Lime burning tradition in field kilns : a case study of the Jämtland tradition in Sweden
This study focuses on the local lime tradition in the region of Jamtland, in central Sweden. Local lime was used when building the medieval stone churches and since they are in a need of restoration there is subsequently a need for understanding the use of local lime. The geology of Jamtland contains several layers of limestone in the folded mountains. There is a broad spectrum ranging from pure Silurian limestone to clay containing Ordovician limestone, giving all kinds of lime from pure air lime to strong hydraulic lime. The preserved historic mortarshave mostly been made with the hydraulic lime. Several old field kilns have been preserved in the forest landscape as prehistoric monuments, showing the model of the local lime burning tradition. This paper discusses the process of identifying the historic lime kiln constructions and their burning technique. It also describes the process of slaking this hydraulic binder in order to produce a lime mortar with workability and compatibility required from a restoration mortar. Newly-produced samples of lime mortar have been compared with historic ones in thin section microscope for further understanding.
Understanding historic mortar and their variations – a condition for performing restorations with traditional materials
In order to design a restoration mortar with proper ties and composition similar to the original mortar, it is important to analyze the historic mortar in several ways. A combination of analyses give information about the mixing ratio between binder and aggregates, chemical composition of the mortar, additives, tool marks, application technique etc. This paper shows the variatio ns in Swedish medieval lime mortars with a high rate of binder. By analysing hi storic mortar with a combination of ocular investigations, microscopically stud ies of thin section specimens, Scanning Electron Microscopy and X-Ray Powder Diffr action, all the information needed for designing a restoration mortar, with com p sition and properties similar to the historic mortar, is gained.
Ground Fault Protection for Electric Utility Generating Station Medium Voltage Auxiliary Power Systems
Most generating station designs have medium voltage auxiliary power systems with low resistance grounded neutrals.1 In order to provide even higher reliability, the auxiliary power distribution system configurations supply increasingly redundant process equipment.