Lime, definition and history

Lime, a widespread mineral product, is suitable for various uses according to its hydraulic or air hardening properties. As an introduction, this article presents a general, geological, historical and chemical presentation of lime and firstly describes limestone, its raw material. Used for a long time without any knowledge of the chemical mechanisms at work in its preparation and setting, lime has been used in an empirical and yet subtle way for instance, the addition of volcanic ashes has been a common practice since the times of ancient Greece. In order to define lime and its various states this empiricism has generated a profuse terminology which this article aims at clarifying. As lime is an essential binder in the construction and architecture sectors, this article evokes its use in this field since ancient times. From the 18th century on, the building of great civil engineering structures all over Europe has stimulated research on the quality of lime as a lasting binder for masonry. This article presents the development of the rational knowledge of lime, and especially of its air hardening, hydraulic or even pozzolanic setting. It finally explains the chemical definitions acquired during this period of time.