Durability of Alkali-Resistant Glass Fibers Reinforced Cement Composite: Microstructural Observations of Degradation

Usually, glass fibers in concrete permit the increase of the flexural strength. But the fibers in contact with cement are quickly degraded by alkali reactions due to the presence of portlandite. This article presents the results of investigations carried out to study the influence of curing conditions on the durability of alkali-resistant glass fibers in a cement matrix. Test results showed that alkali resistant fibers treated with zirconium oxide, present the same degradation phenomenon. The used cement nature has a large influence on the protection of the fibers. In addition, the degradation is weakened when silica fumes are added, owing to the pozzolanic effect that decreases the portlandite quantity. In spite of those different ameliorations, the use of such materials in humid environment is proving to be risky. The used techniques to study those phenomena are SEM equipped with energy dispersive spectrometer (EDX) to observe the attack microstructures of the fibers and X-ray diffraction to quantify the portlandite and other phase development.