Introduction

Cement production is a complex process that involves several stages, including raw material extraction, clinker production, and cement grinding. The entire cement production process is an energy intense activity where energy consumption amounts between 110 and 120kWH per metric ton of product. Cement grinding is a critical stage of the entire process where the fineness and quality of the final product are achieved and which amounts to 30% of the total energy consumption.

To enhance the efficiency and performance of the grinding process, cement additives are commonly used.

This article aims to provide a short comprehensive guide of cement additives, the most notable types, and the benefits of implementing them in cement factories.

Cement Additives

Cement additives are chemical compounds that have been successfully used for decades in cement production. Their main role is to prevent cement particle agglomeration during the milling process. As a consequence they reduce mill retention time and improve separation efficiency which decrease energy consumption while ensuring high quantities of cement produced at the highest quality.

These additives enhance the cement’s fineness by producing narrow particle size distribution, which at the same time is shifted towards smaller diameters.

Types of Cement Additives

Grinding Aid Additives

In the cement grinding process, grinding aid additives play a crucial role in improving the efficiency and performance of the grinding operation. Studies that have been conducted on the effects of different grinding aids on granulated blast furnace slag powder, found that the addition of grinding aids, such as triethanolamine (TEA) and triisopropanolamine (TIPA), significantly improved the fineness and specific surface area of the slag powder. These grinding aids reduced the agglomeration of particles, enhanced the grinding process, and promoted the formation of more fine particles.

Further studies on the effects of grinding aid dosage on cement grinding properties and efficiency found that an appropriate dosage of grinding aid additives, such as glycol-based compounds, improved the grinding efficiency by reducing the energy consumption and increasing the specific surface area of the cement particles.

The study highlighted the importance of optimising the dosage to achieve the desired grinding performance.

Performance Enhancers

Performance enhancers are another type of cement additives that focus on improving specific properties of the cement. Examination on the effect of grinding aids on the grinding energy consumed during the grinding of calcite in a stirred ball mill found that certain additives, such as sodium hexametaphosphate and triethanolamine, reduced the grinding energy consumption, indicating improved grindability of the calcite particles.

In the study conducted by Ferraz and Irassar (2019), the effect of grinding aids on the fine grinding of limestone, quartz, and Portland cement clinker was investigated. They found that the addition of grinding aids, such as glycol and amine-based compounds, led to a reduction in the specific energy consumption during the grinding process. These additives improved the particle size distribution and reduced the amount of coarse particles, resulting in a finer and more efficient grinding process.

Mechanisms of Action

It should be stated that while the benefits of the additives are well known due to real life examples, the real action mechanism in the hydration of cement is not completely understood yet. The actual chemical-physical interaction of the additives with cement are not yet all clear and continuous research is taking place on the matter.

Surface Adsorption

One of the primary mechanisms by which cement grinding aid additives work is surface adsorption. The additives adsorb onto the surface of cement particles, reducing inter-particle forces and promoting particle dispersion. This action helps in preventing the agglomeration of particles, facilitating efficient grinding.

Electrostatic Repulsion

Certain grinding aid additives carry a charge, which leads to electrostatic repulsion between cement particles. This repulsion helps to prevent the particles from clumping together, enhancing the flowability and dispersibility of the cement. Many studies have emphasized the role of glycol-based additives in promoting electrostatic repulsion, which improves the grinding efficiency and particle distribution.

Chemical Activation

Some grinding aid additives can chemically react with clinker minerals, improving their grindability and reducing the energy required for grinding. It should be highlighted in this instance the role of sodium hexametaphosphate and triethanolamine as chemical activators that enhance the grinding energy efficiency of calcite particles.

Moisture Absorption

Certain additives have the ability to absorb moisture. This moisture absorption can reduce the surface tension between cement particles, improving their fluidity and flow characteristics. It has been demonstrated the moisture absorption properties of glycol and amine-based grinding aids, leading to enhanced grinding efficiency and finer particle size distribution.

