Shotcreting is the process of applying concrete by the use of a nozzle in which compressed air is introduced to the material flow. Shotcreting is usually classified as a wet mix or dry mix and the type of aggregate used, coarse or fine.

Wet mix shotcrete - Shotcrete in which all of the ingredients including water, are mixed before introduction in to the delivery hose (ACI-506R4).

Dry mix shotcrete - The cement-aggregate mixture is fed into a special mechanical feeder or gun called delivery equipment, which is metered by a device such as a feed wheel, rotor or feed bowl. The material is carried by compressed air through the delivery hose to nozzle body. The nozzle body is fitted inside with a water ring, through which water is introduced under pressure and mixed with the other ingredients. (ACI-506R-4) 1.6.1).

Comparison of Dry & Wet Mix:

Dry Mix

• Control over mixing water
• Suited for light weight mixes
• Material transported longer distance
• Minimal material waste
• High strengths 

Wet Mix

• Water accurately measured
• Mixing more consistent
• Less dust and cement loss
• Normally less rebound
• Greater production

Shotcreting is the process of applying concrete by the use of a nozzle in which compressed air is introduced to the material flow. Shotcreting is usually classified as a wet mix or dry mix and the type of aggregate used, coarse or fine.

Wet mix shotcrete - Shotcrete in which all of the ingredients including water, are mixed before introduction in to the delivery hose (ACI-506R4).

Dry mix shotcrete - The cement-aggregate mixture is fed into a special mechanical feeder or gun called delivery equipment, which is metered by a device such as a feed wheel, rotor or feed bowl. The material is carried by compressed air through the delivery hose to nozzle body. The nozzle body is fitted inside with a water ring, through which water is introduced under pressure and mixed with the other ingredients. (ACI-506R-4) 1.6.1).

Comparison of Dry & Wet Mix:

Dry Mix

• Control over mixing water
• Suited for light weight mixes
• Material transported longer distance
• Minimal material waste
• High strengths 

Wet Mix

• Water accurately measured
• Mixing more consistent
• Less dust and cement loss
• Normally less rebound
• Greater production