Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Shotcrete
…174 unchanged lines
```
−# Materials {toc}
+# Cementitious Materials {toc}
−## Cementitious Materials {toc}
+## Portland cement shall conform to ASTM C150, Type I or Type II, except that Type III may be used where rapid early-strength gain is required and is permitted by the mix design submittal.
−### Portland cement shall conform to ASTM C150, Type I or Type II, except that Type III may be used where rapid early-strength gain is required and is permitted by the mix design submittal.
−
−### Silica fume, where specified, shall conform to ASTM C1240.
−
−### Silica fume reduces permeability and improves cohesion and overhead build-up; it is commonly specified for underground, corrosion-sensitive, and water-retaining applications at 8% to 12% of cementitious weight, with 8% to 15% used in slurry-blended underground mixes. {note}
−
```datasheet
label: Portland cement type
…5 unchanged lines
```
+## Silica fume, where specified, shall conform to ASTM C1240.
+
```datasheet
label: Silica fume content (by cementitious weight)
…6 unchanged lines
```
−## Aggregates {toc}
+## Silica fume reduces permeability and improves cohesion and overhead build-up; it is commonly specified for underground, corrosion-sensitive, and water-retaining applications at 8% to 12% of cementitious weight, with 8% to 15% used in slurry-blended underground mixes. {note}
−### Fine and coarse aggregate shall conform to ASTM C33, with gradation within the limits established by the approved mix design.
+# Aggregates {toc}
−### Shotcrete aggregate is finer and more closely graded than aggregate for cast-in-place concrete, because the mix must pump or convey through a hose and consolidate on impact without segregation; oversize or gap-graded aggregate increases rebound and creates voids behind reinforcement. {note}
+## Fine and coarse aggregate shall conform to ASTM C33, with gradation within the limits established by the approved mix design.
−## Admixtures and Accelerators {toc}
+## Shotcrete aggregate is finer and more closely graded than aggregate for cast-in-place concrete, because the mix must pump or convey through a hose and consolidate on impact without segregation; oversize or gap-graded aggregate increases rebound and creates voids behind reinforcement. {note}
−### Admixtures for shotcrete shall conform to ASTM C1141.
+# Admixtures and Accelerators {toc}
−### Accelerators, where used, shall be alkali-free unless an alkali-based accelerator is expressly approved in writing.
+## Admixtures for shotcrete shall conform to ASTM C1141.
−### Alkali-based accelerators reduce long-term strength and present a significant skin and eye hazard to the nozzle crew; alkali-free accelerators are current practice and should be specified for overhead, rapid-demold, and rapid-early-strength work. {note}
+## Accelerators, where used, shall be alkali-free unless an alkali-based accelerator is expressly approved in writing.
−### Accelerator dosage shall not reduce the 28-day compressive strength of the accelerated mix to less than 80% of the companion unaccelerated mix.
+## Alkali-based accelerators reduce long-term strength and present a significant skin and eye hazard to the nozzle crew; alkali-free accelerators are current practice and should be specified for overhead, rapid-demold, and rapid-early-strength work. {note}
+## Accelerator dosage shall not reduce the 28-day compressive strength of the accelerated mix to less than 80% of the companion unaccelerated mix.
+
```datasheet
label: Accelerator type
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```
−## Reinforcement and Fibers {toc}
+# Reinforcement and Fibers {toc}
−### Fiber type and dosage shall be as specified in the Contract Documents where fiber-reinforced shotcrete is indicated, and shall not be substituted without approval.
+## Fiber type and dosage shall be as specified in the Contract Documents where fiber-reinforced shotcrete is indicated, and shall not be substituted without approval.
−### Where fiber-reinforced shotcrete is shown on the drawings, the fiber type and dosage rate shall be stated; without them the Contractor cannot price the work or submit a mix design. {note}
+## Where fiber-reinforced shotcrete is shown on the drawings, the fiber type and dosage rate shall be stated; without them the Contractor cannot price the work or submit a mix design.
