Tests Regarding the Effect of Dispersed Reinforcement Made with a Prototype Device from PET Beverage Bottles on the Strength Properties of Concrete

Currently, waste generation is a huge problem all over the world. The largest source of generated waste is plastics from plastic packaging made of polyethylene and polypropylene, including PET bottles. Modern ecology aims to reduce the carbon footprint by recycling plastics or by producing biodegradable plastics that are completely broken down by microorganisms into simple particles that occur naturally in nature. Polyethylene terephthalate (PET) has good mechanical properties but is resistant to microorganisms. As a result, it cannot be classified as a biodegradable plastic, but when it is reused for the production of utility products, it becomes a bioplastic. A good way to dispose of PET is to use it for the production of utility products, in which its good mechanical properties can be used. Concrete is a basic material, the consumption of which in the construction industry is enormous. One of the negative features of concrete is its low tensile strength, which can be improved with continuous or dispersed reinforcement. This paper presents the results of compressive and tensile-bending tests of concrete reinforced with dispersed “fibres” of a different length and width, which were produced by a prototype device from PET beverage bottles. The prototype device enables repeatable fibres with a width of 2 mm, and lengths of 38 mm, 62 mm, and 93 mm to be obtained. The highest flexural tensile strength of the concrete was achieved in the case of the PET fibres with a length of 62 mm. It turned out that concrete with such reinforcement has a higher bending tensile strength by 15 % in relation to the tensile bending strength of the concrete without the dispersed reinforcement. The PET fibres also improve compressive strength. PET fibres, in order not to deteriorate in the alkaline environment of concrete, must be secured with an appropriate chemical agent. The effect of concrete reinforcement with the recycled PET fibres was compared to the effect of dispersed reinforcement made of polypropylene and steel fibres. The highest bending tensile strength was obtained in the case of the concretes with the scattered PET reinforcement. However, the differences in the bending tensile strength of concrete are not big and are equal to 0.64 MPa for polypropylene fibres and only 0.09 MPa for steel fibres.