Experimental investigation of the stress-strain behavior of concrete produced with natural perlite aggregate and waste materials

The replacement of conventional aggregates in concrete with alternative and waste-based materials has become an important research area for sustainable construction. This study experimentally investigated the effects of natural perlite aggregate replacement and fiber reinforcement on the mechanical and microstructural properties of concrete. Natural perlite aggregate was used to replace conventional crushed stone aggregate at replacement levels of 0%, 30%, 70%, and 100%, while hemp shives, recycled plastic waste fibers, and polypropylene (PP) fibers were incorporated at volume fractions of 0.0%, 0.5%, 1.0%, and 1.5%. After 28 days of curing, compressive strength, modulus of elasticity, flexural strength, splitting tensile strength, ultrasonic pulse velocity (UPV), compressive stress–strain behavior, and scanning electron microscopy (SEM) analyses were performed. The results showed that 30% perlite replacement increased the compressive strength and modulus of elasticity by approximately 6.67% and 4.08%, respectively, compared with the reference mixture. In contrast, replacement levels of 70% and 100% reduced the mechanical performance due to the porous structure of perlite and the weaker interfacial transition zone. Among the fiber-reinforced mixtures, the optimum fiber content was found to be 1.0%, while PP fibers provided the best overall performance in terms of crack-bridging ability and energy absorption. Overall, the combination of 30% natural perlite aggregate replacement and 1.0% PP fiber was identified as an effective approach for producing low-carbon concrete with balanced mechanical properties.