Mechanical and Fracture Properties of Hybrid Fiber-Reinforced Concrete with Variable Recycled Aggregate Content

Rapid urban development has significantly increased construction waste, contributing to the depletion of natural resources and environmental degradation. As a result, the use of recycled aggregates has gained global attention as a sustainable alternative in construction materials. In the current study, experimental tests were performed on ۷۲ samples where the coarse normal aggregate was replaced by ۰%, ۲۵% and ۵۰% by volume with coarse recycled aggregate. Furthermore, the test samples comprised four types of specimens with Polypropylene fibers (PP) and steel fibers, including with no fibers, with ۰.۴% PP and ۰% steel fibers, with ۰.۴% PP and ۰.۵% steel fibers, and with ۰.۴% PP and ۱.۰% steel fibers, wherein all ratios are volumetric. This study investigated the energy absorption and ductility of notched recycled concrete beams reinforced with hybrid combinations of polypropylene and steel fibers under three-point bending tests. The results were validated using analysis of variance (ANOVA). Findings demonstrated that polypropylene fibers contributed to homogenizing stress distribution by delaying micro-crack initiation, while steel fibers enhanced pull-out resistance and bridged macro-cracks, synergistically improving the energy absorption capacity. However, increasing the recycled aggregate content generally led to a reduction in fracture energy, attributed to the weaker residual cement paste and damage induced during aggregate processing.

کلیدواژه ها:

Recycled Concrete ، Steel fiber ، PP fibers ، Fracture Energy ، Notched beam