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The differences between the refractory castable and refractory plastic
Jan 18, 2018


The differences between the refractory castable and  refractory plastic


There are many kinds of unshaped refractories, such as refractory castable, refractory plastic , refractory ramming materials, refractory spraying coatings, refractory projectiles, refractory clay and so on. Although they are all unshaped refractories, their fire resistance performance are different due to using different parts and their different material formula, different ratio of grain, different construction method, and different target function. Next, we will briefly introduce the differences between refractory castable and refractory plastic

refractory castable

Refractory castable is a kind of granular and powdery material made of refractory materials, which is composed of a combination of quantitative binding agent and water. It has high fluidity and is suitable for construction with pouring method.

Refractory castable is the primary type of refractory materials. According to the different cementing materials used, the maintenance molding mechanism can be divided into three types: hydraulic refractory castable, air-hardening refractory castable and fire hardening refractory castable.

(1) Hydraulic refractory castable or water-hardening refractory castable

    Water is needed in the process of cement hardening to participate in the chemical reaction, which contributes to the hardening strength of the refractory castable. And that's hydraulic refractory castable.

Cement is the primary factor of the castable strength (especially the room temperature strength). But its fire resistance is relatively low, so besides the necessary room temperature strength, the cement dosage should be reduced as many as possible. For the compactness and the simplification of construction, the refractory powder can be appropriately added. Reducing cement dosage is also one of the measures to reduce costs.

It is required to avoid the mixing of aluminate cement and silicate cement or lime in construction. Because after these two chemicals are mixed together, they will have aqueous tricalcium aluminate, which will greatly reduce the strength.


(2) Air-hardening refractory castable

In the maintenance the cementing agent absorbs CO2 from the air and gradually condense sclerosis. The most commonly used refractories are Sodium silicate refractory concrete.

Sodium silicate refractory castable not only has the function of high temperature resistant, it also has the function of the acid, wear-resisting. And therefore it is commonly used as the chemical equipment lining.

Because the hardening process of Sodium silicate refractory castable is slow in natural conditions, so the coagulant should be added in the construction (such as sodium silicofluoride, high alumina cement, etc.).


(3) Fire hardening refractory castable or fire setting refractory castable

Fire hardening refractory castable is cemented by phosphoric acid and phosphate, which need to be heated and baked for the strength and high temperature resistance, therefore called the fire hardening refractory castable or fire setting refractory castable.

Refractory plastic

It is made of the mixture of water and powder bound by the plastic clay and plasticized materials. It is an amorphous refractory with a plaster shape and of higher plasticity in the long term.

Granular and powdery materials are the primary components of plastic, accounting for 70% to 85% of the total. It can be made of refractory materials of various materials and is often classified and named according to the material. The clay clinker and high alumina clinker are commonly used, because this kind of amorphous refractory material is primarily used in various heating furnaces that are not directly connected with the melt. Lightweight materials can be used to produce the lightweight plastic.

Plasticity clay is the most important plastic components. Accounting for 10% ~ 25% of the total plastic, it has great influence on the plasticity, the binding strength of plastic and its hardened body, volume stability and fire resistance. In a certain sense, the nature and quantity of clay is considered to control the properties of plastic.

Generally, plastic should have high plasticity, and after long-term storage, it should still have certain plasticity, which is called plastic operation.

Plasticity is influenced by clay characteristics and the amount of clay used. In addition, it depends on the amount of water, and it progresses with the addition of water. But too much water can have a bad effect. Generally 5% ~ 10% is appropriate.

In order to prevent the plasticity from reducing obviously during its preservation period, a hydraulic binding agent cannot be used.

No special skills is required during construction of plastic. When used to make the lining, the plastic can be removed from the sealed container, which is spread between the hanging brick or the hook, and can be tamped with the wood hammer or air hammer (50mm ~ 70mm thick). Before hardening, it can be processed externally. In order to facilitate the discharge of water in the meantime, holes must be opened at regular intervals. Finally, the expansion joints are arranged according to the plan. If it is used to make the whole furnace cover, it can be constructed on the bottom die,  and be hoisted after drying.

The temperature of plastic base depends on the quality of the granular and powdery materials. For example, the ordinary clay can be used for under 1300 ~ 1400 , the high quality 1400 ~ 1500 ; High aluminum is 1600 ~ 1700 or higher; and Chrome is 1500 ~ 1600 .