Restaurering med naturlig cement

Abstract

This essay has as its purpose to analyse natural cement and the use of this material for restorations. The essay is based on literature studies as well as a number of interviews and may work as a basis for discussion for possible future restorations with natural cement in Sweden. Natural cement, also called roman cement, came to be of great importance as a building material in the 19th century Europe, and it was then used both for constructions on locations exposed to water and, to a great extent, for facing plaster and façade ornaments. In Sweden, the material did not become as widespread, but a minor importation from Great Britain resulted in a number of buildings made out of natural cement in Sweden, most of them located in the Western part of Sweden and Gothenburg. Natural cement stopped being used in the beginning of the 20th century and has until the 1990’s been relatively forgotten. A number of finalized and ongoing European projects have had as their purpose to reintroduce this material on the market, for the restoring of buildings where it has originally been used. Natural cement has earlier been restored with replacement material, which has not been working optimally. Several pilot projects have now been realized in Europe and the newly produced material is available for sale. Natural cement is strongly hydraulic and is characterized by a very quick setting time, generally around three minutes or less. The material is relatively strong and resistant to weather conditions, pollutions and erosion. Its colour varies between different nuances of brown. Restoration with natural cement is in many ways different from restoration with air-lime, hydraulic lime or Portland cement. It is crucial that all the persons involved in the restoration are aware of these differences. The quick setting time is one of the aspects that to a great extent affect the handling of this material. The lack of knowledge and experience is in the present situation making restoration with natural cement a relatively expensive and problematic project. The material has, however, played an important role in the architectonic evolution in Europe, something that motivates its preservation. In Sweden, the existence of the material is, among other things, giving proof of the historical trade contacts between Gothenburg and Great Britain. It is desirable to spread awareness about the material and the number of natural cement buildings in Sweden. It would also be a good idea to take into consideration the existence of natural cement when making a care and maintenance plan for these buildings. By these measures it should be possible, with good planning, to make decisions about future restorations of natural cement buildings in Sweden.