Introduction to Performance Parameters of Fired Bricks
Fired bricks are widely used wall materials nowadays, and their presence can be seen in almost every corner of the city. The quality of fired bricks cannot be judged from the appearance, and can only be judged by performance indicators. The following is a detailed introduction to the performance indicators of fired bricks:
1. Shape and size
The fired brick is a rectangular prism with a standard size of 240mm × 115mm × 53mm. Adding the thickness of the mortar joint used for masonry, 4 bricks are long, 8 bricks are wide, and 16 bricks are exactly 1m thick. Therefore, 512 bricks are required for each cubic meter of brick masonry.
2. Strength level
The strength grade of fired bricks is divided into five grades: MU30, MU25, MU20, MU15, and MU10, based on the average, standard, or smaller compressive strength of 10 bricks. When evaluating the strength grade, if the coefficient of variation of strength is less than or equal to 0.21, the average standard value method is used; If the coefficient of variation of strength δ is greater than 0.21, the average small value method is used.
3. Weathering resistance performance
The anti weathering performance is one of the important durability indicators of fired bricks, and the requirements for the anti weathering performance of bricks should be determined according to the degree of weathering in each region (see GB/T5101-1998 for the regional classification of weathering degree). The weathering resistance of fired bricks is usually divided into three indicators: frost resistance, water absorption, and saturation coefficient. Frost resistance refers to the absence of cracks, delamination, peeling, missing edges, and corners after 15 cycles of freeze-thaw cycles; And the weight loss rate is less than 2%, and the strength loss rate is less than the specified value. The water absorption rate refers to the weight absorption rate of water soaked at room temperature for 24 hours. The saturation coefficient refers to the ratio of the 24-hour water absorption rate at room temperature to the 5-hour boiling water absorption rate.
The frost resistance test of fired bricks used in areas 1, 2, 3, 4, and 5 with severe weathering must be qualified, while frost resistance tests may not be required in other areas.
4. Lime explosion
If lime is carried in the raw materials or CaO is introduced into the internal fuel, it will generate burnt lime during the high-temperature melting process. Burnt lime absorbs water and expands inside the brick, causing the brick to expand and break. This phenomenon is called lime cracking. According to GB/T5101-1998, high-quality products are not allowed to have explosive areas with larger damage sizes greater than 2mm; First grade products are not allowed to have explosive areas with larger damage sizes greater than 10mm; Each group of brick samples in the qualified product must have no more than 15 explosive areas of 2-15mm, with no more than 7 areas of 10mm or more, and no explosive areas greater than 15mm are allowed.
5. Frost covered
Soluble salts in fired bricks gradually precipitate a layer of white frost on the surface of the bricks during use. These white powdery crystals not only affect the appearance of buildings, but also cause the volume expansion of crystals to loosen the surface of bricks and damage the bond between bricks and mortar layers.
GB/T5101-1998 also stipulates that high-quality products are not allowed to have frosting, and qualified products are not allowed to have severe frosting, and are not allowed to contain undercooked bricks, crispy bricks, and spiral patterned bricks.
6. Quality level
According to the national standard GB/T5101-1998 "Sintered Ordinary Bricks", the technical requirements for fired bricks include shape, size, appearance quality, strength grade, and durability. According to size deviation, appearance quality, frosting, and lime cracking, it is divided into three levels: excellent product (A), first-class product (B), and qualified product (C). The porosity of fired bricks is about 30%, the water absorption rate is around 18% to 20%, and the apparent density is around 1800kg/m.
Mastering the knowledge of the six performance indicators of fired bricks mentioned above is very helpful for the selection work. We hope everyone will read it carefully.
