Evaluation of the stability of polypropylene fibers in environments aggressive to cement-based materials

Isotactic polypropylene (PPi) fibers were left in NaOH, H2SO4, synthetic seawater, and cement-with-water solutions at different temperatures and exposure times. Infrared microspectroscopy was used to follow the formation of degradation products. Cement-with-water was the most aggressive bath for the fibers, causing marked oxidation after 100 days exposure; also, the molecular weight of PPi increased as determined by viscosimetry. Mortar test specimens containing PPi fibers and exposed to CO2, synthetic seawater, and MgSO4 0.25M showed a decrease in compressive strength after 260 days. The compressive strength of mortar test specimens containing 0.75 kg m-3 of PPi fibers irradiated with ultraviolet radiation was roughly 10% lower than that of the control specimen, after only 60 days in water.