Investigation on Dynamic Mechanical Properties of Recycled Concrete Aggregate under Split-Hopkinson Pressure Bar Impact Test

The dynamic mechanical properties of recycled concrete (RC) and natural concrete (NC) were studied by impact tests and numerical simulation. The quasi-static tests were conducted by a servo-hydraulic machine, while the impact test used a 50 mm diameter split-Hopkinson pressure bar (SHPB). The ANSYS/LS-DYNA software simulation was selected to validate the experimental results. The recycled coarse aggregates (RCAs) came from the housing demolition and were conducted with the microwave-assisted beneficiation method. The stress-strain curves, compressive strength, dynamic increase factor (DIF), initial elastic modulus and failure modes were analyzed and discussed. The results showed that the quasi-static compressive strengths of the RC were lower than that of the NC by 5.0%. The maximum dynamic compressive strengths of the NC increased by 105.9% when the strain rates varied from 46-108, while the RC increased by 102.2% when the strain rates varied from 42 to 103. The stress-strain curves of the RC and NC demonstrated a similar pattern. The DIF showed an increasing tendency with the increasing of strain rates, while the initial elastic modulus showed a decreasing tendency. The failure modes first initiated from the edge of specimens and then propagated to the center of specimens. An empirical equation was proposed for the estimation of the DIF of the RC which was obtained from the microwave-assisted beneficiation. The simulation results for the prediction of stress-strain curves of the RC showed good agreement with the experimental results. In addition, these results suggested that the RCAs were obtained by the microwave-assisted beneficiation can be recycled and may be used in some actual engineering.

Automated summary

The dynamic mechanical properties of recycled concrete (RC) and natural concrete (NC) were studied using impact tests and numerical simulation. The results showed that the quasi-static compressive strengths of the RC were slightly lower than that of the NC, but the increase in compressive strength under dynamic conditions was similar for both. An empirical equation was proposed to estimate the dynamic increase factor (DIF) of the RC.