Lime mortars for building conservation and rehabilitation: consolidated knowledge and research needs

Abstract Lime mortars were used in construction from immemorial times until at least the beginning of the 20th century. In many regions of the world they continued to have an important role in buildings until the 1950s. This material can tell the history of construction, as perhaps none other can. With the emergence and quick expansion of the use of cement, the traditional knowledge of lime techniques, which was directly transmitted across the generations, started to be lost. In order to recover the lost knowledge, a number of scientific studies were undertaken, involving the analysis of old mortars, the study of old treaties and research about new lime mortars. In spite of all those efforts, and the evidences that lime mortars are the most adequate for the conservation of old buildings, their use in conservation interventions is still rare. What is lacking in terms of knowledge in order to make their widespread use possible? Which are the main research and action needs?