Applications for Lime Mortar
Natural Hydraulic Lime mortar consists of two building materials, lime and sand. They can be used for a variety of applications for laying brickwork, bedding tiles, rendering and plastering. By using appropriate sharp sand will help the mortar have excellent workability, whilst keeping a consistent water retention when applied to bricks, blocks and bedding surfaces. Using a lower strength of natural hydraulic lime mortar when compared against Portland cement, will work together and complement natural stone and soft brick applications; whilst improving plasticity and retaining a high level of solidity with a reduction of shrinkage.
Lime Mortar Mix Ratio
Natural hydraulic lime mortars gain strength by a mixture of hydraulic action and carbonation. It is important to be careful with the mix proportions of mortars. Generally, lime mortar mix ratio for brickwork ranges from 1:3 to 1:5 depending on the strength.
The mix proportions provide below are a guide from which a mix can be selected to suit the construction and local environmental conditions. Other aspects, such as the type of brick or stone, or the sand being used will affect the final mix. It is strongly recommended that trial mix is carried out prior to commencement of work to ensure that the mix design and material combinations meet the requirements of the specification and method of use.
NHL 3.5 Moderate Natural Hydraulic Lime
NHL 3.5 Moderately Hydraulic Lime can be used for permeable masonry materials which is mainly used above ground. Generally, it is used for bricks, facings, commons, blockwork, bedding, sandstone, limestone, flint, terracotta, cavity and solid walls, pointing or repointing.
NHL 5 Eminentely Natural Hydraulic Lime
NHL 5 Eminently Hydraulic Lime is commonly used for the foundations of buildings, coastal locations, or for parapets, coping’s and chimneys in external areas.
Mixing Lime Mortar
It is essential that the lime is consistently dispersed and that any fine agglomerations are broken down. At the time of lime being mixed, it will need to be controlled by an efficient mixer. A roller-pan or a screed mixer has the most effective action; but a simple tilting drum cement mixer can be used if a longer mixing time is required. If it is a large job we recommend to use a mixer with a capacity for a full bag of hydraulic lime. In the bullet points below would be suitable for a tilting drum mixer.
1. When mixing wear protective goggles and water-proof gloves. 2. Introduce half of the sand and add all of the lime, mix well for 2 to 5 minutes until a uniform colour is achieved. 3. Stop the and isolate the drive. Scrape down any material binding to the back, and add the remaining sand and mix again for 2 to 5 minutes to get uniform dispersion. 4. Continue mixing and adding water slowly over at least 10 minutes and giving plenty of time for water to be fully incorporated. The mortar should be more like a dough than a slurry and the less water added to achieve this, the better the mortar performance will be. 5. By having a longer mixing time the more workable (fatter) the mortar will become. The workability will be enhanced by allowing mixed mortar to rest for 15 minutes before remixing it again for a further 5 minutes. (In hot weather do not over-mix as water will be lost through evaporation).