Characteristics of cellular concrete blocks. Cellular concrete blocks

Beton-House.com

Website about concrete: construction, characteristics, design. We combine the experience of professionals and private craftsmen in one place

Cellular concrete block

Materials intended for the construction of walls often become the subject of debate among developers. After all, the choice is so great that making a decision becomes a difficult task.

Each product is good in its own way, but not without its shortcomings. Therefore, it is necessary to first study all the positive and negative aspects of the materials, and only then make a decision.

In this article we will talk about the group of lightweight concrete, or, more precisely, its representatives, which have recently gained wide popularity. Let's figure it out, cellular concrete wall blocks: what are they remarkable for and what are their main characteristics?

Useful tips for doing masonry work yourself

Preparing tools and material for masonry

Stages of building construction

Calculation of mortar composition for masonry work

Conclusion

Features and Pros

A unique feature of cellular concrete as a building material is the harmonious combination of the qualities of stone and wood. This material has all the useful qualities of building stone: high compressive strength, successful resistance to high humidity, and non-flammability. Along with this, it also has the unique properties of wood: it is perfectly processed by cutting tools, is light in weight and has very low thermal conductivity.

Buildings built from cellular concrete have proven themselves well in various climatic zones, as they provide a comfortable temperature with minimal coolant costs.
Cellular concrete, depending on its density, is used as load-bearing structures that can easily withstand the weight of the ceiling, for the construction of interior partitions, and also as an insulating material in the construction of multi-layer walls.
The accuracy of the block sizes makes it possible to abandon the use of cement mortar when constructing walls. The blocks are laid using a special adhesive composition prepared from dry mixtures, which can significantly reduce the thermal conductivity of the walls without creating “cold bridges”
This material provides high sound insulation of the building without additional measures to improve it.

Cons, disadvantages of cellular concrete blocks

The only disadvantage of this material is its fragility and lack of strength, which is especially true for foam concrete. But with correct engineering calculations of structures, it is possible to ensure high durability and complete safety of structures when exposed to natural climatic conditions.

6.1. Technical requirements for block materials and walls made from them

6.1.1. Wall small cellular concrete blocks (hereinafter referred to as blocks) are made from structural, thermal insulation and structural cellular concrete of autoclave and non-autoclave hardening, meeting the requirements of GOST 25485, in accordance with SN 277.

6.1.2. The types and sizes of wall blocks for laying walls using mortar and glue are accepted in accordance with GOST 21520.

The main types and sizes of blocks are given in the table, and the permissible deviations from linear dimensions are given in the table.

Table 6.1
Main types and sizes of blocks

Types	Dimensions for masonry, mm
on solution	on glue
height	thickness	length	height	thickness	length
I	188	300	588	198	300	598
II	188	250	588	198	250	598
III	288	200	588	298	200	598
IV	188	200	388	198	200	398
V	288	250	288	298	250	298
VI	143	300	588	—	—	—
VII	118	250	588	—	—	—
VIII	88	300	588	98	300	598
IX	88	250	588	98	250	598
X	88	200	388	98	200	398

Table 6.2
-
Permissible deviations from the linear dimensions of blocks

Name of deviation of geometric parameter	Maximum deviations, mm
Blocks for masonry with glue	Blocks for masonry on mortar
category 1	category 2
Deviations from linear dimensions
Deviations:	in height	±1	±3
by length, thickness	± 2	+4
Deviation from rectangular shape (difference in lengths of diagonals)	2	4
Curvature of faces and edges	1	3
Damage to corners and ribs
Damage to corners (no more than two) on one block deep	5	10
Damage to: ribs on one block with a total length of no more than twice the length of the longitudinal rib and depth	5	10
*Note* — Cracks in blocks are not allowed.

6.1.3. When designing load-bearing and self-supporting walls made of blocks in accordance with SNiP II-22 and GOST 25485, the following main indicators are indicated:

— grade of concrete for average density “D”;

— concrete class for compressive strength “B”;

— concrete grade for frost resistance “F”;

— calculated thermal conductivity coefficient of the masonry λк

6.1.4. The class of concrete in terms of compressive strength is taken to be cubic strength with 95% certainty, i.e. multiplied by the value (1-1.64CR), where CR is the standard inter-batch deviation of cubic strength, taken, based on experimental data or in the absence thereof, to be equal to 0.18 for autoclaved cellular concrete and 0.2 for non-autoclaved.

Cube strength is determined on cubes with an edge of 150 mm, cut from solid wood and tested at a humidity of 10% in the direction of swelling (filling), i.e. perpendicular to the bottom.

6.1.5. The block grades for average density “D” and the corresponding classes for compressive strength of concrete “B” are taken according to the table, for frost resistance “F” - according to the table.

6.1.6. The release humidity of the blocks is limited by.

6.1.7. According to SP 23-101, sorption humidity at a relative air humidity of 80% is taken as the calculated (based on thermal conductivity) humidity of cellular concrete for operating conditions A, and 97% for operating conditions B. When calculating walls made of small cellular concrete blocks for force effects (according to the limit states of the first and second groups), the calculated average humidity (by mass) is taken equal to 10%.

Note
-
For thermal engineering calculations, it is allowed to take the moisture content of cellular concrete according to experimental data for a specific wall design, its actual finishing and operating conditions, as the average value for wall thickness and cardinal directions after 3 years of operation with a probability of 0.9.

The average density of masonry DK from blocks on light mortars and adhesives, taking into account the concrete moisture content of 10% by weight (to determine the load from the self-weight of structures when calculating their strength and deformation) is taken from the table.

Table 6.3
- Density grades and compressive strength class of blocks

Block type	Structural and thermal insulation	Structural
Concrete grade by average density	D500	D600	D700	D800	D900	D1000	D1100	D1200
Concrete class for compressive strength, not less	B3.5	AT 5	AT 5	B7.5	B7.5	B12.5	B15	B15
B2.5	B3.5	B3.5	AT 5	AT 5	AT 10	B12.5	B12.5
AT 2	B2.5	B2.5	B3.5	B3.5	B7.5	AT 10	AT 10 O'CLOCK*
B1.5	AT 2	AT 2*	B2.5	B2.5*	AT 5*	B7.5*
* Class indicators for compressive strength refer only to blocks made of non-autoclaved concrete.

