What do we know about rammed lime/coal slag?
Résumé
Nowadays, cement mixtures with fly ash or clinker from heavy industry (blast furnaces) for construction are known and still studied to increase their use. This approach is a form of recycling and recovery of by-products from the industry. However, the use of ashes from industry for construction is very old and used in France since the mid-19th century.
This technique appeared then developed in the area of the cities of Lyon and Saint-Etienne, which had many foundry industries in the 19th century during the industrial era. Following a prefectural decree of 19 June 1856 prohibiting rammed earth (due to a flood of the Rhone River in Lyon) in the Region of Lyon and Saint-Etienne, slag coal mixed with lime were then massively used as a replacement of rammed earth thanks to its resistance to water. The construction technique is the same as for edifying rammed earth walls only change the materials. The walls are massive, monolithic and thick (50 cm) and seem to have hygrothermal comfort qualities similar to rammed earth walls. Renowned architects like Gaspard André (1840-1896) and Tony Garnier (1869-1948) used this material for architectural works that are still used today. According to local architects and building professionals in Lyon and Saint-Etienne, rammed lime/slag coal constructions represent hundreds of thousands of buildings. This technique, used for a hundred years in the region, is however largely unknown and no recent study has described the physicochemical characteristics of this material. In the current context of sustainable development and energy renovation of buildings, a thorough knowledge of this material would enable to renovate these constructions rather than destroying buildings because of the lack of knowledge of the material.