More and more private builders are paying attention to the environmental performance of building materials and technologies. That is why the popularity of natural shell material is growing.
This building material, long known and especially popular in the southern regions, is called "shell rock", "shell", "shell" . More dense rocks of the same origin and composition - limestone and marble. The name of the shell rock reflects its constructive essence: all the limestones are of organic origin, and the shell rock, porous limestone, consists mainly of the shells of mollusks and other marine organisms.
The process of its formation took more than one million years. The coastal areas were flooded with sea, the remains of microorganisms and mollusks fell to the bottom and remained in the sea sand. Over time, the water receded, sand banks were gradually covered with a layer of soil, which became a kind of pressure, under which a dense rock was formed.
The shell rock is a soft, porous stone of yellow, red-yellow or light brown color. Material for construction is cut out of the rock mass, getting stones in the shape of a rectangular parallelepiped. They are lightweight, but strong enough for the construction of load-bearing walls of a building up to three floors high. The porous microstructure of the shell rock, filled with air, provides it with excellent heat and sound insulation properties.
The properties and advantages of shell rock as a building material
According to external signs , the shell rock is divided into two groups: yellow, having a compressive strength of 5-15 kg / cm2, and white, with a compressive strength of 10-20 kg / cm2. The chemical composition of the shell rock is constant and does not depend on the field. In addition, it is a material with a pronounced layering.
The main advantages and advantages of shell rock are low thermal conductivity, high vapor permeability, good sound insulation properties and environmental friendliness .
Thanks to its porous structure, the stone “breathes” freely and excess moisture is simply displaced without destroying it. In a shell house, it is always dry, since the moisture that forms inside passes through the walls, and they themselves, if they get wet, dry out quickly. It is cool in summer in such a house, and warm in winter. The material does not rot and does not burn, but under the influence of high temperature it burns out and collapses. The low price can be attributed to its advantages. Thus, the wall of shell rock is about 20% cheaper than the same of foam concrete and almost two times cheaper than brick. Low thermal conductivity and good sound insulation properties of the shell rock are associated with the presence of air pores. The porosity of the material, which may be different (22-70%), causes its low density and lightness. Its volumetric weight is 700-2 300 kg / m3. In construction, several grades of limestone of different strengths are used - from M10 to M35.
The use of shell rock in construction
The wide possibilities of using shell rock can be easily attributed to its advantages.
So, this stone can be used for:
Possibilities of a shell stone as building material
With the health benefits - ecological characteristics of the shell rock
Although the coquina has a lot of advantages, environmental characteristics give it a unique character. So, it has a natural background radiation of about 13 μR / h with a permissible natural rate of 25 μR / h. Moreover, it is the only material in the world that does not transmit 100% radiation. In addition, it is completely inert and does not react with substances contained in other building and finishing materials. And, as experience shows, rodents do not start in buildings made of this stone.
The walls of the shell rock enrich the air with iodine, salt and have bactericidal properties (if the wall is multi-layered, it is useful for the shell rock layer to be turned inside the house). And this stone does not cause allergic reactions. In houses of shell rock, mood and vitality are raised, and the general condition of the body is also improved.
In addition, crushed stone and sand from the shell rock are good aggregates for lightweight concrete. It is used in the production of lime, as well as other binders. The only thing that is not to be done from the limestone is stoves, fireplaces and chimneys.
The ease of processing this material allows you to make various architectural elements of it: rounded walls, arches, etc. Due to the high wear resistance of the bone, dense shell rock varieties are suitable for facing staircases, terraces and porches. For example, steps of a staircase cast from concrete can be revetted with shell rock tile.
Material Heterogeneity: One Problem and Multiple Solutions
Not a single barrel of honey can do without a fly in the ointment. The same can be said about the shell rock. Despite a lot of advantages, it has a significant drawback - the heterogeneity of the structure.
The porosity index of this material varies over a wide range, which causes differences in other physical characteristics, primarily in thermal conductivity. Different layers in the quarry also mean different density and structure of the stone. It is this disadvantage that does not allow to sell shell rock in supermarkets. Therefore, acquiring it, you must be careful: for the construction of the house should select the party with the same characteristics and structure. The heterogeneity of the material is associated with its natural origin and depends on the state of the formation from which it was extracted. Therefore, blocks of shell rock of different brands and with different structures can be found among the proposals of all mining companies.
The heterogeneity of the structure leads to the fact that the material can have through or open pores.
They are especially numerous in the shell of low density. Such pores repeatedly degrade the insulating properties of structures. The wall of such a shell rock does not “breathe”, but rather “shines through”.
