Long-term mechanical properties of steel fiber reinforced concrete under sulfuric acid attack

Steel fiber reinforced concrete (SFRC) has significant advantages for preparing pipes, however, concrete sewer pipes are susceptible to deterioration caused by biological acids (i.e., sulfuric acid). In this study, the mechanical properties-including cube compressive strength, axial compressive and flexural properties, and relative dynamic elastic modulus-of SFRC exposed to sulfuric acid for 36 months were monitored. Further, the evolution of the morphology, alkalinity, and mineral phases was also monitored. According to the morphology and pH evolution, SFRC showed rapid corrosion after 12 months of exposure, and the thicknesses of damaged and transition layers reached approximately 2 and 8 mm, respectively, after 36 months. Further, gypsum was formed and deposited on the specimen surface after exposure to sulfuric acid. Although the SFRC did not deteriorate after 12 months of exposure and still showed good mechanical properties, the cube compressive strength of SFRC showed a slight decrease after 36 months of exposure; however, the axial compressive load and flexural load capacities improved, and the flexural toughness also increased as a result of the exposure to sulfuric acid. This study provides valuable evidence for the potential application of SFRC in sewage environments.