Synergistic enhancement of grinding efficiency, hydration kinetics, and mechanical properties of Portland cement by ethaline

Concrete is the silent backbone of the modern world, a material so ubiquitous that we rarely pause to consider how it is made. At its heart lies Portland cement, a fine powder created by crushing rocks and minerals in massive industrial mills. This powder is the key ingredient that, when mixed with water, hardens into the structures that shelter us and carry our cities. However, the journey from raw rock to finished cement is energy-intensive and generates a significant amount of heat. When the powder is ground too coarsely, it reacts slowly and unevenly; when it is ground too finely without help, the process wastes vast amounts of electricity. Furthermore, once water is added, the chemical reaction that turns the mix into stone releases heat. If this heat builds up too quickly, it can cause the concrete to crack before it even sets, weakening the final structure. For decades, engineers have sought ways to make this process smoother, faster, and more efficient, often using chemical additives to guide the reaction.

A team of researchers at HSNC University in Mumbai has now explored a new path, turning to a class of liquids known as deep eutectic solvents. These are not the harsh, corrosive acids of the past, but rather gentle mixtures created by combining two common, safe ingredients: a salt derived from choline, a nutrient found in many foods, and ethylene glycol, a substance often used in antifreeze. When mixed in a specific ratio and warmed, these two liquids form a new, stable fluid that behaves differently than either ingredient alone. The researchers, Kuldeep Rajpurohit, Ashok Pandey, and Hemlata Bagla, decided to test whether this green fluid, which they named ethaline, could act as a helpful guide for cement. Their goal was to see if adding a tiny amount of this liquid during the grinding process and the mixing process could improve how the cement is made, how it flows, and how strong it becomes.

The study began by creating the ethaline mixture and understanding its basic behavior. The researchers found that the liquid flows smoothly and predictably, much like water, but its thickness changes depending on how hot it is. As the temperature rises, the liquid becomes thinner and flows more easily. This property is crucial because it means the liquid can spread out quickly and coat the cement particles evenly, even under the intense heat and friction of a grinding mill. To confirm that the two ingredients had truly combined into a new substance, the team used a technique that measures how light vibrates through a material. The results showed that the molecules had indeed linked together through invisible forces called hydrogen bonds, creating a unique structure that was distinct from the separate salt and glycol.

With the liquid prepared, the team moved to the cement mill. They took ordinary Portland cement and ground it in a ball mill, a machine that crushes rocks using heavy steel balls, adding different amounts of the ethaline liquid to see how it affected the process. Without any additive, the cement particles tend to stick together in clumps, making them harder to break down. However, when the researchers added the ethaline, the particles stayed separate. The liquid acted like a shield, preventing the tiny grains of cement from re-sticking to one another. This allowed the grinding machine to work more efficiently. At the highest dose tested, which was two percent of the cement's weight, the resulting powder achieved the highest Blaine fineness recorded in the study, even though the machine used the exact same amount of energy. A finer powder means more surface area is exposed to water, which is the first step toward creating a stronger final product.

Once the cement was ground, the researchers mixed it with water and sand to create mortar, testing how the liquid affected the material's behavior from the moment it was poured until it hardened. They found that the ethaline made the wet mortar flow more easily, spreading out further on a test table without needing extra water. This improved flow is vital for construction, as it allows workers to place the material into tight spaces and mold it into complex shapes without it becoming stiff too quickly. The liquid also slowed down the setting process just enough to be helpful. The time it took for the cement to start hardening increased from about 170 minutes to nearly 200 minutes at higher doses. This delay gave workers a longer window to mix, transport, and finish the concrete before it became too rigid to work with.

Perhaps most importantly, the addition of ethaline changed the way the cement reacted chemically. When cement hardens, it releases heat. If this heat is released too fast, it can cause the concrete to crack internally. The researchers measured the heat generated over time and found that the ethaline reduced the total amount of heat released by up to eleven percent. This slower, more controlled release of energy suggests that the chemical reaction was happening in a more orderly fashion. When they looked at the hardened cement under a powerful microscope, the difference was visible. The control samples, made without the additive, showed a somewhat loose structure with gaps and tiny cracks. In contrast, the samples treated with the right amount of ethaline appeared much denser and more compact, with the particles packed tightly together and fewer voids. This tighter structure is the physical reason why the material becomes stronger.

The strength tests confirmed that this denser structure translated into real-world performance. The researchers tested cubes of the hardened mortar at various ages, from three days to two months. At the optimal dose of one and a half percent ethaline, the cement reached a compressive strength of 62 megapascals after 28 days, a significant improvement over the 56 megapascals achieved by the untreated control. The material also became more resistant to pulling forces, which is a key measure of durability. However, the study revealed a critical balance: adding too much of the liquid, specifically two percent, actually reduced the strength. While this higher dose produced the highest Blaine fineness, it slowed the chemical reaction so much that the material did not harden as effectively. This finding highlights that the goal is not simply to make the powder as fine as possible, but to find the precise amount of additive that balances grinding efficiency with the chemical needs of the cement.

The work by Rajpurohit and his colleagues demonstrates that a simple, green liquid can serve as a powerful tool for improving one of the world's most important building materials. By reducing the energy needed to grind cement, improving its flow, slowing its setting time to prevent cracks, and ultimately making the final structure stronger, ethaline offers a multifunctional solution. The research suggests that this approach does not require complex machinery or exotic chemicals, but rather a careful understanding of how these molecules interact with the cement. While the study focused on a specific type of cement and a specific additive, the results open a door to a new way of thinking about cement additives, moving away from harsh chemicals toward sustainable, tunable liquids that can be customized for better performance. The findings indicate that with the right amount of this green solvent, the concrete of the future could be made more efficiently, last longer, and stand stronger.