A grinding aid is a specialty chemical agent used to make it easier to grind and mix cement. Specifically, grinding aids prevent cement particles from re-agglomeration, or re-adhering, during and after the grinding process. Grinding aids make it possible to streamline the cement-making process by increasing process efficiency and material fluidity. These benefits of cement grinding aid use also contribute to lower energy costs on the part of industrial mills.
The grinding aid began to gain popularity in the mid-20th century as a reliable tool for cement processing. Its effectiveness and reputation for reliability lie in its ability to reduce surface tension between cement particles brought on by the stress of the grinding process. Chemical compounds known for their polar properties, such as alkanolomines, disperse charges on the surface of the cement particle. This covering of charges prevents individual particles from clumping together.
Hydration is also an important factor in the grind aid process. When a grinding aid comes in contact with a cement particle, it forms an instant gel around the particle. This gel hydrates the grain and initially serves as a barrier from other cement particles. With time, the gel crystallizes. This crystallization allows the cement particle to attach itself to others, forming a fluid lattice structure.
Cement griding aids can come in the form of gas, liquid, or solid. Typically, mills will use one of the following additives in their cement mixtures: various types of alkanolomines, monoethylene glycols, diethylene glycols, sodium oleate, oleic acid, dodecylbenzene sulphonic acid sodium lignosulphonate, or sulphite waste liquor. These chemicals ensure that the integrity of the cement is kept intact while at the same time helping to pulverize the cement into manageable grains.
A reduction in energy costs is a notable benefit of grinding aid use. Mills save money and power when using these aids because the aids transform the cement-making process into an endergonic process, consuming energy from the surrounding environment. Because cement aids allow the cement mixture to absorb energy, less external energy is needed for the reactions to take place. In this way, industrial mills save a tremendous amount of money by employing cement grinding aids.
In addition to a grinding aid, mills will coat the balls and liners which constitute the griding apparatus with a powder. This powder further reduces the energy needed to carry out the cement-making process. It also bolsters the efficiency of the process.