Degradation Process of Postconsumer Waste Bottle Fibers Used in Portland Cement–Based Composites

The degradation of synthetic fibers derived from postconsumer wastes and used in fiber-reinforced cement mortars was studied. Polyethylene terephthalate (PET) and high-density polyethylene postconsumer bottles were immersed in an alkaline medium of a 1-M solution of sodium hydroxide and portland cement paste. Then, the fibers’ surfaces were analyzed by scanning electron microscopy (SEM). This study showed that the fibers have a progressive surface deterioration over time when immersed in either of the two media. Degradation of fibers immersed in pozzolan-portland cement pastes was also observed. The results from the degradation process of these fibers show that it was stronger when they were immersed in the portland cement system ($\mathrm{pH}=12.9$ ), although the pH value was lower than that of the NaOH solution ($\mathrm{pH}=13.8$ ), suggesting that the degradation process in portland cement also depends on the formation of solid hydration products. The preliminary results of this study show overall good behavior of the studied fibers. This behavior generally improves when using pozzolans. Considering that fibers and pozzolans are obtained from wastes, and therefore have low economic and environmental costs, the possibility of using these materials in developing countries should be considered. The use of these wastes would, on the one hand, improve the properties of construction materials, and on the other, enable proper management of waste that could otherwise eventually pollute the environment.