What are the standards of refractory concrete ?
Refractory concrete is generally divided into three categories: Light insulating concrete (for insulation); medium-quality refractory concrete (It is used for the parts where requirement of refractory temperature is not very high, and it can withstand a certain erosion of air); heavy refractory concrete (It is used for the parts where requirement of refractory temperature is fairly high, and it can withstand a certain intensity of erosion of air). It mainly depends on the design temperature and the using parts. There are a variety of raw materials, of which aluminum oxide is one of the most commonly used materials, others are alumina hollow ball, magnesium oxide, zircon, etc. It depends on the design temperature and the parts on use. Commercial concrete station generally can not produce it, instead it is compound by professional refractory concrete factories.
The special concrete compound by uitable binding materials, refractory aggregates, admixtures and water at a certain ratio. It can maintain the desired mechanical property at high temperature of above 900 ℃ for a long time. The property depends on the material and matching of all the aggregates, admixtures and binding materials. Its material, composition and ingredients are similar to these of refractory castable. Refractory aggregate can be dry slag, broken refractory bricks, basalt, bauxite, magnesite, etc. According to the binding material, it can be divided into Portland cement refractory concrete, aluminate cement refractory concrete, sodium silicate refractory concrete, phosphate refractory concrete, magnesia refractory concrete, etc. (8) The particle material and powder material in refractory concrete are called aggregate and admixture respectively. The mixture of concrete can be moulded by casting, vibrating or ramming. And proper measures to promote their hardening can be used in accordance with the hardening characteristics of the binding materials (such as air hardening, water hydraulicity, thermal hardness, etc.). It is mainly used to build the monolithic lining of industrial furnace and procast blocks. Of all the concrete, the ones used for under 900 ℃ is called heat-resistant concrete, and they are used for the foundation and chimneys, etc. of industrial furnaces and thermal equipment.
Heat-resistant concrete refers to the kind of concrete which remain undamaged, do not lose the necessary bearing capacity at 200 ~ 1300 ℃ high temperature for long term, and still maintain its physical and mechanical properties.
It can be divided into: 1. Ordinary refractory concrete Aggregates used include high alumina, clay, silica, basic materials (magnesite, chromite, dolomite, etc.) or special materials (carbon, silicon carbide, zircon, etc.). It can also use several combination of refractory material. 1. Thermal insulated refractory concrete It is mainly formulated with refractory light aggregates. The light aggregate used can be expanded perlite, vermiculite, ceramsite, porous chamotte, alumina hollow ball, etc. It can also be a combination of several refractory light aggregates or combination of the refractory aggregates. The aggluetination material used in refractory concrete can be high alumina cement, phosphate binders, water glass binder and clay, etc.
General requirements (1) All the materials for compounding refractory concrete must meet the design requirements and they should be checked according to the relevant standard. (2) The compounding of refractory concrete should be done strictly in accordance with the compounding proportion (usually weight), and the using of various binders, aggregates, coagulant, and water should be accurately measured. Tolerance of difference of cement, powder and water should be not more than 1 %; weight of aggregates does not exceed 3%. (3) The mix of different varieties of concrete must be prevented. (4) A variety of raw materials should be piled separately according to different species, mark numbers, dates of manufacture. Do not mix with limestone, silica, railroad ballast, dirt and other harmful debris.
