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Title: Mechanical Properties and Microstructure of Self- Consolidating High-Strength Concrete Including Palm Oil Fuel Ash

Author(s): Md. Abdus Salam, Md. Safiuddin, and Mohd. Zamin Bin Jumaat

Publication: Materials Journal

Volume: 119

Issue: 1

Appears on pages(s): 233-249

Keywords: high-strength concrete (HSC); mechanical properties; microstructure; palm oil fuel ash (POFA); self-consolidating concrete (SCC); water-binder ratio (w/b)

DOI: 10.14359/51732982

Date: 1/1/2022

Abstract:
Palm oil fuel ash (POFA) was used as a supplementary cementitious material to investigate its effects on the major mechanical properties and microstructure of self-consolidating high-strength concrete (SCHSC). Different SCHSC mixtures were prepared based on the water-binder ratios (w/b) of 0.25 to 0.40 and using the POFA contents of 10 to 30% by weight of cement. The hardened concrete specimens were tested at the ages of 28 and 56 days to determine the key mechanical properties, such as compressive strength, splitting tensile strength, flexural strength, and static and dynamic moduli of elasticity. The compressive strength was also determined at the ages of 3, 7, 14, and 91 days. The effects of the w/b and POFA content on the aforementioned mechanical properties were observed. The microstructures of the 56-day-old concretes were also analyzed based on their scanning electron micrographs (SEMs) in the cases of 0 and 20% POFA contents, considering all the w/b. Test results revealed that the compressive strength, splitting tensile strength, flexural strength, and static and dynamic moduli of elasticity increased with lower w/b and up to 20% POFA contents owing to a greater amount of calcium silicate hydrate (CSH) obtained from cement hydration and pozzolanic reaction. The SEMs of the concretes revealed that 20% POFA contributes to producing a denser microstructure with additional CSH, which enhanced the mechanical properties of the SCHSC with POFA. However, a POFA content substantially higher than 20% (for example, 30%) has a diminishing effect on the tested mechanical properties of the SCHSC, mainly because of reduced cement content and deficient pozzolanic reaction, leading to a lower amount of CSH. The overall research results revealed that the optimum POFA content and the best w/b are 20% and 0.35, respectively.