Shotcreting

shotcreting [′shät‚krēd·iŋ]

(engineering)

A process of conveying mortar or concrete through a hose at high velocity onto a surface; the material bonds tenaciously to a properly prepared concrete surface and to a number of other materials.

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Shotcreting 

a method in concrete work in which the concrete mix is applied in layers under the pressure of compressed air.

Shotcreting is done with a special unit, which consists of a mortar gun or concrete sprayer and a compressor. A dry mix of cement and aggregate, usually sand, is prepared for shotcreting. The compressed air forces the mix through a hose to the nozzle, moistens it with water supplied through another hose, and then projects it at high velocity (130–170 m/sec) onto the surface being shotcreted. A single shotcrete layer is 10–15 mm thick and has high mechanical strength (40–70 meganewtons per sq m), density, watertightness, and cold resistance. A distinction is made between dry-mix shotcrete, which has an aggregate particle size of up to 10 mm, and wet-mix shotcrete, for which the size is up to 25 mm.

Shotcreting is used in building thin-walled reinforced-concrete structural components, such as shells, vaults, and tanks, and in producing the lining in tunnels. It is also used for hydraulic insulation, for finishing the joints of reinforced-concrete structural components, and for repair and strengthening of concrete and reinforced-concrete components and articles.

K. N. POPOV