MSc Thesis Title: Qualitative and quantitative analysis of plastic waste from electronic equipment and their application in cement mortar

Monday 5 November 2018, at:11:30, Venue: Assembly Hall Κ1

Examination Committee

• Professor Evangelos Gidarakos (advisor)
• Assistant Professor Nikolaos Xekoukoulotakis
• Professor Ioannis Yentekakis

Abstract:

Over the last few decades the rapid technological development that has emerged has led to the ever-increasing demand for electrical and electronic equipment (EEE). Consequently, the production of new products in this sector, with a particularly complex structure and composition, was deemed necessary to serve the market. However, the result of the increased consumption of EEE products is a significant increase in waste of electrical and electronic equipment (WEEE), which creates the need for new techniques and methods of management.

WEEE consists of a wide variety of materials, while it is remarkable that 20% of their weight consists of plastic parts. Plastic, as waste, can be a significant environmental hazard because it is not biodegradable. In fact, while the use of plastic in all areas has facilitated everyday life, it has recently created a global concern in the scientific community, as plastics and microplastics are detected not only on the surface and bottom of the seas, but also on the salt we consume.

To date, alternative ways of managing plastic wastes have been studied in both research and industrial level, which includes mechanical recycling, thermal and energy recovery, as well as its re-use in the construction sector. The selection of each method mainly depends on the wastes’ characteristics, the need for use of the respective end products, as well as economic factors.

In the present study, the physical and mechanical properties of cement mortars were studied by partially replacing the aggregates with plastic, derived from computer screens’ waste. Samples from fourteen screens were used, the plastic shells of which were characterized in terms of their composition (elemental analysis, calorific value, total digestion, infrared spectroscopy). Acrylonitrile-butadiene-styrene (ABS) polymer was used to synthesize the cement mortar, as it is the most commonly found plastic in EEE, at a ratio around 30%. The replacement rates of aggregates were 2.5, 5, 7.5, 10 and 12.5%, while maintaining a constant water to cement ratio in all tests. Basic properties of mortars were also examined, which include compressive strength, modulus of elasticity, density, porosity and water absorption.

The results obtained were quite encouraging for all replacement ratios, especially for the 7.5 and 10% plastic replacement of the specimens. These percentages showed an increase in the compressive strength by 15.4 and 7.8%, respectively, while the elastic modulus decreased in both cases by 18.1 and 23.8%, respectively. Also, the variance of the other measured physical properties of the specimens (density, porosity, water absorption) is consistent with the results of their strength and elasticity, thus indicating greater strength but lower ductility than the reference cement specimen. Hence, the use of plastics in the construction sector as substitutes for aggregates may be a satisfactory method of reusing plastics from WEEE, contributing to the reinforcement of the right management of hazardous waste.