At Guild we use our own Heritage Range of specially blended lime mortar mix to achieve the correct ratios for consistent results.
Blend # 1- Feebly Hydraulic NHL 2 based Lime mortar mix for internal areas and those not exposed to the elements, very flexible and good for soft masonry
Blend # 2 – Moderately Hydraulic NHL 3.5 based Lime mortar mix for general use such as render, brick work & pointing
Blend # 3 – Eminently Hydraulic NHL 5 based mortar mix for areas of high exposure to harsh environmental conditions such as chimneys, parapets, copings, sea defences
Blend # 4 – Stone repair mix – NHL 3.5, blended with aggregates and stone dust for Portland, Bath & York stone repairs. Other stone types can be matched with the addition of natural earth & mineral pigments which have greater UV stability compared to synthetic dyes. Stone repair mixes are available in base coat & finishing top coat
Applying lime mortars, the traditional way is still the ideal approach.
A Brief history of lime mortar
Lime mortar is composed of lime and an aggregate such as sand, mixed with water. The Ancient Egyptians were the first to use lime mortars. About 6,000 years ago, they used lime to plaster the pyramids at Giza. In addition, the Egyptians also incorporated various limes into their religious temples as well as their homes. Indian traditional structures built with lime mortar, which are more than 4,000 years old like Mohenjo-daro is still a heritage monument of Indian civilisation. It is one of the oldest known types of mortar also used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.
Lime Mortar has been utilised in the construction of ancient buildings and landmarks that survive to this day, which is testament to its superior properties as a mortar. Ancient and historical structures built by civilisations from across the world, are still standing thanks to the use of lime mortars.
Compared to modern cement based mortars and due to its unique beneficial properties lime mortar:
Lime acts sacrificially in that it is weaker and breaks down more readily than the masonry, thus saving weaker masonry such as sandstone, limestone or brick from the harmful effects of temperature expansion and mortar freeze.
It has a lower firing temperature than Portland cement, and is thus less polluting.
Other environmental advantages of using Lime mortars…
Coal-powered electricity is currently the largest emitter of greenhouse gases, cement manufacture is the next, accounting for approximately 5% of annual anthropogenic global CO2 production. In 2011, we used approximately 3.6 million tonnes of the stuff within the construction industry – the problem being that for every tonne of cement produced, one tonne of CO2 is also produced.
The production of Lime requires less energy compared to cement production.
here’s the technical bit…
Calcium oxide (CaO) is usually made by the thermal decomposition of materials, such as limestone or seashells, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. This is accomplished by heating the material to above 825 °C (1,517 °F), a process called calcination or lime-burning, to liberate a molecule of carbon dioxide (CO2), leaving quicklime.
CaCO3(s) → CaO(s) + CO2(g)
The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air until, after enough time, it will be completely converted back to calcium carbonate unless slaked with water to set as lime plaster or lime mortar.
Annual worldwide production of quicklime is around 283 million tonnes. China is by far the world’s largest producer, with a total of around 170 million tonnes per year. The United States is the next largest, with around 20 million tonnes per year.
Approximately 1.8t of limestone is required per 1.0t of quicklime. Quicklime has a high affinity for water and is a more efficient desiccant than silica gel. The reaction of quicklime with water is associated with an increase in volume by a factor of at least 2.5