In simple words, a cement clinker is a ball shaped combination of various raw ingredients used for creating cement. It is formed by subjecting the component materials slurry to the high temperatures in a cement kiln.
The consistency of the cement clinker is dependent on many factors which determine the overall quality of the final product. One such factor – composition of raw materials – plays the primary and most significant role in defining the quality of the end product. Also important is the efficiency of the clinker grinding plant.
The use of inappropriate raw materials and improper blending of raw material influences the quality of the cement clinker and subsequently affects the quality and durability of structures constructed using the product.
The primary raw materials used in a cement clinker are limestone and clay, which are ground into fine powdery form. The powdered raw material which is called raw meal is then subjected to a high temperature at about 1450 degrees in a cement kiln.
The heat breaks the existing material bonds, forms new combinations, and subsequently results in the formation of a new compound in the shape of rounded nodules with a diameter range of about 1mm to 25mm.
The new product, called the cement clinker, is then that processed in the clinker grinding plant, which further breaks it into powder by further processing.
Improving the composition of the cement clinker has been found to have a significant impact on the quality of the cement produced and the strength of structures constructed from it. Following are the methods that can be used to better the cement clinker quality:
Stabilisation of Raw Meal Quality
It is essential to note that the raw materials and their composition play a significant role in determining the quality of the resultant cement clinker. Thus, any improvements in raw materials, through the use of homogeneous components, reduction in the variability, and increased consistency, has been found to deliver significantly better cement clinker.
Also, adequate analysis and sampling of the raw materials to test for variability, which may affect the consistency of the cement clinker quality, should be done at set intervals.
Installation of an automatic sampler which takes samples of raw materials fed into the cement mill should also be considered to improve quality.
Improvement of the Clinker grinding plant
Improving the process and efficiency of the clinker grinding plant also plays an essential role in obtaining the desired end product, in terms of fineness and surface area. Increased efficiency of the clinker grinding plant can be achieved through incorporation of the low energy consuming yet high-pressure roller press technology.
Other grinding technology includes the ball mill and the VRM. The blender should be fitted with an automatic sample system which takes samples and thus determines the fineness of the particles in line with the set standards.
Drying of Raw Materials
The presence of moisture in raw materials used for the production of cement clinker has been found to affect the quality of the end product negatively. Improper dryness of raw materials negatively impacts the burnability of the material when subjected to a high temperature and also increases fuel consumption. Also, dryness of raw materials used plays a major role in the determining the strength and durability of the structures constructed.
Clinker Cooling Rate
The cooling rate of cement clinker also affects the quality of the end product. A faster cooling rate has been found to cause smaller C3A crystals, which produce a more reactive and higher quality clinker. The product is easy to grind and as a result, improves the strength and water demands of the cement produced.
Additionally, a fast cooled clinker prevents decomposition of C3S into C2S and free lime. This property also increases cement strength.
Compared to slowly cooled clinker, a fast cooled clinker increases the chances of trapping other elements such as Magnesium, Aluminum and Iron in its crystal structure.
Trapping of other items in the clinker enhances the reactivity of the clinker during hydration and thus increase strength and shorten time span for solidification and setting.
These are the best practices to ensure that you use the best clinker, and thus create sturdy and strong cement.
Ravi Kumar is a mechanical engineer with over a decade of work experience in the manufacturing industry. He is a key member of the product architecture team at Chanderpur Group. He is always keen to study and try out new technologies.