Hydration
Hydration turns up in 2 fields: refractories, concrete. Here is what it means to the people in each one.
Hydration in refractories
Reaction of magnesia or lime in a refractory with water or humidity, causing swelling, cracking and dusting.
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."
Hydration in concrete
The heat-releasing reaction of cement with water that turns the paste into solid binder.
Calcium silicates in cement react with water to form calcium silicate hydrate, the gel that binds the mix, along with calcium hydroxide and heat. Concrete hardens through this reaction, not by drying, so it keeps gaining strength for weeks and months as long as moisture and warmth last. The heat released is what makes mass pours run hot in the core and lets blankets keep a winter slab from freezing.
"Leave the blankets on, hydration is the only heat that slab has until the sun comes up."