Influence of polypropylene fibers on the microstructure and physical and mechanical properties of concrete

The construction sector significantly impacts the environment due to its high consumption of natural resources and the production of plastics. This research addresses this challenge by incorporating pretreated polypropylene fibers (PPF) into concrete. The study aims to evaluate the physico-mechanical properties and microstructural characteristics of concrete partially reinforced with polypropylene fibers. PPF was incorporated in volumetric proportions of 0.5%, 1%, 1.5%, and 2%, with fiber dimensions ranging from 15 to 30 mm in length and 0.05 mm in diameter. The water/cement (w/c) ratio was 0.706, and no superplasticizer additive was used. The results indicated that the optimal PPF content was 1.5%, where the slump, unit weight, and air content decreased but remained within acceptable limits, and there was no significant temperature increase. Additionally, improvements were observed in compressive strength, elastic modulus, flexural strength, and tensile strength, with increases of 12.40%, 7.44%, 24.59%, and 20.76%, respectively, compared to standard concrete. However, increasing the PPF content beyond 1.5% led to a reduction in strength, although it remained superior to that of standard concrete. X-ray diffraction (XRD) analysis of the sample containing the optimal PPF percentage revealed elevated levels of silicate, calcium, and silicon dioxide, underscoring the significant impact of PPF on the concrete’s properties. Scanning electron microscopy (SEM) of the 1.5% PPF-reinforced concrete showed a more homogeneous, dense, and less porous cement matrix compared to standard concrete. It is concluded that PPF-reinforced concrete can be effectively used in structural elements such as beams, columns, slabs, pavements, sidewalks, and foundations, contributing to more sustainable construction practices.