Thesis (MSc) - Cyprus International University. Institute of Graduate Studies and Research Civil Engineering

The massive volume of plastic garbage generated globally has significant environmental effects, polluting air, water, and soil. On the other hand, aggregate which accounts for 60-75% of concrete volume, consumes millions of tons of non-renewable resources annually. In addition to improving the mechanical and durability qualities of concrete, recycling plastic waste as a natural aggregate and using silica fume instead of cement throughout the concrete-making process can help to create a more sustainable environment and lower carbon dioxide emissions. To create sustainable concrete, this thesis study aimed to examine the characteristics of lightweight concrete made using silica fume and plastic. The study is based on a design of experiment by incorporating 25, 50, and 75% plastic as a natural aggregate replacement and 5, 10, 15, 20, and 25% Silica Fume as cement replacement with a fixed w/b ratio of 0.375. According to experimental findings, mixture flowability rose in this study when replacement levels increased up to 50%. Conversely, flowability declined as the replacement amount of silica fume increased. In comparison to the control mix, the compressive and flexural strengths were reduced by 64.8% and 75.12% when 75% of the natural aggregate was replaced with plastic, however, substituting 20% cement of the control mix with silica fume increased the flexural and compressive strength by 19.63% and 60.12% respectively. The density of the mixtures decreased as the plastic replacement level increased. Plastic aggregate increased the water absorption however it was decreased by incorporating Silica Fume. The acid attack resistance increased by incorporating plastic aggregate and silica fume into the mixtures. It was also observed that both silica fume and plastic waste increased the shrinkage of the mixture. The fire resistance shows that the plastic used in this study was not fire resistant and the specimens cracked due to plastic expansion at 200 C and the plastic aggregate melted at 400 C. In addition, the fire resistance of Silica fume specimens decreased as the temperature increased as compared to the control mix.