Written by Dan Jennings
I have been extremely fortunate in my career to work for and learn firsthand from one of the largest lightweight producers in the United States. I have also seen and implemented these same ideas as a professional groundskeeper over the last decade. The topic of understanding the differences between both products comes up daily and I wanted to take a few minutes and walk through the heating practices of each material. In my next blog, “What should I know when managing clay infield mix soil surfaces with Calcined or Vitrified topdressings (Dirt Infields or Mounds)”, I will talk about using these materials in greater depths for the topdressing material application on infield mix soils.
What exactly is calcination and vitrification? Calcination and vitrification are both heating practices that involve the process of heating a material to a specific range of degrees which is achieved in a large rotating furnace called a kiln. During the heating process, these temperatures will range from 1,000-1,200 °F for calcination and 1,800-2,200 °F for vitrification, depending on the needs of each product. These heating practices change clay material into ceramic, which is a hard clay material that has been baked. Clay becomes ceramic at around 1,000 °F. During these processes, each material will be oxidized, which is the process of removing or purifying ions. Both heating practices are quintessential to daily living. We use the calcined materials for hazardous contamination spills, which have great absorption capabilities. Vitrified products are used for precast molds and bridge structures due to its internal curing abilities and overall particle strength.
Clay is made up of several different rock minerals in varying proportions. Clay structures, like montmorillonite or kaolinite, are used during the calcination process which are also heated from 1,000-1,200 °F followed by the cooling process. After the cooling process, the material is screened to specific gradation to meet proper recommendations for each specific application. Calcine clay materials are heated/baked to lower temperatures compared to the vitrification process since softer clay materials will have higher moisture holding capability. The raw materials that can be used for the vitrification process include montmorillonite, illite clay, and shale. When heating these clays to 1,800-2,200 °F, they expand and yield thousands of gas bubbles which gives the particles the ability to absorb moisture at lower volumes in comparison to calcined clays. These materials are also known as expanded clay or expanded shale once the vitrification practice is completed. Since the United States has regional climates, which involve several differing microclimates, this information should be catered to your particular region.
Vitrified and calcined products at the proper gradations make great playing surfaces. These producers of each material have been able to supply several gradations to make them economical at all levels for sports fields. However, over the last several years, new testing procedures have become discovered that continue to give us a greater understanding of mechanical breakdown. These types of test can be found using a testing procedure called the Micro Deval Abrasion Test. The Micro Deval Abrasion Test involves identifying mass weight of the sample to the nearest gram, then immersing the sample into tap water for at least an hour, followed by placing the sample into the Micro Deval machine. After the machine runs for 90-120 minutes, the multiple steel balls inside of the rotating cylinder goes through the process of breaking down the material, similar to a large washing machine (see attached picture of “Deval Machine”). After this cycle is completed, the material is taken out, reweighed and rescreened to show the breakdown or loss of gradation. Heated materials are more likely to break down when wet or saturated, which is a normal practice during sports field groundskeeping. These test results can be found by reaching out to the DuraEdge team at duraedge.com.
The reason this data is valuable to Field Managers is because you can build your own return on investment (ROI) which can be justified and explained prior to buying topdressing material. This can be highly informative and can save money down the road, in this case with less breakdown. The breakdown of topdressing material can lead to several issues in your clay infield mix soil structure. When these particles break down, they can lead to an increase in small particle buildup, also known as “fines”, which leads to negatively affecting your clay soil playing surfaces. This can also lead to your infield mix soil becoming unstructured which can cause stability issues under your players’ feet. It can also produce large delays prior to opening the field after a rain event, which can cause not only a headache but also extra cost of material including labor hours to dry the infield mix soils.
Since these are both raw clay materials prior to heating, the data will indicate that less heat applied to the material equals higher absorption rates, which also causes a higher breakdown percentage. Calcined clays will absorb 43-52% moisture by weight and vitrified materials will absorb at a significantly lower amount. This is dependent on if the raw material is an expanded clay or expanded shale which ranges from 24-45% moisture by weight. Due to the different heating practices of each material, the data will indicate that lower heating temperatures lead to higher absorption rates of moisture, which is due to less oxidation. With this, if you want to soak up a puddle quickly, I recommend calcined products. Due to the very small pores calcine materials have they will soak of moisture very quickly. I never recommend using significantly smaller particles of calcine because these particles do break down which can lead to issues of destructuring of your infield mix soil. It is always a great idea to make sure if you use these tight gradations of calcine, the material should meet a specific gradation requirement like ProDry from DuraEdge.
If you’re new to these products, I always recommend using a 50/50 blend. Once you recognize how each product works in your specific situation, you can start adjusting your percentage of each material to master your clay soils. These products are a great solution to ensure that your infield mix soil is at the proper hydration level. At the end of the day, having the correct hydration with an appropriately structured infield mix will give you a safe playing surface.
I recommend both products for increasing soil Cation Exchange Capacities (CEC). These materials will increase nutrient holding capacities in heavier sand content rootzones. I’m going to lean on vitrified products for my pick because after vitrifying a raw clay, these particles are usually neutral in their pH levels which helps fight against fungus and mold. Therefore, you are seeing hydroponic growth being done with expanded materials that have been vitrified.
I really want to thank you for taking the time to read this blog. It truly means a lot and I hope this makes your groundskeeping life easier.
Stay safe and never hesitate to call/text/email with any questions you may have. No question is ever dumb, the only dumb part is not asking.
For now,
Dan Jennings
#inspiredbysoils