Table 6.4
-
Average density of block walls

Type of masonry	Average masonry density DK, kg/m3, depending on grade D
500	600	700	800	900	1000
on a light solution	650	760	870	980	1090	1200
on glue	570	680	790	900	1010	1100
*Note* - For laying walls made of blocks with heavy mortars, the DK values given in the table increase by 50 kg/m3.

Where are cellular blocks used?

These blocks are used to build various buildings:

residential buildings no more than three floors high;
outbuildings and garages;
industrial premises;
country houses.

The main advantage of aerated concrete over other wall materials is the thermal insulation properties of the material.
Porous composites are used for the construction of:

load-bearing and internal walls;
interior partitions;
thermally insulated floors.

The heat-saving properties of the material make it possible to use it for insulation of building structures.

TRANSPORTATION AND STORAGE

4.1. Blocks are transported in containers in accordance with GOST 20259 or on pallets in accordance with GOST 18343 with rigid fixation with shrink film or bandaging them with steel tape in accordance with GOST 3560 or other fastening that ensures the immobility and safety of the blocks.

4.2. Transportation of blocks is carried out by any type of transport in accordance with the requirements of GOST 9238 and Technical conditions for loading and securing cargo.

4.3. It is prohibited to load blocks in bulk and unload them by dropping them.

4.4. Blocks should be stored sorted by type, category, strength class, grade by average density and stacked in stacks no more than 2.5 m high. Blocks must be protected from moisture.

Scheme for measuring the depth of damage to corners

and block edges

Wall blocks made of cellular concrete - material features

Porous concrete blocks have the following features:

good workability. It is easy to make a hole in block building materials or cut the block into pieces;
resistance to temperature changes. The material retains the structure of the array during repeated freezing and thawing;
resistance to biological factors. Fungal colonies and microorganisms do not develop inside the block and on its surface;
long period of operation. Concrete retains its performance and strength for a long time.

When deciding to purchase porous composites, carefully study their features.

Types of porous compositions

There are 2 types of porous concrete:

Aerated concrete obtained by mixing a cement solution with aluminum powder. When mixed, the interaction results in the formation of cavities that increase the volume of the array fivefold. Aerated concrete acquires a spongy structure. When the composition is placed in an autoclave, the mixture hardens and the products acquire an industrial appearance. The process is possible industrially and requires special equipment.
Foam concrete produced by adding foamed reagents to the cement composition, forming air bubbles. The composition acquires porosity when thoroughly mixed, hardens and turns into foam concrete. The specifics of the technology include the production of material on a construction site and in a handicraft manner.

Table of properties and characteristics of foam concrete and aerated concrete

Place different types of products nearby. There are visual differences. Aerated concrete products have a clear geometry, are light, and sink. Foam concrete is similar in appearance to cement and floats on the surface.

How are U-blocks made from aerated concrete?

It is made from the following components:

a binder, which is Portland cement marked M400;
pre-sifted medium-sized quartz sand, which acts as a filler;
aluminum powder used to form the cellular structure of the gas silicate mass;
water, which is added to the required consistency of the composition and, reacting with aluminum, promotes the formation of air cavities;
additives based on calcium chloride and silicate, which improve the strength characteristics of the composite.

The percentage of components is determined experimentally. During the chemical reaction, gas is actively released, which forms evenly distributed cavities. Thanks to the air cells, the heat capacity of the gas silicate increases.

Products are manufactured according to the following algorithm:

Mix Portland cement, lime and sand according to the recipe.
Add technical water and aluminum powder.
Special forms are filled with silicate composition.
Wait for gas formation, as a result of which the material increases in volume.
Products are steamed in autoclaves at elevated pressure and temperature.
Products are removed from the formwork, stored on pallets, and packaged.

An important factor is that these blocks can be laid on either side

The technological process provides for the possibility of manufacturing only in the conditions of production enterprises. This requires special equipment, adherence to autoclave processing regimes and laboratory quality control. Thanks to industrial technology, air cells are evenly distributed in the concrete mass. The autoclave production method makes it possible to obtain products popular in the construction industry.

When purchasing a Y-shaped aerated concrete block, pay attention to the following points:

product color. Autoclaved products are white in color, in contrast to the gray foam concrete products produced on the construction site;
quality certificate. The presence of a document confirming the compliance of product characteristics with the requirements of the standards indicates a quality control system.

Main characteristics of cellular blocks

The strength of cellular concrete is 35 - 150 kg/cm2, depending on the density and type of material.
The volumetric weight of cellular concrete is directly related to its density and is designated by the material grade D300 - D1200. The numerical indicator characterizes the mass of 1 m3 of blocks.
The thermal conductivity of cellular concrete is directly proportional to its density and is 0.11 - 0.16 W/m.deg
The frost resistance of cellular concrete is directly related to its density and ranges from 35 to 75 cycles.
Shrinkage deformation during drying is 0.35 – 0.47 mm/m.
The fire resistance of the material complies with GOST 30244-94.
Water absorption of foam concrete is in the range of 12-70% depending on the brand, for gas silicate - 20-35%.
The cost of the material varies depending on its density and is approximately 2300 - 3700 rubles/m3.
Cellular concrete as an element of the supporting structure is used for two-story construction in the presence of light floors.

Comparative characteristics of aerated concrete and gas silicate

Which is better, gas silicate or aerated concrete blocks, can be decided by comparing their main characteristics. The main differences in the most important operational characteristics are presented in the table.

Parameter	Aerated concrete	Gas silicate
Strength (kg/cm2)	28-40	10-50
Thermal conductivity coefficient (W/mG)	0,10-0,14	0,15-0,3
Volumetric weight (kg/m3)	400-600	200-600
Frost resistance (number of cycles)	35	10
Water absorption (in%)	20	25-30
Soundproofing	average and below	high
Durability	More than 70 years	From 50 years and above
Vapor permeability coefficient, (µ) mg/m h Pa	0,2	0,17 – 0,25

In addition to this, it can be noted that in aerated concrete, due to the use of a different binder, the pores are distributed more evenly, which affects its density, strength and other characteristics.

