Investigation of anionic group characteristics of PCEs on the behavior of fly ash cementitious systems

This study investigated the compatibility of polycarboxylate-based water reducing admixtures (PCE) having different carboxylate, phosphate and sulfonate anionic groups with paste and mortar mixtures containing fly ash. According to the results, with the increase of the fly ash content of the mixtures, PCE requirement for the target flow decreased, as well as consistency retention performance improved due to the decrease in the amount of hydrated cement. An improvement in rheological parameters was observed with the increase in fly ash content from 15% to 30%. However, increasing the fly ash replacement level beyond 30% caused stability problems in the mixtures. This problem was eliminated with PCE addition. In the paste and mortar mixtures, regardless of the fly ash substitution ratio, the best performance was obtained with PCEs containing 7% and 5% phosphate and sulfonate, respectively. The most suitable fly ash replacement ratio in terms of rheological parameters and 28-day compressive strength was 30% and 15%, respectively. It was observed that PCE anionic group content did not have any significant effect on all fly ash substitution ratios.