Investigation of high range water-reducing admixture requirement in cementitious systems containing fly ash with different utilization ratio and fineness

Abstract

Mineral additives are widely used in cementitious systems to reduce CO2 emissions. In this context, it was understood that fly ash, an industrial by-product, is the most widely used mineral additive. It is necessary to examine the binder-water reducing admixture compatibility in cementitious systems containing mineral additives. The fineness and utilization ratio of mineral additives seriously affect the compatibility in question. In this study, the effect of the use of fly ash in different utilization ratios and fineness on the flow value and consistency retention performance of mortar mixtures containing water-reducing admixture in different ratios was investigated. For this purpose, 4 different usage dosages of water-reducing admixtures (0%, 1%, 1.5% and 2%), 2 different utilization ratios (0, 15% and 30%) and fine fly ash (4000 and 6000 cm2/g) were used. A total of 20 mortar mixtures were prepared. The flow performance of the prepared mixtures for 60 minutes was examined. As expected, the initial and 60th-minute flow values of all mixtures increased with the increase in the use of water-reducing admixture. It was understood that the change of fly ash fineness did not have a significant effect on the initial and 60th-minute flow values of the mixtures. Similarly, it was observed that the change in the utilization ratio of fly ash did not have a great effect on the initial and 60th-minute flow performance in the mixtures with no admixtures, 1% and 2% admixture usage dosages. However, it was determined that the increase in fly ash utilization ratio in mixtures with an admixture usage dosage of 1.5% increased the initial and 60th-minute flow values of the mortar mixtures. Also, it was observed that mortar mixtures containing 2% water-reducing admixture generally have the highest consistency retention capacity (95-100%), regardless of fly ash fineness and utilization ratio.