When we talk about history and lime, the first thing that comes to mind is its use in masonry in Ancient Rome, but its use is much older and more diverse…
As is often the case with technologies dating from before the Neolithic revolution, it is very difficult, and probably impossible, to know whether this was a single discovery that then spread with the advance of sedentarisation, or whether it was a multiple discovery with four main documented centres: the Middle East, the Indus, China and Mesoamerica.
The discovery of lime is simple: it results from heating a limestone stone in a hearth, then extinguishing it with water. The domestication of fire predates 800,000 years, and heating stones for lithic industries has been confirmed as far back as 100,000 years ago in Stillbayen.
The earliest recorded use of lime by humans dates to the Negev Kebarites in the Sinai desert ≈12,000 BC. on the Lamaga north VIII site. Lime was used as a microlithic tip adhesive on the shaft of an assegai or arrow. The use of lime in mortar as a funerary ornament is then attested in the Natoufian Epipalaeolithic (10,000 BC) in the Jordan Valley. The first remains of a lime kiln discovered in the same region date to 8,400 BC. The first documented mortar containing hydraulic elements dates from Pre-Ceramic Neolithic B (8,700 to 7,000 BC) in Anatolia.
From this centre, lime followed the path of Neolithisation: eastwards to Mesopotamia, westwards to Egypt, where mortars were found in the pyramids, and into the Hellenistic world via the Minoan civilisation. The Greek and Phoenician colonies dispersed this knowledge to the Pontic area, the Italian peninsula and their colonies in the Mediterranean (Massalia, etc.). The Gauls also used lime before the Roman conquest, notably on ceramics and as a hair dye, according to Strabo.
The expansion of the Roman Republic, and later the Empire, spread use of lime in the construction of prestigious buildings throughout Europe. Lime production is described by authors such as Pliny the Elder in ‘Naturalis Historia’, Tacitus in ‘Agricola’, and above all Vitruvius in ‘De Architectura’. In it he describes the architectural uses of lime in mortars and concrete, and the various techniques he was able to identify. Unfortunately, the oldest manuscript available is Carolingian (800 years after it was written), and numerous copying errors make the text difficult to interpret. The 1st-century Gallo-Roman villa of Vesuna (in Périgueux) was built on the same limestone bed as Saint-Astier®
Lime was not only used in construction; it was also used in tanning and disinfection for its sanitising properties, such as sealing amphorae or containing epidemics. Lime was also used for its basic properties in many recipes by apothecaries and alchemists. The Meso-Americans also used it to make maize edible via the nixtamalisation process, and thus avoid the pellagra that struck Europe after this cereal was imported. Throughout the Pacific Rim, lime is used in conjunction with alkaloids such as tobacco, coca or betel.
Until the beginnings of the industrial revolution, lime production was confined to intermittent vernacular kilns or at the foot of large buildings under construction (churches, castles, fortifications, etc.). Hydraulic limes (of varying degrees) or airlimes were then described as lean or fat lime, without fully understanding the difference between them. It was only with the development of technology that lime began to specialise. The needs of steel production and the chemical industry would lead to the search for deposits with the lowest water content in favour of the aerial part. Infrastructure (bridges, engineering structures, etc.) and maritime construction (ports, lighthouses, etc.) needs led to research into the hydraulic properties of lime.
Significant work then began in France and England, particularly with Parker and Smeaton, to understand what gives lime its hydraulic properties. However, it was Frenchman Louis Vicat who came up with the solution to the problem. He carried out one of the first modern scientific studies by touring France and visiting all the lime producers, whether air or hydraulic (he also visited Saint-Astier). He pointed out that the more ‘clay’ a limestone contains, the more hydraulic properties it will develop after cooking by increasing the proportion of clay in the raw material.
This discovery opened the door to the manufacture of ever more hydraulic products,ciment dit moderne. including modern cement.
It is a common mistake to attribute the appearance of Natural Hydraulic Limes to this same period, when it was only at this point that Natural Hydraulic Limes and Airlimes were differentiated and characterised according to the mineralogy of the limestone.
With industrialization, vernacular kilns were increasingly being disused. Only the ‘specific’ and constant ‘single-use’ quality products used in the steel and chemical industries would remain. These products have a high hydroxide content. As for building and civil engineering, the most hydraulic products continue to be used.
The massive and rapid construction needs of the 20th century, combined with a gradual loss of traditional techniques and know-how, increased the need for cement to the detriment of Natural Hydraulic Lime. This gradual decline would only be halted by awareness of the deterioration of the built heritage.
The creation of state services such as Bâtiments de France and other conservation bodies would redefine the right qualities of use to reinstate lime and its solutions in the conservation of built heritage.
The oil crisis of 1973 (which led to the gradual closure of industries such as the steel industry) reduced outlets for calcic lime, prompting a search for new uses in the construction industry. CAEB (hydrated airlime for the building industry) was then created. They competed with XHN natural hydraulic lime then in use. Cement manufacturers at the time, to clear stocks of low-quality cements, mixed the latter with a limestone filament sold as XHA artificial hydraulic lime; the latter, which did not meet the same quality requirements as XHN, caused confusion among users.
In 1995, construction limes came under European standardisation, with CAEB becoming CL or DL, XHN natural hydraulic lime being renamed NHL, and XHA becoming MC (Masonry Cement). MC Masonry Cements do not contain lime. A CL or NHL lime mixed with cement, dye or another component became HL (Hydraulic Lime). In 2012, the construction lime standard introduced a new category of lime known as FL (Formulated Lime). This is an HL hydraulic lime, the formulation of which is declared in the product’s CE label.
Today, lime continues to be used in the restoration of the world’s built heritage, rehabilitating our characterful homes and gradually taking its place in the construction of healthier, more environmentally-friendly buildings, often by reappropriating tried and tested old techniques where lime was already used.
The use of lime, combined with bio-sourced, low carbon footprint and technically efficient building materials, is already a solution for the housing of the future.
