Experimental Study on Some Properties of Recycled Polypropylene Plastics as a Partial Replacement of Coarse Aggregate in High Strength and Normal Strength Concretes

Previously, various studies were performed to identify safety and environmentally friendly methods for disposing of plastics. Recently, various forms of plastics have been incorporated in concrete to prevent direct contact of plastics with the environment because concrete has a longer service life. In this thesis, the effects of coarse aggregate replacement of Polypropylene as a waste material on fresh and hardened properties of normal strength concrete (NSC) and high strength concrete (HSC) was investigated. To do so, different percentages of polypropylene were replaced by various volumes (0%, 10%, 20%, 30%, 40% and 50 %) of normal and high strength concretes, with the water to cement ratio of 0.58, 0.34 for normal and high strength concrete, respectively. In addition, Superplasticizer (Glenium 27) was added to the NSC and HSC mixed by 0.3% and 2% cement weight, respectively. Slump and VeBe time tests were done to analyse the physical properties of fresh concrete. Moreover, the influences of PP replacement in the hardened concrete were executed by performing splitting tensile strength (fs), compressive strength (fc) and flexural strength (ff) tests. Rapid chloride permeability (RCP), heat degradation at 200 °C, water absorption, and non-destructive tests such as Ultrasonic Pulse Velocity (Pundit) and Schmidt hammer (rebound) were also conducted. The results showed changes in mechanical properties of normal strength concrete and high strength concrete as the percentages of PP increases. The amount of fs, fc, and ff of normal and high strength concrete decreased with the increase in the amount of polypropylene at 28 days. Furthermore, high water absorption was observed with the increasing of PP. According to the results of the Pundit test the replacement of Polypropylene increased the quality of concrete up to 50% in comparison with the control samples. It is worth noting that negative effects in fc, fs, ultrasonic pulse velocity, and crack development were observed after 200 °C heat exposure. Keywords: Polypropylene (PP), Normal strength concrete, High strength concrete, workability, Mechanical properties, Non-destructive test, Water absorption, Permeability, Heat exposure