Wood-concrete blocks - disadvantages, advantages and features

By Admin | Construction Materials
20 April 2016

Arbolit most sources describe as a material with wonderful properties.Advertising articles extol the wood-concrete blocks of material deficiencies modestly silent.But miracles do not happen, there are disadvantages, too.To make maximum use of the positive qualities and neutralize the negative, it is a good deal with the properties arbolita, its characteristics and features of application.

Wood-concrete blocks - flaws and characteristics

Contents:

  1. composition and production arbolittovyh blocks
  2. density arbolita
  3. strength of wood-concrete blocks
  4. thermal conductivity arbolita
  5. Dehumidification
  6. Frost
  7. material shrinkage
  8. Fire resistancewood-concrete blocks
  9. Soundproofing
  10. Water vapor transmission Disadvantages
  11. wood-concrete blocks
  12. Benefits wood-concrete blocks

composition and production units arbolittovyh

We start our material is a composition and manufacturing process.The fact is that the quality of certain processes depends on the presence or absence

of certain material deficiencies.And this is very important.Arbolit it positioned as one of the varieties of coarse lightweight concrete.As a filler it uses wood chips.Chips binds in cement paste monolithic structure.

material used in the construction of several kinds:

  • large format masonry blocks;
  • hollow blocks;
  • insulating panels;
  • mixture to fill the walling at the place.

Masonry blocks found the most widely used and the term "arbolit" means, first of all, they are.The most common size of wood-concrete blocks is 500 × 300 × 200 mm.But in recent time, manufacturers began to expand its product line and offer arbolit in other sizes.

Technology of blocks is relatively simple, but like everywhere else, there are some nuances.The quality of future products depends on compliance with several important aspects of production.If the manufacturer uses the name of their products, the term "arbolit", he must comply with the requirements of regulatory documents for such products is:

  • 1. GOST 19222-84 "Arbolit and its products. General specifications."
  • 2. CH 549-82 "Instructions for the design, construction and use of structures and products from arbolita."

composition of wood-concrete blocks

to manufacture wood-concrete blocks used:

  • Wood chips;
  • Chemical additives;
  • Water;
  • Cement.

The structure of the wood-concrete blocks

# 1. Wood chips. Final strength is highly dependent on the caliber of chips.To output was just arbolit whose properties are strictly rationed for the production of wood chips is to be used.Its dimensions are regulated.Guests are recommended maximum particle size of 40 × 10 × 5 mm (length / width / thickness).

best performance at the block size of the chip intervals:

  • length - 25 mm;
  • width - 5..10 mm;
  • thickness - 3..5 mm.

sawdust and Stipa, fire, straw and anything else that they are trying to mix with cement for the production of arbolita for its production is not suitable.Only clean wood chips without bark, leaves, soil and other unwanted impurities.It is believed that the addition of up to 10% or 5% of the cortex foliage does not have a major impact on the performance of arbolita.But it is better when these impurities are absent.

often produce wood-concrete blocks arranged at sawmills and other wood processing plants.For them arbolit is not a core focus.As a result, unscrupulous manufacturers to increase the profitability of production, except for the chips added that there is.From the unpredictable quality.

Wood chips for wood-concrete blocks
at specialized enterprises establish productive roll crushers, calibrated for the correct size of wood chips.

for the end user is not important type of wood from which the raw material is produced, but the technology must take this into account for the correct dosage of mineralizing and select the degree of compaction.Thus, larch chips requires a double amount of additives relative to other conifers.More often than others in the manufacture of chips are pine, spruce, rarely deciduous species.

# 2. Chemical additives. Wood filler comprises sugars that prevent quality adhesion of cement paste to the surface of the particles of wood.

To solve this problem apply two basic strategies:

  • 1. Drying of raw wood to use in production for a few months.
  • 2. Mineralization surface of the chip in a solution of chemical components.

best results are achieved through an integrated approach to solving the problem.Reducing sugar content and mineralization of raw materials allows us to solve other important tasks:

  • increase the biological stability of the material;
  • permeability reduction during operation of the finished product.

