Shotcrete / Gunite Order Quantity with Rebound
Cubic yards of shotcrete or gunite to order once rebound (the fraction that bounces off and never stays) is grossed up.
Example
You enter
- Area to shoot (ft²) 500
- In-place section thickness (in) 4
- Rebound loss (% of material shot) 20
- Volume actually shot so far (cy) 7
You get
- In-place volume 6.17 cy
- Shotcrete to order 7.72 cy shot
- Rebound (lost) 1.54 cy
- Naive add (cy) 7.40741
- In place from shot (cy) 5.6
- Achieved thickness (in) 3.6288
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopeshot = in-place / (1 - rebound). A 500 sf face at 4 in holds 6.17 cy but needs 7.72 cy shot at 20% rebound, 8.82 cy at 30%. The applicator's field rebound governs.
Formula or tablein_place_cy = area_sf x (thickness_in/12) / 27; shot_cy = in_place_cy / (1 - rebound_pct/100); rebound_cy = shot_cy - in_place_cy.
Source and editionRebound gross-up identity by name (ACI 506 shotcrete practice); first-principles volume arithmetic.
Free accessThe rebound gross-up identity is public shotcrete practice; ACI 506R describes rebound ranges.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_sf, thickness_in, rebound_pct, shot_actual_cy, in_place_cy, shot_cy, rebound_cy, naive_add_cy, in_place_from_shot_cy, achieved_thickness_in
- Rebound loss 20% default (wet-mix ~5-15%, dry-mix/overhead ~15-30%); the applicator's field record governsACI 506 / field practice
- Volume constant 27 ft^3 per cubic yard (exact)physical fact