A Study of Energy Dissipation of Polypropylene Fiber Reinforced Recycled Concrete Under Uniaxial Compression

The energy dissipation and stress-strain characteristics, and characteristic stresses, namely the crack initiation σ_ci , dilatancy σ_cd , and peak σ_f stresses, of polypropylene fiber-reinforced recycled concrete under uniaxial compression were studied. According to the research results, the crack initiation and peak stresses of the specimen with single-blend polypropylene coarse fiber (No. 3) and the specimens with mixed-blend coarse and fine polypropylene fibers (No. 4 and No. 5) are higher than those of the specimen with single-blend fine fiber and plain concrete. The analysis of the energy characteristics and failure mechanism of polypropylene fiber-reinforced recycled concrete during loading based on the principle of energy conservation showed that the total strain energy, elastic strain energy, and dissipation energy absorbed per unit volume increase with the blending of polypropylene fiber. The strain energy and elastic strain energy of coarse aggregates with a 5-10 to 10-20 mm coarse aggregate size ratios of 5:5 are higher than those of 4:6 and 6:4. It was found that the continuous blending of polypropylene fiber increases the elastic strain energy, causing the point at which the dissipation energy exceeds the elastic strain energy move further and further back. The position where the dissipation energy exceeds the elastic strain energy can be used to evaluate the blending effect of polypropylene fiber. The further back the position, the better the blending effect.