Size effects in compressive and splitting tensile strengths of polypropylene fiber recycled aggregate concrete

Polypropylene fiber1 (PPF) recycled aggregate concrete2 (RAC) specimens with different strength grades (C25, C35, and C45) were prepared. Each strength specimen contained three sizes (100, 150, and 200 mm) and three PPF contents (0, 0.6, and 1.2 kg/m3). The size effect of the compressive and splitting tensile strengths of the PPF-RAC with different PPF contents and concrete strength grades was analyzed. The Bažant size effect law formula was used to predict the strength of PPF-RAC. The empirical formula of variables in the size effect law formula is proposed. Additionally, the relationship between regression coefficient and standard compressive strength was analyzed. The validity of this method was verified using previous experimental data. Moreover, the relationship between ultimate size and ultimate strength based on Bažant size effect law formula was analyzed. The model has a good prediction accuracy, The ultimate size and ultimate strength have a strong linear relationship.