Factors Affecting the Quality of Wet Shotcrete Sprayed by Robotic Wet Shotcrete: The "mix ratio, condition, and storage" of wet shotcrete directly impact the quality of the spraying (such as strength, adhesion, and impermeability) and require strict control:

   1. Concrete Mix Compliance

   ① Control the water-cement ratio (usually 0.4-0.5), sand content (45%-55%), and aggregate gradation (maximum coarse aggregate size ≤16mm to avoid clogging the delivery pipe) according to design requirements. Accelerators added must be compatible with the cement (liquid accelerators are preferred, with a dosage of 2%-4%).

   ② Concrete that has segregated, initially set (exceeds the initial setting time), or contains impurities (such as oversized stone or mud lumps) is prohibited.

  2. Concrete Condition Monitoring

   ① Check the concrete slump before operation: For ground operations, the slump should be controlled at 120-160mm; for operations at height (such as tunnel vaults), the slump should be controlled at 140-180mm (to ensure fluidity and avoid pipe clogging).

   ② Concrete must be continuously stirred during transportation (at a speed of 2-4 rpm) to prevent segregation. If the transportation time exceeds one hour, the slump must be retested and any unsatisfactory results must be discarded.

   3. Material Storage Standards

   Cement and accelerators must be stored in a moisture-proof, well-ventilated warehouse. Accelerators must be protected from direct sunlight to prevent degradation. Sand and gravel aggregates must be stored separately to avoid mixing.