Shell rock is a special material, its unique properties - regulating the microclimate in the house and saturating the air with sea salt and iodine - are due to its absolutely natural origin and absolute naturalness. The share of human participation in the production of shell rock is limited only to cutting the stone into pieces of the required sizes. The only effect on shell rock is hydrophobization.
Construction of a house from shell rock
The durability and reliability of shell rock does not need confirmation. In Crimea, the North Caucasus and even in the cities of Foggy Albion there are structures made of shells - undestroyed! - standing for hundreds, and even a thousand years. The material from a natural conglomerate, calcareous shells of ancient mollusks that lived in the sea millions of years ago, is surprisingly resistant to atmospheric influences, frost, and heat. Frost resistance of dense varieties is about 60 - 80 cycles, thermal conductivity is low, and heat resistance is high. In terms of fire, shell rock is safe and itself serves as a barrier to fire for some time. But we must remember that in the structural “pie” of the walls there will be more than one shell rock, so insulation and finishing materials should be chosen accordingly.
For the construction of load-bearing walls, shell rock of at least grade M25 is used; outbuildings, fences, bathhouses, garages, gazebos, etc. are built from stone of lower grades; the best shell rock with a density of M35 is several times higher in price than porous varieties, and the price this one is justified. The decorative and beauty of the shell is most visible in small forms of landscaping, retaining walls, fountains and grottoes. Landscape design with shell rock not only amazes with its beauty and functionality, it carries a special mood and atmosphere that none of the brightest and most prestigious building materials can provide.
Shell wall blocks are used for both load-bearing and enclosing structures, and the inside of the house is faced with sawn polished tiles treated with a water-repellent compound. For tiles, only durable shell rock M35 is used, the thickness of the tiles is usually 20 - 30 mm, non-standard sizes - usually 170 * 350 mm.
Properties of shell rock
One of the important properties of shell rock is that with its own low level of background radiation (up to 12-13 microroentgens per hour), the shell has the ability to reflect radiation directed from the outside, that is, it serves as a radio barrier. The permissible level of radiation is defined as 25 micrograms/hour; in our homes it generally ranges from 12 to 18 micrograms/hour.
The porosity of the shell determines the ability to allow air and water vapor to pass through, which has a beneficial effect on the microclimate in the house. The capillary-porous structure for building materials is considered a useful factor, and at the same time requires protective measures - not only vapors and moisture can penetrate into too large pores, microorganisms that destroy limestone can also grow there, so hydrophobization cannot be avoided.
Yes, shell is an unusually attractive building material for people who value a good microclimate, coziness and comfort in their home. But we have to remember and soberly assess the realities of our lives - there are cases when people are sold completely different blocks under the guise of shells. In addition, after cutting, the shell rock is stored in different ways and delivered the same way. At the site of extraction, the price of the shell is low, but transportation costs can be high. You need to remember the human and “economic” factor and choose the material very carefully.
The appearance of shell rock is so diverse that it is completely unrealistic to visually distinguish the stone by brand. Brands M35 and M25 may not differ in any way in appearance, and only a laboratory test will bring clarity. The press will give accurate figures for compressive strength. And at the point of purchase, you can use a simple method - blow. Throwing a shell block onto something solid from a height and assessing the destruction. It is very difficult, even impossible, to break a durable M35 shell without using a tool. And the M15 brand will most likely fall to pieces. But exact values can only be obtained by ordering a test in a construction laboratory, and then decisions can be made about the need for reinforced belts, reinforcement of masonry, and in general about the possibility of using blocks for load-bearing walls.
There is one more feature of the shell - a huge range of qualities depending on the place of extraction. As a mineral of sedimentary origin, shell rock depends on the geological layer and horizon in which it was formed, that is, on the deposit. In Crimea, the most durable shell rock is mined at Inkerman. All variations in chemical composition, colors and shades, porosity and moisture permeability depend on the place of extraction.
Advantages and disadvantages of building materials
For construction purposes, shell rock is used in the form of blocks for building walls. The convenient shape allows you to assemble vertical structures in a short time.
Shell rock blocks have advantages and disadvantages, after assessing which you can decide on the advisability of their use.
pros
The shellfish has many advantages:
- Convenient size 390×190×190 mm (universal);
- The ease of cutting and processing makes shell rock convenient for installation, which significantly speeds up the process of preparing products for the construction of walls;
- Excellent technical characteristics;
- Vapor permeability allows the walls to “breathe” without retaining moisture on the interior walls of the premises;
- Exclusively natural origin ensures a healthy microclimate without synthetic impurities;
- Shell rock consists of compounds of calcium, iodine and sea salt, which means that the indoor air will be endowed with healing properties, albeit small.
