ABSTRACT
This research aimed at the development of appropriate combination of composite materials such as cement, aggregates and inclusion of Polyethylene Terephthalate (PET) in varying proportion in order to determine the optimal measure for the optimal strength, and establish empirical relationship between some mechanical properties of concrete produced. This work also investigated the effect of PET aggregate on some mechanical properties of waste aggregate concrete. Mix design targeting grade 25 concrete strength, using the Department of Environment (DOE) approach was adopted. Five different concrete samples were prepared accordingly, using natural aggregate as control mix and four others which consist of PET aggregate as partial replacement of fine aggregate at 5%, 10%, 15%, and 20% ratios respectively. The recycled fine aggregate (PET) was processed from bottle water waste, it was crushed, pressed and processed into finely material having river sand resemblance. The required quantity of PET for replacement of fine aggregate was mixed thoroughly to form homogeneous mixture of fine aggregate before sieve test was conducted on it and thereafter mixed with other mixture constituent of concrete.The batching was done by weight. Cubes specimens were prepared, cured for 7, 14, and 28days and tested for compression, while beam concrete specimens were prepared, cured for 28days and flexural strength was tested. The results of the tests were analyzed statistically using regression method (Mintab) to establish optimal strength require mixture and empirical relationship between mechanical properties. The preliminary test results gave 5.05, 6.18 and 0.51 as the moisture content values for sand, PET and granite respectively. The specific gravity of the aggregates were given as 2.59, 1.37 and 2.70 for sand, PET and granite respectively. Also, the water absorption of the sand, PET and granite stood at 3.36, 6.65 and 0.20 respectively. Results and analysis established that there were reduction in compressive strength and flexural strength of the concrete containing PET aggregate and reduction rates increased with increase in the amount of PET aggregate inclusion in the concrete. The compressive strength values for 5%, 10%, 15% and 20% replacement of sand with PET at 28-day were 29.70N/mm2 , 25.95N/mm2 , 24.28N/mm2 and 23.23N/mm2 respectively. When compared with the control concrete specimens with an average value of 33.08N/mm2 gave 11.38%, 27.48%, 36.24% and 42.40% reduction in strength respectively. Also, the flexural strengths at 28-day were 5.82N/mm2 , 4.94N/mm2 , 4.14N/mm2 , 3.62N/mm2 , and 2.97N/mm2 for concrete samples made with 0%, 5%, 10%, 15% and 20% replacement of fine aggregate with PET respectively. It was recommended that, though, the use of PET aggregate in the production of concrete does not have significant appreciable effect on the strengths and cost of concrete production; it use will protect our environment and as well preserve our natural resources used as materials in production of concrete elements which are currently excessively depleted.
