January 2024 • Florida Pool Prosm 11 DIGGING UP IDEAS in a mixer truck. Dry mix traditionally comes in a volumetric truck. The material is then placed into either a dry hopper or a concrete pump. Dry mix is then, with the use of compressed air, shot through a series of hoses to the nozzle where water is introduced. A mixer truck will put the concrete into a concrete pump and, with the use of air, comes out of the nozzle at a high velocity. The velocity of the material gives compaction that allows us to remove voids, when properly installed, instead of forming both sides of a structure and vibrating out air voids. Shotcrete is technically a verb. What shotcrete is actually doing is placing concrete in a method that is easier to install and less likely to have voids. An example that helps many of my customers understand is to reference Xerox. Gunite is to Xerox as shotcrete is to “copying.” Xerox or scanning is technically the verb. Just like Gunite, Xerox is a name brand. Through my years in the industry, I have found many people have a preference to wet mix or dry mix depending on what they've been taught. I frequently bounce between the two products depending on many variables, such as engineering design and site conditions. One of the variables that never determines which one I go with is strength. If you order 4,000 psi wet mix or 4,000 psi dry mix, in theory and in a laboratory, they should be the same strength. This would be the equivalent to the question, what is heavier: a ton of feathers or a ton of iron? They weigh the same as they're both set at one ton. Neither wet mix or dry mix has an advantage of strength with proper mix, design and execution. Then there are arguments on both sides that the product can be flawed. Wet mix has the potential to have a weaker product from a longer delivery time, additional water being added to the truck to delay clumping, and poor shooting practices courtesy of the nozzleman. Dry mix has the same potential for a weaker product due to the nozzleman adding too much water or too little water while shooting. Both methods can result in a poor product if applied improperly. As pool contractors who are buying the concrete product, I encourage everyone to get educated on all facets of the product and application. The most important thing a contractor who is working with shotcrete can do is make sure the crew, and more specifically the nozzleman, is trained properly. Requesting that your nozzleman have the ASA, American Shotcrete Association, certification of nozzleman is one of the best things you can do
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