−### Steel fibers are typically dosed at 30 to 50 lb/yd³ for structural shoring ductility and 50 to 75 lb/yd³ for tunnel ground support; synthetic macro-fibers are typically dosed at 3 to 7.5 lb/yd³. The choice between steel and synthetic depends on required toughness, durability exposure, and finish. {note}
+## Steel fibers are typically dosed at 30 to 50 lb/yd³ for structural shoring ductility and 50 to 75 lb/yd³ for tunnel ground support; synthetic macro-fibers are typically dosed at 3 to 7.5 lb/yd³. The choice between steel and synthetic depends on required toughness, durability exposure, and finish. {note}
−### Conventional reinforcing bar encased in shotcrete shall be positioned and supported so the shotcrete stream fully encases each bar without shadow voids; bar spacing and cover shall be as shown and as governed by [[sync/concrete-reinforcement]].
+## Conventional reinforcing bar encased in shotcrete shall be positioned and supported so the shotcrete stream fully encases each bar without shadow voids; bar spacing and cover shall be as shown and as governed by [[sync/concrete-reinforcement]].
```datasheet
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### Each nozzleman shall hold a current ACI Nozzleman (CP-60) certification for the process — wet-mix or dry-mix — and the orientation — vertical or overhead — in which they will place shotcrete.
−### ACI Nozzleman certification requires both a written examination and a practical examination in which the candidate shoots a qualification panel; certification is valid for five years and is issued by ACI, while the American Shotcrete Association provides training. {note}
−
−### Where the Contract Documents require a project-specific qualification program in addition to certification, each nozzleman shall successfully shoot project qualification panels before placing shotcrete in the work.
−
−### Failure to require ACI certification explicitly allows uncertified operators to be proposed and is a frequent source of quality disputes; certification shall be verified before any placement. {note}
−
```datasheet
label: Nozzleman qualification requirement
…15 unchanged lines
```
+### ACI Nozzleman certification requires both a written examination and a practical examination in which the candidate shoots a qualification panel; certification is valid for five years and is issued by ACI, while the American Shotcrete Association provides training. {note}
+
+### Where the Contract Documents require a project-specific qualification program in addition to certification, each nozzleman shall successfully shoot project qualification panels before placing shotcrete in the work.
+
+### Failure to require ACI certification explicitly allows uncertified operators to be proposed and is a frequent source of quality disputes; certification shall be verified before any placement. {note}
+
# Preconstruction Test Panels {toc}
−## Preconstruction test panels qualify the mix, the equipment, and each nozzleman together as a placement system before production work begins; they are the basis of acceptance and shall not be omitted. {note}
+## Preconstruction test panels qualify the mix, the equipment, and each nozzleman together as a placement system before production work begins; they are the basis of acceptance and shall not be omitted.
### Each nozzleman shall shoot preconstruction test panels for each mix, process, and orientation they will use in the work, using the production equipment.
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### At least one test panel shall be shot per nozzleman per day, or per 50 yd³ placed, whichever results in more panels.
−### Omitting or under-specifying the panel program leaves the acceptance basis ambiguous and creates delay and rejection disputes; the number of panels and the test ages shall be stated in the Contract Documents. {note}
+### Omitting or under-specifying the panel program leaves the acceptance basis ambiguous and creates delay and rejection disputes; the number of panels and the test ages shall be stated in the Contract Documents.
```datasheet
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### Where fiber-reinforced shotcrete is specified, flexural toughness shall be determined by ASTM C1550 on round panels, with the energy-absorption class stated in the Contract Documents.
−### For underground and ground-support fiber-reinforced shotcrete an energy absorption of at least 270 J at 40 mm deflection (a D500-equivalent class) is commonly specified; the required class shall match the ground-support design. {note}
+### For underground and ground-support fiber-reinforced shotcrete an energy absorption of at least 270 J at 40 mm deflection (a D500-equivalent class) is commonly specified; the required class shall match the ground-support design.
