Calcined clays have attracted significant attention as a low-carbon supplementary cementitious material. In this study, the dispersing performance of three PCE superplasticizers varying in chemical structure (MPEG, HPEG and IPEG based polymers) were investigated in composite cements containing two different calcined clays. These two calcined clays were obtained from different regions and differ significantly in their metakaolin contents (~ 23 wt.% vs. ~ 51 wt.%). They were blended with Ordinary Portland cement (OPC) at a clinker substitution ratio of 30 wt.%. It was found that as compared to OPC, both calcined clays decrease workability and substantially increase the water demand due to their higher fineness. Furthermore, the results differ depending on the mineral composition of the calcined clay. For example, an increase in superplasticizer dosage of ~ 400 % as compared to neat OPC was recorded for the sample holding 51 wt.% metakaolin, while it was only ~ 60 % for that containing 23 wt.% metakaolin. In addition, among all the PCE samples tested, the HPEG PCEs disperse these composite cements best, followed by IPEG PCEs while MPEG PCEs performed the least. It is concluded that the workability of calcined clay blended cements significantly depends on their specific mineral composition. High metakaolin content present in a calcined clay decreases the workability of the composite cement considerably.    «

Calcined clays have attracted significant attention as a low-carbon supplementary cementitious material. In this study, the dispersing performance of three PCE superplasticizers varying in chemical structure (MPEG, HPEG and IPEG based polymers) were investigated in composite cements containing two different calcined clays. These two calcined clays were obtained from different regions and differ significantly in their metakaolin contents (~ 23 wt.% vs. ~ 51 wt.%). They were blended with Ordinary...    »