Volume 6, Issue 5 (May 2009)
Performance of Fibrous Concrete under Sulfate Cyclic Treatment
An experimental study was undertaken to investigate the potential of using steel fibers in controlling expansion and reducing damage of concrete under cyclic treatment in a sulfate solution. Cylindrical (100 × 200 mm) and prism (70 × 70 × 300 mm) concrete specimens were prepared without and with different volumetric fractions (0.5–2 %) of hooked steel (HS), brass-coated steel (BCS), or a blend of both fibers, before being cured for three weeks, and subjected to sulfate cyclic treatment in 5 % Na2SO4 solution for about 4 months. Throughout the treatment period, cracking initiation and development were monitored and expansion-time history established for the concrete prisms whereas compressive mechanical properties of the concrete cylinders were obtained and compared to those of controls. Fibrous concrete mixtures experienced less expansion and cracking extent under sulfate cyclic treatment as compared to those of plain concrete. HS at volumetric fractions of 1 to 2 % contributed more to reducing expansion and delaying cracking as compared to that of BCS fibers. Under sulfate cyclic treatment, concrete mixtures with fibers showed higher residuals for compressive strength, modulus of elasticity, toughness, and the strain at peak stress as compared to those of plain concrete. The statistical model developed for predicting the residual compressive strength as a function of induced strain, fiber type, and content showed excellent fit of the data used. Use of steel fibers in concrete contributes to maintaining its mechanical properties and elongates its lifetime in structures that are located in sulfate contaminated environments.