What are the similarities/differences between a structural shotcrete mix design and a typical formed wall mix design?

Q: What are the similarities/differences between a structural shotcrete mix design and a typical formed wall mix design?

Compressive Strength : structural shotcrete is designed to meet or exceed specified compressive strength requirements. Cement Content : shotcrete mixes are typically high cementicious mixes (420kg/m 3 to 450kg/m 3 ) compared to conventional formed wall mixes (310kg/m 3 to 330kg/m 3 . Water to Cement Ratio : due to the nature of placing shotcrete, mixes are typically designed with a low water to cement ratio (maximum 0.5) to maintain a high degree of plastic material cohesion. As with any properly proportioned concrete mix, lower water to cement ratios will typically yield improved strength, permeability, and durability results. Aggregate : Shotcrete differs from conventional mixes in aggregate makeup. Typical concrete mixes contain high volumes of course aggregate (40 to 70% volume/volume of concrete depending on nominal maximum aggregate size) and only moderate volumes of sand fill (5% to 10% volume/volume of concrete). Wall mixes will generally utilize a 20mm nominal maximum size of course aggregate. Shotcrete mixes contain relatively high volumes of sand (40% to 60% volume/volume shotcrete) and moderate volumes of course aggregate (10% to 20% volume/volume shotcrete). Further, course aggregate size is generally limited to nominal maximum size of 14mm.

Compressive Strength: structural shotcrete is designed to meet or exceed specified compressive strength requirements.

Cement Content: shotcrete mixes are typically high cementicious mixes (420kg/m³ to 450kg/m³) compared to conventional formed wall mixes (310kg/m³ to 330kg/m³.

Water to Cement Ratio: due to the nature of placing shotcrete, mixes are typically designed with a low water to cement ratio (maximum 0.5) to maintain a high degree of plastic material cohesion. As with any properly proportioned concrete mix, lower water to cement ratios will typically yield improved strength, permeability, and durability results.

Aggregate: Shotcrete differs from conventional mixes in aggregate makeup.

Typical concrete mixes contain high volumes of course aggregate (40 to 70% volume/volume of concrete depending on nominal maximum aggregate size) and only moderate volumes of sand fill (5% to 10% volume/volume of concrete). Wall mixes will generally utilize a 20mm nominal maximum size of course aggregate.

Shotcrete mixes contain relatively high volumes of sand (40% to 60% volume/volume shotcrete) and moderate volumes of course aggregate (10% to 20% volume/volume shotcrete). Further, course aggregate size is generally limited to nominal maximum size of 14mm.