| 1. |
- Balksten, Kristin, 1977-, et al.
(författare)
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A method to recreate historic mortars applied at Norrlanda church on the island of Gotland, Sweden
- 2008
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Konferensbidrag (refereegranskat)abstract
- In this work, scanning electron microscopy analysis of lime slaked in different ways and analysis of thin section limeputty and mortar specimens by light microscopy was combined with practical tests and field studies in order to evaluatethe impact of the slaking technique on the properties of the lime putty, and also the structure of the fresh and carbonatedmortar. The lime slaking methods studied were wet slaking and earth slaking. These techniques give lime putties withvery different consistency and workability. The aim of this work was to use microscopy techniques to explain thesedifferences in properties and to investigate if it is possible to use these analytical methods to recognize the lime slakingtechnique used in a historical lime mortar.The results obtained by electron microscopy show significant differences in structure between the lime puttiesstudied. The earth slaked lime consists of relatively large particles that are packed in a porous system as compared to thewet slaked lime with very small particles closely packed in a dense structure. After storing, the wet slaked lime gives aputty, that has a dense and clearly defined stratified structure, whereas the earth slaked lime is porous and has nostratification. The earth slaked lime is tixotropic and has a light, smooth consistency reminding of well whipped creamcompared to the wet slaked lime that has a strong orientation and a rather stiff consistency reminding more of pudding.Microscopy investigations of thin section mortar specimens showed how the lime affects the mortar concerninghomogeneity, density, pore structure and crack patterns.
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| 2. |
- Balksten, Kristin, 1977-
(författare)
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Beständighetsproblem för kalkputs
- 2005
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Ingår i: Byggnadshyttan på Gotland 2003-2004. - Visby : Byggnadshyttan på Gotland. - 9789197467926 ; , s. 23-30
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Bokkapitel (populärvet., debatt m.m.)
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| 3. |
- Balksten, Kristin, 1977-, et al.
(författare)
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Construction and materials of Visby medieval city wall – risk of damage
- 2014
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Ingår i: 9th IMC, Book of Abstract. - 9789728692858
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Konferensbidrag (refereegranskat)abstract
- The City Wall in Visby was built in two periods in 13th and 14th century. The first wall was made as a lower three-leaf wall with two shells built of lime stone and fat lime mortar and a soft and porous rubble core of lime stone and clay mortar. The second wall was built higher on top of the old one. It was mostly built as a solid wall in lime stone and lime mortar. Due to its construction and form, a major part of the force is carried by the outer shell of the wall. As restorations have been made during 20th century the joints of lime mortar has been partly repointed with strong cement mortar, followed by leached lime inside from the mortar in the wall. In February 2012 a part of the wall collapsed and fell down as the outer shell of the masonry collapsed. This paper presents an analysis of the wall structure and its materials as well as the increased risk of damage due to the restorations of the 20th century.
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| 4. |
- Balksten, Kristin, 1977-
(författare)
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Det gotländska bruket av kalk
- 2008
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Ingår i: Från Gutabygd 2008. - Visby : Gotlands hembygdsförbund. ; , s. 125-140
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Bokkapitel (populärvet., debatt m.m.)
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| 5. |
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| 6. |
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| 7. |
- Balksten, Kristin, 1977-, et al.
(författare)
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Increased salt and frost damages in solid neo-Gothic brickwork masonry due to low permeable restoration materials of the 20th century
- 2014
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Ingår i: 9th IMC, Book of Abstract. - 9789728692858
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Konferensbidrag (refereegranskat)abstract
- In Gothenburg many stone buildings of brickwork were built during the neo-Romanesque and neo-Gothic period in the late 19th century. The masonry was solid with a wall of bricks often covered with facing bricks with a hard burned water repellent surface. At Örgryte new church the bricks were put in lime mortar but the surface of the joints was made with a thin cement mortar layer. Salt problems are known in this church since early 20th century and the subsequent need of maintenance have led to several extensive restorations with replacement of external facing bricks and internal lime plaster during the years. In each restoration more low permeable facing bricks and more low permeable cement mortars have been chosen, followed by new problems inside the wall as the water transport properties in the wall has changed. Whereas salts have caused problems mainly on the surface, the restoration materials have caused problems with frost and salt damages in bricks and lime mortars in the wall core behind them.
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| 8. |
- Balksten, Kristin, et al.
