Lime mortar is a type of mortar made from lime, water and an aggregate such as sand. Lime mortar is distinct from cement-based mortars, such as Portland cement mortar, commonly used today. Lime mortar has been used as a binder in construction and masonry work for centuries. There are several types of lime mortar.
- Hydraulic Lime Mortar;
- Non-Hydraulic Lime Mortar;
- Hot Mixed Lime Mortar and
- Pozzolana Mortar:
Types of Lime Mortar
1. Hydraulic Lime Mortar:
Natural Hydraulic Lime (NHL) is used in the production of this mortar. Excellent stability of power and flexibility is provided by it, and it is available in a variety of strengths to suit different applications. The setting process takes place in damp conditions and a power preventing frost damage is reached soon. Simultaneously, when fully cured, the masonry remains softer and is treated sympathetically. The material is available in powdered form, similar to modern cement mortar, for mixing, and it is also the most tolerant of the unconfirmed.
2. Non-Hydraulic Lime Mortar:
Non-hydraulic lime, commonly known as lime putty, is used in the production of this mortar. This mortar is characterized by being extra soft and versatile, making it ideal for the conservation of delicate masonry. The process of carbonation occurs very slowly in this mortar. However, in cold conditions, it is susceptible to frost damage, and it is not suitable for use in damp conditions. The material is provided as a moist, pre-mixed mortar, which has practically unlimited shelf life if stored properly.
3. Hot Mixed Lime Mortar:
Quicklime is used in the production of this mortar, and lots of heat is generated during the mixing process. This sticky, lime-rich mortar is widely favoured by preservationists for hot mixing. However, non-hydraulic lime mortars exhibit low resistance to frost. The material is provided as a moist, pre-mixed mortar, although it is typically facilitated in cold and aged conditions.
4. Pozzolana Mortar:
An addition of pozzolana will be made to “air lime” mortars to impart hydraulic setting characteristics. This addition will result in a preliminary hydraulic set that enhances initial strength and can provide some frost resistance in non-hydraulic and hot-mixed lime mortars.