I have a specific question regarding the material properties of marlstone, particularly why this rock is so sensitive to moisture. I have noticed that marlstone building elements or natural formations tend to erode faster or appear more porous under high humidity compared to other types of limestone. This seems to be related to the mineral composition and porosity, but also to the interaction between water and certain components. Could someone explain in detail the exact reasons for this high sensitivity to moisture? Are there typical physical or chemical processes that make marlstone especially vulnerable? And how can these characteristics be best taken into account in construction projects or in the preservation of historic buildings?
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flo-Theres5 Jul 2023 11:03An important aspect not to overlook regarding the moisture sensitivity of marl is its microporous structure and its influence on capillary action. Marl has a porous network of very fine pores, allowing water to penetrate quickly and remain retained for a long time.
This results in prolonged exposure to moisture, which promotes chemical reactions and worsens frost damage.
Additionally, marl often contains dolomitic components that react differently with water than pure limestone material. The interaction of these factors requires tailored protection measures in construction, such as the use of vapor-retardant layers or controlled ventilation.
This results in prolonged exposure to moisture, which promotes chemical reactions and worsens frost damage.
Additionally, marl often contains dolomitic components that react differently with water than pure limestone material. The interaction of these factors requires tailored protection measures in construction, such as the use of vapor-retardant layers or controlled ventilation.
Tinaneo schrieb:
The question of why Malm is so sensitive to moisture needs to be specified: Which exact Malm are we talking about? Thank you for the clarification. In my case, I am referring to Malm from southern Germany, mainly Jura Malm, which is commonly used in historic buildings and is abundant in the region.
I suspect that the mineral structure and the content of finely dispersed clay or organic particles may also play a role, in addition to the immediate physical reaction of calcium carbonate to water.
Does anyone have specific recommendations on how to significantly reduce moisture absorption in these types of Malm used in construction without compromising their visual character?
dranau36 schrieb:
Does anyone have specific recommendations on how to significantly reduce moisture absorption in these types of marl stones used in construction without affecting their visual character?Technically, Jura marl is often treated with a combination of physical protection and chemical treatment. An impregnation using hydrophobic but vapor-permeable materials is important. Silane- or siloxane-based products are well established in practice because they make the pores water-repellent while still allowing drying and preserving the natural appearance.
Additionally, it is advisable to maintain the protected area, carry out regular visual inspections for capillary moisture, and avoid coatings that create vapor barriers, as these can trap moisture and cause damage.
In addition to impregnation, proper installation is crucial.
Errors in joints and connection points allow water ingress, increasing vulnerability. Good drainage and coverings prevent water accumulation and reduce long-term moisture exposure. The construction climate and site humidity must also be taken into account.
Errors in joints and connection points allow water ingress, increasing vulnerability. Good drainage and coverings prevent water accumulation and reduce long-term moisture exposure. The construction climate and site humidity must also be taken into account.
Lucien schrieb:
Silan- or siloxane-based products are proven in practical useCorrect. In general, I advise against using aggressive chemical agents on malm. Hydrophobic impregnations based on silane provide a good balance between protection and maintaining breathability.
Also, make sure that the applied substances are tested for the specific type of malm. Some impregnations slightly alter the appearance – a small test area can help here.
In summary: minimize porosity, keep moisture away from the rock, avoid trapping moisture, and inspect regularly. This way, malm can be properly protected.
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