Curtain wall material is a kind of decorative maintenance material which fixed outside the wall by supporting structural system, divided into stone, glass, metal and terraccota panel as the four kinds of representative artificial materials.
According to GB / T21086-2007 "Archtecture Curtain Wall;, qualified ceramic curtain wall should meet a series of performance norms: not only to meet general requirements of the Archtecture Curtain Wall materials (wind resistance, water tightness, air tightness, thermal universality, airborne sound insulation performance, plane deformation and shock resistance, impact resistance, optical and load-bearing performances, etc.), but also to meet the special requirements of ceramic curtain wall (water absorption, fracture modulus, size error, surface quality, etc.).
In the actual use of terracotta panel, overseas customers, customers of Hong Kong and domestic big project pay more attention to the following aspects:
1、 Safety performance
A、 Bending strength / fracture modulus
B、 Anchoring strength (also known as mounting system structural strength)
C、 Shock resistance
D、 Wind pressure deformation resistance
F、 Impact resistance
Caption: The performances above are not only the requirements of Archtecture Curtain Wall norm, but also the most attention performance regarding terracotta panel as curtain wall material, since the safety of the Archtecture Curtain Wall is always the first.
2、 Aesthetic Appearance
Dimension Error, Edge Straightness, Concavity and Convexity, Center Curvature, Color Difference etc.
Caption: These requirements are mainly related to the decorative effect after terracotta panel installated, and reflect the appearance quality, such as color difference which is the most concerned problem by user.
3、 Physical and Chemical Properties
Water absorption, pollution resistance, anti-ultraviolet aging, anti-freeze-thaw etc.
Caption: These are related to the inherent characteristics and basic requirements of terracotta panel. Although invisible, it intrinsically linked with the safety, external impressions and durability. For example, the anti-freeze-thaw requirement is relatively high if application in cold areas. So different climate zones require different water absorption in national standard, For instance, water absorption should not be greater than 6% if the region has more than one month freezing perod. Because lower water absorption, better resistance to freezing and thawing. Therefore the standard of terracotta has classification of water absorption 3% ≤ E ≤ 6% and 6% ≤ E ≤ 10%.
In the many properties involved in the terracotta panel, The water absorption has popular public attention, due to the concept is relatively easy to understand, and it regarded as a reference of classification by GB and trade standards. Some customers asked the question of the suitable water absorption, is not the lower the better?
As the external wall decoration materials, the water absorption rate is mainly related to anti-freeze-thaw cycle performance. The different climatic conditions have different requirements of water absorption: the more cold, the lower water absorption requirements.
In view of China's overall climate conditions, GB/T21086-2007 "Archtecture Curtain Wall" has a clear definition of water absorption for terracotta panel:
In other words, too low water absorption (≤ 3%) is only applicable to some special alpine region, so it is basically unnecessary in our country. And too high water absorption (≥ 10%) will lead to frost cracking of terracotta panel, so it is unqualified.
The lower water absorption requirements mainly for . standard of the ground tiles, such as porcelain tiles (tiles, polished tiles, full body tiles, antique tiles, etc.) require water absorption below 1%, because they are used as floor tiles with higer requirements of abrasion resistance and strength. The water absorption of the porcelain tiles is low, not just because the firing temperature is higher than 1200 ° C (the firing temperature of terracotta panel is generally around 1170 ° C), but also use the fine raw materials and high tonnage press. However, there are limitations of the lower water absorption to the porcelain tile, the gorgeous brick red, brilliant yellow etc. can not be achieved in full body porcelain tile.
The teracotta panel is the process of extrusion molding with specific grain gradation and raw material formula, it bring the sense of moderate density, nature ,gentle and moist for its rich and coarse surface texture. Terracotta panel is mainly used for building exterior curtain wall dry hanging, so it has lower requirements for abrasion resistance and compression strength. Terracotta panel can be rich in color after firing because of the wide range of water absorption, so that meet the pursuit of architectural colors by designers to the utmost. This is the porcelain brick can not be incomparable.
In fact, the water absorption rate of terracotta panel varies with different colors, even if the firing temperature is the same. For example, water absorption is generally between 3-6% for gray, brown, brownish red, white, and brick red, but brick red and yellow is generally more than 6%. We tested and compared the water absorption to samples of domestic and international brands, the results show that there is a big difference between different colors. It proved our view above. Refer to Appendix.
From the attached test table, the water absorption of high iron red both Terreal and CN are more than 9% because of gorgeous color, while the Frontek did not produce such products. We also specifically tested the water absorption of Frontek samples which has seven varieties of four series colors red, black, yellow, gray, there are three varieties between 3% -6%, and four varieties between 6% -10%. The interval distribution of water absorption is similar to CN products. However, due to different technology and raw materials of each manufacturer, there is great difference for water absorption of the same color. For example, the water absorption is 5.48% for Frontek brownish red, but only 4.2% for CN brownish red; the water absorption is 4.66% for Frontek dark gray (red) , but 5.1% for CN dark gray (red).
Of course, it is not difficult to pursuit of low water absorption. As mentioned above, we can improve the firing temperature, or grinding the raw material particles more finely. However, from the detection standard of the terracotta panel, the test results is unqualified for the water absorption less than 3%. Moreover, the unique texture of gentle & moist and natural color disappeared, so there is no difference between terracotta panel and tiles. The dry hanging system promoted by the Cimic, Dongpeng and other well-known tiles, polished tiles brands for more than 20 years, but it has not been widely accepted by the market. However, it is in hot pursuit in market for only 3 to 5 years promotion of terracotta panel. It shows that the market agrees more with the texture and decorative effect of terracotta panel.
In fact, it is completely enough to meet the regional requirement of water absorption as per freezing period. As a customer, should pay more attention to safety, and concern if colors can meet the design requirements.