Lightweight insulating bricks are a type of insulating and heat-resistant material with low bulk density, high porosity, and low thermal conductivity. Their low density and low thermal conductivity make them irreplaceable in industrial furnaces. However, low density and low thermal conductivity are often in conflict with strength. The national standard (GB/T 3996-1983) sets performance indicators for lightweight insulating bricks. As the thermal conductivity of different types of insulating bricks decreases, the corresponding strength also decreases. People always hope to have a type of insulating brick that has low thermal conductivity and good strength at the same time. According to the current standard, when the thermal conductivity is 0.13 W/m-K, the refractoriness is 800-900℃, the linear change is no more than 2% under 900℃ for 8 hours, the compressive strength is 0.8 MPa, and the bulk density is 0.5 g/cm3.

In a production example, the quantities of raw materials are as follows: 300 kg of silica sand with more than 96% SiO?, 10 kg of lime with more than 85% CaO, 70 kg of fireclay with more than 90% SiO?, 30 kg of aluminum phosphate cement, and 1 kg of industrial aluminum. The total water consumption is 400-500 kg. The preparation process is as follows:

1.Weigh the raw materials according to the ratio, grind all the materials into powder, add water to the silica sand to make a slurry and preheat it to a temperature of 45-50℃.

2.Add the remaining materials to the slurry and stir until completely mixed. Pour the mixed slurry into the mold, heat it to 65-70℃ for foaming. The foaming volume should be more than 40% of the total volume. After foaming, keep the mixture at 40℃ for 2 hours.

3.After the 2-hour period, move the mixture into a steam room for steaming. The steaming pressure is 1.2 MPa, the temperature is 190℃, and the steaming time is 9 hours.

4.Finally, perform high-temperature sintering at 800℃.