How to Mix Lime Mortar

Lime mortar is among the oldest types of mortar used in construction. It is prepared by mixing together lime, construction aggregate, sand, and water. The first people to use lime mortar in construction were the Greeks and the Romans. Traditionally, the lime mortar was made by mixing lime putty with construction aggregates. Today, in addition to these two ingredients, washed high-grade sand is also used to prepare lime mortar; sand enhances the durability and compactness of the end product. With modernization, the use of lime mortar has tapered down due to its long setting times and complicated handling.

Lime mortar is mostly used with softer building materials such as natural stone and terracotta. So, if you are trying to restore old villas or trying to give your house that old world charm, it would be best to prepare lime mortar the old-fashioned way. However, as the type of lime mortar depends on the nature of the construction project, it is important to find out what kind of lime mortar will suit your needs the best.

It is almost impossible to mix all the ingredients of lime mortar with your bare hands; hence, it would be good to use a vertical shaft mixer for mixing purposes. These mixers can be rented for short periods of time. Ensure that the lime, sand, construction aggregates, and water should be added in the correct proportions in order to obtain good-quality lime mortar. The procedure involved is described below.

Step 1 – Pound the Lime Plaster

Before commencing the work, protect yourself from making any reaction to the lime by wearing rubber gloves and make sure to wear safety glasses. Make sure that the lime plaster has been mixed thoroughly to render it more plastic and workable. Pounding the lime plaster between two hawks can do the trick.

Step 2 – Mix the Ingredients Using the Mixer

Switch the mixer on and alternate between adding sand and lime. Allow the mixer to mix the ingredients together till the point where the mixture becomes crumbly.

Step 3 – Add Water Carefully

Do not add more water to the mixture as lime plaster already has the amount of water it requires. Also, adding more water at this stage will shrink the mortar, which will make it harder to work on later.

Step 4 – Note the Texture before Adding Other Aggregates

In approximately 20 minutes, the mixture will attain a crumbly texture. It is recommended that the mixer lid be covered with a rubber sheet to maintain the quantity of water in the mixture. Check if the mixture has developed a cream-cheesy texture. You can add other aggregates and fibers to the mixture at this stage and let the mixer do its work for another 30 minutes.

Step 6 – Remove Excess Water

The lime mortar is almost ready now. Remove excess water from the mixture if it appears to be too wet. For this purpose, spread out the mortar on a plywood plank and incline it at an angle. This will allow any excess water to run off or evaporate. However, do not leave the mortar in this position for more than an hour.

Important Tips

You can keep the mortar stored in the mixer, provided it is completely covered and mixed well again before use.

Mortar in which fibers have not been added can be stored for longer periods of time in air-tight containers.

Wear rubber gloves so that your hands do not react to lime.

Wear safety glasses to protect your eyes from any debris.