Why are common bricks red? How are traditional blue bricks made in China? Why in the eighties and nineties?

Its main raw material is silty or sandy clay, and its main chemical components are silica, alumina, iron oxide and crystal water. Due to different geological conditions, Al2O3 may contain a small amount of alkali metal and alkaline earth metal oxides.

Red bricks are made of ordinary clay. The soil contains high iron content, so the bricks are red.

The production of blue bricks is:

The main raw material of ancient blue brick is clay, which is mixed and extruded with water, burned in a brick kiln to about (1000℃), and cooled with water, so that the iron in the clay is not completely oxidized, and it has good weather resistance and water resistance.

The hardness of blue bricks and red bricks is similar, but the cooling method after firing is different, while red bricks are naturally cooled, which is simpler, so more red bricks are produced, while blue bricks are cooled with water (in fact, it is a kind of anoxic cooling), which is more troublesome to operate, so less is produced.

Advantages of ancient blue bricks:

1, the hardness of blue brick is higher: the manufacturing process of red brick is relatively simpler and the price is lower, so there are red bricks in ancient times. But just like we build houses in the countryside, brick-concrete houses use red bricks. Who dares not to stick tiles on the exterior wall or brush the exterior wall paint? In addition to looking good, it is also to protect red bricks. Those old houses with red bricks and unprotected external walls can be seen that the red bricks have weathered and loosened.

2. Excellent performance: the hardness and strength of blue bricks for ancient buildings are much greater than that of red bricks. Blue bricks have high density, no deformation, good frost resistance, oxidation resistance, waterproof foaming, wear resistance, wind and rain erosion resistance, and will not rot for thousands of years. Blue bricks have strong air permeability and good water absorption, and can keep indoor air humidity. The ancient "Qin Brick Hanwa" can still be well preserved after thousands of years, which is the best proof of the excellent performance of blue bricks.