1.Refractory aggregates and powders are made from calcined excellent clay clinker and high alumina bauxite clinker. The maximum particle size of the refractory aggregate depends on the thickness of the engineering lining, generally 10mm, and its particle equipment share is: 10-5mm, 30%-40%, 5-3mm, 20%-30%, 3-0.15 m, accounting for 30%-40%. In general, when manufacturing low-cement refractory castables, less use is used, but three-stage and four-stage grading are used to reach the maximum bulk density, and the amount of refractory aggregate is 68%-72%.
2. Refractory powder generally uses secondary, first-grade or extra-grade high-alumina bauxite clinker as material. After grinding, iron removal treatment should be carried out. When the fineness is 0.09mm or <0.044mm, it should be ≥90%. Can be used alone or in combination. Advanced refractory materials such as fine alumina powder, white corundum powder or brown corundum powder are sometimes added to improve the matrix function of low cement refractory castables. The amount of refractory powder is 18%-25%. In the meantime, if the advanced data is mixed, the dosage is 5%-10%. There are many types of refractory ultrafine powders, and active SiO2 powder (ie, silica fume) is used throughout the country, and a-A2O3 powder and C2O3 powder are also used. It is used in an amount of 2% to 12%.
3.The calculation of refractory powder and ultrafine powder is 28%-32%. It should be pointed out that the types of low-cement refractory castables are different, and the amount of ultrafine powders is also different, and there is a corresponding optimum amount, which needs to be determined by experiments. The optimum dosage is 4%-10%.
4.In the low cement refractory castables, the admixtures selected are mainly high-efficiency water reducers and dispersants, and the types thereof are NNO, MFJN.SM, humic acid, citric acid and tartaric acid, etc., and salts thereof. Sodium polyphosphate, sodium hexametaphosphate and boric acid are generally used in an amount of from 0.033% to 1.0%. When using an admixture, it should be compatible with ultrafine powder. The origin of the data should be considered together, and the convenience and cost should be considered. In general, organic admixtures are superior to inorganic admixtures in reducing water and dispersing. In addition, a swelling agent such as blue crystal and sillimanite is added to make the low cement refractory castable exhibit a micro-expansion condition at a high temperature.
Knowing these basic manufacturing guidelines, it is possible to formulate a wide variety of low cement refractory castables. For example, use 80% of alumina bauxite aggregate of 8-0mm, 20% of clinker clinker powder of the same grade, 5% of CA-50 cement of 625, 5% of silica fume, 65% of sodium tripolyphosphate and 65% of water. The castable, after the compressive strength of 20N140 °C, the compressive strength and the line shortening are respectively 0.2% and 6.5% of water are equipped as castables, the drying compressive strength is greater than 20 MPa, the compressive strength after burning at 1450 °C and the county The shortening is 70 MPa and 0.01% respectively; the amount of water used to form a good low cement refractory castable is generally not more than 7%, and the less the better.