To solve all these problems, the production of arbolita can use the following components: calcium chloride (GOST 450-77), liquid glass (GOST 13078-67), silicate lump (GOST 13079-67), alumina sulphate (GOST 5155-74), lime (GOST 9179-77).

# 3. water. Receive wood-concrete blocks, which correspond to the characteristics specified, by following a certain order of technological operations.Water with the addition of mineralizing prepare in advance.Consumption of components taken in the following proportions:

addition CaCl2 Al2 (SO4) 3 Al2 (SO4) 3+ Ca (OH) 2
Consumption per 1m3 arbolita kg 12 12 8+ 4

chips poured into the compulsory mixer.Conventional Gravity concrete mixers do not provide sufficient homogenization.Water with dissolved mineralizer mixed and uniformly distributed over the surface of the chip.Stirring takes place for 20 seconds.The next stage is the addition of cement.Stirring cement lasted 3 minutes.

# 4. Cement. Sufficient for construction material strength can only be achieved when applying the cement to mark not lower than 400. Cement tends to rapidly lose brand in storage.Even at the exit from the cement plant often does not meet the specs.Therefore it is better when wood-concrete blocks, specifications which must comply with the requirements for construction materials, made from 500 th cement.

Forming blocks

Forming must be completed within the next 15 minutes after mixing.Depending on the degree of mechanization of the following processes are following molding methods:

  • manual molding without vibration;
  • manual molding by vibration;
  • production at vibrostanke;
  • production at vibrostanke with prigruza.

mechanization of processes allows to obtain higher quality and stable parameters of wood-concrete blocks.The dimensions, geometry and density of the product stored in the product.

Aging product in the formwork used for handicraft production, when the removal of the formwork immediately after molding prevents too liquid consistency of the solution.In general, the form is removed without delay.

The blocks on the pallet
Raw blocks are removable head-on pallet or directly on the floor of the shop.

wood-concrete blocks, whose composition is identical, may receive a variety of characteristics depending on the method and degree of compaction.The main purpose of compressing the mixture to form is increasing its density.The main task - is to create an evenly distributed in terms of the structure of randomly oriented, completely sheltered cement paste, chips.

vibration compaction is used very dosed.Excessive vibration leads to precipitation of the cement paste at the bottom of the form.It is important to maintain uniform distribution by volume with a full shelter grain filler.Even Arbolit high density chips do not float in the solution cement with water.The cement paste is working as glue, coating grain filler.Changing only the concentration of chips in volume and thickness of the coating of its cement stone.

seal units made on the values ​​that are sufficient for mutual reorientation of the grain filling and increase the area of ​​contact.Compression and deformation of the chip does not occur.This ensures that the block size after removing the sealing force.

Need for accurate dosing of all components and compliance technology

precision dispensing components are regulated by GOST.Tolerances can not exceed a few percent.Under the conditions of lack of water does not occur the total volume of cement hydration.Its excess is undesirable for several reasons:

  • Excess water-cement ratio decreases the strength.
  • excess ductility prevents the unit from taking out a crude form directly after molding.
  • increasing the storage unit on the pallet to the primary setting.

concentration of mineralizing chips going into arbolit is important for the strength and durability of the material.Dosage components driven by regulations, designed to aggregate a certain caliber and humidity at 25%.The optimum dosage is chosen empirically based on tests of finished samples.

order of the process of hydration is important temperature of the solution of water with a mineralizer.It should not be less than 15 ° C.To set the desired temperature in the cold season, the water is heated or kept in a heated room.It is also possible chemical heating water for use as a mineralizer CaCl2.

density arbolita

By appointment material conventionally divided into 2 types:

  • thermal insulation;
  • structural.

The determining factor is the density of the product.It is believed that the blocks with a density of 500 kg / m3 are not suitable for use in bearing structures.But they can be used for insulation in the construction of exterior walls in buildings, where the load on the roof or overlap seen columns or other elements.

