THE INFLUENCE OF CHEMICAL ADMIXTURE TYPES ON THE MECHANICAL PROPERTIES OF CONCRETE WITH 100% FLY ASH SUBSTITUTION

Abstract

Concrete is a fundamental construction material, with production processes, particularly cement manufacturing, posing significant environmental challenges due to high CO₂ emissions. To address these challenges, fly ash, a by-product of coal combustion, presents a sustainable alternative by partially or completely replacing cement in concrete to reduce CO₂ emissions. Despite the potential, previous research reported that concrete with 100% fly ash substitution faced issues in achieving adequate workability and initial strength. The strategic use of chemical admixtures can mitigate these issues, but further investigation is required to optimize the mix proportioning effectively. Therefore, this research aimed to evaluate the influence of various chemical admixtures on the mechanical properties of concrete using 100% fly ash as a binder. The experiment included comprehensive testing of raw material properties, designing mix formulations with different chemical admixtures, and conducting laboratory tests on both fresh and hardened concrete. Fresh concrete was assessed for workability, while hardened concrete was tested for dry density, compressive strength, and split tensile strength at 3, 7, 28, and 56 days. The specimens used will be cylindrical, measuring 100 mm x 200 mm, and cured by water immersion. The study indicated that using Class C fly ash for 100% fly ash concrete, combined with chemical admixtures, resulted in compressive strength and split tensile strength that increased from 28 to 56 days. Chemical admixtures combination enhanced the concrete's density, while superplasticizers improved the slump value, creating self-compacting concrete (SCC). Notably, a 60:40 ratio of superplasticizer to accelerator (MD2) was most effective in enhancing strength.