Attention should be paid to the construction of castable blocks



Castable, also known as refractory castable, is a mixture of granular and powdery materials made from refractory materials and binders. It is used after a certain degree of mixing, so that it tends to uniform, and has a certain flow construction, but also has a suitable construction time and hardening time, if it is dried by pouring way, it is called amorphous refractory. The castable can be used without sintering process, and the castable body should be baked when used. Compared with firebrick, it is more suitable for complex, special-shaped structure construction, with simple production process (because there is no fixed size requirements, save the pressing and firing process), easy to mechanized construction, construction speed and other characteristics, in some thermal equipment use effect is better than firebrick.

The biggest advantage of castable is good integrity, but when the construction area is too large, such as the area is greater than 2 square meters ~3 square meters, without expansion joint castable may produce irregular fracture. This kind of crack is caused by the expansion of refractory by heat or the shrinkage of refractory by cooling after use. According to the different conditions of the structure of the castable construction site, the more complex the structure of the castable construction site, the more irregular the cracks. If these cracks are not treated in time, they will gradually expand with the extension of the use time. Cracks are usually narrow in width, but the depth is easy to penetrate, the cracks can not be completely repaired, repair cracks can only be filled with refractory fiber, coated with refractory mud and other methods. The above methods are usually difficult to construct and completely repair the damaged castable. Even if repaired, if the expansion joint is not reserved, there will still be cracks in other parts.

In order to avoid cracks, especially through cracks, castables are usually constructed in blocks. The block construction of castable should be set in combination with the working conditions, construction thickness, construction difficulty, material characteristics and other conditions. Usually, the side length is not more than 2 meters ~3 meters. The shorter the spacing of expansion joints, the more irregular cracks can be reduced, but too small spacing of expansion joints will greatly increase the difficulty of construction. In the construction of single-layer structure, the expansion joint of castable should be set up in the form of "Z" shape and "concave and convex". The expansion joints of different refractory layers of multilayer structure should be constructed by staggered joints. Expansion joint supporting materials should be expanded joint plate, fiber felt and other soft high temperature resistant materials. When the corrugated plate is used, attention should be paid to straightening the corrugation on the side of the heating surface when the heating surface is laid, so as to avoid the corrugation squeezing the heating surface leading to local shedding. The expansion joint should also be set up to bypass special structures such as anchoring parts, burner, manhole and thermocouple hole. It should be fully considered before design and construction, and the key inspection should be carried out after the support die to avoid the defects caused by improper setting of expansion joints in special parts.

Block construction castable, on the one hand reduce the occurrence of irregular cracks, prolong the service life; On the other hand, the lining structure is clear and convenient for maintenance. Of course, block construction also increases the difficulty of construction, should pay attention to the reasonable design of block size and appropriate support mode. (Expert Group of Beijing United Rongda Engineering Materials Co., LTD.)