| 摘要 |
<p>A lignosulfonate-based cement-dispersant that produces high fluidity in cement pastes, mortar, and the like, without causing excessive set-retardation. Cement compositions dosed with this dispersant harden rapidly, and therefore this dispersant is especially beneficial for use in pre-cast concrete where free flowing but fast-setting cement mixes are highly desirable. The lignosulfonates that can be used in making this dispersant are either sugar-lean, i.e. processed to eliminate most if not all of the otherwise existent sugars, or are modified, i.e. have been ammoxidized by a reaction with ammonia or an amine in the presence of an oxidant. The sugar-lean or the modified lignosulfonate, or a combination of such lignosulfonates, is blended with a ligand such as a carbonate, a bicarbonate, a silicate or a metasilicate that can precipitate multivalent cations, namely, calcium (Ca), magnesium (Mg), and aluminum (Al). The weight ratio of lignosulfonate and the precipitant or a combination of precipitants could vary in the range of 1:0.5 to 1:6, while the dosage of the lignin portion of the dispersant must be at least 0.1 % by weight of the cement.</p> |