There are two ways out of this situation.
First exit.
Choose material without open pores, inspecting and setting aside stones heavier, weighing at least 16 kg (they have a denser structure and smaller pores), and also check the quality certificate. The main way to check the density of a stone is to hit it on a hard surface. If it splits into no more than three parts, then the mark of the mother is M25 and it is rather dense. The less density, the more parts and sand will arise from the impact. Shell M35 brand is not broken at all. If the stone has a uniform structure, the correct geometry and high density, the wall will reliably protect the house from the winter cold.
However, due to the same porosity, the coquina easily absorbs moisture and substances dissolved in it. Therefore, upon completion of construction work, it is desirable to cover it with a special water- and dirt-repellent solution, which will protect the surface of the material from the effects of rain, mud and water-soluble salts. If the building is located on a street with heavy traffic, it will also require treatment with an oil-hydrophobic compound. The bactericidal composition will protect the stone from depriving moss and fungi. There are also special compounds that protect the shell rock from the effects of acids, alkalis, paints and organic solvents.
The second way to protect the house from drafts, and from the effects of the environment -
The device is an external barrier, that is, protection of the wall structure.
The outer barrier involves the finishing of vapor-permeable plaster or brick lining with a ventilation gap from the main wall. It is also possible to mount outside a layer of insulation from mineral wool plates of stoves using the “wet facade” or “ventilated facade” construction. Such a house will be warm, reliable and natural inside.
A new effective method is the construction of a ventilated wooden facade by the ecohouse, developed by a Kharkov company that builds eco-friendly houses. This technology is interesting with a combination of natural materials: wood and shell rock. On the supporting wall of the limestone "worn" sheathing of wood, of course with a ventilation gap. At the same time, unlike the usual ventilated facade, there is no special system of profiles, the facade is mounted on a wooden beam using self-tapping screws. Wooden bearing bars are laid in the wall during the laying of shell rock blocks. Such a wall is made easily, quickly and simply.
Features of construction and finishing of shell rock
The size of the coquette stone is about 20 x 20 x 40 cm, the exact standard is 18 x 18 x 38 cm. Accordingly, building 1 m2 of a wall one block thick (38-40 cm) will require 30 blocks, or 18 if you put it in half a block (wall thickness 18-20 cm). One block of shell rock replaces 7-9 bricks. Walls one block wide are enough for our climate, provided that a wind barrier is installed, and the wall in half a block will have to be insulated.
The construction of a shell house can be conducted independently: due to the large size of the stone, laying it is quite simple and does not require serious skills, as is the case with ceramic bricks. There are no special requirements to the foundation: you can use different types of it, depending on the type of soil, characteristics of the relief, etc. If there is no confidence in the quality of the foundation, it is better to make the foundation monolithic or use a foundation slab. Also over the wall
From the shell rock it is possible to stack overlaps of any kind: wooden, metal, reinforced concrete, but for environmental reasons it is better to use wooden beams. In seismic areas, monolithic reinforced concrete belts are made around the perimeter of the walls and overlapping is already laid on them.
Lamination of shell rock facilitates its processing. It may be necessary for dressing with other walls or structures, inserting jumpers, installing beams and solving other constructive tasks. This stone is easy to cut with any saw, including the manual one.
Strength and reliability of shell rock
The lightness of the shell rock makes a deceptive impression. It seems that such a stone will not withstand a large static load. However, the minimum grade of mined shell rock, M10, implies such a calculated load on one stone, which is an order of magnitude greater than that required for the stone of the lower row of a two-story building. That is, even with a minimum density of shell rock, the safety margin is at least tenfold. Kharkiv Institute of Forensic Expertise them. Bokariusa examined the strength and reliability of this material and received a positive result.
However, a less dense stone is bad because during loading and unloading operations it falls off, acquiring an uneven surface, and this increases the consumption of the solution when laying the wall. Therefore stones of the M10, M15, M20 brands weighing 8-12 kg are better for using for construction of garages, baths, economic extensions, and also the third, mansard floors of houses. Stone M25 weighs about 14-17 kg and is best suited for the construction of 2-3-storey houses, even with reinforced concrete floor panels. Finally, a stone brand M35 weighing 22-25 kg will be a reliable foundation and is suitable for the construction of the first floors of buildings with a height of more than two floors. But it is rarely used, because it is not cheap, and the M25 brand is sufficient for most structures, especially in low-rise construction.
Shell brand
The stronger the shell rock, the more noticeable its pores. Typically used in the construction of shell rock brands: M35, M25, M15, M10.
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