Examination of Concrete Elements Bending Strength Reinforced by Polyethylene Terephthalate (PET) Waste

Abstract

Ukrainian enterprises of PET (Polyethylene Terephthalate) waste recycling are still capable of processing only 1 thousand tons, and more than 10 thousand tons of PET granulate are imported to Ukraine every month. Therefore, the issue of reuse and disposal of used polyethylene terephthalate, especially in construction, is one of paramount importance. The aim of the research is experimental-theoretical study of the strength of bending of prisms, reinforced with fibers and strip reinforcement of used PET bottles. Objectives of the research: the study of the percentage of reinforcing fibers in volume (1% and 1.5%) influence on the flexural strength of concrete reinforced prisms, and the possibility of using ribbon reinforcement from used PET bottles for bending concrete elements, elaboration of proposals for the deformation method of calculation of PET fibrobone bent elements. In this research the experimental methods for determining the bending strength of prisms, reinforced by fibrous, trips and PET waste tapes; methods of materials resistance theory have been used. During the research, two concrete prisms of 400x100x10 mm were constructed and tested for compression together with two concrete prisms of three-point bend for a run of 350 mm, two PET-fibrous concrete prisms for bending with percentages of reinforcement in volume of 1% and 1, 5% and two prisms for bending, reinforced with glued PET strips, with 1% reinforcement per section area. As a disperse reinforcement, pre-fabricated PET bottles of 50x3x0.2 mm were used, designed in way that the required length of sealing in the concrete is no longer than half the length of the fibers. Strip fittings are made of 4 fragments of PET bottles of 200x80x0.25 mm in size, glued with cyanacrylate adhesive with each other, and 2 fragments of 120x80x0.2 mm in size, which glued on both ends to 4 glued sheets with a length of 30 mm. Thus, the total length of the reinforcing strip is equal to 380 mm. At the final sections of the tapes, 6 openings with a diameter of 5 mm were punched to improve the anchoring. The reinforcing strips were placed in the forms located 10 mm from the lower edge. According to the results of the tests, the average cubic strength of concrete is 31.21 MPa, of prisms - 23.23 MPa, the initial module of deformation - 28.02·103 MPa. The flexural strength of prisms without a fibre is 58.54 kN·cm, with 1% fibers in volume - 64.31 kN·cm, with 1.5% fibers in volume - 71.84 kN·cm, and of prisms, reinforced with glued PET ribbons – 79.80 kN·cm. As a result of the tests, it was demonstrated that the strength of the tapes was not used properly, and the fracture was fragile due to the loss of adhesion to concrete. Analysis of the results of experimental studies allowed us to develop a deformation methodology of calculating PET-fiber-concrete bending elements.