Calculator Inputs
Example Data Table
| Scenario | Geometry | Key Inputs | Thickness | Allowances | Estimated Net Volume |
|---|---|---|---|---|---|
| Shotcrete wall panel | Wall face (L×H) | L=18 m, H=4 m, Layers=1 | 80 mm | Rebound 15%, Overbreak 5% | ~6.6 m³ |
| Slab repair zone | Rectangular slab/area (L×W) | L=10 m, W=6 m, Layers=2 | 50 mm | Rebound 12%, Pump 2% | ~6.9 m³ |
| Circular tunnel lining | Circular tunnel lining (πD×L) | D=5 m, L=25 m, Layers=1 | 100 mm | Rebound 20%, Overbreak 8% | ~53.0 m³ |
Example values are illustrative. Field conditions can shift rebound and overbreak significantly.
Formula Used
1) Surface area (A) depends on selected geometry:
- Rectangular area:
A = L × W - Wall face:
A = L × H - Circular tunnel lining:
A = (π × D) × L - Custom tunnel lining:
A = Perimeter × L - Custom area:
A = user input
2) Base volume is:
V_base = A × (t × layers)
3) Allowances are applied as multipliers:
V_net = V_base × (1+r) × (1+o) × (1+p) × (1+w)
4) Weight estimate:
Weight = V_net × density
Unit conversions used: 1 in = 0.0254 m, 1 ft = 0.3048 m, and 1 m³ = 1.30795 yd³.
How to Use This Calculator
- Select a geometry that matches the sprayed surface.
- Choose dimension and thickness units, then enter measurements.
- Enter thickness per layer and the number of layers.
- Set allowances for rebound, overbreak, pump loss, and trimming.
- Optionally set density, cement content, truck capacity, and cost.
- Click Calculate to view results above the form.
- Use Download CSV or Download PDF for reporting.
For tendering, keep a conservative allowance and note site assumptions.
Shotcrete Volume Planning Article
Shotcrete is widely used for slope stabilization, tunnel linings, retaining structures, and structural repairs because it can be placed quickly and formed to irregular surfaces. Accurate volume planning reduces cost overruns, avoids cold joints caused by short deliveries, and improves scheduling for pumps, crews, and finishing activities. This calculator estimates net shotcrete volume by combining your surface area with total thickness and practical allowances. It is suited for both dry-mix and wet-mix operations, as long as you set rebound and loss percentages to reflect your site conditions.
Start by selecting the geometry that matches the sprayed face. For a wall or slab, use the rectangular or wall-face options. For tunnels, use the circular lining formula πD×L or a custom perimeter if the section is horseshoe or box shaped. Next, enter thickness per layer and the number of layers. Multiple passes are common when building up thickness in high sections or when reinforcing mesh and drainage elements require staged placement. The calculator converts units automatically and produces base volume in cubic meters.
Field quantities are rarely equal to theoretical quantities. Rebound, trimming, and delivery losses should be treated as controlled allowances rather than surprises. Rebound can increase with poor nozzle angle, high air pressure, dry surfaces, or overhead work. Overbreak or extra thickness is common in rock excavations and rough substrates. Pump loss captures line priming, cleanout, and residual material. When you apply these allowances, the calculator multiplies them into a net volume you can use for ordering and logistics.
Example: A tunnel lining with D = 5.0 m, L = 25 m, and t = 100 mm (one layer) has an area of about 392.7 m². The base volume is roughly 39.3 m³. With 20% rebound, 8% overbreak, 2% pump loss, and 1% trimming, net volume becomes about 53.0 m³. At 2200 kg/m³ density, the placed material is about 116 t, and at 6 m³ truck capacity it is about 8.8 loads. Use the CSV or PDF export to document assumptions in your takeoff notes and align them with project specifications and method statements.
FAQs
1) What thickness should I enter for shotcrete?
Enter the design thickness per pass. If the work requires multiple passes, set the number of layers and keep the per-layer thickness realistic for your placement method and access.
2) How do I choose a rebound percentage?
Use values based on past production data, test panels, or site trials. Overhead work and poor access typically increase rebound. Improve nozzle angle and surface preparation to reduce it.
3) Does this calculator include steel fibers or mesh volume?
The volume calculation is for concrete material placed. Fibers and mesh are reinforcement and do not meaningfully change volume, but they can affect rebound and finishing waste.
4) Why are pump losses included?
Pump losses account for line priming, hose cleanout, and residual material. These losses can be small on continuous pours but noticeable on short runs or frequent stoppages.
5) Can I estimate cement bags from this tool?
Yes. Enter cement content in kg/m³ and bag weight. The calculator estimates cement mass and number of bags for planning, but always confirm mix design and batching tolerances.
6) How accurate is the weight estimate?
Weight is based on your selected density. Actual density varies by aggregate, moisture, admixtures, and air content. Use laboratory or supplier data when available for better accuracy.
7) Should I use net volume for ordering?
Net volume is a practical ordering target when your allowances reflect real conditions. For critical pours, add a contingency and coordinate delivery timing to avoid interruptions and waste.