You can consider these points in more detail to understand how to make the right choice:

The strength of gas silicate blocks ranges from 10-50 kg/sq.cm, which is explained both by the properties of quartz sand and the uneven distribution of pores. Therefore, the indicators of aerated concrete (28-40 kg/sq.cm) indicate more stable characteristics.
The thermal insulation properties of aerated concrete are higher, since it has a lower thermal conductivity coefficient. This is also explained by the characteristics of the binder.
The volumetric weight (density) of both materials varies approximately in the same range. But there is more dense aerated concrete, which is used in monolithic construction.
In terms of frost resistance, aerated concrete is significantly ahead of its competitor. This makes it the best choice for regions with harsh winters.
The moisture absorption coefficient of aerated concrete is much lower, which makes it possible in most cases to do without additional processing.
The sound insulation properties of gas silicate are slightly higher.
The vapor permeability coefficient of gas silicate varies over a fairly wide range. From this point of view, aerated concrete is a material with a more stable indicator.
In terms of durability, aerated concrete is superior to gas silicate. This is mainly due to the fact that it has lower moisture absorption and higher frost resistance. However, with additional processing and compliance with the rules of construction and operation, both materials can last quite a long time.

When considering how a gas silicate block differs from an aerated concrete block, one should also note the external data. Aerated concrete with its white surface looks more attractive.

Application area

The high technical characteristics of cellular blocks have expanded the scope of application of the material in the construction market. The main types of building materials are used in the construction of low-rise and industrial buildings. Load-bearing, self-supporting and non-load-bearing walls, wall partitions are laid out in blocks, and structural elements of the building are made from them. Due to its low thermal conductivity, it is used as insulation for floors, roofs, and walls.

The density of concrete varies, depending on the number of pores - the greater the cellularity, the higher the thermal and sound insulation characteristics, but the lower the density. With small cellularity, everything is exactly the opposite. Such characteristics simplify the use of concrete, allowing you to take into account the nuances of individual construction.

Return to contents

Description and Application

Cellular concrete is a building composition of hardened cement with quartz sand and lime, mixed with water and set during the process of hydration.

Its peculiarity is the presence of evenly distributed air voids (pores), creating a cellular structure. They occupy up to 85% of the volume, which significantly reduces the density and increases the thermal insulation properties. A variety of elements are made from cellular concrete:

Standard blocks for load-bearing walls. Aerated concrete can be used for buildings up to five floors high. Buildings up to three floors high can be erected from foam concrete.
The slabs are suitable for internal partitions of buildings. When reinforced, they are used as load-bearing internal elements. Slabs made of highly porous concrete are used as insulation inside buildings.
U-shaped blocks are an excellent material for the construction of tray lintels.
Monolithic structures are made from foam concrete on site, it is used for floors and ceilings with good thermal insulation properties.

Purpose

Cellular concrete blocks, depending on the pore concentration, have different areas of application and are conventionally divided into the following types:

structural compositions with a density of 600–1200 kilograms per cubic meter;
thermal insulation composites, with a specific gravity of 400–600 kilograms per cubic meter.

Porosity determines the density of the product. As the volume of cavities increases, sound insulation and heat protection characteristics increase, but strength decreases. Therefore, when constructing permanent external walls of a building, which require increased strength, a denser porous material is used. Products for structural purposes are used for the construction of:

capital walls;
internal light-loaded walls;
partitions.

Cellular blocks are well suited for the construction of houses of any complexity

Construction thermal insulation measures are carried out using thermal insulation elements that allow:

insulate the surfaces of reinforced concrete floors;
create a thermal insulation contour of multilayer wall structures;
thermally insulate attic floors;
provide thermal insulation of special equipment, the surface of which is heated to 700°C, using heat-resistant mixtures;
protect the surfaces of pipelines and technological equipment, the operating temperature of which rises to 400°C.

Multi-storey buildings and private buildings made of porous concrete have increased thermal properties compared to brick buildings.

Reduced dimensional tolerances of products allow masonry to be carried out using special glue with a seam thickness of up to 3 mm. Thanks to this, there are no cold bridges that form when laying on cement mortar.

Areas of use

The production of products made from cellular concrete includes a wide range of reinforced concrete structures:

Wall panels;
reinforced concrete floor slabs;
block and tray lintels;
hollow brick;
thermal insulation materials;
warm ceramics (porous ceramic block);
masonry blocks.

In individual construction, foam concrete and aerated concrete blocks are most in demand. The outer wall of the house, made of porous products, has good load-bearing capacity. The dimensions and strength characteristics of the material allow the construction of buildings of any shape and various functional purposes.

also used in the reconstruction of buildings, when it is necessary to increase the number of storeys of a building without strengthening the existing foundations.

Product categories

Porous concretes differ in density and thermal insulation properties.

Based on these characteristics, they can be divided into 3 categories:

thermal insulation materials;
thermal insulation and structural;
structural.

Concrete with a density of D300-D500 is usually used only as insulation. The standard operational load of such products is at a low level, which does not allow their use for laying walls and partitions.

Blocks with a density of D600-D900 are the main building material for the construction of external and internal structures. They are intended for the construction of residential and public buildings up to 3 floors high.

Structural porous concrete D1000-D1200 has the highest strength characteristics. It is widely used for the production of precast concrete, masonry and foundation blocks, floor slabs, etc.

Application

Cellular concrete is used in the following areas of construction production:

Monolithic housing construction.
Production of piece structural and decorative products.
Thermal insulation of utility networks, roofs and external walls of buildings.

In addition to construction, crushed porous concrete, together with manure, serves to fertilize the soil. On livestock farms, the material is used as warm bedding for livestock.

Nuances of block laying technology

Masonry technology has its own characteristics. Important points:

the laying of blocks is carried out at positive temperatures or glue with anti-frost additives is used;
defects and irregularities on the surface of the blocks are eliminated with a grater for grinding;
the sequence of operations provides for the initial installation of corner blocks;
block rows are reinforced with steel reinforcement at intervals of 3 levels.

