+---
+title: Cast-in-Place Site Concrete Structures
+category: Sitework
+toc_depth: 3
+description: >
+ When to use: Cast-in-place reinforced concrete formed and poured in place for
+ civil and utility site work - drainage headwalls and wingwalls, cast-in-place
+ utility vaults (pull, splice, and meter vaults), trench-interceptor walls and
+ channel liners, culvert end walls, junction chambers, catch basin collars and
+ adjustment rings, yard drainage sumps, outfall aprons with integral curbs, and
+ low walls integral to drainage or utility routing. Covers exposure
+ classification, mix selection for buried and exposed conditions, reinforcement
+ cover, formed pipe and conduit penetrations, cast-in anchor hardware, jointing
+ and waterstops, curing, surface sealers, backfill sequencing, and field
+ testing.
+ Not intended for: Building structural concrete - foundations, slabs, columns,
+ beams, elevated decks (see sync/cast-in-place-concrete, the parent material
+ reference); isolated equipment pads (sync/concrete-pads); site retaining walls
+ carrying significant soil surcharge (sync/retaining-walls); precast utility
+ structures supplied from a plant (sync/utility-manholes-and-handholes); storm
+ pipe, inlet, and network design (sync/storm-drainage); reinforcing steel
+ procurement and fabrication submittals (sync/concrete-reinforcement);
+ below-grade waterproofing membranes for habitable spaces
+ (sync/below-grade-waterproofing); site flatwork - sidewalks and traffic
+ slabs-on-grade (sync/cast-in-place-concrete); the independent inspection and
+ testing program (sync/special-inspections-and-testing); earthwork and backfill
+ operations (sync/earthwork); and under-structure vapor barriers
+ (sync/vapor-barriers-under-slab).
+---
+
+# Scope {toc}
+
+## This Standard covers cast-in-place reinforced concrete structures that are civil and utility site scope rather than building structural scope; these structures are formed and poured in place at their final location, as distinct from precast structures fabricated at a plant and set in a single lift, and the applications gathered here share a working environment - they sit in soil, carry or convey drainage water, host pipe and conduit penetrations, and are frequently exposed to weather and deicing salts. {note}
+
+## Typical applications covered by this Standard include the following. {note}
+- Drainage headwalls and wingwalls at culvert and storm outfalls
+- Cast-in-place utility vaults - pull vaults, splice vaults, and meter vaults
+- Trench-interceptor walls and cast-in-place channel liners
+- Culvert end walls and junction chambers where multiple pipes converge
+- Catch basin collars and cast-in-place adjustment rings to bring precast units to grade
+- Yard drainage sumps and outfall aprons with integral curbs
+- Low walls (under 4 ft of exposed face) integral to drainage or utility routing
+
+## This Standard is a child of [[sync/cast-in-place-concrete]] and inherits its material and mix-design requirements; the parent standard governs building cast-in-place work - the structural frame, foundations, and slabs - and is the authoritative reference for concrete materials, mix qualification, formwork practice, and field testing; this Standard does not restate those material rules in full but adopts them and adds the site-specific requirements that building concrete does not address: exposure classification for buried and water-contact conditions, formed pipe and conduit penetrations, vault and headwall configurations, waterstopped construction joints, and backfill sequencing; where a material or testing requirement here is silent, the parent standard governs. {note}
+
+## Cast-in-place site concrete shall be designed and constructed in accordance with ACI CODE-318-25 and ACI 301-20 as adopted by the authority having jurisdiction.
+
+## Concrete cast-in-place site structures subject to a building permit shall comply with IBC Chapter 19 as adopted by the authority having jurisdiction.
+
+## Several adjacent standards own work that is easy to conflate with this Standard: building structural concrete belongs to [[sync/cast-in-place-concrete]]; isolated mechanical and electrical equipment pads belong to [[sync/concrete-pads]]; site retaining walls carrying significant retained-soil surcharge belong to [[sync/retaining-walls]]; precast manholes, vaults, and box culverts supplied from a plant belong to [[sync/utility-manholes-and-handholes]]; storm pipe, inlet sizing, and network layout belong to [[sync/storm-drainage]]; and the excavation and backfill operations around these structures belong to [[sync/earthwork]]. {note}
+
+## Where a single structure is part cast-in-place and part precast, the Contract Documents shall identify unambiguously which portions are governed by this Standard and which by [[sync/utility-manholes-and-handholes]]. {note}
+
+## Catch basin collars and adjustment rings poured onto precast base units are the common mixed case; combining cast-in-place forming procedures with precast plant tolerances on the same element produces conflicting requirements, and the scope split must be explicit on the drawings so the requirements do not collide. {note}
+
+# Referenced Standards {toc}
+
+## Materials, design, and construction shall comply with the latest adopted edition of each of the following unless a specific edition is cited in the Contract Documents.