### Rebound number testing per ASTM C805 may be used as a supplemental in-place uniformity check but shall not be used as the basis of strength acceptance.
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### Existing concrete and masonry substrates shall be scarified to expose sound material and brought to a saturated surface-dry condition before placement.
−### Where shotcrete is placed over a waterproofing membrane, existing concrete, or other bond-critical surface, the surface preparation required to achieve bond shall be specified; omitting it leads to delamination. {note}
+### Where shotcrete is placed over a waterproofing membrane, existing concrete, or other bond-critical surface, the surface preparation required to achieve bond shall be specified; omitting it leads to delamination.
```datasheet
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# Placement {toc}
−## Shotcrete shall be placed by qualified nozzlemen using technique that consolidates the material on impact and fully encases reinforcement and embedments without shadow voids. {note}
+## Shotcrete shall be placed by qualified nozzlemen using technique that consolidates the material on impact and fully encases reinforcement and embedments without shadow voids.
### The nozzle shall be held approximately perpendicular to the receiving surface and at the distance that produces dense, well-consolidated material with minimum rebound.
…11 unchanged lines
### Typical rebound is 5% to 15% for wet-mix, 15% to 30% for dry-mix walls, and up to 35% for overhead dry-mix; rebound shall be removed from the work area before it can be entrapped by subsequent passes. {note}
+### The total shotcrete thickness required for each application shall be specified, and shall be achieved through layers not exceeding the thickness the material can support in the placement orientation.
+
```datasheet
label: Total specified shotcrete thickness
…18 unchanged lines
# Thickness Verification {toc}
−## Because shotcrete has no formed back face, placed thickness cannot be read from formwork and shall be verified by an independent method. {note}
+## Because shotcrete has no formed back face, placed thickness cannot be read from formwork and shall be verified by an independent method.
### Minimum placed thickness shall be verified using depth gauge pins, thickness probes, or drilled-and-measured checks at a stated frequency.
### Depth pins or gauge wires shall be installed before placement at a spacing that lets the nozzleman judge build-up, and the verified minimum thickness shall meet or exceed the specified thickness.
−### Thickness enforcement is commonly overlooked because there is no formed surface to measure against; the verification method and frequency shall be specified rather than left to the Contractor. {note}
+### Thickness enforcement is commonly overlooked because there is no formed surface to measure against; the verification method and frequency shall be specified rather than left to the Contractor.
```datasheet
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### Curing shall begin as soon as the surface has hardened enough that the curing method will not mar or erode it.
−### Where a curing compound is used on a surface that will receive a bonded subsequent layer, the compound shall be compatible with that bond or removed before the next placement, because most curing compounds act as bond breakers. {note}
+### Where a curing compound is used on a surface that will receive a bonded subsequent layer, the compound shall be compatible with that bond or removed before the next placement, because most curing compounds act as bond breakers.
```datasheet
…25 unchanged lines
### The Owner's testing agency shall observe placement, obtain and test cores, and verify that placement, encasement, rebound control, and thickness conform to this standard.
−### Defective shotcrete — including delaminated, voided, sand-pocketed, rebound-contaminated, or under-strength material — shall be removed and replaced with conforming shotcrete.
−
−### Coordination between the shotcrete contractor and the geotechnical and structural engineers is required on shoring and ground-support work; this standard governs placement and quality, while load and stability design is governed by [[sync/excavation-support-and-dewatering]] and the structural documents. {note}
−
```datasheet
label: Field quality-control inspection
…10 unchanged lines
```
+### Defective shotcrete — including delaminated, voided, sand-pocketed, rebound-contaminated, or under-strength material — shall be removed and replaced with conforming shotcrete.
+
+### Coordination between the shotcrete contractor and the geotechnical and structural engineers is required on shoring and ground-support work; this standard governs placement and quality, while load and stability design is governed by [[sync/excavation-support-and-dewatering]] and the structural documents. {note}
+
# Delivery, Storage, and Handling {toc}
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default: 1
```