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Employment of plastic waste to produce light weight concrete

Kontova Vasiliki

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Summary

Plastic is undoubtedly a material with many valuable uses in everyday life. Nevertheless, the properties that make plastics so useful, such as their durability and the fact that they do not degrade, are what make them so hazardous to the environment, as most plastics never completely disappear, ending up in the oceans and in human or animal food.It is estimated that more than 8.3 billion tonnes of plastic have been produced since the early 1950s and about 60% of this plastic has ended up in either landfills or the natural environment, causing serious environmental impact. It is therefore necessary to reduce the production and use of plastic, but it is also necessary to improve the management of plastic waste.Alternative methods of plastic management, such as mechanical and thermal recycling, energy recovery and reuse in the construction sector, are all promising technologies. The most appropriate method depends mainly on the characteristics of the plastic waste, the needs for the use of the final products, as well as the economic factors.The aim of this dissertation was to study the physical and mechanical properties of cement mortar by partial replacement of aggregates with plastic type PET (Polyethylene Terephthalate), PP (Polypropylene), LDPE (Low Density Polyethylene) and a mixture of the above. Aggregate replacement rates were 1, 2 and 4% for each type, while a constant ratio of water to cement was maintained in each test. Basic properties of the mortars were examined, such as compressive strength, elasticity and bulk density,for plastics in the form of flakes, but also in the form of resins.The results showed that thebulk density decreases as the replacement percentage of plastics increases. The reduction also has small variations between the flakes and the resins. Based on the results, the plastics selected are a suitable choice for the manufacture of lightweight concrete. On the contrary, the measurements of the tests for resistance to compression, mainly showed that the reduction of the compressive strength becomes more intense as the percentage of plastic increases. Several cement mortars, such as the resin form, showed quite good strength, as there was a better correlation between the aggregate mixture and the cement mortar, resulting in greater resistance to increased displacement loads. The elasticity of the mortars presented different results, depending on the shape of the plastic. An increase of elasticity was appeared, in resin plastics, while the elasticity of flakes decreased as the plastic increased. This is probably due to the reduction of the density of the cement mortars, as well as the low elasticity of the plastic flakes.As a result, the use of plastic waste as a substitute for aggregates in the construction sector can be a satisfactory method of reusing them, contributing to the circularity and protection of the environment.

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