Lime Mortars and Plasters

Lime is one of the most geographically widespread building materials, used extensively in areas where limestone or shells exist in large quantities. High-calcium lime is one of the oldest components in ancient and historic floors, masonry, wall paintings, renders, and architectural sculptures. Lime Mortars and Plasters aimed to identify and interpret current scientific knowledge on high-calcium lime mortar to provide insights into the fundamental properties of this ubiquitous building material.

• A comprehensive bibliography

Use of high-calcium lime dates to at least 8000 BCE in the Middle East and to between 2000–1000 BCE in Central America and Mexico. Although it remains in use around the world as a primary construction material, more recent construction practices have incorporated hydraulic components in mortar mixes: pozzolana, natural hydraulic (hydrated) limes, and, since the end of the nineteenth century, ordinary Portland cement (OPC). These materials produce mortars that are comparatively faster setting, stronger, and stiffer. Their use shortens construction time and reduces wall thickness.

These widely available materials may also have properties that are incompatible with historic high-calcium lime mortars, plasters, and renders, including high strength, low porosity, and high salts content. Many mistakes have been made with their use in architectural conservation as repair or replacement material. Complicating the inappropriate use of cement and cement blends is the difficulty of removing or replacing them without causing major damage to existing mortars, brick, and stone.

The damage caused to original high-calcium lime mortars and plasters by such misuse has led to a search for more compatible conservation materials of similar composition and properties and sparked interest in the revival and use of traditional technologies of high-calcium lime production and application. However, there is a lack of modern scientific knowledge and little relevant technical information about these traditional techniques and the reasons and circumstances for the durability of ancient and historic architectural elements incorporating high-calcium lime.

The University of Granada, Spain; Catholic University, Leuven, Belgium