Although there are an astonishing 6,000 kinds of stone materials available for construction, if the stone materials are systematically classified, they can be divided into two categories
Granite, marble, sand, SLATE, artificial stone and other five categories.
So what kind of stone is usually used in stone curtain wall?According to the world's current stone curtain wall specifications, the following requirements should be considered:
Corrosion resistance and durability
Generally speaking, the stone with high content of SiO2 has high strength and durability. The stone with more than 50% SiO2 content is suitable for the exterior curtain wall.
Conversely, the stone material with high content of calcium oxide (CaO), easy to be corrode by the gas such as sulfur dioxide in the atmosphere, this kind of stone material is used in curtain wall, want to undertake more perfect surface treatment, take more effective anticorrosion measure.
Density and uniformity
1, the same type of stone, the volume density has a certain range of distribution.Usually the bulk density of stone, material density, high strength and good durability.
G volume density less than 2.1 G /cm3 stone is low density;G=2.1g/cm3 ~ 2.5g/cm3 is the medium density.G≥2.5 G /cm3 is high density.For the stone material used for curtain wall, its density should meet the requirements of table 1.
2, used for the curtain wall stone, should be more uniform.
(1) there should be no weak interlayer or weak vein in the stone.
(2) there is a layered pattern of rock, not suitable for coarse, loose, porous stripes.
(3) the pore size of porous rock should not be too large or too deep.The number of holes should not be too much.Otherwise, take measures to seal the hole.
As an important index of stone strength is dry.The average bending strength test value of igneous rock (including granite) should not be less than 10N/mm2. When the bending strength of the specimen is less than 8n /mm2, the stone should not be used in the curtain wall.
Other stone FM should not be lower than 4 N/mm2. When the bending strength of the specimen is lower than 3 N/mm2, this batch of stone should not be applied in the curtain wall.
Sometimes the strength of sedimentary rock is not consistent in all directions, then the strength along the main stress direction of the stone panel should meet the above requirements.
Stone after the freeze-thaw cycle, the strength has been reduced.The freeze-thaw cycle test of granite was carried out according to national standard GB9966.2.The ratio of strength to original strength after freezing-thawing cycle is called freezing-thawing coefficient.For the stone of curtain wall, its freeze-thaw coefficient should not be less than 0.8.
Stone bibulous rate should be less than 0.8%