What is refractory mortar and its application range

Refractory mortar is the material used to bond refractory bricks when laying kiln linings. Its function is to fill the brick joints and make the brickwork bonded as a whole. There are magnesia, high-alumina and clay refractory muds. Different types of bricks use corresponding refractory muds. Generally, water glass can be used as a binder for all kinds of refractory muds.

1. Types of refractory mortar

Refractory mud can be divided into dry earth refractory mud, high-alumina refractory mud, siliceous refractory mud, magnesia refractory mud, etc. according to the different components. Refractory mud can be divided into the following three categories according to the different binders:

(1) Ceramic bonded refractory mortar It is a mixture of refractory fine aggregate and ceramic binder (plastic clay). It is delivered in dry state and needs to be used after adding water. It hardens through ceramic bonding at high temperature.

(2) Hydraulic bonded refractory mud It is a mixture of refractory fine aggregate and hydraulic binder (cement) that plays the main bonding role. The delivery state is only dry, and it can be used after adding water. No heating is required during hardening.

(3) Chemically bonded refractory clay is a mixture of refractory fine aggregate and chemical binder (inorganic, organic-inorganic, organic). The delivery state can be either slurry or dry, and it hardens at a temperature lower than the ceramic bonding temperature. According to the hardening temperature, this refractory clay can be divided into gas-hardening and heat-hardening types. Gas-hardening refractory clay is often prepared with gas-hardening binders such as water glass. Heat-hardening refractory clay is often prepared with heat-hardening binders such as phosphoric acid or phosphate. After hardening, this heat-hardening refractory clay has high strength at all temperatures and has the characteristics of small shrinkage, tight joints, and strong corrosion resistance.

Refractory clay is divided into finished products and semi-finished products. The so-called finished refractory mud means that the raw materials and clinkers have been mixed in proportion by the manufacturer. When used on site, you only need to add water and stir evenly according to the standard; semi-finished or unfinished refractory mud means that the raw materials and clinkers are not mixed together. When used on site, they are fully mixed according to the composition of different muds, and water is added and stirred evenly according to regulations.

2. Quality requirements of refractory mud

① Good construction performance, with appropriate fineness, viscosity, extensibility, and water retention, and it is easy to obtain the required brick joint thickness.

② It has strong adhesion and hardness at operating temperature and is resistant to gas erosion and wear.

③ Brick joints cannot crack due to expansion and contraction caused by drying and firing.

④ The chemical composition is the same as that of masonry bricks.

⑤ It has the necessary refractoriness.

3. Composition and use of refractory mud

Refractory mud is an amorphous refractory material composed of powdered materials and binders for preparing mud. It is mainly used as a joint and coating material for masonry refractory brick masonry. When used as a joint material, its quality has a considerable impact on the quality of the masonry. It can adjust the size error and irregular shape of the bricks to make the masonry neat and balanced, and can make the masonry form a strong and tight whole to resist external damage and prevent the invasion of gas and molten liquid. When used as a coating, its quality is closely related to whether the protective layer can make the bottom layer fully exert its due effect and extend its service life.

Refractory mud is mostly used by adding water (or aqueous solution) to make mud. Refractory mud must have good fluidity and plasticity for easy construction; after construction and during use, it should have the necessary adhesion to ensure that it is integrated with the masonry or the bottom layer, so that it has the effect of resistant to gas and slag erosion; it has the same or equivalent chemical composition as the masonry or the bottom layer material to avoid the refractory mud from being destroyed first and avoid harmful chemical reactions between different materials; it also has a thermal expansion similar to that of the masonry or the bottom layer material to avoid separation from each other and cracking of the mud layer; the volume should be stable to ensure the integrity and tightness of the masonry and the protective layer.

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