Applications, characteristics, pros and cons.
Lime is a versatile raw material and one of the most widely used in construction. Its two main types, quicklime and hydrated lime, are classified by purity, production process, composition and other factors.
QUICKLIME
Also known as burnt lime, quicklime is obtained by mining and calcining the ore (thermal decomposition of limestone). It is divided into three types: CV-E, CV-C and CV-P.
Here again, the different types of quicklime reflect the different purity levels of the raw material and the characteristics of the industrial production process.
HYDRATED LIME
Hydrated lime also comes in three types: CH I, CH II and CH III.
Each has distinct chemical and physical characteristics. CH I has a requirement for total oxides, which are responsible for the material's binding capacity, while CH III allows a higher limit of residual carbonate material, a fraction of the original raw material that is typically present as a result of the manufacturing process.
APPLICATIONS
Quicklime is used mainly within the lime industry itself, to produce hydrated lime. Some places, however, use it as a building material.
The usual practice is to mix quicklime and sand with plenty of water and leave the mix to "rest" for several days so the lime hydrates properly. Cement is then added and the mortar is mixed to its final consistency, ready to be used for laying masonry or for rendering.
Hydrated lime, on the other hand, is used basically to prepare mortars, both for laying masonry and for rendering walls, partitions and slab ceilings.
ADVANTAGES VS DISADVANTAGES
Using lime in mortars has environmental advantages: as the lime hardens, it reacts with the CO2 in the atmosphere and fixes it as calcium or magnesium carbonate. This chemical reconstitution practically zeroes out the generation of CO2, the gas behind the greenhouse effect.
The drawback is lower productivity. Plain lime mortars cure extremely slowly because of the carbonation process, taking days to harden enough for use.