve,stress-strain relation curve and waveform diagram of ordinary concrete are basically the same as that of recycled concrete.But under the same strength,the dynamic compressive strength of ordinary concrete is slightly higher,the dynamic elastic modulus is also slightly larger,and the waveform oscillation is less.(4)ANSYS/LS-DYNA software was used to completely simulate the dynamic impact process of two kinds of concrete under the strength of C40,it is found that the simulation results of stress waveform diagram,stress-strain relation curve and failure process of concrete are basically consistent with the test results.Under the same strength and impact,the damage degree of recycled concrete is heavier,the stress peak is smaller and the elastic modulus is smaller.And the reliability of the experimental results is further verified.(5)The dynamic mechanical properties test results of two kinds of concrete were compared and analyzed,combined with numerical simulation results,it is found that in the case of low strength requirements,recycled concrete can basically replace ordinary concrete into engineering applications.