Abstract
The continuous proliferation of plastic materials in industries has led to the generation of huge volumes of waste plastics, which must be properly disposed of to prevent contamination of the natural environment. In line with current global efforts to tackle the enormity of plastic debris in the environment including ocean, this research evaluate the possibility of immobilising high volumes of waste plastics in cementitious systems using encapsulation technology. It also investigates the aptness of using the resulting encapsulated plastic waste forms in civil engineering applications. In order to evaluate the usability of the encapsulated waste form, material characterisation of the aggregates and binding materials were conducted along with the physical, mechanical and durability performances of the encapsulated plastic waste forms (concrete). The research work was also extended to provide an inferential statistical analysis of the physical and mechanical properties of the encapsulated plastic concrete relative to the control conventional concrete.The overall results suggest that, it is possible to immobilise waste plastics in cementitious materials using encapsulation technology. The encapsulated plastic waste forms (encapsulated plastic concrete) have shown that high volumes of waste plastics can be mechanically bounded into solid monoliths, and based on the physical, mechanical and durability properties investigated as part of this work may be suitable for use in civil engineering applications. The encapsulated plastic waste-form demonstrated densities within the range 1400 – 1700kg/m3, porosity within the range 8.9 – 21.2% and water absorption ranging between 3.7 – 15.4%. Furthermore, the unconfined compressive strength of the encapsulated plastic concrete ranged between 2.8 N/mm2 – 17.4N/mm2 after 28 days of water curing. Like concrete made from natural aggregates, the encapsulated plastic concrete also exhibited good resistance to frost action, sulphate attack and tolerated temperatures up to 150oC.
On the possible applicability of the encapsulated plastic concrete in civil engineering applications, the lightweight property of the encapsulated plastic concrete makes it particularly suitable for off – site production and other lightweight applications such as concrete fills, landscaping and structural formworks, sandwich concrete with an outer load bearing leaf of precast concrete and, boundary and retention walling. The encapsulated plastic concrete may be of particular benefit in low fire risk buildings such as sport centres and playgrounds, farmhouses, DIY outlets, outbuildings, storage units, garden centres among others. The high porosity of the encapsulated plastic concrete may also distinguish them as pervious concrete capable of applications in concrete flatwork applications such as driveways, sidewalks, parking lots, road drainage and flood defence applications. Other possible applications of the encapsulated plastic concrete include low- energy and low-carbon construction, speedy construction and extreme weather construction.
Fire safety measures such as safeguarding ignition sources, fire and smoke alarms, and sprinkler systems may have to be deployed due to the fire risk associated with the use of plastic materials in building construction. In addition, the low tensile strength of the encapsulated concrete implies that mesh or other reinforcements may be required, depending on the use of the concrete. The encapsulated plastic concrete also has low workability which may be mitigated through mechanical mixing, power vibration using poker vibrators, roller compactors, high-pressure concrete pumps and/or compacting in thin layers.
| Date of Award | Jan 2018 |
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| Original language | English |
| Supervisor | John Kinuthia (Supervisor) & Jonathan Oti (Supervisor) |