Expanding Cement Manufacturing
What is expanding cement? Expanding cement, also known as expansive cement, is a kind of Portland cement that produces slight volume expansion during the hydration and setting process. It is widely used in repair works. In the preparation of reinforced concrete, the expansion of the cement is utilized to stress the reinforcement.
Ordinary Portland Cement VS Expanding Cement
When ordinary Portland cement slurry hardens in the air, its volume usually shrinks by 0.20% – 0.35%, which will lead to cracks in the hardened cement paste, thus reducing its compactness and affecting the impermeability, frost resistance, and corrosion resistance of the structure. The expansive cement can be used to compensate for the effects of shrinkage in ordinary Portland cement, extend the safe use period of buildings or projects, and help to achieve greater economic benefits.
Expanding Cement Features
Types of Expanding Cement
There are many types of expanding cement according to different classification methods. According to composition, the expansive cement can be classified into silicate-type, aluminate-type, sulphoaluminate-type, and calcium aluminoferrite-type. According to expansion value, the expansive cement includes shrinkage-compensating cement and self-stressing cement. Based on Portland cement, there are type K expanding cement, type M expanding cement, and type S expanding cement. They are all based on silicate cement and made by adding the proper amount of expansion component into silicate cement clinker or cement powder.
Type K Expansive Cement
Type K expansive cement is a mixture of Portland cement, anhydrous tetracalcium trialuminate sulfate (C4A3S), calcium sulfate (CaSO4), and lime (CaO).
Type M Expansive Cement
Type M expansive cement is composed of Portland cement, calcium aluminate cement, calcium sulfate, etc.
Type S Expansive Cement
Type S expansive cement is made from Portland cement with high tricalcium aluminate (C3A) content and an amount of calcium sulfate.
Expanding Cement Applications
Expanding cement has a wide range of applications. It can be used in caulking, repairing, waterproofing, and other operations, as well as many large-scale water conservancy projects, low-temperature projects, emergency repair projects, etc. According to different properties, the expansive cement is roughly divided into the following types, which are applied in different fields.
Silicate Expansive Cement
Silicate expansive cement is mainly used to prepare waterproof mortar or waterproof concrete, which is suitable for ruggedizing structures, casting machine bases, or fixing anchor bolts. It can also be applied in caulking and repairing works.
Low Heat Expansive Cement
Low heat expansive cement can be used to prepare concrete or mass concrete with low hydration heat and shrinkage-compensation. It is suitable for engineering that requires impermeability and sulfate corrosion resistance.
Sulphoaluminate Expansive Cement
Sulphoaluminate expansive cement is available in casting component nodes and many concrete projects that require impermeability and shrinkage-compensation.
Self-stressing cement is usually used to manufacture self-stressing reinforced concrete, pressure pipes, and some related accessories.
Expanding Cement Manufacturing Process
How to manufacture expanding cement? The expansive cement has almost the same properties, except for higher percentages of sulfates and aluminates, as the ordinary Portland cement. It can be produced by adding aluminate compounds before or after the ordinary Portland cement clinker is made. Therefore, the expanding cement manufacturing process is similar to the ordinary Portland cement, which is divided into raw material preparation, clinker calcination, cement grinding, and cement packing.
Raw Material Preparation
1.Raw Material Preparation
In the raw material preparation process, limestone, gypsum, and other raw materials and fuels need to be first crushed into smaller particles by cement crushers, and then be pre-homogenized and stored in a stockyard. After that, the raw mill will further grind raw materials and fuels into the fineness required for calcination.
Clinker calcination is the core of the expansive cement manufacturing process. The pulverized raw meal will be calcined in a cement kiln to form cement clinker under a high temperature, and then be cooled to normal temperature by a cement cooler. If we adopt the new dry method cement production process, the raw meal needs to be pre decomposed in a preheater and precalciner before entering the cement kiln.
Calcined cement clinker can be mixed with various additives according to the application demand and then be fed into the cement mill for fine grinding to achieve the cement powder fineness required by the market.
In the last step, cement powder will be stored in cement silos and conveyed to the cement packing machine for the final bagging. After that, they will be stored in a warehouse, waiting for transport.
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