INVESTIGATING THE PROPERTIES OF AGGREGATES MADE WITH DEMOLISHED CONCRETE AND FLYASH

Abstract

The rapid expansion of the construction industry has led to a significant depletion of natural resources and a surge in construction and demolition (C&D) waste, necessitating sustainable alternatives for infrastructure development. This study investigates the physical and mechanical properties of recycled concrete aggregates (RCA) derived from demolished structures, integrated with fly ash as a supplementary pozzolanic material. The experimental program evaluates key parameters, including workability, density, compressive strength, and water absorption, by replacing natural coarse aggregates with RCA at varying percentages (e.g., 0%, 25%, 50%) and partially substituting cement with fly ash to enhance durability and environmental performance. Preliminary findings indicate that while higher replacement levels of recycled aggregates may slightly reduce initial mechanical strength due to increased porosity, the addition of fly ash helps mitigate these effects over time by improving the micro-structural density and overall concrete quality. Ultimately, this research aims to establish an optimized mix design that effectively utilizes waste materials, thereby reducing the carbon footprint of concrete production and promoting eco-friendly construction practices. This project investigates the feasibility of using recycled concrete aggregates (RCA) from demolished structures and fly ash as sustainable replacements for natural aggregates and cement in concrete production. With the increasing demand for construction materials and the rising environmental burden of construction waste, this study aims to evaluate the performance of ecofriendly "green concrete." The experimental phase involves replacing natural coarse aggregates with RCA at various levels (e.g., 25%, 50%, 75%, and 100%) and cement with fly ash (e.g., 15% to 25%). Key properties such as compressive strength, flexural strength, and split tensile strength are tested at 7 and 28 days to determine the optimal mix design. While RCA typically increases water absorption and can reduce initial strength, the pozzolanic activity of fly ash is expected to enhance long-term durability and workability. The study concludes by identifying the most effective replacement percentages to ensure structural integrity while significantly reducing the carbon footprint of concrete.