In modern constructions, the development of high-rise buildings requires producers to reduce the dead weight of fired bricks and improve their insulation and sound absorption, and thus fired porous bricks, hollow bricks and hollow blocks come into being. Compared with fired common bricks, they have a series of advantages when used: the dead weight of walls can decrease by 30%-35%; the efficiency can be improved by 40%; the cost of mortar can be saved by about 20%; the insulation and sound absorption of walls can be improved. In addition, the clay raw materials and fuels can be saved, the quality and the yield can be increased, and the cost can be reduced in production.
(1) Fired Porous Bricks
A fired porous brick is a porous brick with bedding surfaces (240mmx 115mm). The size of pores is small [the round hole diameter S 2 2 m m ; the incircle diameter of non-round hole< 15mm; the hole made by hand (3040)mmx(75-85)mm 3, with the hole ratio equal to or more than 15%.
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Item
@ Color(a side face and a end face)
@Finished face (2) (mm)
The pores are perpendicular to the load face when used. Because the strength is high, the fired porous bricks are often used in the load-bearing parts of buildings.
According to Fired Porous Brick (GB13544-2000), its appearance is a right-angled hexahedron, and its length, breadth, and height should be in line with the following requirements: 290mm, 240mm, 190mm, 180mm; 175mm, 140mm, 115mm; and 90mm respectively. And 190mmx 190mmx90mm (Type M) and 240mmx115mmx90mm (Type P) are the two common specifications, shown in Figure 7.2. Other dimensions should be negotiated by the supply and the demand parts. The bricks whose strength and weathering resistance are qualified can be divided into three quality levels: the excellent (A), the first-class (B) and the qualified (C), according to the size deviation, appearance quality, and physical property.
Qualified Class Excellent Class First Class
The same A side face and a end face
-
Almost the same A side face and a end face . Figure 7.2 A Fired Porous Brick (Unit: mm)
1) Size Deviation.
The size deviation of porous bricks should accord with GB13544-2000 for 2) Appearance Quality.
The appearance quality of porous bricks should be in line with Table 7.3.
the sake of the masonry quality.
Table 7.3 Appearance Quality of Fired Porous Bricks (GB13544-2000)
7 Wall and Roof Materials 177
Item Excellcnt Class
@The thrce damagcd dimensions of the arris defect should not hc more than at the samc time (mm)
@The length of cracks (<) (mm)
(a) the Icngth, above 15mm dccp in the hole wall, in the breadth direction on the bedding face and the length extending to the side faccs
(b) the length. above l5mm dccp in the hole wall, in the breadth dircction on the bedding face and the length extcnding to the end faccs
(c) the horizontal crack on the side and the end faces
@The convex height (<) (mm)
I5
60
60 80 3
COI
First Class 20
80
100 I00
4
nued Qualified
Class 30
100
120 120 5 Note: 1) 1\11 the dccorative color diffcrcnce, raiscd grain, sculling. and embossing are not dcfccts.
2 ) It should not be callcd finishcd face, if it has one of the following defects:
(a) the damagcd dimensions of the defect on the side face or the end face are more than 20mm.
30mm at the same time;
(b) the breadth and the length of the crack on the side facc or the end face are more than I mm and 70mm respectively;
(c) the concave and the convcx heights of the compressed mark, adhcsive backing and burnt flower on the side face or the end face are more than 2mm. and the dimensions are more than ZOmm. 30mm at the samc time.
3) Strength Grade.
The strength grades can be divided into MU30, MU25, MU20, MU15, and MUlO, the five grades. The determination of the strength grades of fired porous bricks is the same with that of fired common bricks. And all the grades should be in line with Table 7.2.
In addition, the weathering resistance, efforescence and lime burst of fired porous bricks should accord with GB13544-2000. And there should be no place bricks, crisp bricks and screw bricks.
The fired porous brick products are coded by name, variety, specification, strength grade, quality degree and standard numbers. For example, the excellent fired clay bricks with the specification of 290mmX 140mmX90mm and the strength grade of MU25 should be marked as: fired porous brick N 290X 1 4 0 x 9 0 25A GB13544.
(2) Fired Hollow Bricks
The fired hollow bricks and hollow blocks (simply called hollow bricks) are the bricks or blocks with pores on the end faces. The pores are large and not many, with the hole ratio more than 30%. Because pores are big, the dead weight is light, and the strength is low, the bricks are usually used in the non-bearing parts.
