Compared with sintered brick, industrial waste residue baking-free brick uses industrial waste residue without sintering and steam curing, and its production cost is lower than that of sintered brick. Large amount of slag, outstanding social and environmental benefits; Regular edges and corners, accurate size, high compactness, low water absorption and good durability with compressive strength higher than 7.5MPa.
1, raw material for producing industrial waste residue baking-free brick.
The raw materials for producing industrial waste residue baking-free bricks generally include three parts: industrial waste residue, curing agent and admixture.
3. 1 physical and mechanical action
The initial strength of industrial waste residue baking-free brick is obtained in the process of pressure molding of brick blank. Molding not only makes the green brick have a certain strength, but also ensures that the physical and chemical interaction between raw material particles can be carried out efficiently because of the close contact between raw material particles, which provides conditions for the formation of later strength. General industrial waste residue baking-free brick forming pressure is not less than 20MPa. The experimental results show that
Under the same other conditions, the strength of industrial waste baking-free brick specimens increases with the increase of molding pressure; Without high pressure forming, even if cement and lime are added, high strength cannot be formed.
3.2 Hydration reaction
The hydration products of cementitious materials such as cement and lime provide the early strength of industrial waste residue baking-free brick. The main hydration reactions are as follows:
3Ca0。 SiO 2+mH2O-& gt； xCaO。 Silicon dioxide, calcium hydrogen oxide
2Ca0。 SiO 2+mH2O-& gt； xCaO。 Silicon dioxide, calcium hydrogen oxide
4CaO。 al2o 3 . fe2o 3·7H2O-->3CaO。 Al2o 3·6h2o·CaO Fe2O3 H2O
Ca0h2o-> calcium hydroxide
Raw materials (such as fly ash, clay, slag) for producing industrial residue baking-free bricks contain a lot of active silica and movable alumina, which react with calcium hydride under the action of additives to generate hydraulic cementing substances similar to cement hydration products, such as hydrated calcium silicate and hydrated calcium aluminate, thus continuously improving the strength of bricks. The reaction formula is as follows:
xCa(OH)2·SiO 2·mH2O->XCaO。 SiO2.nH2O (calcium silicate hydrate)
xCa(OH)2·al2o 3·mH2O->XCaO。 Al2O3.nH2O (calcium aluminate hydrate)
In addition, Ca(OH)2 absorbs CO2 in the air and generates CaCO3 crystal structure, namely:
Ca (oh) 2co2-> calcium carbonate H2O
If gypsum is present in the raw material, the following reactions will occur:
xCaO。 Alo3 nh2o caso2 2h2o-> xcao Al2O3. (N2) H2O (ettringite)
3.3 Particle surface exchange and agglomeration
Under the action of water molecules, the hydration film of 1 was formed on the surface of industrial waste baking-free brick particles. Under the action of two hydration films, some chemical bonds began to break and ionize, forming a colloidal particle system. Most of the surfaces of colloidal particles are negatively charged and can adsorb cations. However, cations with different valences and different ionic radii can be exchanged with Ca2 in Ca(OH)2.
Due to the ion adsorption and exchange on the surface of these colloidal particles, the charged state of the particle surface is changed, and the particles form small aggregates, thus generating strength in the later reaction.
3.4 interphase interface reaction
Interface scientists believe that all chemistry begins at the interface. There are reactions between liquid phase and solid phase, gas phase and solid phase in the strength formation process of industrial waste residue baking-free brick. For example, the hydration reaction of cement after adding water is the reaction between liquid phase and solid phase; The reaction that Ac(OH)2 in batch is carbonized by CO2 in air to generate CaCO3 is a reaction between gas phase and solid phase. These reactions start from the two-phase interface and continue to deepen, so that the strength of bricks continues to increase.
To sum up, the full mixing of the batch and the pressurization in the molding process laid a solid foundation for the later strength of the brick; Through the ion exchange and agglomeration on the particle surface, the hydrolysis of cement and lime, the hydration reaction between raw materials and the interface between phases, the generated crystals cross and overlap together to form a spatial grid structure, which gradually enhances the strength of industrial waste baking-free bricks.