Durability and thermal properties of prepacked aggregate concrete reinforced with waste polypropylene fibers

The prepacked aggregates fiber-reinforced concrete (PAFRC) is an innovative type of concrete composites that recently has gained popularity and pulled the attention of researchers worldwide. The PAFRC components can be manufactured by initially placing the mixture of coarse aggregates with various sizes and shapes and short fibers in the designed molds and then grouted with an especially ready mix mortar. Although prepacked aggregate concrete (PAC) or two-stage concretes have been used widely as construction materials, long-term performance, particularly in aggressive environments, have not been studied. Therefore, the current study investigated the long-term strength properties, resistance against acid and sulfate environments, as well as thermal properties. Two methods of grouting were used, namely, gravity and pumping. For each method, a total of six mixes comprising 30 mm length waste polypropylene (PP) fibers at dosages of 0–1.25% was prepared. The outcomes of the study revealed that the PAFRC specimens obtained a remarkable improvement in the long-term strength values. The findings expose that the rates of sulfate and acid attacks, in terms of mass and strength losses, were controlled significantly by adding PP fibers and POFA into PAFRC specimens. The combination of PP fibers and POFA, which provides a denser microstructure, resulted in the lower depth of carbonation and better performance of PAFRC specimens to delay the time of heat transfer to the middle part of concrete.