Polyethylene terephthalate usage as a partial replacement for recycled fine aggregate in the subbase layer

The best way to dispose of construction waste and plastic materials (in Mosul city in the north of Iraq) is to use them as subbase layer of the road to make them both environmentally friendly and cost-effective. Because these materials are not cohesive, a certain percentage of clay was added. The research aimed to dispose of these materials scientifically and deliberately with appropriate California Bearing Ratio (CBR) values obtained from a mixture of (clay soil + recycled concrete aggregates (RCA) + polyethylene). These values are much greater than the CBR values obtained from natural materials used in the design of the road subbase layer. Clay was added to soil in specific proportions: 10 % to type A and 20 % to type B. Various tests were carried out for the mixture to determine Maximum Dry Density (MDD) and Optimal Moisture Content (OMC), and then CBR and swelling. Tests were also carried out to determine the soil permeability (both the permeability rate in centimeters per hour (cm/h), and the coefficient of permeability k in meters per second (m/s)). Polyethylene was added in different proportions as a replacement for the remaining fine aggregate on the sieve No. 8. Multiple percentages of polyethylene terephthalate were used, ranging from 2.5 to 10 for type A (2.5, 5.0, 7.5, 10 %) and from 5 to 20 for type B (5.0, 10, 15, 20 %), in order to obtain an ideal mixture of (RCA + polyethylene + clay). The CBR was 12 %, which had been more than that of natural soil. The coefficient of permeability was more than 32 m/day, indicating that these mixes could be used for subsurface drainage purposes. This value was reasonable and no noticeable erosion was observed. The subbase would help draining and prevent settlement and channeling. Apart from the sustainable benefit, the mixture (clay soil + RCA + polyethylene) was found to be suitable for use in road pavements, according to the methodologies used in this study. Due to the encouraging results it is recommended to use these techniques to dispose of the waste and debris materials and obtain optima benefits.