Lime is one of the earliest binding materials used in buildings because its raw materials are rich and widely distributed, the production process is simple and low-cost, and it is easy to use. Therefore, lime is still widely used in construction until now.
Characteristics of Limestone
1. Good Water Retention
The lime mortar generated by the aging of lime has good water retention, so it can be mixed in cement mortar to improve the water retention of mortar to facilitate construction.
2. Slow Setting and Hardening, Low Strength
Because the carbonization of lime mortar in the air is very slow, the production of calcium carbonate and calcium hydroxide is a little and quite slow. And thus, the strength of hardened lime is low. According to tests, 1 : 3 lime mortar of 28d has only 0.2-0.5 MPa strength which should not be the basis for important buildings.
3. Poor Water Resistance
Calcium hydroxide is soluble in water, so if it is exposed to moisture or immerses in water for a long time, the hardened lime will scatter. If lime mortar is in humid environment before complete hardening, the water in lime cannot evaporate, and the hardening will be hindered. Therefore, lime should not be applied in humid environment.
4. Large Shrinkage
In the hardening process of lime mortar, a large amount of water evaporates, which cause the shrinkage of volume. And desiccation cracks will appear. Thus, lime mortar should not be used alone except for the lime cream for thin painting. In use, it is often mixed with sand, hemp fiber, paper pulp, and other things to resist cracking caused by shrinkage.