Study of the Dynamic Splitting Tensile Mechanical Properties and Damage Evolution of Steel Fiber-Reinforced Recycled-Aggregate Concrete Based on Acoustic Emission Technology

Aiming at effectively utilizing recycled coarse aggregate (RCA) in sustainable construction, it is necessary to study the internal damage evolution of steel fiber-reinforced recycled-aggregate concrete (SFRAC) under dynamic tensile loads and the reinforced mechanism of steel fiber. The influences of the steel fiber content, the recycled-aggregate replacement ratio, and the loading rate on the mechanical properties and dynamic damage of SFRAC were studied using the Brazilian disc splitting test and acoustic emission (AE) technology. Then, the mechanism of crack evolution was investigated by means of the parameter analysis method. The results indicate that the existence of RCA makes the mechanical properties of recycled-aggregate concrete worse than those of normal concrete and weakens the strain rate effect of splitting tensile strength, whereas this negative influence can effectively be improved by steel fiber. The preferable steel fiber contents obtained from the splitting tensile strength and peak displacement are 1.0% and 1.5%, and under these conditions, the SFRAC replaced by 30% RCA has a mechanical performance superior to that of normal concrete. It is also found that the damage degree and energy absorbing capacity of SFRAC can be identified by analyzing the ring and energy counts of the AE signal. Furthermore, the evolution of the crack pattern of SFRAC under dynamic axial tensile load is well reflected by the rise angle and average frequency. Increased steel fiber content and recycled-aggregate replacement ratio can change the failure mode to a complex tensile-shear mixed failure, and the shear crack gradually becomes the main crack with increasing loading rates. The public environment crisis from the greenhouse effect led to a series of measures from all industries worldwide. The widespread use of concrete has brought with it serious environmental and energy-saving problems. The construction industry preliminarily attempts to replace natural aggregate by recycled aggregate obtained by crushing construction solid waste in green low-carbon buildings, which shows considerable carbon sequestration and emission reduction. However, recycled aggregate has poor mechanical properties such as low strength and high porosity. When participating in concrete configuration, this defect seriously affects the strength of the material and limits its wide application in construction engineering. For a component with strength requirements or special purposes, fiber can be adopted to improve the mechanical properties of recycled-aggregate concrete. This study examines the damage process of fiber-reinforced recycled-aggregate concrete with the microscopic method and proposes a satisfactory mix proportion. Naturally, these analysis methods require more time and effort than a basic macroscopic analysis. Moreover, proper research on the mechanism of damage evolution under dynamic loading is crucial.