Minuses
Shell shell has very few disadvantages, but they must be taken into account:
- The stone is not hard, so it easily crumbles and breaks if improperly transported, stored and laid;
- High vapor permeability and a significant softening coefficient require careful insulation of the walls from water and high humidity;
- The relatively low load-bearing capacity does not allow the construction of massive tall houses.
A house made of shell rock has the same pros and cons as the material itself: the structures are light and warm, but require significant vapor barrier.
Main technical characteristics of shell rock
Density is the main indicator; strength, weight, and durability directly depend on density. The range is from 750 to 2300 kg/m3, and depends on the location of production. The “weakest” shell rock is comparable in density to raw wood, and the strongest is comparable to heavy concrete!
The blocks are cut in standard sizes, although any sizes are possible - made to order. Standard - 380*190*188, weight from 10 to 25 kg, depending on the brand.
The lightest block M15 has a compressive strength of 15 kgf/cm2 and is used for one-story houses, garages, bathhouses and any outbuildings, and small forms of improvement. M25 is quite suitable for load-bearing walls of a two-story house. Brand M35 - used even for the basement parts of foundations and basement walls, with mandatory horizontal and vertical waterproofing.
The frost resistance of shell rock is no lower than that of red ceramic brick - on average 50 freeze-thaw cycles. And shell concrete is 1.5-2 times more frost-resistant than cellular concrete.
If you do not protect the shell from water and moisture, it will absorb water - up to 15-17% by volume. External plaster or cladding is necessary, or during the rainy season, shell rock can contribute to dampness in the house.
The temperature resistance of shell rock is low, slightly greater than that of aerated concrete, and it is not suitable for lining chimneys.
Ecology is one of the main advantages of natural stone. Being a sedimentary rock of bottom sediments, the shell does not contain harmful impurities; on the contrary, it releases beneficial iodine and salts into the room. This plus can be reduced by insulating the shell walls with polystyrene foam. Mineral and stone wools are mainly used as insulation.
The geometry of shell blocks leaves much to be desired. The actual size usually differs from the declared one by 20-30 mm, if not more. For this reason, many builders prefer blocks made of cellular concrete, ceramic blocks and brick. There are reasons - laying shell rock really takes a lot of mortar, and plastering uneven walls also takes a lot of over-expenditure.
The cost of shells is low only in the quarry after cutting, and delivery throughout Russia is very expensive, especially to the northern regions. A threefold rise in price may reduce interest in this unique building material, and this is understandable. It turns out to be more than twice as expensive as blocks made of gas silicate concrete. In addition, shell rock is fragile - especially M15 and M25, and it cannot be done without fighting in transport. Damage and chips during unloading are also not uncommon. For shell rock, they usually go to the mining site and solve all the issues there; at the same time, you can make sure of the quality of the material.
The porosity of shell rock varies greatly - from 25% to 70% (for low-grade ones). Shell walls provide excellent sound insulation and noise protection.
In terms of manufacturability, everything is excellent - you can saw, cut, drill and groove, pass communications. The weight of the blocks is from 12 to 26 kg; no mechanisms are needed during operation.
Construction of a strip foundation when there is a difference in height on the site
huntdogs
I decided to pour a classic Crimean strip foundation for a house made of shell rock. Foundation dimensions:
- length - 10200 mm;
- width – 6900 mm.
To do this, they dug a trench (removing the layer of chernozem to dense clay) 1000 mm deep and 450 mm wide.
A “cushion” of ASG, about 30 cm, is poured onto the bottom and compacted thoroughly.
Our article talks about how it can cause harm.
huntdogs
We decided to take ASG because it is cheaper than sand. Compare: sand in Crimea costs 2 thousand rubles. for 1 ton, and ASG with a small admixture of sea pebbles - 1200 rubles. for 1 ton. The prices are high, but it needs to be built. We ordered 5 tons.
ASG was poured into buckets and poured out of them into a narrow trench.
About prices: the cost of renting a vibrating plate (the vibrating plate will not fit in a trench) is 1200 rubles/day + a deposit of 10 thousand rubles.