Benefits of Implementing Cement Grinding Aid Additives

Increased Grinding Efficiency

The incorporation of grinding aid additives in cement grinding processes leads to increased grinding efficiency. These additives, as shown in various studies, reduce the energy consumption per ton of cement produced. By improving the efficiency of the grinding process, cement plants can achieve higher production rates, reduce grinding time, and lower operating costs.

Improved Cement Quality

Grinding aid additives contribute to the improvement of cement quality by enhancing several key properties. The finer particle size distribution achieved through the use of grinding aids results in a more uniform and consistent cement product. This improved fineness enhances the cement’s reactivity and hydration, leading to better strength development and improved overall performance.

Reduced CO2 Emissions

The implementation of cement grinding aid additives can have a positive environmental impact by reducing carbon dioxide (CO2) emissions. By improving grinding efficiency and reducing energy consumption, the use of grinding aids helps lower the carbon footprint associated with cement production. This reduction in CO2 emissions aligns with sustainability goals and environmental regulations.

Enhanced Workability and Finishability

Performance enhancers in cement grinding aid additives improve the workability and finishability of cement. These additives can enhance the flowability and plasticity of the cement paste, making it easier to handle, mix, and place. Improved workability allows for better construction practices and can lead to superior surface finishes in applications such as flooring or decorative concrete.

Compatibility with Blended Cements

Cement grinding aid additives are compatible with various types of cement, including those containing supplementary cementitious materials (SCMs) such as fly ash or slag. Blended cements, which incorporate SCMs, often exhibit challenges in terms of grindability and setting time. The use of grinding aids can mitigate these challenges, allowing for efficient grinding and improved performance of blended cements (Zhang et al., 2019).

Factors to Consider for Selecting Grinding Aid Additives

Cement Properties

Different types of cement may require specific types or dosages of grinding aid additives to achieve optimal results. Factors such as the composition, fineness, and reactivity of the cement should be considered when selecting appropriate additives.

Grinding Mill Design

The choice of grinding aid additives should align with the characteristics and limitations of the grinding mill used in the cement factory. Factors such as mill type, size, operating conditions, and grinding media influence the effectiveness and performance of the additives.

Environmental Impact

The environmental implications of grinding aid additives should be taken into account. Factors such as the biodegradability, toxicity, and potential long-term effects on the environment should be considered when selecting additives. It is important to choose additives that align with sustainable practices and comply with environmental regulations.

Conclusion

Cement grinding aid additives play a crucial role in enhancing the grinding efficiency, quality, and overall performance of cement grinding. They work through various mechanisms, including surface adsorption, electrostatic repulsion, chemical activation, and moisture absorption. By implementing these additives, cement plants can reap several benefits, including increased grinding efficiency, improved cement quality, reduced CO2 emissions, enhanced workability and finishability, and compatibility with blended cements.

When selecting grinding aid additives, it is important to consider factors such as the properties of the cement, the design of the grinding mill, and the environmental impact of the additives. By carefully choosing the appropriate additives and optimizing their dosage, cement manufacturers can maximize the benefits and cost-effectiveness of their grinding processes.

In summary, cement grinding aid additives are valuable tools in the construction industry for enhancing the efficiency and quality of cement grinding. With their ability to improve grinding efficiency, reduce energy consumption, increase mill output, and improve cement properties, these additives offer significant advantages to cement factories. By incorporating cement grinding aid additives into their processes, construction industry professionals can achieve higher-quality cement products, lower production costs, and a reduced environmental footprint.

As research and development continue in this field, it is expected that new and more effective cement grinding aid additives will be developed, further enhancing the performance and sustainability of cement grinding processes. The ongoing collaboration between cement manufacturers, researchers, and additive suppliers will continue to drive innovation and improvements in the industry, ensuring the continued growth and success of the construction sector.