Gradation is the classification of the different particle sizes you find in granular or powdered materials. For soil based particles (like sand, gravel, clay, solid deicers, etc.), each particle size will have different industrial applications.
Industrial particles and powders, including soil based particles, have a very wide range of sizes. The ASTM (American Society for Testing and Materials) has constructed a standardized method of measurement for these particles. They are filtered down by sieves that are categorized by the size of the openings in their mesh.
From the graphic above you can see that sieve opening sizes vary greatly and can filter large or fine particles. These technical standards help manufacturers accurately describe their products so they will appropriately match their application. When it comes to granular deicers, particle size definitely matters. Let’s take a look at how gradation affects deicing performance.
According to the Federal Highway Administration, “fine particles have more surface area for an equivalent load weight and will go into solution faster.” That means smaller deicing granules will melt and turn into brine quickly, but their effects are not long lasting. The University of Nebraska, Lincoln (UNL) civil engineering department conducted deicing tests and found that “smaller gradations of solid deicers tend to work more quickly, but may also refreeze more quickly.”
They also discovered that “finer gradations should not be used for large amounts of precipitation because they are quickly diluted and washed away.” Fine granules, on their own, are also not typically heavy enough to penetrate to the road surface where brine is needed the most.
Where fine granules melt and form brine quickly, larger gradations last longer and are more ideally suited for heavier ice and snow. The same UNL study discovered that larger granules performed better during the refreeze test and had “begun to dissolve into smaller particles and then dispersed more evenly onto the ice.” Think of larger granules like time-released medicine for the road that deliver longer ice melting relief. Larger deicing granules also penetrate ice and snow more effectively to produce brine right on the road surface.
Not only does granule size matter, but so does granule texture. When it comes to deicing granules, the rougher the better. Rough grains have greater surface area contact with the ice and snow for brine production. They also provide more gripping pavement traction and are less likely to bounce and scatter away from the road surface during application than smooth grains.
The highest performing solid deicers contain the best of both worlds: a mixture granule gradations. Using a mix with a variety of sizes yields multiple benefits:
Large, coarse granules vertically penetrate ice and snow while smaller granules get to work melting right away to form brine.
Gradation variety helps deicing materials stay where they are distributed, and reduces bounce and scatter seen in smooth grains.
Smaller granules melt fast and form brine while larger granules break down slower and prevent paved surfaces from refreezing.
Our flagship product, Ice Slicer RS, is a fast-acting and long lasting deicing compound with the perfect blend of granule sizes. With a mix of superfine, fine, medium, and coarse grains, Ice Slicer RS vastly outperforms other granular deicers in both lab and field tests. We are also proud to offer other specialty blends of granule sizes that are tailored to match a variety of equipment models and winter environments.
© 2024 Redmond Minerals Inc.