Let us add that the height difference in the area in the foundation construction spot is 1200 mm (from the highest to the lowest point). Based on this, as well as to save concrete, the user decided to pour the foundation in two stages. First, the underground part is erected, the embedded parts (reinforcement) are released, and then the above-ground part of the foundation is poured. Moreover, in order to reduce costs, the top of the tape is made into steps, which are then filled with shell rock, and the plane is brought to “zero” before further laying of the walls.
The foundation construction process was divided into a number of sequential steps:
1. Permanent formwork made of sheets of flat slate was installed in the trench. According to the user, at first he thought of pouring the solution directly into the ground, covering the trench with polyethylene, but in the end the trench, especially the corners, began to crumble.
We bought used slate for 100 rubles. per sheet measuring 0.9x1.4 m. The sheets were sawed in half. A new slate of the same type costs 500 rubles. for 1 sheet.
Total for slate formwork huntdogs
spent 10 thousand rubles.
2. Reinforcement of strip foundation. Reinforcement “ten”, three rods were laid at the bottom, two rods in the middle of the strip and three rods at the top of the foundation, not forgetting to leave embedded reinforcement outlets under the “base”.
The clamps were made from “six” reinforcement.
3. Pouring the underground part of the foundation.
huntdogs
The foundation was poured using a concrete pump. The thing is convenient, but expensive. In total, 15 cubic meters of concrete were needed to pour. 1 cubic meter of concrete costs differently, but on average they charge from 4,500 to 5,200 rubles. Rent of a concrete pump – 8 thousand rubles for 1 hour.
When pouring the foundation, you need to remember the need to vibrate the concrete.
4. Assembling the formwork for the above-ground part of the strip foundation.
The base part of the “ribbon” comes with two ledges.
The most difficult thing is to level the formwork, doing it alone.
1 cube of boards cost almost 10 thousand rubles.
After assembly, the formwork was covered with polyethylene film with a density of 200 microns.
Lifehack from FORUMHOUSE: huntdogs,
Having set the hydraulic level to “zero” along the entire perimeter of the formwork, I took advantage of the portal users’ suggestion on how to control the horizon when pouring concrete. To do this, take an ordinary 10 mm plaster “beacon” and attach it with screws to the walls of the formwork along the marks left from the hydraulic level.
In addition to a clear visual reference, which, unlike stretched fishing lines or steel cables, will not go astray, an additional bonus of the method is that internal guides are obtained along which it is convenient to pull the concrete mixture with a wide spatula to achieve a level top of the foundation.
There is material on the portal where they are given that will not collapse when pouring concrete.
5. Reinforcing the corners of the strip foundation and pouring concrete.
Additionally, the user made a tray for feeding concrete into the formwork.
huntdogs
Concrete was poured using a hydraulic chute to a depth of 9 meters. It is convenient to supply the mixture to the far corners of the foundation. At the same time, I tested plaster “beacons” to control the horizon level. The idea works 100%!
This is what the user ended up with after stripping.
Features of shell masonry
There is perhaps only one difference from the technology of masonry made from lightweight concrete blocks - it is more difficult to build a stone wall with a variation in geometric dimensions, and the variation reaches 30 mm and above. In addition to the overconsumption of mortar for the seams, the thickness of which is required to be 20-30 mm in order to align the rows, there is also the issue of the mortar itself. You need a solution with very good plasticity, but dense, so plasticizers are used in large doses. The masonry is carried out as usual - from the corners along the lighthouse cord and with horizontal and vertical alignment. The thickness of the walls is taken to be one or one and a half stones. Walls 580 mm thick do not need an additional layer of insulation; they are only plastered. For internal non-load-bearing partitions and walls of outbuildings, edge-on masonry with a thickness of 180 mm is sufficient.
It is impossible to leave shell walls without external plaster in the fall and winter; drainage from the roof also needs to be addressed without delay. Roof overhangs and canopies are made large - 60 - 70 cm.
Regarding the issue of armored belts, everything is decided individually and depends on many factors - the number of storeys of the house, seismicity of the construction area, soil properties and the type of shell, and of course, it is linked to the width of the masonry. The need for a base reinforced belt is more a question of the foundation; if there is a slab at the base, a lower reinforced belt is not needed. But under the ceiling and the mauerlat, armored belts are often poured, since the shell is still a fragile material. M35 grade stone can withstand both the weight of two floors and the reinforced concrete version of the floor. The M25 grade also withstands reinforced concrete hollow-core floor slabs, but still builders often decide on the need for an armored belt. As an option, reinforcement is arranged by casting columns at the corners of the house and combining them with an armored belt. This option gives the house even more architectural expressiveness.