+
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| ACI CODE-318-25 | Building Code Requirements for Structural Concrete and Commentary |
+| ACI 301-20 | Specifications for Structural Concrete |
+| ACI 117-10 (R2015) | Specification for Tolerances for Concrete Construction and Materials |
+| ACI 305R-20 | Guide to Hot Weather Concreting |
+| ACI 306R-16 | Guide to Cold Weather Concreting |
+| ACI 347R-14 | Guide to Formwork for Concrete |
+| ASTM C33/C33M | Standard Specification for Concrete Aggregates |
+| ASTM C39/C39M | Compressive Strength of Cylindrical Concrete Specimens |
+| ASTM C94/C94M | Standard Specification for Ready-Mixed Concrete |
+| ASTM C138/C138M | Density, Yield, and Air Content (Gravimetric) of Concrete |
+| ASTM C143/C143M | Slump of Hydraulic-Cement Concrete |
+| ASTM C150/C150M | Standard Specification for Portland Cement |
+| ASTM C172/C172M | Sampling Freshly Mixed Concrete |
+| ASTM C231/C231M | Air Content of Freshly Mixed Concrete by the Pressure Method |
+| ASTM C260/C260M | Air-Entraining Admixtures for Concrete |
+| ASTM C309 | Liquid Membrane-Forming Compounds for Curing Concrete |
+| ASTM C494/C494M | Chemical Admixtures for Concrete |
+| ASTM C618 | Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete |
+| ASTM C1064/C1064M | Temperature of Freshly Mixed Hydraulic-Cement Concrete |
+| ASTM A615/A615M | Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement |
+| ASTM A706/A706M | Deformed and Plain Low-Alloy Steel Bars for Concrete Reinforcement |
+| ASTM F1554 | Anchor Bolts, Steel, 36, 55, and 105-ksi Yield Strength |
+| OSHA 29 CFR 1926.703 | Requirements for Cast-in-Place Concrete |
+| IBC Chapter 19 | Concrete (International Building Code, 2024) |
+
+# Submittals {toc}
+
+## Action submittals are reviewed and accepted before the related work proceeds; for site concrete structures they establish the mix that will satisfy the project exposure class, the formwork that will hold tolerance and resist fluid pressure, and the layout of penetrations and embeds that cannot be corrected after the pour. {note}
+
+### The Contractor shall submit the following action submittals for review and acceptance before placing concrete:
+- Concrete mix design for each strength and exposure class, with the supplier's qualification data (trial batch or field test record per ACI 301-20)
+- Aggregate source and gradation report per ASTM C33
+- Admixture product data - air-entraining (ASTM C260), chemical (ASTM C494), and any supplementary cementitious materials (ASTM C618)
+- Reinforcing steel shop drawings and bar bending schedule (coordinate with [[sync/concrete-reinforcement]])
+- Formwork design for walls over 8 ft tall or where lateral pressure exceeds code-default assumptions, stamped by a licensed engineer
+- Penetration and embed layout drawings showing cast-in sleeves, knockouts, anchor hardware, and conduit stubs coordinated against the civil, mechanical, and electrical drawings
+- Waterstop product data and joint-layout drawing for below-grade structures
+- Curing compound product data (ASTM C309) where membrane curing is proposed
+
+```datasheet
+label: Action Submittals
+type: checkbox
+options:
+ - Concrete mix design (per strength and exposure class)
+ - Aggregate source and gradation report
+ - Admixture and SCM product data
+ - Reinforcing shop drawings and bar bending schedule
+ - Formwork design (engineer-stamped where required)
+ - Penetration and embed layout drawings
+ - Waterstop product data and joint layout
+ - Curing compound product data
+default:
+ - Concrete mix design (per strength and exposure class)
+ - Aggregate source and gradation report
+ - Admixture and SCM product data
+ - Reinforcing shop drawings and bar bending schedule
+ - Penetration and embed layout drawings
+```
+
+## Informational submittals document that the delivered materials and field conditions match what was accepted; they are recorded but do not by themselves hold the work. {note}
+
+### The Contractor shall submit the following informational submittals:
+- Concrete delivery tickets per ASTM C94 showing batch time, mix designation, water added, and quantities
+- Field test reports - slump, air content, temperature, and cylinder strength results
+- Cold-weather or hot-weather placement plan when triggered by ambient or concrete temperature limits
+- Backfill release records showing concrete age or field-cured cylinder strength before backfill against walls
+
+```datasheet
+label: Informational Submittals
+type: checkbox
+options:
+ - Concrete delivery tickets
+ - Field test reports (slump, air, temperature, strength)
+ - Hot-weather placement plan
+ - Cold-weather placement plan
+ - Backfill release records
+default:
+ - Concrete delivery tickets
+ - Field test reports (slump, air, temperature, strength)
+ - Backfill release records
+```
+
