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So many kinds of ceramsite, do you know which kind of refractory should be used? (Ⅰ)

Ceramsite is the granule of ceramic. Most of the appearance characteristics of ceramsite are round or elliptical spheres, but some imitation stone ceramsites are not round or elliptical spheres, but are irregularly gravel-like. The shape of the ceramsite varies from process to process. Its surface is a hard outer shell, which is ceramic or enamel, has a water-tight gas barrier, and gives the ceramsite a higher strength. Because there are many raw materials for the production of ceramsite, there are many varieties of ceramsite, so there are many colors. The color of the roasted ceramsite is mostly dark red and blush, and some special varieties are grayish yellow, grayish black, grayish white, and cyan.

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The particle size of ceramsite is generally 5-20_and the maximum particle size is 25_. Ceramsite is generally used to replace gravel and pebble in concrete. Fodamon Machinery has ceramsite rotary kiln production line. Ceramic production line can be configured according to customer requirements.
Because there are many raw materials for producing ceramsite and many varieties of ceramsite, there are also many colors. Because of different solid wastes and different colors, non-burnt ceramsite is usually grey-black with no gloss on its surface, which is not as smooth as roasted ceramsite.
Lightness is the most important of many excellent properties of ceramsite, and it is the main reason for its replacement of heavy sand. The internal structure of the ceramsite is characterized by fine honeycomb micropores. These micropores are closed, not connected. It is formed by the gas being wrapped into the shell, which is the main reason for the lightness of the ceramsite.
 
The fine particles of the ceramsite are called pottery sand. There are many fine particles of less than 5 mm in the ceramsite. In the production, this part of the fine particles is sieved out by a sieving machine, which is customarily called ceramic sand. Pottery sand has a slightly higher density and good chemical and thermal stability. Pottery sand is mainly used to replace light natural aggregate sand or mountain sand to prepare light aggregate concrete, light mortar, and also as acid and heat resistant concrete fine aggregate. The main varieties are clay pottery shale pottery sand and fly ash pottery sand. The purpose of using pottery sand is also to reduce the building's own weight. Pottery sand can also be used for soilless cultivation and industrial filtration. 
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Characteristics of ceramsite:
1. Low density and light weight.
The bulk density of ceramsite is less than 1100 kg/m³, generally 300-900 kg/m³. The density of concrete made of ceramsite aggregate is 1100-1800 kg/m³, and the corresponding compressive strength of concrete is 30-40 MPa. Ceramic grains are characterized by their hard appearance and numerous micropores in the interior. These micropores give the ceramsite light properties. The density of No. 200 ceramsite concrete is about 1600 kg/m³ while that of ordinary concrete with the same label is as high as 2600 kg/m³ with a difference of 1000 kg/m³.
2. Insulation, heat insulation.
Because of its internal porosity, ceramsite has good thermal insulation properties. The thermal conductivity of concrete prepared with it is generally 0.3~0.8W/(m.K), which is 1~2 times lower than ordinary concrete. Therefore, ceramsite buildings have a good thermal environment.
3. Good heat resistance.
Ceramic grains have excellent fire resistance. Ordinary ceramsite concrete or ceramsite concrete block combines heat preservation, earthquake resistance, frost resistance and fire resistance, especially the fire resistance is more than four times that of ordinary concrete. For the same refractory period, the thickness of ceramsite concrete slab is 20% thinner than that of ordinary concrete. In addition, ceramsite can also be used to prepare refractory concrete with refractoriness below 1200℃. Ceramsite concrete can maintain 85% of its strength at room temperature at 650 C. The strength of ordinary concrete is only 35%~75% at room temperature.
4. Good seismic performance.
Ceramsite concrete has good seismic performance because of its light weight, low elastic modulus and good deformation resistance. During the 1976 Tangshan earthquake, four ceramsite concrete slab buildings built in Tianjin were basically intact and could be used as usual. And a considerable number of brick and concrete buildings around them have been damaged to varying degrees. Although this is related to the building structure system, the excellent seismic performance of ceramsite concrete is also an important reason. In 1976, a strong earthquake of magnitude 9 occurred in Feliuli, Italy. Statistical data show that the damage rate of brick-concrete buildings is 40%-60%, that of frame-structure clay hollow brick buildings is 33%, and that of ceramsite concrete buildings is only 5%. The seismic performance of ceramsite can be seen from this.
5. Low water absorption, good frost resistance and durability.
Ceramsite concrete is superior to ordinary concrete in acid resistance, alkali corrosion and frost resistance. The strength loss of No. 250 ceramsite concrete during 15 freeze-thaw cycles is less than 2%. In 1996, the relevant departments carried out tests on ceramsite concrete projects built in China since 1985. The results show that the steel bars in the precast and cast-in-situ, indoor and outdoor are not corroded. The measured carbonization depth is generally less than 30 mm, and the later strength can continue to increase. It can be seen that ceramsite concrete is a good building material and should be widely used.
6. Excellent impermeability.
According to many tests, the impermeability of ceramsite concrete is better than that of ordinary concrete. Taking 20MPa ceramsite concrete and ordinary concrete as examples, the impermeability index of ordinary concrete is B6, and that of ceramsite concrete can reach B18 to B25. In 1970, Tianjin built an air-proof passage (depth 3M, groundwater level 0.9M) with ceramsite concrete of 20Mpa. No leakage was observed during the inspection in 1980. Ningbo built two 20 MPa ceramsite concrete hoarding boats (carrying capacity 80T), which had been working on water for 13 years and had never seen leakage. Therefore, ceramsite concrete is one of the excellent building materials for dam and underground engineering.
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