Investigation of fresh and hardened properties of lightweight self-compacting geopolymer mortars containing waste polyethylene terephthalate

In this study, the substitutability of different proportions of polyethylene terephthalate wastes with aggregates of self-compacting lightweight geopolymer mortars was investigated with experimental methods. In all experiments, the aggregate/fly ash, alkali/fly ash, sodium silicate/sodium hydroxide, super plasticizer/fly ash ratios were kept constant and the aggregate was replaced with polyethylene terephthalate at levels of 0%, 5%, 10%,15%, 20% and 25% by volume. In order to ensure self-compacting, various experiments were carried out in the laboratory and the ratios of aggregate/fly ash, alkali/fly ash, sodium silicate/sodium hydroxide, extra water/fly ash and super plasticizer/fly ash were 2, 0.6, 2, 0.05 and 0.04, respectively were selected. In order for geopolymer mortars to be light the aggregate is designed by volume 25% as pumice aggregate and 75% as river sand. While the prepared mixtures were fresh, mini V funnel, mini slump flow table, rheology and fresh unit volume weight experiments were performed. After fresh experiments, the samples were cured in an oven at 60 ℃ for 24 hours and kept at room conditions for 27 days, then compressive strength, flexural strength, thermal conductivity, water absorption and capillary water absorption tests were applied.The amount of slump flow in all mixtures remained within the range of 24-26 cm, but it was determined that as the percentage of polyethylene terephthalate increased, the mini-V funnel flow time increased. It has been observed that the use of waste polyethylene terephthalate in the mentioned percentages does not have significant negative effects on the mechanical properties of lightweight geopolymer mortars. The best results of mechanical properties were measured in samples with 5% PET replacement. As a result of the study, it was determined that a more environmentally friendly building material could be obtained by adding up to 25% waste polyethylene terephthalate as aggregate in the production of self-compacting lightweight geopolymer mortars.