The combination of conventional Roller Compacted Concrete (RCC) with the substitution of fly ash for fine aggregate replacement

¹ Department of Civil Engineering, Universiti Tenaga Nasional Putrajaya Campus, Malaysia
² Sri Sivasubramaniya Nadar (SSN) College of Engineering

^* Corresponding author: daud@uniten.edu.my

Abstract

This study aimed to investigate the characteristics of roller-compacted concrete when fine aggregate is replaced with fly ash. The investigation focused on assessing workability, compressive strength, flexural strength, and split tensile strength of the concrete mixtures. Four testing methods were employed, including the slump test for workability assessment, the compression test for determining compressive strength, the flexural test for evaluating flexural strength, and the split tensile test for measuring split tensile strength. The fly ash used in this project was sourced from the powerplant in Malaysia. Various fly ash contents, specifically 0%, 55%, 65%, and 75%, were utilized to replace the fine aggregate. The concrete mixtures were subjected to water curing for 7, 14, and 28 days before testing. Following the mixing process using a concrete mixer, the mixtures underwent a slump test to evaluate their workability. It was observed that the workability of the concrete decreased as the percentage of fly ash used to replace the fine aggregate increased. Mixtures with fly ash exhibited zero slump, while the control mixtures displayed true slump. Subsequently, compression, flexural, and split tensile tests were conducted after 7, 14, and 28 days of water curing. In terms of compression strength, an increase in fly ash content resulted in higher compressive strength in the concrete mixtures. The mixture with 65% fly ash content demonstrated the highest compressive strength at 49.84 MPa. Regarding flexural strength, the concrete with 75% fly ash content exhibited the highest value, measuring 5.45 MPa. However, for split tensile strength, the concrete without fly ash content showed the highest value at 8.84 MPa compared to other mixtures, indicating that the fly ash content exceeded the optimum amount for the mix design. In summary, the concrete mixtures with fly ash displayed several advantages, but their suitability depends on the specific type of construction.