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    Autoclave and non-autoclave aerated concrete 

    Automated lines for AAC production


    Aerated concrete
    is a type of blown-out concrete. Aerated concrete is artificial stone with spherical pores evenly distributed throughout its volume.  Aerated concrete is obtained from a mixture of binding, siliceous component and water with adding of gas-forming and modifying agents.

    Portland cement and limestone (gas silicate) are commonly used as binding component. CHP ash, granulated blast furnace slag and silica sand are commonly used as siliceous component. As a rule, aluminum powder works as gas forming agent. Adding of aluminum powder to the mixture causes a chemical change which leads to hydrogen evolution.  In its turn, hydrogen forms pores. Regulators of structure formation and plastic strength development, hardeners and plasticizers are used as modifying agents.   


    Aerated concrete types

    There are many different types of aerated concrete which are classified according to the following criteria:

    1. By functionality:

    • structural;
    • structural and heat insulating;
    • heat insulating.

    2. By curing conditions:

    • autoclave (synthetic hardening) — hardening in saturated steam media at pressure above atmospheric;  
    • non-autoclave (hydration hardening) — hardening  under natural conditions with electrical heating, in saturated steam media at atmospheric pressure. 

    3. By type of binding component:

    • limestone;
    • cement;
    • mixed;
    • slag;
    • ash;

    4. By type of siliceous component:

    • natural materials: floured silica sand and other kinds of sand; 
    •  secondary products of industry: CHP fly ash,  hydro removal ash, afterproducts of different ores, ferroalloys waste and etc. 

    Main characteristics of aerated concrete

    Types of autoclave and non-autoclave aerated concrete strength are specified by classes according to compression strength, due to ST SEV 1406.

    For aerated concrete the following classes are specified : В0,5; В0,75; В1; В1,5; В2; В2,5; В3,5; В5; В7,5; В10; В12,5; В15.

    For constructions designed without taking into account requirements of ST SEV 1406 compression strength indexes of aerated concrete are characterized by marks: М7,5; М10; М15; М25; М35; М50; М75; М100; М150; М200.

    By average density the following marks of aerated concrete in dry condition are specified: D300; D350; D400; D500; D600; D700; D800; D900; D1000; D1100; D1200.

    The physical and mechanical properties of concrete types are given in Table 1.


    Table 1 - The physical and mechanical properties of concrete types

    Concrete type

    Concrete mark

    Autoclave concrete

    Non-autoclave concrete

     

    by average density

    Class by  compression strength

    Mark by cold resistance

    Class by  compression strength

    Mark by cold resistance

     

    D300

    В0,75

     

    -

    -

     

     

    В0,5

     

     

     

    Heat insulating

    D350

    В1

    Is not specified

     

     

     

     

    В0,75

     

     

     

     

    D400

    В1,5

     

    В0,75

     

     

     

    В1

     

    В0,5

    Is not specified

     

    D500

    -

    -

    В1

     

     

     

     

     

    В0,75

     

    Structural and heat insulating

    D500

    В2,5

     

     

     

     

     

    В2

    From F15 to F35

    -

    -

     

     

    В1,5

     

     

     

     

     

    В1

     

     

     

     

    D600

    В3,5

     

     

     

     

     

    B2,5

    From F15 to F75

    В2

    From F15 to F35

     

     

    В2

     

    В1

     

     

     

    B1,5

     

     

     

     

     

    В5

     

    В2,5

     

     

    D700

    В3,5

     

    В2

    From F15 to F50

    Structural and heat insulating

     

    В2,5

     

    В1,5

     

     

     

    В2

    From F15 to F100

     

     

     

     

    В7,5

     

    В3,5

     

     

    D800

    В5

     

    В2,5

     

     

     

    В3,5

     

    В2

     

     

     

    В2,5

     

     

    From F15 to F75

     

     

    В10

     

    В5

     

     

    D900

    В7,5

    From F15 to F75

    В3,5

     

     

     

    В5

     

    В2,5

     

     

     

    В3,5

     

     

     

     

     

    В12,5

     

    В7,5

     

     

    D1000

    В10

     

    В5

     

     

     

    В7,5

     

     

     

    Structural

     

     

    From F15 to F50

     

    From F15 to F50

     

     

    В15

     

    В10

     

     

    D1100

    В12,5

     

    В7,5

     

     

     

    В10

     

     

     

     

    D1200

    В15

     

    В12,5

     

     

      

    В12,5

     

    В10

     


      Drying shrinkage of aerated concrete should be not more than 3,0 mm/m for non-autoclave concrete of marks D600—D1200. Heat-conductivity coefficients of aerated concrete should not exceed the values given in the Table 2 in more than 20%.


    Table 2- Regulated physical and technical properties of aerated concrete types

    Concrete type

    Concrete mark

    Coefficient

     

    Sorption humidity of concrete, max %

     

    by average density

    Of heat- conductivity

    W/(m ·°С), max, of ready concrete in dry condition

    Vapour permeability

    mg/(m · h · Pa), max, ready concrete

    at relative humidity 75 %

    at relative humidity 97 %

     

     

     

     

    Ready concrete

     

     

    With sand

    With ash

    With sand

    With ash

    With sand

    With ash

    With sand

    With ash

    Heat insulating

    D300

    0,08

    0,08

    0,26

    0,23

    8

    12

    12

    18

     

    D400

    0,10

    0,09

    0,23

    0,20

    8

    12

    12

    18

     

    D500

    0,12

    0,10

    0,20

    0,18

    8

    12

    12

    18

    Structural and heat insulating

    D500

    0,12

    0,10

    0,20

    0,18

    8

    12

    12

    18

     

    D600

    0,14

    0,13

    0,17

    0,16

    8

    12

    12

    18

     

    D700

    0,18

    0,15

    0,15

    0,14

    8

    12

    12

    18

     

    D800

    0,21

    0,18

    0,14

    0,12

    10

    15

    15

    22

     

    D900

    0,24

    0,20

    0,12

    0,11

    10

    15

    15

    22

    Structural

    D1000

    0,29

    0,23

    0,11

    0,10

    10

    15

    15

    22

     

    D1100

    0,34

    0,26

    0,10

    0,09

    10

    15

    15

    22

     

    D1200

    0,38

    0,29

    0,10

    0,08

    10

    15

    15

    22