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Equipment Overview | Dry Process Equipment | Wet Process Equipment | Equipment FAQs
The dry process was developed in the early 1900's, culminating in patents granted in 1909 and the process being commercialized in 1911.
Pre-blended dry or semi-dampened materials are placed into the shotcrete equipment and metered into a hose. Compressed air conveys material at high velocity to the nozzle, where water is added. Material is consolidated on the receiving surface by the high-impact velocity. The dry process can be used for any shotcrete application, from the smallest patching and sealing projects up to the largest, such as tunnel linings, pools, canals or reservoirs.
The maximum production achievable with dry-process equipment is 10-12 cubic yards per hour of dry mix, depending on conditions. To achieve this ultimate capacity, it is necessary to use 2" or 2 1/2" hose and a 900 cfm or larger compressor. Most applications have production rates of 2-6 cubic yards per hour of mix, using 1 1/4" or 1 5/8" hose and a 450-600 cfm compressor. Patching and sealing are done at even lower rates with 1" or 1 1/4" hose and a 250-350 cfm compressor. Rebound (rejected components of a mix) is an inherent part of the shotcrete process. Skill and expertise is required for control of rebound and overspray and must be a consideration when calculating in place volume.
• Easy start-up, shut-down, and clean-up
• Control of the materials is on-site
• Nozzleman can be up to 1000 ft. horizontally or 500 ft. vertically from the gun
• The large amount of compressed air required for high-volume placement
• Control of rebound
The wet process was developed in the 1960's with pressure tanks being used to force a stiff mortar through the hose. Additional air was added at the nozzle and the process came to be known as Shotcrete. The subsequent development of dependable concrete pumps of various types hastened the advancement of this technology, and today the wet process is widely used and favored for certain applications.
All ingredients, including water, are thoroughly mixed and introduced into the shotcrete equipment. Wet material is pumped to the nozzle where compressed air is introduced to provide high velocity for placement and consolidation of the material onto the receiving surface.
Most wet-process shotcreting is done with premixed mortar or small aggregate concrete. The mix design and consistency of supply are very important in order to provide a mix with the workability or plasticity to be pumped through a small-diameter hose. The most common problem with the wet process is improper mix design or material variations which cause blockages in the pump or hose.
Sand gradation is the same as for the dry process and for coarse aggregate mixes, 20-30 percent of 3/8" aggregate is added. Cement content will vary according to the aggregate gradation and surface area. However, most mixes contain approximately 700 pounds or more of cement.
• Little or no formwork is required
• Cost effective method for placing concrete
• Ideal for irregular surface applications
• Allows for easier material handling in areas with difficult access
• Equipment is more costly
• Wet concrete requires special handling
• Clean up must be a consideration
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