Alkanol amines as concrete admixtures and cement grinding aids.
Views: 18 Author: Sam Lee Publish Time: 2019-03-07 Origin: SiteInquire
Alkanolamines are amines containing a single, double, or triple hydroxyalkyl group. They are frequently used as concrete admixtures and grinding aids. The action of triethanolamine (TEA) in the hydration of cement is not described explicitly in the literature since it has still not been concluded whether it is an accelerator or a retarder. Dodson  claimed that “The most popular addition rate of TEA is in the range of 0.010 to 0.25% on the weight of cement. The conclusions show that at a dosage of 0.02%, TEA acts as an accelerator, at 0.25% as a retarder, at 0.5 % as a severe retarder and 1.0% as a flash-set accelerator.” Similar behavior was found by Ramachandran  when measuring the initial and final setting characteristics of Portland cement mortar mixed with 0–0.5% TEA. Other studies have shown that the most prominent feature of TEA is its ability to act as both a set retarder and a set accelerator depending on its dosage. TEA accelerates C3A hydration as well as delays C3S hydration [2, 3]. Jolicoeur et al.  used TEA amounts ranging from 0.02 to 0.15% in their study, and when 0.1% was used, a strong accelerator effect was observed due to the rapid hydration of C3A (false setting). Heren and Olmez  investigated the hydration, and mechanical effects of ethanolamine oligomers added to the consistency water in varying amounts of 0.1 to 1%. They compared monoethanolamine, diethanolamine, and TEA at doses of 0.1 to 1.0% in white Portland cement and found no significant effect on the initial setting times at low doses but considerable retardation at higher doses for all three types. TEA is a weak base, and in the aqueous phase, it is mostly in the molecular state. Furthermore, it can chelate with specific metallic ions such as Fe3+ in highly alkaline media .