+## Closeout submittals are delivered at completion and become part of the project record for the owner's future operation and maintenance of the structure. {note}
+
+### The Contractor shall submit the following closeout submittals:
+- Record drawings showing as-built penetration locations, invert elevations, and cast-in hardware
+- Consolidated field test reports with the Engineer's acceptance status for each placement
+- Curing and sealer application records for exposed structures
+
+```datasheet
+label: Closeout Submittals
+type: checkbox
+options:
+ - Record drawings (as-built penetrations and inverts)
+ - Consolidated field test reports
+ - Curing and sealer application records
+default:
+ - Record drawings (as-built penetrations and inverts)
+ - Consolidated field test reports
+```
+
+# Quality Assurance {toc}
+
+## A pre-pour inspection hold point is the single most important quality control on site concrete structures because reinforcement placement, cover, penetration and sleeve locations, anchor hardware, and waterstop continuity are all permanently buried by the pour and cannot be corrected once concrete is placed; several of the most expensive field failures - cored penetrations through reinforced walls, missing waterstop at a cold joint, mislocated anchor bolts - trace directly to a pour that proceeded without a verified inspection. {note}
+
+## A pre-pour inspection hold point shall be established for each structure, and concrete shall not be placed until the Engineer or designated inspector has verified reinforcement, cover, penetrations, embeds, and waterstop continuity.
+
+## This Standard specifies the work and the contractor's quality control; the independent special inspector's role - continuous or periodic inspection, sampling oversight, and reporting to the authority having jurisdiction - is governed by [[sync/special-inspections-and-testing]], which is complementary to this Standard: this Standard says what to build and test, that standard says who independently verifies it. {note}
+
+## The independent inspection and testing program shall be administered in accordance with [[sync/special-inspections-and-testing]].
+
+## Field testing shall be performed by a technician certified as an ACI Concrete Field Testing Technician Grade I or equivalent.
+
+## The concrete supplier shall hold current NRMCA plant certification or shall demonstrate equivalent production quality control acceptable to the Engineer.
+
+### One composite sample shall be obtained for each 50 cubic yards placed or for each day's pour, whichever is more frequent, per ACI 301-20.
+
+### Each composite sample shall include slump (ASTM C143), air content (ASTM C231), concrete temperature (ASTM C1064), and a set of strength cylinders.
+
+### Each strength set shall consist of a minimum of two cylinders tested at 28 days and one cylinder tested at 7 days (ASTM C39), with sampling per ASTM C172.
+
+```datasheet
+label: Field Test Sampling Frequency
+type: select
+options:
+ - One sample per 50 CY or per day's pour, whichever is more frequent
+ - One sample per 25 CY or per day's pour, whichever is more frequent
+ - One sample per 100 CY or per day's pour, whichever is more frequent
+default: One sample per 50 CY or per day's pour, whichever is more frequent
+```
+
+```datasheet
+label: Strength Test Cylinders per Set
+type: radio
+options:
+ - Two at 28 days plus one at 7 days
+ - Two at 28 days plus two at 7 days
+ - Three at 28 days plus one at 7 days
+default: Two at 28 days plus one at 7 days
+```
+
+# Environmental and Service Conditions {toc}
+
+## Exposure classification is the decision that drives mix selection for site structures and is where site concrete diverges most from building concrete; building interior concrete typically sees benign exposure, but site structures sit in soil that may be sulfate-bearing, are in frequent contact with drainage water, and - for headwalls, aprons, and curbs - are fully exposed to freeze-thaw cycling and deicing salts; ACI CODE-318-25 Table 19.3.1 classifies exposure in four categories and the governing category sets the maximum water-cementitious ratio and the minimum compressive strength; the most common error on site work is to reuse the building interior mix without re-evaluating exposure. {note}
+
+## The exposure class for each structure shall be determined from ACI CODE-318-25 Table 19.3.1 based on the project geotechnical report and the structure's service condition.
+
+### The freezing-and-thawing (W) class shall be assigned per the structure's exposure to moisture and freeze-thaw cycling, with deicing-salt-exposed surfaces classified no lower than W2.
+
+### The sulfate (S) class shall be assigned from the water-soluble sulfate content of soil and groundwater reported in the project geotechnical report.
+
+### The corrosion-protection (C) class shall be assigned based on exposure to chlorides from deicing chemicals, brackish water, or seawater.
