Production and optimization of cement based and recycled polyethylene terephthalate (PET) composite using bottom ash waste and pumice aggregate

The waste generated from energy production, such as bottom ash, and the commonly used polyethylene terephthalate (PET) waste in daily life, pose concerning issues for both the environment and living organisms' health. In the event of ineffective management of these wastes, a substantial increase in waste volume is inevitable. Within the scope of the thesis study, the potential to create a lightweight construction material composite mortar mixture was investigated by examining the long degradation times of PET and bottom ash waste in nature, along with their physical and chemical properties such as lightweight and high thermal insulation. In the study, the composite mortar mixture was developed using PET, bottom ash waste, pumice aggregate, cement, and water. A prototype of the construction block product commonly used in the construction industry was produced using this composite mortar, and its compliance with existing construction block standards was assessed. In the thesis study, a literature review was conducted on the raw material properties used in the development process of cement-based composite materials and the methods for developing construction materials. Preliminary experiments were carried out based on these findings. Following the results of these preliminary experiments, a Taguchi design was employed to formulate nine types of composite mortar mixtures using varying levels of cement, pumice/bottom ash, and PET parameters. With this experimental design, nine different types of composite mortar mixtures were prepared, involving three different parameters at three levels: cement content (250, 275, 300 kg/m3), pumice-bottom ash ratio (%30-70, %40-60, %50-50), and PET aggregate percentage (%0.04, %0.07, %0.1). Using a specialized structure block printing machine, compressive strength, dry unit weight, water absorption, void ratio, capillarity, thermal conductivity, high temperature, and sound transmission tests were conducted on nine different types of specimens that were produced. Additionally, cost and CO2 equivalent emission analyses were carried out on the specimens. The performance characteristics of the specimens were statistically evaluated. The optimal composite mortar mixture formula was determined to be the composition of the third type specimen, with a cement content of 250 kg/m3, a pumice-bottom ash ratio of 50%-50%, and a PET aggregate ratio of 0.1%. Verification experimental studies were not conducted as the optimization values coincided with one of the nine types of specimens within the experimental design. Following the Taguchi design, commercial prototype productions were carried out using the formulation values of type three, which were considered as the optimization design. The potential of the developed composite mortar formulation to be used as an alternative to commonly used construction blocks in the construction industry, such as bricks, autoclaved aerated concrete blocks, and lightweight concrete blocks, was evaluated through testing and analysis results. The produced prototype of the construction block was found to fall within the lightweight concrete category in terms of weight and exhibited significantly higher compressive strength compared to partition wall construction blocks. The thermal conductivity, water absorption, high-temperature resistance, and weight loss values were found to be within the standard range of existing construction blocks. Furthermore, it was observed that the product offered advantages in terms of both cost and CO2 equivalent emissions. Within the scope of the thesis study, it is believed that the information shared in the literature will contribute to the use of PET and bottom ash waste as raw materials in the construction sector, enhancing waste management practices and promoting circular economy principles. This is expected to lead to the discovery of new waste sources, the development of composite mortar formulations, and research and development efforts aimed at creating innovative products for the construction industry.