Chapter 11 - Mechanical properties of recycled polyethylene terephthalate (PET) fiber-reinforced fly ash geopolymer and fly ash-slag-blended geopolymer composites

Abstract

This chapter presents the effect of recycled polyethylene terephthalate (PET) fiber as reinforcing fiber for geopolymer composites. Tensile and flexural behavior of PET fiber-reinforced heat-cured fly ash geopolymer composite (HCG) and ambient-cured fly ash-slag-blended geopolymer composite (ACG) are studied and compared with those of counterpart cement composite (CC) reinforced by the same fiber and volume fractions. The results are also benchmarked with commercially used polypropylene (PP) fiber-reinforced similar composites. Results show that the compressive strength of both geopolymer composites is higher than that of cement composite irrespective of fiber types. Among geopolymer composites, the ACG composite showed slightly higher compressive strength than the HCG composite. The compressive strength of all three composites reinforced by PP fiber is slightly higher than that of PET fiber composites. The increase in volume fraction from 1% to 1.5% shows a reduction in compressive strength in all three types of composites reinforced by both fibers. The increase in PET fiber volume fraction from 1% to 1.5% improved the flexural strength of both geopolymer composites. However, in PET fiber-reinforced cement composite no such improvement in flexural strength is observed. The PP fiber reinforcement, however, shows opposite trends. The tensile and flexural strengths of PET fiber-reinforced geopolymer and cement composites are higher than those of PP fiber counterparts at both fiber volume fractions. Microstructure observation in terms of scanning electron microscope (SEM) images shows significant damage to some PET fibers in the HCG composite. However, in cement and ACG composites no such damage to PET fibers is observed. No such damage to PP fibers is observed in the heat-cured geopolymer composite.