178 Building materials in civil engineering
According to Fired Hollow Brick and Block (GB 135452003), the fired hollow brick and block is a right-angled hexahedron, shown in Figure 7.3.
And its length, breadth and depth should be in line with the following requirements: 390mm, 290mm, 240mm, 190mm, 180 (1 75)mm, 140mm, 115mm, and 90mm; because the raw materials are different, there are clay brick and block (Y), coal gangue brick and block (M), and fly ash brick and block (F); the compressive strength of fired hollow brick and block has five grades: MU10.0, MU7.5, MU5.0, MU3.5, and MU2.5, and the fired bricks and blocks in each grade should be in line with Table 7.4; there are three bulk density grades: 800, 900 and 1100, in line with Table 7.5. The bricks and blocks qualified in strength, density, weathering resistance and radioactive substance can be divided into three classes: the excellent (A), the first-class (B) and the qualified (C), based on the size deviation, appearance quality (the appearance quality should be in line with Table 7.6), the arrangement and structure of pores, efforescence and lime burst, as well as water absorption.
I 3
Figure 7.3 The Appearance of Fired Hollow Brick
I . end face; 2. bedding face; 3. side face; 4. rib; 5. concave groove; 6. shell; 1. length; 6. breadth; d. depth
The fired hollow brick and block products are coded by name, variety, specification, density grade, strength grade, quality degree and standard numbers. For example, the excellent shale hollow bricks with the specification of 290mmX 190mmX90mm, the density grade of 800 and the strength grade of MU7.5 should be marked as: fired hollow brick Y (290X190X90) 800 MU7.5 GB13545; and the first-class clay hollow bricks and blocks with the specification of 290mm X 290mm X 190mm, the density grade of 1000 and the strength grade of MU3.5 should be marked as: fired hollow brick N (290X290X 190) 1000 MU3.5 GB13545.
5
Average Coeflicicnt of Coeflicient of Strength Standard strengthf, Minimum strength of a Strength Compressive Variation S 0 . 2 1 Variation >0.21
7 ( 2 ) ( 2 ) brick .fmin(2)
Grade
MU 10.0 10.0 7.5 8.0
MU7.5 7.5 5.0 5.8
MU5.0 5 .O 3.5 4.0 g1100
Density grades (kg/m’)
MU3.5 I 3.2 2.5 2.8
MU2.5 I 2.5
Items
@The bending degree (<)
@The three damagcd dimensions of the arris defcct at the same time (>)
@ Error of perpendicularity (<)
@Un-through-wall cracks ( G ) I
(a) the length in the breadth direction ofthe bedding face and the length extending to the side faces (b) the length in the length direction on the bedding face or the length in the horizontal direction on the side face
@ Through-wall cracks
(a) the length in the breadth direction of the bedding face and the lcngth extending to the side faces (b) the lcngth along the length direction on walls or ribs, the breadth direction and the horizontal direction
@ The damaged length of ribs and inside walls (<)
1.5 1.8 I G800
Excellent Class 800
900 1000
3
<800 80 1-900 901-I000
15 3 I100
Inadmissible inoi-1100
Inadmissible
Inadmissible Inadmissible Inadmissible A side face and a
bedding face
6 ‘Finished face ( 3 )
First Class
4 30 4 100 120
40 40 40 A sidc face or a bedding face
Qualified Class
5
* 40 5
120 140
60
60 60 -
:cts:
1) the damaged dimensions of the dcfect on the bedding face and the side face are more than 20mm X 30mm at the same time;
2) thc breadth and the length of the crack on the bedding face and the side face are more than Imm and 70mm respectively;
3) the concave and the convex heights of the compressed mark, adhesive backing and burnt flower on the side face or the bedding face are more than 2mm, and the dimensions are more than 20mm X 30mm at the same time.
’
180 Building materials in civil engineering
Compressive Strength (MPa) Average Single
( 2 ) o n e ( > , )
25.0 20.0
20.0 16.0
15.0 12.0
10.0 8.0
7.1.2 Non-Fired Bricks
Bending Strength
(MPa) Frost Resistance
Compressive Dry weight Average Single strength after frost loss of a
( 2 ) o n e ( > , ) (MPa) brick (%)
5.0 4.0 20.0 2.0
4.0 3.2 16.0 2.0
3.3 2.6 12.0 2.0
2.5 2.0 8.0 2.0
Average ( 3 ) (q
The bricks made not by roasting are called non-fired bricks.