The use of glue instead of cement mortar allows you to avoid the formation of cold bridges and create thin joint areas.

Features of masonry

An adhesive mixture is used to hold the cellular material together. The optimal temperature for masonry is from 5 to 25 degrees Celsius; if the work is carried out in cold weather, you need to select glue with anti-frost additives. The glue is prepared immediately before work on the construction site. It is worth paying attention to some features of the masonry, observing which we will get a high-quality result:

Proper transportation is an important part of getting started. The concrete must have packaging that protects it from precipitation and secures the material.
Using a sanding float to level the surface avoids surface unevenness and subsequently the formation of cracks. The ability to choose the required size ensures even laying.
First of all, corner blocks are laid, gradually moving to the perimeter.
Reinforcement of every fourth row to avoid the formation of cracks.
The use of an adhesive solution allows you to make thin connecting seams. Glue is an economical option, without the formation of “cold bridges” and resulting in smooth masonry.

Wall blocks or partition blocks made from cellular mass are of high quality and have an ideal shape. Using them for construction is the right decision.

Block buildings are characterized by increased comfort, good sound insulation, and high heat-protective functions.

What to choose: foam concrete or aerated concrete?

Let's figure out which cellular concrete blocks are better? It is difficult to answer the question unambiguously. The answer depends on the conditions where you plan to use the wall material. Let's look at the main points:

It is advisable to use aerated concrete for the construction of load-bearing walls. It has increased strength.

Comparison table of the main properties of foam concrete and aerated concrete

In terms of their ability to withstand negative temperatures, both compositions have equal properties.
Foam concrete is less hygroscopic and surpasses aerated concrete in terms of water absorption.
Aerated concrete is more expensive, which is due to the autoclave production method.

The characteristics of cellular concrete blocks confirm the economic feasibility of using aerated concrete for the construction of load-bearing structures. The foam composition is used for insulation and construction of room partitions.

Manufacturing technologies for these materials

The process of creating foam concrete blocks:

Cement and sand are poured into an industrial concrete mixer in the required proportions. All components necessary for the manufacture of the product are pre-weighed. Depending on the proportional ratios of sand and cement, the strength grade is determined from D400 to D1000. The higher the grade of foam concrete, the stronger and more massive the material.
The required amount of water is added to the dry mixture to obtain a solution of the desired consistency.
The composition is mixed until a homogeneous consistency is formed.
When the solution is ready, foam is added to the industrial mixer.
The cement-sand mixture with foam is mixed.
After the solution is ready, it is poured into molds.
After pouring, the molds must stand for up to 4 hours, during which time initial setting occurs.
After 4 hours, the forms are loaded and transported to a place where the foam concrete will dry under natural atmospheric conditions. Within three weeks, the material reaches sufficient strength for the construction of load-bearing structures of the building.
The remaining strength is gained over the next six months. In the future, the strength of the material only increases. This process lasts for 50 years of operation.

Manufacturing technology of aerated concrete blocks:

Cement, quartz sand and lime are dosed in the required proportion. All components are immersed in a special mixer and mixed thoroughly.
Aluminum powder and water in the required quantity are added to the dry mixture.
After thorough mixing, the composition is immersed in molds.
It settles for several hours and during this period a chemical reaction occurs, as a result of which carbon dioxide is released. The reaction occurs as a result of the interaction of water with aluminum powder. As a result of the chemical process, pores are formed and the material increases in volume. During settling, initial setting of the material occurs.
After initial setting, a half-baked mass is formed. Blocks are cut to size using a special cutting machine. This technology allows for very precise cutting. The scraps of material are collected, re-kneaded and again sent for cutting.
The cut material is sent to an autoclave, where the blocks are steamed at a temperature of 180 degrees for several hours under a pressure of 11.5 atmospheres. When steamed under pressure in an autoclave, the piece material gains its full strength.
At the exit from the autoclave, the gas blocks are placed on pallets and covered to prevent moisture from entering. In this condition, the material is sent for sale.

https://youtube.com/watch?v=iDaqzVVx_kE

Separately, we note that the equipment for making blocks from aerated concrete is quite complex and expensive.

Having studied what gas blocks and foam blocks are made of, their technical characteristics, production technology and differences, it is easier to decide what to build a house or cottage from. Which material to choose for the construction of a building, foam block or gas block, depends on the technical requirements and financial capabilities of the future owner of the house.

Advantages of a porous composite

Blocks made of cellular concrete have many positive properties. Main advantages:

Ability to conduct heat. In terms of thermal conductivity, the material is close to wood, but there is no restriction on the width of the walls being built. When the thickness of walls built from composites corresponds to the dimensions of the brickwork, a favorable thermal regime of the room is ensured. The integrity and uniformity of the building structure is due to the absence of the need for special insulation materials. This is relevant for the construction of private facilities, where the developer is interested in saving heat and, naturally, material resources.
Economical. The insignificant weight of the porous product, which is lighter than brick, allows minimizing the costs of construction and installation activities and arrangement of the foundation. The composite does not require additional insulation, and the use of special adhesives allows for savings in masonry.

Advantages of cellular concrete

The ability to pass steam-saturated moist air. With an increase in the coefficient of vapor permeability, the microclimate improves. A room made of porous concrete provides comfort in winter and coolness in summer. Ventilation of the building reduces the likelihood of mold and mildew formation.
Flame resistant. Cellular blocks have high fire resistance, which makes them different from wood. There is no need for additional fire protection. The material is used as a refractory.
Increased dimensional accuracy. The tolerances are ± 2 millimeters, which allows for a minimum thickness of the masonry joint, reducing the consumption of the adhesive mixture, and increasing the thermal insulation of the walls.

Material classification

According to the quality standard, all cellular concrete is divided according to the following indicators:

use;
option for obtaining pores;
the binder used;
type of silica component;
hardening mechanism.

Considering the functional purpose, the following types of cellular concrete can be distinguished:

Thermal insulation type. This material is used as a thermal insulation building element. The volumetric mass of such concrete is 300-500 kg/m3.
A structural option used to create structural parts of structures and buildings of various types.
Structurally, it is a heat-insulating type that contains both properties.

