Self-Consolidating concrete (SCC) can be placed without vibration and flows easily in very narrow gaps. It is widely used in Japan, has recently been used in Europe, but is very little used in the U.S. Nevertheless, it must be expected that SCC will be used more in the future because of its good performance, such as ease of placement. Due to its rheological properties, the expense of vibration can be eliminated while still obtaining good consolidation. Heavily reinforced structures can be designed and built using this material. According to Kim et al. [52], the major factors defining SCC are rheological properties of the cement paste, the volume ratio of paste/coarse aggregates and the unit volume of the coarse aggregates. If we examine the rheological properties that characterize SCC, the yield stress must be zero or very low and the viscosity must be controlled. The range of viscosities needed to obtain good consolidation without vibration and without segregation has been the topic of various papers [52, 53, 54, 55]. Most of them used semi-empirical tests such as the filling ability test to characterize concrete flow behavior. The properties of the cement paste or the mortar of SCC were found to be very important to avoid segregation. If the viscosity of the mortar is high enough, the coarse aggregates will be supported by the mortar, thus avoiding segregation. Often, viscosifiers such as welan gum or mineral admixtures are added to increase the viscosity of the paste, without significantly increasing the yield stress [55, 56]. NIST research should provide a tool for use in linking cement paste rheology to the performance of SCC and lead to a full specification for SCC.