Typical structural units are the density values ​​in the interval from 550 to 700 kg / m3.But it is possible to purchase the product and with a density of 850 kg / m3.Too high values ​​indicate good bearing capacity of the elements, but inferior easier to heat-insulating qualities.The density of the material is measured at steady weight when the unit ceases to lose moisture.

Walls of cast arbolita may have a density of 300 kg / m3, but not inferior bearing capacity of stones with a density of 550 kg / m3.

Comparison of density arbolita and other materials

strength of wood-concrete blocks

bearing capacity units is characterized by their compressive strength.As a result of testing of the product can be assigned to a class mark and compressive strength.In general, they are associated with the density of materials.

density, kg / m3 Mark Class
400 - 500 M 5 In 0,35
450 - 500 M 10 0.75
500 M 15 in 1,0
500 - 650 - in 1,5
500 - 700 M 25 in 2,0
600 - 750 M 35 in 2,5
700 - 850 M 50 in 3,5

As in the case of products from heavy concrete grade is the averageon the test results of test samples.The class characterizes the guaranteed strength, 95% of the samples shall be maintained at klassnosti.

For real test sample with a good relationship between the mark and the class through the conversion factors is not correct.In this case, the gap between the mark and the class can tell you about the culture of production at the plant.The smaller the gap, the higher the organization of production.In domestic practice, the manufacture of wood-concrete blocks is taken into account by the coefficients of variation.For products of 1st quality category is permitted value of 18% for the highest - 15%.

in masonry small size of the product makes the concept meaningless klassnosti.When buying a large masonry stones, what are the wood-concrete blocks, is to give preference to products with the assigned class.

To build single-storey buildings bearing walls up to 3 m may be used blocks of Class B 1.0.For higher walls are necessary elements of the class B 1.5.For 2 - 3-storey buildings used blocks of classes B 2.0 and B 2.5.

arbolita strength in compression is typical of cellular concrete.An important difference is that the flexural strength of the blocks, that is from 0.7 to 1.0 MPa.Modulus elements can reach up to 2300 MPa.These values ​​do arbolit special among cellular concrete.If the foam and aerated concrete is likely crack, then arbolita a problem not worth it.

arbolita

Thermal conductivity Thermal conductivity for arbolita is one of the key parameters.

It grows with increasing density in the following progression:

The thermal conductivity of wood-concrete blocks, and its dependence on density

GOST Recommended thickness of walling arbolita in temperate latitudes is 38 cm. But this wall thickness are rarely built.In practice for the walls of houses blocks 500 × 300 × 200 mm in lay flat one row.Along with the interior and exterior of this is enough to maintain a comfortable room temperature without causing problems with condensation.

Additional insulation is often performed with the help of warm plaster systems 1.5-2 cm thick with the addition of perlite.For non-heated or intermittently heated premises (baths) are often used masonry blocks on the edge.

Comparison of thermal conductivity arbolita

Dehumidification arbolita

arbolita The characteristics indicate the amount of water absorption of up to 85% for the heat-insulating blocks and up to 75% for construction.These values ​​require interpretation.The structure of the block is glued cement stone chips scattered grain.They are oriented relative to each other randomly.

water is poured on the surface of the block, flowing freely through it.Naturally, when dipping water can displace a large volume of air contained within the block.If the unit is out of the water, the water flows and the cement stone dries quickly.

wood-concrete blocks are in the natural environment such as the wall of a house without actually accumulate moisture from the ambient air.This is due to a very low moisture sorption material, t. To. The mineralized wood chips and cement are non-hygroscopic and poorly wetted materials.This was the reason for the popularity of using the material for the construction of baths.

If watered unobstructed wall arbolita from the outside of the water, there is a chance to see her inside.Therefore, the material is not used without the front trim.For arbolita recommend finishing plaster mortar or a device mounted facade systems.

Frost

gradual destruction of the products in the freezing and thawing occurs as a result of expansion of freezing water in the voids.The more water they contain, the less cycles of freezing - defrosting material can withstand without breaking.

low sorption moisture absorption arbolita gives good resistance to freezing.The minimum value of F25 and comes to F50.Arbolita protection from direct exposure to moisture, frost improves the real material structure.It was not clear moments?