Workability, Setting Time and Strength of High-Strength Concrete Containing High Volume of Palm Oil Fuel Ash

Introduction: Palm oil fuel ash in two various forms-ground (GPOFA) by heat-treated carbon-free ultrafine of a median particle size of 2 μm (UPOFA) were utilized to produce high strength concretes (HSC-GPOFA (HSCgx), HSC-UPOFA (HSCux), and HSC-OPC) at different levels ordinary Portland cement (OPC) partial replacements (x) of 20, 40 and 60%. Methods: The workability (slump, slump loss, and compacting factor), initial and final setting times and strength in both forms of concrete were investigated. Results and Conclusion: The results showed that HSCu had improved physical properties and chemical compositions, extended setting times, enhanced workability, better strength, and enhanced workability retention compared to HSCg and HSC-OPC. Further, POFA carbon content negatively influenced the workability and setting time, while its specific gravity had a positive influence due to the enhancement of paste volume and particles lubrication effects. However, carbon content and surface areas of POFA did not significantly influence the compressive strength of HSC at the level of partial OPC substitution not exceeding 40%.