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