The acceleration and retardation of set high alumina cement by additives

✍ Scribed by B.R. Currell; R. Grzeskowlak; H.G. Mldgley; J.R. Parsonage

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 588 KB
• Volume: 17
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(87)90006-8

✦ Synopsis

The set of hlgh alumlna cement (HAC) pastes may be considerably Influenced by the addltton of very small quantities of chemlcal compounds, From the measurement of settlng tlme and temperature flee.

wlth a conduction calorimeter. It ls shown that both catlons and anlons have a profound effect on the chemlcal reactions whlch cause the hardening of HAC, The effects on the tlme of settlng may be summarlsed as follows:for catlons LI ~ Na < none < K, ~ Ca < Mg < Sr < NH 4 for anlons OH ~ none < CI < NO 3 < Br < acetate The effect of anlons, except for the hydroxyl lon, causes a retardation In the settlng as a result of replacement of OH groups llnked to AI, referred to as lon penetration, preventing the formation of oxobrldges. The retardation ot sot wlll be governed by the rate of replacement of OH by other anlons and the stability of the new specles formed. The dramatlc effect of OH ls due to the replacement of H20 by OH In the AI environment leadlng to a further centre for oxobrldge formation.