Experimental investigation of the effect of pet bottle waste on mechanical and thermal properties of fly ash based self-compacting geopolymer mortars

In this study, it was aimed to examine the changes caused by the use of waste Polyethylene Terephthalate (PET) bottle as aggregate in different proportions on the mechanical and thermal properties of fly ash-based self-compacting geopolymer mortars. To this, six different mixtures were prepared by replacing PET bottle waste with aggregate at the rates of 0%, 5%, 10%, 15%, 20% and 25%. The ratio of fly ash, sodium silicate, sodium hydroxide, additional water and superplasticizer were kept constant in all mixtures. River sand was used as aggregate and the particle size of the aggregate was kept smaller than 4 mm in order for the mortars to meet the self compacting criteria mentioned in EFNARC 2002. A sieve analysis was also performed for the waste PET bottle particles used and their particle sizes were determined to be 0-4 mm. While the mortars were fresh, mini V funnel, mini slump flow and rheology tests were carried out and the fresh unit weights of the samples were also measured. While the slump flow diameter was measured between 24-26 cm in all samples, the flow time through the mini-V funnel increased as the PET percentage increased. As the replacement amount of PET, which is a lighter material than river sand in terms of unit weight, increased, the density of the samples naturally decreased. After the fresh tests were completed, each of the samples was left to cure in an oven at 60 ℃ for 24 hours. After oven curing, the samples were kept in an environment of 25 ℃ and 50% humidity up to 28 days and then were subjected to compressive strength, flexural strength, water absorption, capillary water absorption and thermal conductivity tests. The use of waste PET bottle crumbs in geopolymers caused a general decrease in compressive and flexural strengths. The best results in terms of both compressive and flexural strength were observed in mixtures with 5% PET replacement. On the other hand, as the PET percentage increased, a fluctuating behavior was detected in water absorption and capillary water absorption values. As a result of the study, it is painted out that PET waste could be used in the production of self-compacting geopolymer mortars, which could be brought into economy and more environmentally friendly materials.