Residual fracture energy of natural and recycled aggregate concrete after exposure to high temperatures.

Fracture energy (GF) represents the average total energy consumed in the whole process of crack propagation. Using one parameter of GF, it is not sufficient to describe the fracture behavior during crack stable and unstable propagation periods. In this study, the GF, stable fracture energy (GFS) and unstable fracture energy (GFU) of natural and recycled aggregate concrete (RAC) were investigated by using three‐point bending tests. Totally, 128 cubic specimens (100 mm × 100 mm × 100 mm) and 64 notched beams with size of 510 mm × 100 mm × 100 mm were manufactured to test the compressive strength (fcu), splitting tensile strength (ft), load–deflection (P‐δ), and load‐cracking mouth opening displacement (P‐CMOD) curves, considering different replacement levels (0%, 30%, 70%, and 100%) of recycled coarse aggregate (RA) and high temperatures exposure (20, 100, 200, and 300°C). The effects of RA substitutions and temperatures on basic mechanical properties, GF, GFS, and GFU were analyzed. The results demonstrated that the fcu, ft, and elastic modulus (E) decreased with the incremental temperature. The GFS of concrete with different RA substitutions first decreased and then increased, and the minimum value appeared at 200°C. The GF and GFU of concrete with different RA substitutions increased with the elevated temperature, and the increase rate decreased with RA substitutions. When the temperature is less than 100°C, the GF and GFU of concrete remained mostly unchanged with the increase of RA substitutions, while the temperature reached 200 and 300°C, the GF and GFU of concrete increased and decreased with the increase of RA substitutions, respectively. [ABSTRACT FROM AUTHOR]