Shotcrete Quantity Calculator
Back-calculate batched volume and material use from rebound.
Inputs
Result
Formula
| Net volume = area × thickness | |
| Batch = net ÷ (1 − rebound) | rebound is a loss, so invert |
| Cement = batch × cement per m³ | |
| Loss = batch − net |
Side wall 100 m² at 100 mm with 15% rebound: net 10.00 m³ but 11.76 m³ must be batched, so 1.76 m³ (about 4.05 t) is lost to rebound; at 420 kg/m³ that is 4.94 t of cement.
FAQ
Why is crown rebound so much higher than side wall?
Gravity. On a wall the material sticks on impact; overhead it must overcome its own weight, and coarse aggregate falls away first. Crown rebound is typically 1.5-2 times the wall value and is richer in coarse aggregate, which leaves the in-place layer sandier and weaker. Hence the requirement for lifts of 70-100 mm at the crown.
Can rebound be reused?
No. It has lost water, picked up dust and fines, and its grading is destroyed (coarse-heavy, fine-poor), so reusing it cuts strength and durability - codes prohibit it. Clear it promptly and treat rebound rate as a process KPI: every 5 points of rebound saved is over 5% of material cost.
How much do nozzle distance and angle matter?
A lot. Rebound is lowest at about 1 m with the nozzle perpendicular; at 2 m or 45 degrees it roughly doubles. Air pressure must match too - too low and the stream cannot compact, too high and aggregate bounces. Much of the on-site quantity variance is nozzle technique and air pressure, not mix design.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.