Optimum Use of Recycled Waste Materials as Partial Replacement of Fine Aggregate in Portland Cement Concrete Mixes

Abstract

This study explored the independent utilization of five common waste materials - rubber, plastic, glass, slag, and sewage sludge ash (SSA) - as partial replacement of fine aggregate in Portland cement concrete (PCC) mixes. The main objective was to determine an optimum substitution range for each waste material that would offer well performing concrete in terms of workability, compressive strength, and durability. To this end, multiple concrete batches were prepared, incorporating each waste material at four different levels: 5%, 10%, 15%, and 20% by weight of fine aggregate. Then, concrete samples (100-mm diameter × 200-mm tall cylinders) were cast from each batch and were moisture-cured for 7, 14, and 28 days prior to testing. Also, the chemical composition of each waste material was identified using FTIR spectroscopy to understand its impact on the development of concrete strength. While most waste led to the diminished strength gains at all substitution rates, the addition of glass, slag, and SSA contributed positively to the strength development at specificreplacement levels: 5% for glass, 10 - 15% for slag, and 5 – 15% for SSA. Furthermore, these additions of glass and slag exhibited comparable workability and durability although SSA did not exhibit comparable workability and durability. The findings of this study can hold significant implications for environmental sustainability and cost effectiveness in construction projects