Flexural behavior evaluation and energy dissipation mechanisms of modified iron tailings powder incorporating cement and fibers subjected to freeze-thaw cycles

Abstract

Waste iron tailings with cement-based inorganic binder is an economical and sustainable highway engineering base material, which is an effective way to reduce iron tailings inventory and affinity for engineering promotion. The flexural behavior considering the freeze-thaw action plays a crucial role for highway engineering base material. In this study, two types of fibers including polypropylene (PP) fiber and glass fiber were used to modify cement iron tailings powder (CITP), i.e., PPCITP or GCITP. Based on flexural tests, the influences of fiber length and freeze-thaw cycles on flexural behavior of modified CITPs were discussed. The results showed that the failure flexural strength of PPCITP reached the highest value at PP fiber length of 12 mm, while the flexural strength of GCITP presented a wavy downward trend with the increase of glass fiber length. The freeze-thaw cycle test results showed that the flexural strength of both PPCITP and GCITP decreased with the increase of freeze-thaw cycles, and the frost resistance of GCITP was better than that of PPCITP under the condition of the same volume of fibers. Then the single fiber pull-out test results implied that the interface action between glass fiber and CITP (G-CITP) was higher than that between PP fiber and CITP (PP-CITP) considering various curing ages and freeze-thaw cycles. Moreover, it is corroborated that PP fiber and glass fiber with length of 12 mm have the better reinforcement role in CITP specimens from the perspective of dissipative energy of fiber failure. Meanwhile, the dissipative energy results of both modified CITPs with fibers showed a downward trend with freeze-thaw cycles as a whole, and the dissipative energy of GCITP was higher than PPCITP at the specimen broken, which is consistent with the conclusion drawn in the single fiber pull-out test. The quantitative relationship models among dissipative energy, effective fiber length and freeze-thaw cycles of PPCITP and GCITP were further established, which could provide a reference for the large-scale production of waste iron tailings in highway engineering base materials.