Influence of Chemical Admixtures on Properties of Structural Concrete

Abstract

Chemical admixtures play a vital role in enhancing the strength and performance of concrete mixes. These admixtures modify various properties of concrete during the production stage as well as during the setting and hardening periods. The strength and durability of concrete structures significantly depend on the appropriate use of chemical admixtures. They contribute to early strength gain, adjust setting times, improve curing efficiency, and help achieve the desired mechanical properties as per design requirements. Chemical admixtures also interact with the cement hydration process over time, offering long-term protection to concrete against environmental factors. In coastal or high-rainfall regions, their application is especially beneficial, as they help safeguard reinforced concrete structures from corrosion and deterioration. This study focuses on the use of chemical admixtures in concrete incorporating coir fibers and Class C fly ash, using an M30 grade mix design. A PC-200 superplasticizer was employed as the chemical admixture during the experimental phase. PC-200 is a high-range water-reducing admixture based on polycarboxylate ether (PCE) technology. [9]. It is commonly used to improve the workability and strength characteristics of concrete without increasing water content. As a third-generation superplasticizer, PC-200 offers superior dispersion of cement particles, resulting in enhanced flowability, reduced water-cement ratio, and improved early and final strength development. The test results demonstrated that the inclusion of coir fibers effectively controlled cracking and improved tensile strength, while the addition of fly ash enhanced the long-term durability of the concrete. Comparative analysis between the nominal mix and the mix with chemical admixtures showed that the modified concrete mix exhibited superior performance in both strength and durability.  These findings suggest that judicious use of fly ash and coir fibre that can contribute significantly to sustainable constructions, lowering construction costs, and minimizing environmental impact.