Experimental data from the Brookfield viscometer and curve fitting results for all pastes are indicated in Fig. 5. The Herschel- Bulkley model resulted in an adequate fitting, with all values of the coefficient of determination (R2) higher than 0.99. It is clearly seen that the shear stress is higher for the RHA-based mixtures than P-REF, with the increase of the shear rate. The rheological results listed in Table 5 indicate that the replacement of cement by RHA was responsible for an increase in both s0 and a Herschel-Bulkley parameters, especially for 15 and 20% RHA contents (in volume, which is equivalent to 11 and 14% in mass). This is consistent with the particle characteristics of RHA, mainly, the high specific surface area [26]. For any given RHA dosage, no expressive difference in the rheological parameters was found. In this case, s0 values ranging between 7.63 and 8.23 Pa and a values between 0.18 and 10 6 Pa sb. Both s0 and a highest values were observed for P-RHA20. The rheological tests also indicated a shear thickening behavior for all pastes, i.e., the apparent plastic viscosity which increased in response to the increase in the shear rate (parameter b > 1). This behavior was also reported by Celik and