Dr. Md Abdul Karim

This study is a preliminary investigation of the independent utilization of two types of fly ash (FA)–FA Type C and FA Type F-as partial replacement of fine aggregate (sand) and cement in Portland cement concrete (PCC) mixes. The main objective was to determine an optimum substitution range for each type of FA that would offer well-performing concrete in terms of workability, compressive strength, and durability. To this end, multiple concrete batches were prepared, incorporating each type of FA at four different levels: 5%, 10%, 15%, and 20% by weight of fine aggregate replacement and 10%, 20%, 30%, and 40% by weight for cement replacement. 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. The addition of FA contributed positively to the strength development at specific replacement levels: all percentages for both FA Type C and Type F for fine aggregate replacement and up to 30% FA content for both Type C and F for cement replacement, 10% for both FA Type C and Type F provided the higher strength for aggregate replacement, and 10–20% for both types of FA provided the higher strength for cement replacement. Furthermore, these additions of FA exhibited comparable workability and durability except for FA Type F, which did not exhibit comparable workability for aggregate replacement. FA Type C can be recommended for both early and long-term strength for fine aggregate replacement, whereas FA Type C is suggested to be used for early strength and Type F provides for long-term strength for cement replacement. Type C provides better durability and Type F provides better workability for cement replacement.

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 specific replacement 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.