Experimental Study on High Strength Concrete Using Fly Ash

Abstract

This study investigates the compressive strength performance of high-strength concrete incorporating fly ash as a partial replacement of cement, with an emphasis on achieving sustainability without compromising strength characteristics. Although fly ash offers significant environmental and durability benefits, its use at higher replacement levels is often associated with reduced early-age strength. To overcome this limitation, the present research focuses on reducing the water–binder ratio and utilizing a high-range water-reducing admixture. Concrete mixes were prepared with fly ash replacement levels of 0%, 20%, and 40% by weight of binder. The control mix was designed with a water–binder ratio of 0.283, while the fly ash blended mixes were produced with reduced water–binder ratios of 0.220 and 0.205, respectively. A Sika high-range water-reducing admixture (HRWR) was incorporated in all mixes to ensure adequate workability at low water–binder ratios. Cylindrical concrete specimens were cast and cured under standard conditions, and compressive strength tests were conducted at 28 days. The results indicate that a reduction in the water–binder ratio significantly enhances the compressive strength performance of fly ash blended concrete. Despite the higher fly ash content, the mixes with lower water–binder ratios exhibited improved strength behavior due to reduced porosity, enhanced particle packing, and a denser cementitious matrix. The findings demonstrate that the combined use of reduced water–binder ratio and superplasticizer effectively compensates for the early-age strength reduction typically associated with fly ash. This approach provides a viable and sustainable method for producing high-strength concrete while reducing cement consumption.