Types of cellular concrete by porosity:

cellular aerated concrete and silicate;
gas silicates and aerated concretes;
foam silicates and foam concretes.

Important!
Gas foam technology combines gas generation and aeration method. In the manufacture of such building materials, various binding components are used: cement, lime, gypsum.

The silica component is: ash, slag from metallurgical production, quartz sand.

According to hardening option:

there are autoclave ones, which harden in a saturated steam environment at a pressure exceeding atmospheric;
non-autoclave, hardening in natural conditions using electrical heating or at atmospheric pressure in a saturated steam environment.

Comparison with brick and wood

The positive performance characteristics of cellular concrete blocks allow them to successfully compete with wood and stone. Let's look at the features of the materials:

Machinability. Nails are easily hammered into the block, it can be processed with a plane, and quickly sawed with a hacksaw.
Weight. Unlike heavy bricks, cellular blocks are lighter. This makes it possible to use products of increased dimensions and significantly reduce the consumption of material for connecting seams. Low weight allows savings to be achieved when transporting composites to the construction site. It is convenient to erect buildings using porous compounds on soils with low bearing capacity and use light, less massive columnar foundations for buildings

Comparison table for the thermal conductivity of cellular concrete with brick and wood

Flammability. The composite is fire-resistant, which makes it advantageously superior to wood.
Ability to conduct heat. Due to its high porosity, the leader is the foam composition, which has low thermal conductivity and is similar in characteristics to wood.
Frost resistance. The structural features of porous concrete and brick allow them to retain their properties for 100 freezing cycles.
Strength. The porous composite is quite hard, but less durable compared to brick, which is due to the structure. Having decided to build a building with a ceiling made of heavy slabs, use bricks for load-bearing structures that can withstand an increased load per unit area.
Ability to absorb moisture. The water absorption coefficient characterizes the volume of water that a material can absorb. Brick can absorb moisture in a volume of 8-12% of the mass. It is superior to cellular compositions, which have water absorption of up to 20%, and it is generally difficult for wood to compete with them.

Having analyzed the parameters, it is difficult to confidently determine what is preferable to use for the construction of a building: porous compounds or ordinary bricks. It is clear that wood has a limited scope. Materials have their advantages and disadvantages, which must be taken into account when choosing raw materials for construction.

Advantages and disadvantages of aerated concrete blocks.

Aerated concrete blocks are a universal building material suitable for creating all kinds of buildings and structures. Its advantages are most evident in low-rise construction.

Cellular concrete can significantly reduce the cost of construction:
Due to the same low weight of gas blocks and their precise dimensions, due to the ease of adjustment, the labor intensity of the work is significantly reduced. The developer gets the opportunity to speed up construction and reduce labor costs for masons.
Due to the low weight of the entire structure, the cost of the foundation is reduced: the owner can build a larger house on a lightweight foundation.
A house made of aerated concrete blocks is characterized by high performance.
Sound insulation of premises is better than in stone, wooden or frame buildings.
All walls are firewalls by definition: aerated concrete promotes a ceasefire.
The excellent steam removal ability of the blocks will ensure an optimal microclimate in the room.
The material is frost-resistant: aerated concrete is one of the champions in resistance to low temperatures.

Some properties of cellular concrete can result in disadvantages if constructed poorly or improperly used.

Low strength of blocks when bending.
Walls should be reinforced. To do this, every 4 rows the masonry is reinforced with steel or fiberglass wire, and monolithic strapping contours are installed at the level of floors and coverings.
Moisture permeability.
High vapor permeability.
This quality is the advantage of cellular concrete. However, if insulation is incorrect, it can easily turn into a disadvantage. Experienced builders know one secret: in multilayer walls, the vapor permeability of the outer layers should be higher than the inner ones. Then moisture will not accumulate in the room, but will safely evaporate through the walls.

If you follow these fairly simple rules, a house made of aerated concrete blocks will last as long as a traditional brick one.

Useful tips for doing masonry work yourself

Since we already know all the features of the material, let’s figure out how to use it correctly so that these properties are preserved.

Preparing tools and material for masonry

Masonry begins with the preparation of tools and material. If you decide to use an adhesive composition, then it is enough to purchase it in a store. The assortment is quite wide.

Attention should be paid to the following indicators specified by the manufacturer:

Viability of the mixture;
Plastic;
Thermal conductivity;
Resistance to temperature changes;
Strength;
Consumption.

The average consumption is about 1.3-1.5 bags of mixture per 1 m3. If you still decide to use the solution, then you should stock up on cement, water, and sand. You will also need a concrete mixer for mixing.

The following tools are needed:

Square;

Square

Construction level;

Building level

Container for the mixture;

Construction bucket

A thread;

Construction thread

Rubber hammer;

Kiyanka

Fittings;

Armature

Manual wall chaser;

Wall chaser

Grater;

Construction grater

Bucket scraper;

Bucket scraper

Drill and mixer attachment.

Drill with mixing attachment

Stages of building construction

Now - about the stages of work during masonry.

Table 4. Masonry technology: stages of work:

Preparation	It is necessary to waterproof the base. It should be smooth, without visible defects such as chips or bulges.
Start of masonry	Masonry begins from the corners of the future building. Moreover, the first product is placed at its highest point (corner, again). The thread is pulled, which is then used as a guide.
First row	The first row is laid out completely; it is recommended to use a solution.
Second row and subsequent	Laying is done with the seam offset; as a rule, an adhesive mixture is used. The thickness of the seam should be as small as possible.
Correction and control	Control is carried out using a level, correction - using a mallet. Experts recommend doing this as often as possible, since the vital activity of the solution does not allow you to wait long. If the glue sets, it will no longer be possible to change it.
Reinforcement	A necessary step during installation. It is recommended to carry out reinforcement when laying the first and every third or fourth row.
Product cutting	You can use a hacksaw, saw or power tool.
Armopoyas	Upon completion of laying the walls, it is necessary to carry out its installation.

The video in this article: “Wall blocks made of cellular concrete d600” will demonstrate the process of laying popular products.

