The physical and chemical properties of the unburned brick machine soil can be roughly summarized as follows:
(1) The soil contains large and small sand particles, which are inert materials, that is, they cannot chemically react with cement and lime. However, proper particle gradation and appropriate content in the soil can play a skeleton role in the strength of unburned bricks (similar to sand and stone in concrete) and improve the strength of bricks. And in the semi-dry pressing of bricks, the air is removed to reduce the delamination of bricks.
(2) The clay contained in the soil is mainly composed of secondary minerals, such as illite, montmorillonite, kaolinite, etc., which are called mineral colloids and are active parts in the soil. This kind of clay is negatively charged, has strong adsorption, has great surface energy and physical and chemical replacement capacity, and can produce ion exchange and agglomeration.
(3) Silicic acid hydrogel, ferric hydroxide hydrate, trioxide and silicon dioxide contained in the soil. In the manufacture of unburned bricks, these substances have physical and chemical interactions with quicklime and calcium hydroxide, the hydration product in cement. The generated calcium silicate hydrate has a strong cementation effect, and can cement the soil particles of rabbit burnt bricks into a hydraulic whole.
(4) Both the octahedron and tetrahedron in the layered silicate structure can produce lattice distortion, which makes the clay mineral unstable, thus giving it a certain potential activity.
