Preparation of Active Hydrated Alumina by Mechanical Activation and its Application to Rapid Cement Hardener

Milling of gibbsite by an agitation ball mill brought about mechanochemical dehydration and amorphization. A remarkable increase in hydration reactivity with Ca(OH)2 is demonstrated by using a conduction calorimeter. An integral heat of hydration from mechanically activated gibbsite is about 300 times larger than that from the intact gibbsite. We found high correlation between the integral heat of hydration and the 3h compressive strength of conventional Portland cement paste containing milled gibbsite with or without Ca(OH)2. Acquired high activity of milled gibbsite was sustained for at least 2 months under 50%RH. These properties warrant applicability of mechanically activated gibbsite to rapid hardening agents for Portland cement.