PROCEDURE OF WORK

Finishing work can begin only after completion of construction and installation work. It is recommended to carry out finishing work at temperatures from +5 ºС to +25 ºС. At higher air temperatures, as well as in sunny weather and at wind speeds of more than 10 m/s, it is necessary to take measures to protect freshly laid layers of exterior finishing from dehydration. To carry out finishing work at temperatures below +5 ºС, it is necessary to use special finishing compounds that allow work at low temperatures. This possibility must be expressly stipulated by the manufacturer of the finishing material. The use of plaster compositions with antifreeze additives prepared under construction conditions is not permitted.

The finishing of the outer surface of the walls is carried out using devices for working at height: scaffolding, self-lifting cradles, mast lifts, equipment for industrial mountaineering and other means. Scaffolding, if possible, is installed to the full height of the building. It is recommended to cover scaffolding with mesh, which increases the safety of work, promotes sun protection and protection from slanting rain.

Preparing the surface of cellular concrete walls for exterior finishing depends on its condition and the type of finishing to be done. Depressions, chips and other surface defects are eliminated using a repair mixture, if this was not done during masonry work. Check surface unevenness and vertical and horizontal deviations of the surface of masonry walls made of aerated concrete blocks, which must comply with the requirements of Table 4. Local protrusions in the masonry, repair areas and other surface defects are processed with a grinding float until a gap of no more than 2 mm is obtained under a 500 mm long lath. In the corners of the masonry (internal and external) and along the protrusion line of the masonry in the plinth area, it is recommended to install appropriate corner protection and/or beacon profiles made of perforated galvanized steel or polymer materials. In areas where cellular concrete masonry interfaces with other types of materials, as well as in places of possible stress concentration (corners of masonry, corners of openings and areas along the length of lintels, window sill areas), it is recommended to constructively reinforce the finishing layers with a mesh of fiberglass or other material. Notching, cutting and other methods of mechanical processing (in order to increase the adhesion of plaster layers to the base) are not required for cellular concrete surfaces. Upon completion of the preparatory work, the surface of the masonry is cleaned of dust with brushes or compressed air.

The surface of the cellular concrete masonry prepared for finishing must be visually homogeneous. The following are not allowed on the surface:

cracks in concrete (except for surface ones) with an opening of more than 0.2 mm
grease and rust stains
dust
holes, chips, scratches with a depth of more than 2 mm and a diameter (width) of more than 5 mm
scuffs and sagging heights of more than 1.5 mm
frost, snow, ice

Preparation of plaster compositions is carried out according to the manufacturer's instructions in plaster stations or manually. When performing drafts and architectural elements, special templates and rules are used. Corners are cut using husk and spatulas. The slopes are plastered along corner beacons or guide rails. The technology for plastering surfaces includes applying and leveling the plaster mortar, carrying out the work with grips in accordance with the instructions of the dry mix manufacturer. On each of the grips, uniformity and continuity of plastering work is ensured. The duration of technological breaks when performing individual plastering operations is established by the manufacturer of dry mixes. Caring for freshly made plaster consists of protecting it from rapid dehydration and freezing until the solution has completely set. During the period of strength development, the coating is protected from mechanical damage.

Summarizing the above, we can formulate basic rules that will help to carry out finishing with minimal risks. It is preferable to buy cellular concrete blocks from a trusted manufacturer. The laying should be carried out using mortars (adhesives) recommended by the manufacturer, with a thin joint, based on factory-ready dry building mixtures and with careful execution. Due to their porous structure, blocks can absorb moisture under unfavorable conditions; therefore, the masonry should not be over-moistened. If necessary, measure humidity (preferably using the carbide method to determine moisture content using an SM device). Equilibrium humidity should be no higher than 5% and only after this can plastering work begin. From practical experience, humidity should drop to the required value approximately a year after the construction of the enclosing structure. Finishing with plaster compositions should be carried out only after the construction moisture has left! It is preferable to carry out interior finishing before performing exterior finishing work (due to the removal of excess moisture from the structure).

Benefits of use

Wall blocks made of cellular concrete have irrefutable advantages that all developers need to know:

Ideal sizes and shapes are the advantages of cellular concrete.
The dimensions and shapes of wall concrete are ideal. Nowadays you can easily purchase blocks of the desired shape and size. The ideal size has a positive effect on the minimum thickness of the connecting layer, increasing the thermal insulation characteristics.
Economy. Lightweight wall material reduces the financial costs of pouring the foundation. There is no need for additional insulation. Savings are also felt in the consumption of the adhesive mixture.
Thermal conductivity. The cellular block is capable of retaining heat and is unlimited in the formation of wall thickness. With a small thickness, the room remains warm and cozy. There is no need for additional insulation, which benefits private developers who want to have a warm home and are looking for an opportunity to save money.
Vapor permeability. The porous structure of the wall blocks allows the walls to “breathe”. The throughput of air and steam is maximum, the humidity level is reduced, so the formation of fungus does not threaten the concrete.
Fire resistance. High temperature resistance is high. There is no need to make additional fire protection; on the contrary, cellular concrete is often used as a fire-resistant material. For example, a wall ten cm thick can withstand direct fire for two hours with all characteristics fully intact.

Main advantages of the material

Currently, many builders give their preference to cellular materials. The reasons for this choice are obvious:

Natural material is difficult to process and transform, and cellular blocks created by man are easy to machine. The introduction of innovative technologies into the construction industry helps to constantly improve the performance characteristics of concrete and increase the cost-effectiveness of its use.
This material has amazing thermal insulation characteristics. There is air inside the pores, which exhibits excellent thermal insulation properties. A house built using cellular concrete will be warmer than a house made of natural wood or brick.
The cellular structure of this material gives it good soundproofing characteristics.
The material contains only mineral components, so concrete does not rot.
These materials do not contain toxic substances and are safe for humans and the environment.

The disadvantage of the material is that buildings made of cellular blocks require additional protection from natural phenomena. Gusts of wind and heavy rain can cause destruction of this material.

Advice! To protect the building from negative natural phenomena, it is advisable to carry out exterior cladding work.

