In this blog post, we take an interesting look at how small but powerful calcium carbonate is used in both everyday life and industry.
What do chalk, newspaper, and toothpaste have in common? They all use calcium carbonate as a raw material. Making chalk white and soft, creating a smooth surface on newspaper that’s ideal for printing, and polishing teeth—all of these are the roles of calcium carbonate. Although calcium carbonate is included in many products we encounter daily, its importance is often overlooked. Calcium carbonate does more than simply improve the properties of products; it also helps reduce production costs and increase production efficiency. In this way, calcium carbonate can be considered a hidden helper in every corner of our lives.
The history of calcium carbonate, also known as limestone, dates back to 1 billion years ago, when shellfish thrived on ancient Earth. Countless seashells that lay on the ocean floor were deposited over a long period of time. Buried underground due to tectonic shifts, they were subjected to geothermal heat and pressure, eventually transforming into limestone. Thus, limestone—created by nature’s time and power—has become an essential resource for us today. Since limestone is widely found in its natural state, it is easy to obtain and inexpensive. This is one of the reasons why limestone is used for various purposes across all industries.
Calcium carbonate is the primary raw material for cement, the foundation of construction materials, and is widely used in the steel, agricultural, and chemical industries. When used as the main ingredient in cement, it enhances the durability of architectural structures through its strong binding properties, and in the steel industry, it plays a crucial role in refining iron ore and removing impurities. In agriculture, it regulates soil acidity to promote crop growth. Given its wide-ranging applications across various fields, calcium carbonate can be considered an essential element of modern industry.
It also serves as a filler and reinforcing agent to strengthen rubber and plastics. When added to rubber and plastic products, calcium carbonate enhances their strength and durability while helping to reduce production costs. Because it is used in such a wide range of fields, it is important to have manufacturing methods that process natural calcium carbonate to suit the specific needs of each industry. For this reason, manufacturing processes for calcium carbonate are being developed and applied in ways optimized for each industry. In the following sections, we will explain the methods used to manufacture calcium carbonate.
Calcium carbonate manufacturing methods are broadly divided into physical grinding methods and chemical synthesis methods. First, the physical grinding method involves applying impact to large limestone particles to break them down. However, simply applying force does not guarantee that the particles will break completely. When impact energy is applied to calcium carbonate particles in a grinder, part of that energy is converted into kinetic energy, causing the particles to recoil. The remaining impact energy is absorbed into the particles, acting as crushing energy that causes them to break apart. Since the goal is to crush calcium carbonate, the energy converted into kinetic energy is actually useless. As the particle size decreases through continuous crushing, the proportion of impact energy converted into kinetic energy increases; eventually, when 100% of the energy is converted into kinetic energy, the process reaches a crushing limit where no further crushing occurs.
There are various physical grinding methods; the method of grinding calcium carbonate in air is called “dry grinding,” while the method of grinding it in water is called “wet grinding.” In dry grinding, due to the grinding limit, particle sizes can only be reduced to between 1 and 46 microns.
However, the calcium carbonate industry sometimes requires smaller particles. This led to the development of the wet grinding method. When calcium carbonate is dissolved in water and ground, the resistance of the water reduces the degree to which the particles are crushed. This means that a smaller proportion of the impact energy is converted into kinetic energy. Consequently, much smaller particles, ranging from 0.35 to 1.2 microns, can be obtained. High-precision wet grinding costs about two to three times more than dry grinding. The particles obtained through this physical grinding method are called heavy calcium carbonate.
Next, the principle of the chemical synthesis method is easy to understand by looking at the molecular formula of calcium carbonate. When quicklime reacts with carbon dioxide, it forms calcium carbonate. Since natural quicklime does not react well with carbon dioxide, the quicklime is dissolved in water to form calcium hydroxide, which is then reacted with carbon dioxide. After the reaction, calcium carbonate and water are obtained, and that water is reused to dissolve more quicklime. You may have seen stalactites in limestone caves that resemble icicles. The chemical synthesis method utilizes the recrystallization of calcium carbonate particles in this way.
The first advantage of the chemical synthesis method is that the particle size can be freely controlled. As calcium carbonate particles recrystallize one molecule at a time, adding a growth inhibitor stops the crystallization process once particles of the desired size are formed. Therefore, particles can be produced down to an extremely fine scale. Colloidal calcium carbonate produced by the chemical synthesis method has a particle size of 0.03 to 0.08 microns, which is more than 10 times smaller than that achieved by physical grinding. Hard calcium carbonate is also produced, with a particle size of approximately 0.08 to 3 microns.
The second advantage of the chemical synthesis method is that it allows for the control of the desired particle shape. Calcium carbonate particles produced by physical grinding have been subjected to physical impact from all directions, resulting in a nearly spherical shape with no sharp edges. However, the chemical synthesis method allows for needle-like, rectangular prism, or plate-like structures depending on the orientation of the calcium carbonate layers, making it suitable for various industrial applications. For example, needle-shaped calcium carbonate is used as a filler in lightweight paper. Spherical calcium carbonate produced by physical grinding forms a dense cluster when aggregated, whereas needle-shaped calcium carbonate forms a loose, interlaced structure. Consequently, even for the same volume, needle-shaped calcium carbonate is significantly lighter, which is why it is used in lightweight paper.
However, due to the intricate processes involved, chemical synthesis methods are costly. In the case of hard calcium carbonate, it is more than 10 times more expensive than dry grinding, and for colloidal calcium carbonate, the process is far more sophisticated, resulting in a cost difference of more than 20 times. Therefore, in general industries where price is a priority, heavy calcium carbonate produced using physical grinding methods is used. When specific shapes or ultrafine particles are required, the chemical synthesis method is used even at a higher cost.
Calcium carbonate has been one of the most widely used raw materials on Earth for the past 5,000 years. Although we may not readily notice it, calcium carbonate has established itself as a key material in numerous products closely tied to our daily lives—such as paper, toothpaste, rubber, and plastics. Furthermore, the chemical synthesis process has eco-friendly benefits, as it can capture carbon dioxide emitted from other processes to produce calcium carbonate, thereby reducing carbon dioxide emissions. Recently, as climate change and environmental issues have become global concerns, the calcium carbonate manufacturing process is gaining attention as a carbon dioxide reduction technology. It is highly likely that calcium carbonate will play a significant role in the environmental industry of the future.
