High-strain rate compressive and tensile behavior of concrete with substituted Polyamide sand

This study presents the first investigation on the high-strain rate compressive and splitting tensile behavior of Recycled PolyAmide sand Concrete (RPAC). Polyamide (PA) granules were adopted to substitute fine aggregates at three levels: 10%, 20%, and 30% by volume. Compressive and splitting tensile tests were conducted using a conventional quasi-static loading machine and a 80 mm-diameter Split Hopkinson Pressure Bar (SHPB), with strain rates up to 250 s−1 for compressive tests and 6 s−1 for splitting tensile tests. The incorporation of PA granules led to a reduction in compressive and tensile strength across all substitution levels, with a maximum decrease observed at 30% substitution. However, this was accompanied by an improvement in ductility and energy dissipation capacity. The dynamic tests indicates a significant influence of strain rate on the mechanical properties of RPAC. A high-speed camera captured damage development during dynamic tests. Experimental results were used to determine the compressive and splitting tensile Dynamic Increase Factor (DIF). Furthermore, an analysis of image-based damage development processes was conducted using high-speed camera footage showing a unique damage development processes in RPAC, indicating a distinct mechanism of energy absorption and dissipation. This study reveals that RPAC exhibits significant strain rate sensitivity within the tested range. The substitution of PA granules considerably reduces strength but enhances ductility improving dissipation energy performances.