Use of recycled waste plastic bottles in a ground engineering technology

Abstract

Previous studies have investigated internal reinforcing of granular columns to further improve the loading, settlement and deformation characteristics of these columns which are popular for improving load carrying capacity, reducing settlement, mitigating liquefaction and improving drainage. This research expanded on past studies where reinforcement materials, generated from the recycling process of waste polyethylene terephthalate (PET) bottles, were used to improve the engineering characteristics of granular columns so as to potentially generate more sustainable construction technologies which is in line with the Sustainable Development Goals of the United Nations. A series of laboratory tests were undertaken on single columns which were installed in a steel cylindrical tank and subjected to a vertical compression load; the reinforced granular columns were improved with PET bottles in the form of flakes. The load-settlement characteristics were electronically recorded and a physical model of the deformation of each column was built using a paste of plaster of Paris. Modelling of the deformed columns was necessary to establish the maximum bulging diameter and the position at which it occurred along the length of the column. The results obtained showed that the highest improvement in vertical applied load was 143% and it was recorded for a test which was conducted on a column installed in the wetter silt bed, with a flakes concentration of 5.6%. In terms of settlement, a drastic reduction in settlement was observed with the inclusion of the flakes in the columns for tests on the wetter silt. The lowest settlement of 13 mm was obtained in the test with the wetter silt bed and flakes content of 5.6%. Additionally, inclusion of the flakes also reduced the extent of lateral bulging, depending on the testing conditions.