Limestone shell rock is a sedimentary rock and belongs to the so-called zoogenic formations. It consists of the remains of organisms that died millions of years ago: shells, carapaces, eggshells, etc.
🔍Shell limestone, as a stone, is characterized by high porosity (macroporosity), ranging from 21-60%; bulk density of 1100-2240 kg/m3; thermal conductivity of 0.29-0.99 W/(m•K); compressive strength of 0.4-28 mN/m2. Chemical analysis shows that shell limestone mainly consists of calcium carbonate and contains a small amount of impurities of magnesium salts and alumina compounds.
In 1986, the Soviet Union was developing 149 deposits of shell limestone, from which 9,585 thousand m3 of this limestone was extracted. In the treeless areas of the former Soviet Union, local natural stone materials were widely used, among which limestones-shells occupied a significant place. In Moldova, Azerbaijan, southern Ukraine, Crimea, Kalmykia, and Kazakhstan, they are widely used in construction as wall and facing materials. Gravel and sand from shell limestone are of interest as excellent fillers for lightweight concrete.
"The Soviet Union in 1986 was developing 149 deposits of shell rock."
Building limestones-shells are easily cut even with a hand saw, which is why they are called "sawable" limestones. The limit of sawability of limestones during manual cutting is considered to be the compressive strength limit of 35-50 kg/cm2. Therefore, soft limestones-shells were classified as sawable.
Limestone-shell stones are divided into grades: 4, 7, 10, 15, 25, 35, and 50. The strength of the stones is characterized by the compressive strength, determined by testing samples. The grade of the stone indicates the compressive strength in kg/cm2.
Frost resistance of saw limestone is the ability of water-saturated stone to repeatedly withstand alternating freezing and thawing. The stone is considered frost-resistant if the average compressive strength limit of control cubes of the stone subjected to freezing and thawing is at least 75% of the average strength before the frost resistance test, and if there are no signs of destruction found upon external inspection of the stone sample.
🔍It should be noted that the freshly mined stone from most shell limestone quarries usually does not withstand frost resistance tests. This stone, after being exposed to air for 3 months, typically becomes frost-resistant. It can be assumed that the destruction of freshly mined limestones and shell limestones occurs due to the filling of the naturally quarry moisture in the thinnest and deeply located capillaries of the stone. Complete water saturation of the stone is the cause of its destruction during freezing due to the increase in volume of the water freezing in the pores of the stone.
The pink, and less often light or yellowish-gray, medium and large shell limestones of the Mangyshlak Peninsula in Kazakhstan have high decorative properties.
Shell limestone from Europe
In Europe, there are also many deposits of shell limestone. For example, in the Federal Republic of Germany (Germany), in Lower Franconia, Würzburg (Federal State of Bavaria) and Jena (Federal State of Thuringia), there are deposits of shell limestone with a distinctly layered structure.
🔍This stone was formed about 240 million years ago during the so-called Triassic period. This material has a color range from light gray shades to dark gray with a bluish tint. Depending on the layer of deposition, the material can have a coarse-pored structure or be completely solid.
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🔍Currently, shell rock is actively used as a finishing material, both in interiors and for the exterior decoration of buildings.
Characteristics of shell rock
Due to its physicochemical characteristics, shell rock can even be used as paving elements.
🔍Shell limestone facade
Some types of this stone are well-suited for polishing, which allows it to be used for making countertops in kitchen interiors.
🔍Given the limited annual extraction and processing of this stone, it is primarily used for the exclusive finishing of the exteriors and interiors of expensive real estate properties.
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