An investigation using waste pet bottles as aggregate in lightweight mortars

In this work, the usability of waste Poly-ethylene Terephthalate (PET) granules as ligtweight aggregate in lightweight mortar was investigated. The tests were carried out on two mortar group samples, one made with only PET aggregates and, second made with PET and sand aggregates together. Additionly, blast-furnace slag and fly ash were also used as the replacement of cement on mass basis at the replacement ratio of 50 % to reduce amount of cement and provide savings. The PET-binder (P/B) ratios used in the mixtures were chosen 0.50 and 0.60; water-binder (w/b) ratios were 0.45 and 0.50. Two different maximum size of PET granules were used, 1-2mm and 0-4 mm in the preparation of mortar mixtures. The results of laboratory study and testing carried out showed that, mortar containing only PET as aggregate, mortar containing PET and sand as aggregate, and mortars modified with slag as cement replacement can be drop into structural lightweight concrete category. Altouhg, the increase in P/B ratio from 0.50 than 0.60 did not influence the compressive strength of the samples, however, it reduced the flexural-tensile strength a bit, also it caused a reduction in the shrinkage of mortar. The samples containing slag showed higher compressive and flexural-tensile strengts than the samples made with fly ash as cement replacement. The decrease in the w/b ratio from 0.50 to 0.45 influenced and improved the properties of the mortars including strength, shrinkage, carbonation etc. The test results also showed that, the waste PET granules were suitable as aggregate in the production of structural lightweight concrete for producing the earthquake resistance building structures. Furthermore, it was thougth that, the use of industrial wastes such as PET granules, blast-furnace slag and fly ash, in producing concrete provide advantages such as reducing of using natural sources, disposing of wastes, prevention of pollution, and energy saving.