Influence of bentonite, silica fume, and polypropylene fibers on green concrete for pavement and structural durability

This study examines the influence of bentonite in combination with silica fume and polypropylene fibers (PPFs) on the workability, mechanical properties and durability properties of structural concrete. A total of 17 concrete mixtures were prepared for the experimental work with bentonite replacement levels of 5% and 15%, a constant 10% silica fume, and different PPF dosages of 0.25%, 0.50%, 0.75%, 1.00%, and 1.25%. Slump tests were used to determine the workability performance of the mixture, and the mechanical performance was evaluated through compressive strength, split-tensile and flexural strength tests. The concrete durability properties were measured through tests consisting of water absorption, acid attack and rapid chloride migration (RCM). The results revealed that the workability decreased across all mix proportions as a result of incorporating SCM and PPF. The mechanical properties of the concrete were increased with addition of bentonite along with silica fume and PPF. The mixtures with 5% bentonite, 10% silica fume, and 1% PPF presented the best compressive strength and split tensile strength. The incorporation of these materials improved the impermeability and consequently reduced water absorption. The evaluation through sulfuric acid demonstrated that the mixtures containing 5% bentonite, 10% silica fume, and 0.75% PPF resulted in the lowest mass loss, thus showing better acid resistance properties. The results from RCMT indicated that the use of bentonite together with silica fume and PPF significantly reduced chloride migration, i.e., the mixture of 5% bentonite, 10% silica fume, and 0.75% PPF resulted in the lowest chloride migration, thereby increasing chloride resistance.