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Table 1. Technical reguiremants for limę according to the PN90/B 30020

No	Requirements	Kind of limę
		burnt limę in lumps				burnt limę powdered				hydrated limę
		sort
		extra	01	02	03	extra	01	02	03	01	02
1	CaO content, % not less than	94	91	88	85	94	91	88	85	70	68
2	MgO content, %, not morę than	0,6	1,0	1/5	2,0	0,6	1,0	1,5	2,0	3,0	-
3	available CaO & MgO content, % not less than	84	82	80	75	84	82	80	75	64	-

4. Time and temperaturę of slaking

The ratę of hydration and the ending temperaturę determine quality of limę.

The ratę of hydration is determined by the type of stone that is fired to start with, and the conditions to which it is subjected during firing. Complete hydration can take place in a matter of a few minutes or continue over a period of months. The factors which determine the ratę of hydration are:

a)    A quicklime with a high MgO content has a slow ratę of hydration sińce it is normally overburnt when fired at the temperaturę necessary to calcine CaC0₃.

b)    A pure, high calcium limę hydrates faster than one containing impurities. Impurities cause the stone overburnt at lower temperatures which reduces porosity and consequently the ratę of hydration.

c)    A lighty burnt, porous quicklime will hydrate faster than an overburnt, dense one.

d)    If quicklime is crushed to a size smaller than 25 mm the ratę of hydration is increased.

e)    The ratę of hydration increases with an increase of both the temperaturę of quicklime lumps and of the water used for slaking. If the quicklime lumps are slaked immediately after they are extracted from the kiln.

f)    The use of an exess amount of water applied to the quicklime at a rapid ratę retards the ratę of hydration.

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