Effects of modified bamboo aggregate on strength and microstructure of ceramsite concrete

To reduce the dependence of ceramsite concrete on ceramsite resources and alleviate the environmental impact of ceramsite production, this study investigates the performance of modified bamboo aggregate (MBA) as a novel sustainable lightweight aggregate in ceramsite concrete at different volume substitution rates (0 %, 5 %, 10 %, 20 %, 30 %, and 40 %). Cube compressive strength tests, splitting tensile tests, and cylindrical compressive strength tests were conducted to systematically evaluate the effects of MBA replacement on the mechanical properties and failure modes of ceramsite concrete. The results show that traditional ceramsite concrete exhibits brittle failure, while crack propagation is effectively inhibited with increasing MBA substitution. When the MBA substitution rate rises from 5 % to 40 %, cube compressive strength increases by 2.2–10.9 %, splitting tensile strength increases by 4.0–28.0 %, and the peak strength and elastic modulus of cylindrical specimens improve by 10.1 % and 37.9 %, respectively. However, the increase in splitting tensile strength tends to plateau beyond a 20 % substitution rate. As the MBA substitution rate increases from 0 % to 40 %, the compressive toughness index of cylindrical specimens rises from 1.76 to 2.23, representing a 26.7 % improvement, indicating enhanced energy absorption and fracture resistance under compression. To further quantify the mechanical constitutive behavior of MBA ceramsite concrete, axial compression stress-strain curves of cylindrical specimens at different substitution rates were analyzed, and a predictive model for the complete stress-strain relationship was proposed. Finally, fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses revealed microstructural changes at the interface between MBA and the cement matrix. Modified bamboo aggregate significantly enhances the mechanical properties of ceramsite concrete.