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.