Study on Mechanical Properties and Carbon Emission Analysis of Polypropylene Fiber-Reinforced Brick Aggregate Concrete

Given the current construction waste accumulation problem, to utilize the resource of red brick solid waste, construction waste red brick was used as a concrete coarse aggregate combined with polypropylene fiber to prepare PPF (polypropylene fiber)-reinforced recycled brick aggregate concrete. Through a cube compression test, axial compression test, and four-point bending test of 15 groups of specimens, the influences of the aggregate replacement rate of recycled brick and the PPF volume on the mechanical properties of recycled brick aggregate concrete reinforced by PPF were studied, and a strength parameter calculation formula was constructed and modified based on the above. Finally, combined with a life cycle assessment (LCA), the carbon emissions of raw materials were analyzed and evaluated. It was found that the mechanical properties of recycled concrete enhanced by PPF are critical at an addition rate of 50% and then decrease slowly with an increase in the aggregate content. PPF effectively alleviates the problem of strength reductions caused by regenerated aggregate substitution through the fiber-bridging effect. Based on the experimental data, a mechanical transformation model considering fiber reinforcement and BA weakening was constructed, and the regression accuracy R2 was around 0.90. The environmental benefit obtained when only replacing the natural aggregate is low. Although the incorporation of fiber improves the carbon emissions of the material to a certain extent, the benefits are more noticeable compared with the increase in strength. The results show that garbage recovery and strength demand benefits are achieved when the amount of recycled brick aggregate is 50% of the total. The strength conversion model established in this paper has of high accuracy and was created with careful consideration of fiber reinforcement and the regenerated aggregate weakening correction, providing it with more robust adaptability and extensibility. The mechanical properties of the recycled brick aggregate concrete enhanced by PPF are excellent and sustainable when the replacement rate of BA is 50% and the PPF volume is 0.1%.