PVA fiber-reinforced ultrafine fly ash concrete: Engineering properties, resistance to chloride ion penetration, and microstructure

The aim of the study was to systematically investigate effect of the particle size of fly ash on the resistance to chloride ion penetration of concrete as well as the workability and mechanical properties. Two different particle sizes, i.e., D50, particle size <15.22 μm (FA) and D50, particle size <3.12 μm (ultrafine fly ash, UFA) were used for the investigation. The use of PVA fibers helps minimize issues such as brittleness. The mechanical properties of polyvinyl alcohol fiber-reinforced ultrafine fly ash (PVA-UFA) composites as well as the resistance to chloride ion penetration were investigated. The results showed that UFA has a higher engineering value in terms of work performance improvement. UFA is useful in improving the mechanical properties of concrete and the resistance to chloride ion penetration at all ages. The optimum content of UFA is 25%. The 28 d flexural strengths of PVA-UFA specimens were 11.01% higher than those of control group. Moreover, the electric flux and DRCM decreased by 10.96% and 42.58%, respectively. The flexural strength and chloride ion penetration resistance of the composite material with PVA fibers were improved compared with those of the single UFA material owing to their better microstructure. Therefore, PVA-UFA can be applied in coastal highways, bridges, and other structures.