The optimum dosages of both HRWR types obtained with various w/c ratios are compared in Fig. 1. Variation of flowability with time for mixtures made with PNS and PC HRWR types are presented in Fig. 2 and Fig. 3, respectively. When used with PNS, BC is shown to require slightly higher HRWR dosages than OC to ensure a given dispersed system, regardless of the w/c ratio. It is worthy to mention that these results are valid for the cement used in this SNDX-275 study. For example, mixtures made with BC and PNS required dosages of 0.45%, 0.45%, and 0.36%, by mass of cement, for w/c of 0.30, 0.33, and 0.36, respectively. In the case of mixtures made with OC, Chlorophyta dosages are 0.40%, 0.40%, and 0.35%, respectively. When PC HRWR is used, BC requires, however, lower HRWR dosages than OC, regardless of the w/c. Indeed, BC mixtures require dosages of 0.12%, 0.10%, and 0.08%, while those made with OC require higher dosages of 0.20%, 0.16%, and 0.12%, respectively. A high HRWR dosage reflects a lower efficiency of the HRWR to disperse solid particles and secure a given flowability. This may be affected by reactivity of cement, aluminate phase, calcium sulfate, and alkali content ,  and .