Volume density is the total volume ratio of solid and pore volume in refractory fire brick mass. The volume density affects the porosity, strength, erodibility and wear resistance of firebrick.
The porosity is the percentage of the volume of the porosity in firebrick and the total volume of the product. In other words, the higher the volume density, the smaller the porosity. Because there are also three kinds of pores, and the porosity of firebrick is closed porosity, which is the apparent porosity indicated on the test sheet. The apparent porosity of heavy refractory fire brick is generally between 10% and 28%, and the standard is less than 16% to be called low porosity products. But with less and less raw material resources, and aluminum ore is cut out, the composition is not artificially added to the fired, in the actual production process, less than 20% of heavy firebrick is called low porosity brick.
Porosity is the basic technical index of refractory brick. Its size affects the properties of refractory fire brick, especially strength, thermal conductivity, slag resistance and thermal shock resistance. When the porosity increases, the strength decreases. Low porosity is beneficial to the softening temperature and creep properties of refractory fire brick under load. However, the effect of porosity on thermal shock resistance is complicated, and the thermal shock resistance is better when the porosity is in a certain range. And too low porosity is not good for thermal shock, not all indicators are high or low.
To produce compact firebrick with low porosity, it is necessary to choose raw materials with low porosity. Formulate reasonable particle gradation, rational use of binder, full uniform mixing, high pressure molding and increase firing temperature, and then extend the holding time to reduce porosity. In an amorphous castable, the addition of superfine powder and dispersant can form a tighter packing and obtain a product with low porosity.
The relation between the volume density and porosity in refractory fire brick is that the higher the volume density, the smaller the porosity will be.
