The effect of using polyethylene terephthalate particles on physical and strength-related properties of concrete; a laboratory evaluation

• Adding PET to mortar can influence the physical structure and strength of concrete.
• By using PET, the weight of produced concrete reduces.
• An increase at PET ratio and curing age makes samples more deformable before failure.
• The speed of sound in concrete decreases along with the increase of PET ratio in it.
• Using PET in concrete will significantly reduce environmental pollution.

The present study was an attempt to investigate the effects of adding plastic waste particles on the engineering properties of concrete. To this end, a mix concrete design was adopted in which pre-defined weight-based amounts of the concrete fine aggregates were replaced by equivalent waste fragments. At all the mixtures, the amount of the coarse aggregate (gravel) and the water–cement ratio remained constant. The results of laboratory tests showed that the added plastic fragments changed both physical and strength-related properties of newly produced concretes. More specifically, physical properties (e.g. density and ultra sound velocity) gradually decreased as the presence of plastic fragment ratios increased. On the other hand, compressive, tensile, and flexural strength of samples rose, when 5–10% of the concrete fine aggregates were replaced by the same percentage of polyethylene terephthalate (PET) fragments. The results also indicated that substitutions greater than 10% cause dramatic decline in all strength-related parameters of the concretes. It is therefore argued that replacement of fine particles with PET fragments may positively affect the strength-related values of the concrete samples provided that as long as the substation rate is under 10%.