(författare)
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Increased use of ruins through secured masonry and comfortable climate
- 2010
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Ingår i: Proceedings of the 7th International Conference on Science and Technology in Archaeology and Conservation, Petra, Jordan.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a unique scientific research project, funded by the KK-foundation in Sweden together with several companies participating in the project. A primary goal is to find methods to examine and take care of open masonry constructions thereby enabling an increased use of them in a safe and comfortable way without diminishing their cultural values. A second goal is to establish a long-term cooperation/network of researchers, conservators, engineers, antiquarians and craftsmen that can keep and develop the knowledge. The project takes place in year 2010 and 2011. This paper presents a model of cooperation as well as the ongoing experiment and expected results. The project is divided into three major parts:1) Description and assessment of historic masonry as load bearing structures. 2) Assessment of stone and mortar in old masonry and finding the methods to secure and preserve them. 3) The climate in the ruin with respect to comfort and preservation. The goals for the different parts of this research project are to find the best possible solutions of how to: a) Evaluate the construction of complex masonry structures to enable new additions that are appropriate with respect to statics. b) Find efficient methods to evaluate and conserve the status of the materials (stone, mortar) and walls in old masonry to grant safe accessibility. c) Create a comfortable climate in an open masonry structure without closing it. These three research areas all focus on the historic masonry which at the same time forms the climate shell, the bearer of plaster and the historical setting to the activities that are to take place in the ruin.
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| 9. |
- Balksten, Kristin, et al.
(författare)
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Internal Retrofitting with Hemp-Lime on Brick Masonry : a Study to Prevent Damage Caused by Sodium Sulphate
- 2021
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Ingår i: Proceedings of SWBSS 2021 : Fifth International Conference on Salt Weathering of Buildings and Stone Sculptures - Fifth International Conference on Salt Weathering of Buildings and Stone Sculptures. - 9789463664394 ; , s. 277-286
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Konferensbidrag (refereegranskat)abstract
- In Sweden there are a great number of neo-gothic churches built in brick masonryaround 1870-1910. They are constructed as massive masonry walls with façadebricks attached to a core of massive red bricks. In the majority of these churchesthere is a presence of sodium sulphate causing salt damages. The source of the salts is known to be the red masonry bricks and the damage occurs both internally and externally on the walls. Damages occurred already after a couple of years after the churches were built and ever since they caused expensive renovations with little or no durability. As the sodium sulphate crystallizes inside the plaster the damages cause spalling of the surface.Since 2016 a method to prevent or delay salt damages has been studied and evaluated. By adding a layer of insulation on the internal wall the microclimate on and nearby the plaster surface can be changed and the damages caused by crystallization decrease. When adding an insulating layer made by hemp-lime plaster before adding the lime plaster the salts cause less visible damage to the internal plaster.Full-scale test surfaces have been made both in the laboratory and inside twochurches. After two and three years respectively, there are no visible salts causingdamages inside the churches, where salts previously came back directly after eachrenovation. In the wall in the laboratory at Lund University the bricks where contaminated with sodium sulphate and internally rendered with hemp-lime plaster with a lime plaster surface finish. Even though there are lots of salt-related damages externally there are thus far, more than two years after construction, no signs of any damage internally.
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| 10. |
- Balksten, Kristin, 1977-
(författare)
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Kalkputs : porstrukturens betydelse för beständighet
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When restoring historic lime plaster it can be difficult to reach the required durability. Today newly made lime plaster can fall off due to frost damages after only a couple of winters. To understand and solve these problems, the subject has been studied from different perspectives. Several factors in the production step are making an influence on the durability of lime plaster: 1. A binder, suitable for the building, must be chosen along with sandthat gives good material properties in both fresh mortar and in plasters. 2. The lime/sand ratio and the mixing technique should be chosen from the properties in the lime and the sand, in order to get a mortar with good workability. 3. The craftsmanship should be adjusted to the mortar, the weather and the underlying materials. A plaster with good frost resistance has a certain pore structure. The plaster should have some round air pores that contain air even when the material is filled capillary with water. Such air pores give the water a free space to expand when it is freezing. If the air pores are missing, the ice crystals may damage the plaster when expanding. To increase the chance of making a frost resistant lime plaster, the lime/sand ration must be adjusted so the lime can fill up well in the sand. Otherwise a collapsed pore system can easily occur, which means an open pore system without distinct air pores. A collapsed pore system contains many pores well connected with each other. Such a system is easily damaged by frost. To increase the chance of success, it is of great importance to work the surface of the lime plaster at the right time and in the correct way. Before working on a surface the mortar must be aloud to stiffen. Only then a homogeneous material can be created; cracks due to shrinkage can be pressed together and the result is a more compact material with an open surface. The time necessary for mortars to stiffen is related to the water content of the mortar, the suction of the underlying surface and the weather conditions. If the surface is worked on while the mortar is still fresh, the binder can form a hard lime shell on the surface. Inside thematerial a lack of binder can appear. Such plasters have a very low frost resistance. Other durability problems related to plaster are damages in the underlying materials, i.e. rotten wood in covered constructions or leached lime in old joints. Such damages can occur if the covering mortar is made of strong hydraulic lime or cement, since they form plasters with a low permeability in comparison to lime. Due to mentioned findings, it is important to study how a pore structureis influenced by materials, mixture and craftsmanship. Only then it is possible to understand how damages can be decreased.
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