Effects of reactivity of MgO expansive agent on its performance in cement-based materials and an improvement of the evaluating method of MEA reactivity

Determined by calcining temperature and duration, reactivity of MgO is a dominating role of the hydration and expansive properties of MgO expansive agent (MEA). In the present work, the characteristics of industrially produced MEA and the morphology of its hydration products were investigated with zeta potential analyzer (ZPA), Morphologi G3 optical microscope and scanning electron microscope (SEM). The influence of activity and dosage of MEA on fluidity and expansive properties of shrinkage-compensating binder was also investigated. Results indicated that the reactivity of industrially produced MEA is not a fixed value, but distributes in a range. The fluidity and expansive properties of binders containing MEA is affected by the reactivity and dosage of MEA. Besides, advantages and disadvantages of the standard evaluating method on reactivity of MEA were summarized. A new evaluating method of MEA reacting with ethylic acid buffer solution and weighing residue on the reactivity of MEA has been proposed.