2a (80)

b) Depending on composition:

•    calcium oxide (quicklime, burnt limę, unslaked limę) is a highly reactive materiał which must be stored in dry containers. It has an exothermic reaction with water. It is offered in varying size ranging from lumps to ground powder materials,

•    calcium hydroxide (hydrated limę, slaking limę) when an exact (stochiometric) amount of water is added in a process known as slaking we recive calcium hydroxide (Ca(OH)₂) as a dry powder,

•    when we use an exess amount of water for slaking we get limę putty -(Ca(0H)₂+H₂0)

Setting of limę binders insists on carbonation - the mortar absorbs C0₂ from the air and the limę effectively reverts back to being limestone - calcium carbonate - over quite lenghty period.

Burnt limę (lump) is used in civil engeenering for producing limę binder, and milled burnt limę is used for limę production - silicate brick. Burnt limę is also apllied in production of cellular concrete.Burnt limę has to be slaked to serve as a limę binder. We use exess amount of water for slaking:

Ca0+H₂0->Ca(0H)₂+66kJ

During this exothermic reaction temperaturę of the system is increasing, and part of water evaporates. We recive limę putty using for mortar, roughcast as the hydrated limę could be used. Hydrated limę doesn't absorb C0₂ so easy as limę putty, and could be stored longer.

3. Activity of CaO

The main factor which affects activity burnt limę is content of free CaO - not connected with other components. Depend on sort of limę its activity vary in rangę 72 - 84%, when the total CaO content equals 85 -96%. Addition of magnesium oxide causes delays in hydration, the maximum content of MgO - 3%.

In table 1 there are technical reguirements for burnt and hydrated limes.

2