Fiber Reinforcement Effects on Coal Gangue Concrete: A Review of Mechanical Properties, Durability and Sustainability.

Coal gangue, a by-product of coal mining, has attracted increasing attention as an alternative aggregate in concrete because it can reduce natural aggregate consumption and promote solid-waste utilization. However, its porous, heterogeneous, and source-dependent nature often leads to weak interfacial bonding, reduced strength, and poor durability. Fiber reinforcement has been widely investigated as an effective strategy to compensate for these deficiencies, but the reported results remain scattered because of differences in gangue source, replacement level, fiber type and dosage, and test methods. This review systematically synthesizes the effects of fiber reinforcement on the mechanical performance, durability, and sustainability of coal gangue concrete. Reported results are comparatively analyzed as functions of coal gangue replacement level and fiber dosage. Two strength-normalized sustainability indicators, namely the Cost Coefficient Index (CCI) and Carbon Emission Index (CEI), are further introduced to compare the economic and environmental efficiency of different mixtures. Relatively favorable overall performance was most frequently reported within the commonly reported coal gangue replacement range for coarse aggregates, about 35-70%, with steel fiber and basalt fiber commonly showing favorable intervals of about 0.8-1.0% and 0.12-0.15%, respectively; polypropylene fiber also appeared favorable at about 0.6-1.0%, although the supporting evidence is comparatively less extensive.