Stress-Strain Model for Lightweight Aggregate Concrete Reinforced with Carbon-Polypropylene Hybrid Fibers

This research aimed to investigate the hybrid effects of carbon and polypropylene fibers on the stress-strain behavior of lightweight aggregate concrete (LWAC). The considered test variables were two fiber volume fractions of 0.2% and 0.4% and two water/binder ratios of 0.27 and 0.30. Eighteen groups of prisms fabricated with fiber-reinforced LWAC were tested under axial compressive load. Experimental studies were carried out to analyze the influence of different fiber combinations on the complete stress-strain behavior. It was found that the carbon-polypropylene hybrid fibers led to toughness enhancement that was numerically more significant than the sum of individual fibers, indicating a positive synergistic effect between them. Finally, a mathematical expression of the stress-strain curve accounting for the fiber combinations was developed. Compared with existing stress-strain models, the proposed model shows better accuracy in predicting the effect of carbon and polypropylene fibers in both single and hybrid forms on the stress-strain curve of LWAC.