Differences in raw materials
Red bricks are mainly made of clay, shale and coal gangue, which are crushed, mixed, kneaded and then fired at high temperature. Blue brick is made of clay as the main raw material, which is mixed and extruded with water, baked at high temperature, and finally cooled with water, so that the iron in clay can not be completely oxidized, thus giving blue brick excellent weather resistance and water resistance.
Different firing processes
Adding water or not is the key difference between red brick and blue brick. In short, add water and fire to get blue bricks, and don't add water to get red bricks. Although the raw materials are basically the same, blue bricks are superior to red bricks in oxidation resistance, hydration resistance and atmospheric erosion resistance. This can be witnessed from the ancient "Qin Brick Hanwa". These blue bricks have remained intact for thousands of years.
Feature comparison
Blue brick is superior to red brick in firmness, alkali resistance and durability, but its production process is complex, energy consumption is high, output is small and cost is high, and it is difficult to realize automatic and mechanized production, so the price is usually 2-3 times that of red brick. Relatively speaking, the production of red brick is simple, efficient and widely used. Please note, however, that red bricks are solid bricks and need a lot of clay, which leads to a large loss of clay, so the state controls the output of solid clay bricks.