The reaction of MgO, and even more readily CaO in doloma and lime products, with water or moist air to form hydroxides that take up more volume. Bricks crack and crumble, gunning mixes cake, and magnesia-containing castables can crack during curing or dry-out. Basic products are shipped shrink-wrapped and stored dry, and basic linings are never cured or cleaned with water.
Pallet of doloma sat in the rain and hydration has the bricks dusting and cracked, scrap the whole lot.
Store basic materials indoors on pallets and use the oldest stock first. Hydration starts in the bag long before anyone sees it.
Also heard as
- slaking
- dusting
Related terms
Dead-burned magnesia
Magnesia fired so hard it barely reacts with water, the main raw material of basic refractories.
Mag
Clipped shop word for magnesia, magnesia brick or a magnesia-based mix.
Basic refractory
Refractory based on magnesia, lime or dolomite that resists basic slags with high lime-to-silica ratios.
Dry-out
Controlled first heat-up of a new monolithic lining to drive off water without cracking or spalling.