Abstract
Recently, the use of plastic products, such as polyethylene (PE) bottles and polypropylene (PP), has been significantly increased, which may lead to many environmental issues. Therefore, it is important to find methods to manage these waste materials without causing any ecological hazards. One of these methods is to use plastic wastes as soil stabiliser materials. In this study, PE and PP have been used in the form of fibres. The effect of the stabilisation was evaluated through carrying out standard laboratory tests. These tests have been conducted on natural and stabilised soils with four fibre contents (1%, 2%, 3%, and 4%) of the soil weight. The tests included the standard compaction test, unconfined compressive strength (UCS) test, California Bearing Ratio (CBR) test, and resilient modulus (Mr) tests. In all these tests, the fibre content was added in two lengths, which were 1.0 cm and 2.0 cm. Laboratory test results revealed that the plastic pieces decrease maximum dry density (MDD) and optimum moisture content (OMC) of the stabilised soils, which are required for the construction of embankments of lightweight materials. In addition, there was a significant improvement in the UCS of soils by 76.4 and 96.6% for both lengths of PE fibres and 57.4% and 73.0% for both lengths of PP fibres, respectively. Results of the CBR tests demonstrated that the inclusion of plastic fibres in clayey soils improves the strength and deformation behaviour of the soil especially with 4% fibre content for both lengths 1.0 cm and 2.0 cm, respectively, to a figure of 185 to 150% for PE and PP, respectively. Furthermore, the results of the Mr tests demonstrated that the mechanical properties improved to an extent. For an increase in fibre content, the resilient modulus increased by about 120% at 4% fibre content for PE. However, for PP, improvement in resilient modulus declined at 3% fibre content. Therefore, for soil stabilisation with fibre material, optimum fibre content shall be sought.
Highlights
Disposal of waste materials is becoming a predominant issue for most countries in the world
Plastic wastes are produced in massive quantities such as plastic bottles, which are made from polyethylene terephthalate (PET), and plastic sack and carpet, which are made from polypropylene (PP)
The laboratory compaction tests were performed in accordance with the ASTM D698 procedure. The purpose of this test is to determine the effect of plastic fibre on optimum moisture content (OMC) and maximum dry density (MDD) of stabilised soils and to use OMC that was obtained in this test for preparing samples for unconfined compressive strength (UCS), California Bearing Ratio (CBR), and Mr tests, dry density, and optimum moisture content
Summary
Disposal of waste materials is becoming a predominant issue for most countries in the world. Several researches have been conducted to investigate the effectiveness of plastic waste materials in the form of discrete fibres on properties of soils (Ziegler et al 1998; Babu and Chouksey 2011; Mondal 2012; Ahmadinia et al 2012; Modarres and Hamedi 2014; Fauzi et al 2015; Changizi and Haddad 2015; Rawat and Kumar 2016; Peddaiah et al 2018; Salimi and Ghzavi 2019) These researchers found that using plastic waste materials for soil stabilisation will improve the properties of weak soils such as an increase in UCS, CBR, and Mr and a decrease in the soil plasticity. These tests consisted of soil index properties, standard compaction test (proctor test), unconfined compressive strength test, California Bearing Ratio test, and resilient modulus tests
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