How to properly store cell blocks

The technical characteristics of wall cellular concrete blocks determine storage conditions. It is important to follow them so that the material retains all its beneficial properties. Material is brought to the site and must be unloaded exactly block by block on special pallets. It is important to exclude distortions and the possibility of moisture ingress. In dry weather, each block must be moistened to prevent the material from drying out. The characteristics of this wall material require care and special care during storage.

Dimensions

Wall blocks made of cellular concrete are produced on the basis of mortar grades M20 – M50, which are distinguished by their compressive strength. With a thickness of 150-400 mm, its width is 200-500 mm, and its length varies from 400-600 mm.

Cloisonne blocks are made from a mixture of the M500 brand. With a constant width of 400 mm, the thickness is 100-150 mm and the length is 300-600 mm. A wide range of manufactured products allows the elements to be used in solving construction problems of varying levels of complexity.

Disadvantages of aerated concrete and gas silicate

These materials also have certain disadvantages. The common feature is low tensile strength, characteristic of all porous materials. However, we can correct this shortcoming. Additional reinforcement of the walls is used and an armored belt is installed on top of the blocks. This allows you to achieve the desired level of strength.

But there are disadvantages inherent only to gas silicate blocks:

Lower compressive strength compared to aerated concrete. This means that the wall of the house will shrink more during use, and this will lead to the appearance of cracks. This situation is due to the lower density of gas silicate. You can use blocks of a higher volumetric weight than those provided for in the project. But this will lead to increased costs.
The lower density and smooth surface make it more difficult to choose exterior wall finishes when using gas silicate blocks. This applies not only to plaster, but also to siding.
The high moisture absorption rates of gas silicate means that it absorbs moisture in large quantities, and in winter this can lead to unpleasant consequences. Additional finishing will protect it from moisture, but construction costs will increase.
Due to its high moisture absorption, gas silicate cannot be used to construct partitions in a bathroom, indoor pool, etc.

Characteristics of foam and gas blocks

We have become a little familiar with the composition of the raw materials and the technological process; now it’s time to pay attention to the main set of material characteristics and their numerical values.

GOST establishes a number of requirements for the material that all manufacturers must comply with. However, due to high competition, each of them is trying to differentiate its products by modernizing manufacturing technology and changing the proportions of raw materials to improve basic qualities. Let's look at the minimum allowed by the standard and the maximum offered by manufacturers.

Technical and operational properties

Let us consider, using the table, the main properties of two representatives of the group of materials under consideration.

Table 1. Small wall blocks made of cellular concrete: technical characteristics:

Property name	Its meaning in foam and aerated concrete blocks, comments
Frost resistance	The indicator is set by GOST. The minimum threshold is 25 cycles. Products intended for the construction of external walls must comply with this value in relation to the frost resistance grade. For partition blocks, this value has not been established, and the frost resistance of the heat-insulating type of material is also not standardized. In practice, manufacturers assure potential consumers that the material can withstand up to 150 cycles, and the foam block – up to 100. There has not yet been confirmation from the developers, due to the insufficient period of existence and use of the blocks.
Average density, kg/m3	The value ranges from 300 to 1200. As mentioned above, the density of the material largely determines the Sulfur of its application. In this regard, a classification of material was developed in accordance with the average density indicator. We'll talk about it a little later.
Strength, grade B	Strength grades must correspond to a certain density. The existing ones range from 1.5 to 15.
Thermal conductivity W*mS	The thermal insulation capacity is quite high. The coefficient can be equal to 0.08 and reach 0.34. If there is moisture during operation, this value will increase, but this will not fundamentally affect the thermal efficiency of the wall.
Environmental friendliness	We have already reviewed the composition and were able to verify that the mixture does not contain harmful and toxic components.
Fire resistance	GOST indicates the non-flammability of the material. Moreover, it can withstand high temperatures for up to several hours.
Vapor permeation	Both representatives are capable of vapor permeation. The most favorable climate will be created in the room, since the blocks tend to absorb excess moisture and release it when dry air predominates.
Soundproofing	The least durable products have the maximum soundproofing ability. In general, the structural and thermal insulation material is quite sufficient so that additional sound insulation of the room is not required.

Types of blocks and their application

Let's take a brief look at the classifications.

Above, we already mentioned the existence of several methods of hardening and said that the block can harden by processing it in an autoclave, or naturally. In the first case, the effect is exerted by pressure exceeding atmospheric pressure and high temperature.

In the second case, light heat and moisture treatment is possible, which helps improve properties and shorten the drying process.

Non-autoclave

The autoclave is ahead of its competitor in many indicators, such as:

Frost resistance grade and durability;
The ratio of strength, average density and heat preservation ability;
The autoclave curing block has better geometry and pure white color;
It is less fragile.

In contrast, it is worth mentioning that the cost of hydration hardening products is slightly lower, by about 10%.

Synthetic and hydration hardening material

Density marked the beginning of another classification.

Blocks characterized by a density of 300 or 400 kg/m2 are called thermal insulation. They are used, of course, in the process of thermal insulation.

Note: For this, not only blocks and slabs are used, but also monolithic material. It is actively used for sound and heat insulation of roofs, enclosing structures, and floor screeds.

If products have a density value of 500, 600, 700, 800 or 900 (kg/m3), then they are structural and thermal insulating. With their help, you can erect a building wall or partition. They are excellent as the main material for low-rise construction.
But if you decide to build a 3- or 4-story building, it is better to purchase a gas-foam block with an increased strength and density, that is, structural ones. They are able to withstand a larger load, and with their help you can build a building several floors high.

On a note! The range of foam concrete also includes products called structurally porous. They are especially dense. They are not produced in mass quantities, only on order. GOST does not mention their existence.

Regarding the destination:

Walls are erected using wall blocks;
Partitions – using partition walls;
Stationary formwork can be constructed from y-shaped formwork. They are also used when installing door and window openings.

Y-shaped products
Blocks can have different accuracy categories, which depend on the magnitude of permissible deviations. The photo below shows the requirements of the standard.

Geometric deviations

Note! The thermal conductivity of the future wall largely depends on the category. This is explained very simply. For example, products of the first category are laid on glue, while the thickness of the seam is kept to a minimum. The result is a minimum of cold bridges.

