The relative variations in yield stress as recorded from the truck measurements, ICAR rheometer, and the slump test are shown in Fig. 12 and Fig. 13. The results between different tests were generally consistent. The addition of HRWRA for mix C11, C12, and C13 resulted in decreases in the yield values measured by both the ICAR rheometer and the truck. Many authors [18, 19, 20] have shown that concrete slump is inversely correlated to yield stress, because a high slump indicates a reduced resistance to flow as does a low yield stress. Indeed, the slump increased as the truck measurements and ICAR rheometer indicated a reduction in yield stress due to the addition of HRWRA. The use of a viscosity-modifying admixture for mix C14 resulted in increases in yield value as determined by both the truck and the ICAR rheometer and a decrease in slump as compared to mix C13. For the second mixture, the use of HRWRA again resulted in reductions in yield value as determined by the ICAR rheometer and the truck and an increase in slump. As with the viscosity values, the yield values were dominated by the setting of the concrete for the last two mixtures.
Fig. 12. Relative yield or slump values, as defined by the ratio of the measured yield stress or slump with the control mixture yield stress or slump, as recorded by mixing truck, ICAR rheometer, and slump test. The control mixtures are C10 and C20.
Fig. 13. Correlation of yield value between ICAR rheometer and truck.