Cement quality is affected by many aspects, such as raw materials, cement equipment, technology, and other aspects, AGICO CEMENT is a professional cement plant solution provider, we can supply cement equipment including rotary kilns, cement ball mills, cement crushers, cement roller press, dust filter, cement packer, bucket elevator, etc. Based on the rich experience of cement plant projects, we provide this FREE guide for clients, if you have any confusion about cement production lines, or cement equipment, welcome to contact us!
1. Control of Raw Material Proportions in Grinding
The raw materials used for grinding into cement are clinker, gypsum, and additives, which are mixed in certain proportions. The accuracy of these proportions directly affects the quality of the cement. It mainly depends on the measurement accuracy of the equipment, the stability of material feeding, and the responsibility of operators and on-site personnel. Therefore, strengthening the control of raw material proportions in grinding, regularly calibrating the scales, ensuring that various materials are not mixed in storage, is one of the key steps to ensure the uniformity and stability of cement quality and the planned production of different types of cement. It is also a critical control step in cement production.
2. Control of Cement Fineness and Specific Surface Area
There are three methods to measure the fineness of cement: residue on sieve, specific surface area, and particle size distribution. Improving the fineness of cement has significant benefits for enhancing its early strength and also has some influence on the later strength. Under the conditions of certain quality and proportion of clinker and additives, finer grinding of cement increases the specific surface area, which leads to a larger reaction area between cement and water during hydration. As a result, the hydration, setting, and hardening processes of cement are accelerated. However, excessively fine grinding of cement undoubtedly reduces the production capacity of the cement grinding mill, increases power consumption, and raises product costs. According to the national standard, fineness control should not exceed 10%. The standard used by AGICO Cement restricts it to no more than 6%, while our company’s control is kept below 2%.
3. Control of SO3 Content in Cement Grinding
The SO3 content in cement reflects the amount of gypsum added during the cement grinding process. Gypsum primarily acts as a regulator of the cement’s setting time in Portland cement. Its addition can suppress the early setting caused by C3A in the clinker, and an appropriate amount of gypsum can also improve certain properties of the cement. When the content of SO3 in the cement is insufficient, it cannot counteract the early setting caused by the hydration of calcium aluminate. However, when the SO3 content in the cement is excessively high, the rapid hydration of calcium sulfate can lead to secondary crystallization, which in turn accelerates the cement’s setting reaction. Additionally, in cases where there is a high gypsum content, excess gypsum will continue to react with hydrated calcium aluminate after the cement has hardened, causing expansion and damaging the hardened cement paste structure (also known as affecting cement stability). Therefore, the SO3 content in cement should be appropriate and strictly controlled as it affects the setting time and stability of the cement. The national standard sets the maximum SO3 content at less than 3.5%, while our company controls it at 2.2±0.3%.
4. Control of Additions of Blended Materials
The addition of blended materials in cement production can, on the one hand, improve certain properties of the cement and reduce cement costs. On the other hand, it can reduce environmental pollution, turning waste into a valuable resource, thereby increasing both economic and social benefits. Our Two-Sided Cement Grinding Mill relies on the construction of a fly ash project at the Anqing Power Plant.
The amount of blended materials added depends on the quality of the clinker and the characteristics of the blended materials. If the clinker quality is good, a larger amount of blended materials can be added. However, exceeding the maximum limit of blended materials will significantly decrease the strength of the cement. The amount of blended materials added depends on the type of cement, clinker quality, and properties of the blended materials.
5. Control of Setting Time
The setting time of cement is a reflection of its hydration rate and is related to the amount of gypsum added and the quality of the clinker. The setting process can be divided into initial setting and final setting. According to national standards, the initial setting time of “Grade V” cement should not be earlier than 45 minutes, and the final setting time should not be later than 12 hours. Generally, the actual setting time is controlled within 1 to 3 hours for initial setting and 3 to 5 hours for final setting.
6. Control of Cement Stability
Cement stability refers to the physical property that reflects the volume changes of cement after hardening.
7. Control of Strength Development at Different Ages of Cement
The strength development of cement at different ages is usually estimated based on the strength development pattern at 3 days, which is primarily determined by the strength development of the clinker.
8. Control of Cement Caking
Caking is a common issue in the storage of cement. Whether it is in the cement silos or packaged final products, prolonged storage at high temperatures can lead to caking. Caking is caused by the prehydration of cement. Cement hydration primarily occurs through two sources: 1) water vapor in the air, and 2) water introduced by gypsum. Excessive moisture in blended materials can also cause caking of the ground cement. To prevent cement caking, it is important to minimize the temperature and humidity of the ground cement and shorten the storage period.
9. Management of Ground Cement
In addition to strict control of various quality indicators, effective management of ground cement is necessary to ensure the stability of the cement produced. This includes controlling the storage of ground cement, avoiding cross-contamination, and ensuring proper inventory management. Additionally, maintaining a certain amount of inventory for the ground cement is important.