First category

If you are laying products of the third category, you will not be able to use an adhesive composition; you must use a solution whose layer thickness will depend on deviations from the linear dimension. It can reach 2 cm or 3 cm. As a result, there are many more loopholes for cold penetration.

That is why the third category is recommended for use in the construction of non-residential buildings.

Blocks of the third category look unpresentable

Wall blocks can have a smooth surface or have a groove and tongue. In the latter case, laying the wall will be much easier, and a beginner will have the opportunity to build an almost ideal surface.

Foam blocks are also produced in the form of products with a textured front surface. Purchasing these will save the developer from the need to finish the outside of the building.

Positive and negative aspects of the material

Table 2. Advantages of foam and aerated concrete:

Density and strength	The values of density and strength allow the material to be used both as insulation and in the construction of load-bearing structures.
Heat preservation ability	Provides cost reduction for building insulation.
Frost resistance grade	Indicates the durability of the future structure and its weather resistance.
Environmental friendliness	Eliminates harmful effects. Allows the use of products in the construction of specialized institutions.
Fire resistance	Also an equally important advantage. The possibility of a building fire is reduced.
Variability of sizes, a large number of different manufacturers	This fact indicates the opportunity to save on delivery by searching for the nearest dealer in your region. The size range will allow almost any developer to choose the desired dimensions. The gallery below the table presents some of the most popular and largest manufacturers of products from this group of concretes.
Easy to use	The products can be processed relatively easily and this, you see, is convenient.
Low weight	A particularly important plus, indicating the possibility of reducing costs when constructing a foundation, since the construction of a massive foundation is not at all necessary when building a lightweight structure.
Big sizes	The construction process will be significantly accelerated due to the dimensions.
Possibility of self-production	Any developer can try himself as a manufacturer. This is not only a useful experience, but also a cost reduction.
Low price	This group of materials is highly competitive not only due to its qualities, but also due to its reasonable price.

Table 2. Disadvantages:

Shrinkage	Unfortunately, this property characterizes both representatives of the group.
Hygroscopicity	Despite the fact that foam concrete has this ability reduced to 10-16% due to the closed pore structure, it still needs protection. For aerated concrete the value is 25%.
Fragility	They are afraid of the mechanical effects of the product.
Purchasing special fasteners	Any hardware will not work. This is due to the characteristics of the material
Poor resistance to pull-out loads	Requires planning for securing heavy objects at the project level and strengthening them.

General description of the material, features of composition and production technology

As already mentioned, cellular concrete is a group of materials. Its representatives are foam and aerated concrete, as well as foam aerated concrete, which combines both manufacturing technologies and, as a result, properties.

Now a little about the composition. It is regulated by GOST 21520-89 Small cellular concrete wall blocks.

Such blocks are produced from a mixture of cement, lime, sand, blowing agent, plasticizer and other additives that improve the quality of the future material.

Gas block: composition

Essentially, it is a mixture of a siliceous component, liquid, binder and additives that cause swelling of the solution and, as a result, the formation of cells.
Not only sand, but also highly basic ash and other industrial waste can act as a siliceous component.
The main binder, in addition to cement, can be: slag, mixed binder, ash, lime.
Cement, as a rule, should be used at a grade of at least 400-500.
Sand is mainly added quartz.
Plasticizers are used to increase the plasticity of the solution. In this case, the blocks are of better quality. They are protected from cracking during production.
If we talk about the foam block, the formation of cells in the solution occurs due to the addition of a foaming agent. In the case of a gas block, everything is somewhat different. Pores are formed as a result of the reaction of aluminum powder and quicklime.

As a result, the pore structure of the materials is different: the foam block is closed, and the aerated block is open. This also affected some property values.

Structure of foam and aerated concrete

Note! The ratio of proportions when preparing the mixture directly affects the result. For example, more porous gas or foam blocks with a low cement content will be less heavy. Their thermal conductivity coefficient will be low, as will their strength and density indicators.

Component proportions

You can increase strength using some techniques - here are a few of them:

The use of specialized additives;
Using sand rather than ash as the silica component.
Adding more binder as a percentage;
Autoclave processing makes the material more durable and resistant to mechanical stress.

As for the production process, the production of both types of blocks is similar.

First of all, the solution is mixed, which is then sent to the molds.
They are filled to about one third, since swelling of the mixture can lead to overflow.
After the pore formation process is completed, the product should harden slightly.
Next, stripping is carried out.
The last stage depends on which hardening method will be used. This can be autoclave processing or natural drying.

Hydration-hardening foam and aerated concrete can be produced by hand. This will significantly reduce the cost of construction. The above instructions are quite suitable for use.

A few words about the equipment used. If foam and gas blocks are produced in a factory, there can be two options: a set of conveyor-type machines or a stationary line of equipment.

In the first case, production will be as cost-effective as possible, automated; the volume of production can reach 200 or 300 cubic meters per day.

Conveyor type line element

In the second case, the volume will be significantly less, and the intervention of third-party workers will be required, but the price will be more affordable.

Fixed line

If the wall block is made at home, you can get by with a complete set of molds and a mixer. You can also purchase a mobile unit, with which you can produce up to 20 m3 per day.

What are the advantages of cellular concrete blocks?

Building stone with a porous structure has a number of advantages:

reduced thermal conductivity compared to other building materials. Concrete used as a heat insulator reduces heat loss;
increased dimensions with low weight. These characteristics allow you to increase the speed of wall laying and also simplify transportation;
increased vapor permeability. The cellular structure of the concrete composite facilitates the unhindered release of steam, which allows for comfortable humidity;
resistance to open fire and elevated temperatures. The structure of porous concrete is preserved in the event of fire hazardous situations.

Due to their advantages, blocks are widely used in low-rise construction.

This material is successfully used by both professional builders and individuals who build a cottage for themselves.

What does the term “cellular concrete” mean?

This term refers to several building materials that have similar properties (structure), that is, they have cells.

The physical, mechanical and operational parameters of such materials are similar to plain concrete, but in a foamed version. The presence of a porous structure reduces the density of this concrete and reduces the weight of the finished product.

Among the varieties of cellular concrete are:

aerated concrete;
foam concrete.