Refractory mortar is also called fire clay or joint material (powder). Used as a joint material for refractory masonry.
According to the material, it can be divided into clay, high alumina, siliceous and magnesia refractory mortar. It is composed of refractory powder, binder and admixture. Almost all refractory raw materials can be made into powder for preparing refractory mortar. The ordinary refractory mortar is made of refractory clinker powder and an appropriate amount of plastic clay as binder and plasticizer. The chemically bonded refractory mortar with hydraulic, gas-hardened or thermosetting bonding materials as the bonding agent produces a certain chemical reaction and hardens before the temperature is lower than the formation temperature of ceramic bonding.

The particle size of refractory mortar varies according to the requirements of use, and its limit particle size is generally less than 1mm, and some are less than 0.5mm or finer. The material of refractory mortar should be considered consistent with the material of masonry refractory products. In addition to being used as a joint material, refractory mortar can also be used as a protective coating for the lining by smearing or spraying.
Properties of refractory mortar:
1. Good plasticity and convenient construction;
2. High bonding strength and strong corrosion resistance;
3. High refractoriness, up to 1650°C ± 50°C;
4. Good resistance to slag invasion:
5. Good thermal peeling property.

Application of refractory mortar:
Refractory mortar is mainly used in coke ovens, glass kilns, blast furnace hot blast stoves, and other industrial kilns. The industries used are: metallurgy, building materials, machinery, petrochemicals, glass, boilers, electric power, steel, cement, etc.
When using refractory mortar, it is necessary to pay attention to the properties of the refractory mortar used for masonry refractory bricks, which should be compatible with the physical and chemical properties of the refractory bricks used.

When refractory mortar is used in combination with refractory bricks, the fineness of refractory mortar must be kept above 160 mesh. Otherwise, the drying is too fast and the adhesion is not strong. Before the refractory mortar is used, the viscosity of the refractory mortar and the amount of liquid added (water-bonded, phosphoric acid-bonded, resin-bonded) should be determined. The bonding time depends on the material, size and difficulty of construction of the refractory brick. Generally speaking, the bonding time is 1-1.5min. Drying too quickly or too slowly will not work. Too slow to condense. Too fast refractory bricks are not bonded together with refractory bricks.

When refractory mortar is prepared, when the amount of liquid added is water, use clean industrial water with a pH value of 6-7. Industrial water containing harmful substances and oil pollution cannot be used. It is especially necessary to remind that when preparing refractory mortar in coastal areas , the water used should be tested strictly, and the concentration of chloride ions should not be greater than 300mg/L. Mountain spring water cannot be used when construction is near mountains. The PH value of mountain spring water is 11, so it cannot be used.

Phosphoric acid is added to the refractory mortar when it is prepared. It must be strictly implemented in accordance with the instructions of the refractory mortar manufacturer. The amount of phosphoric acid added should not be too much or too little.

There are many varieties of refractory mortar, and various varieties and grades cannot be mixed. The best refractory mortar prepared on the same day is best used on the same day, and it is not used every other day. The rational use of refractory mortar is based on the material of the refractory brick and the close combination with the construction temperature.