Methods for improved rheological control in cementitious systems

摘要

In accordance with the present invention, a microbial polysaccharide having the features characteristic of S-657 has been found to be effective to improve the rheological properties of a variety of cementitious systems. Thus, the addition of a small, but effective amount of S-657 to such cementitious systems as portland cement, self- leveling grouts, fresh or saltwater oil well cement slurries, microfine cements, and the like, gives rise to substantial improvements in such properties as bleed, flow resistance, fluid loss control, and the like. S-657 addition provides enhanced rheological control in a variety of cementitious systems. In addition, S-657 provides a number of advantages relative to prior art systems, including improved free water and sedimentation control, as well as reduced fines loss during underwater placement. This unique biogum has been shown to enhance the stability of highly diluted microfine cementitious systems, and enhance the flow and workability of superworkable and self-leveling pastes. The homogenous set cement resulting from the introduction of S-657 into cementitious systems promotes bond strength and eliminates the need for vibrated concrete. Efficient free or bleed water control eliminates unsightly vugs or voids adjacent to the form work and thus enhances the appearance of the finished concrete. This highly efficient polymer provides additional benefits as well, such as, for example, enhanced color delivery in pigmented concrete and stabilized bubble entrapment in so called foamed or cellular cement systems. When used in sprayable cementitious systems, S-657 reduces rebound and sag.