+
+```datasheet
+label: Freezing and Thawing Exposure Class (W)
+type: radio
+options:
+ - W0 - not exposed to freezing
+ - W1 - exposed, not in continuous contact with water
+ - W2 - exposed, in contact with water and deicing chemicals
+default: W1 - exposed, not in continuous contact with water
+```
+
+```datasheet
+label: Sulfate Exposure Class (S)
+type: radio
+options:
+ - S0 - negligible (< 0.10% water-soluble sulfate in soil)
+ - S1 - moderate (0.10 to 0.20%)
+ - S2 - severe (0.20 to 2.00%)
+ - S3 - very severe (> 2.00%)
+default: S1 - moderate (0.10 to 0.20%)
+```
+
+```datasheet
+label: Corrosion Protection Exposure Class (C)
+type: radio
+options:
+ - C0 - dry or protected from moisture
+ - C1 - exposed to moisture, no external chloride source
+ - C2 - exposed to moisture and an external chloride source
+default: C1 - exposed to moisture, no external chloride source
+```
+
+## Concrete placement is governed by ambient and concrete temperature and the limits are not optional; concrete placed too hot loses workability, flash-sets, and develops plastic shrinkage cracking; placed too cold, it gains strength slowly and is vulnerable to freezing before it has set; ACI 301-20 sets a concrete temperature window at the point of discharge, and exceeding either bound triggers a documented placement plan under ACI 305R (hot weather) or ACI 306R (cold weather). {note}
+
+### Concrete temperature at the point of discharge shall be maintained between 50 °F and 90 °F unless a placement plan establishes otherwise.
+
+### When ambient temperature exceeds 90 °F or concrete temperature approaches the upper limit, a hot-weather placement plan per ACI 305R shall be submitted and followed.
+
+### When ambient temperature falls below 40 °F, a cold-weather placement plan per ACI 306R shall be submitted and followed, and no concrete shall be permitted to freeze before reaching 500 psi.
+
+# Concrete Materials and Mix {toc}
+
+## Compressive strength shall be selected from the structural design and the governing exposure class, not chosen uniformly across all site concrete; for lightly loaded site walls and aprons 3,000 psi is adequate, the 80% case for buried utility vaults and headwalls is 3,500 psi, walls subject to vehicular surcharge or severe freeze-thaw warrant 4,000 psi, and specifying 5,000 psi across all site concrete without an exposure or load basis is a common overspecification that raises mix cost and - because the higher cementitious content increases heat of hydration - can actually increase cracking in thin site walls; all strengths are verified at 28 days by ASTM C39. {note}
+
+### The specified compressive strength shall be not less than the minimum required by the governing exposure class in ACI CODE-318-25 Table 19.3.2.1.
+
+```datasheet
+label: Specified Compressive Strength (f'c) at 28 Days
+type: radio
+unit: psi
+options:
+ - 3000
+ - 3500
+ - 4000
+ - 5000
+default: 3500
+```
+
+## The water-cementitious materials ratio is capped by exposure class and that ceiling - not workability - governs the maximum; a lower w/cm produces a denser, less permeable paste that resists sulfate attack, chloride ingress, and freeze-thaw scaling; ACI CODE-318-25 Table 19.3.2.1 sets the maximum w/cm by exposure class: general site concrete at W1/C1 is limited to 0.50, soil-contact concrete in moderate sulfate or freeze-thaw Class 2 is limited to 0.45, and severe exposure (C2, S2, W2) is limited to 0.40; workability shortfalls at a low w/cm are corrected with a water reducer, never by adding water at the truck. {note}
+
+### The maximum water-cementitious materials ratio shall not exceed the limit for the governing exposure class.
+
+```datasheet
+label: Maximum Water-Cementitious Materials Ratio (w/cm)
+type: radio
+options:
+ - "0.50 - general site concrete (W1 / C1)"
+ - "0.45 - soil contact, moderate sulfate or freeze-thaw"
+ - "0.40 - severe exposure (C2, S2, W2)"
+default: "0.45 - soil contact, moderate sulfate or freeze-thaw"
+```
+
+## Cement type depends on the sulfate exposure read from the geotechnical report; Type I/II portland cement (ASTM C150) is the general-purpose choice and carries the moderate-sulfate resistance of Type II; where the geotechnical report shows high water-soluble sulfate in soil or groundwater (Class S2 or S3), Type V sulfate-resisting cement is required to prevent sulfate attack on the buried structure; the cement decision must be made from the geotechnical data, not assumed. {note}
+
+### The cement type shall be selected per ASTM C150 to match the governing sulfate exposure class.
+
+```datasheet
+label: Portland Cement Type
+type: radio
+options:
+ - Type I/II - general purpose, moderate sulfate resistance
+ - Type V - high sulfate resistance (S2 / S3 soils)
+default: Type I/II - general purpose, moderate sulfate resistance
+```
+
+## Supplementary cementitious materials improve durability and reduce heat of hydration; replacing a portion of the portland cement with Class F fly ash (ASTM C618) reduces permeability, improves sulfate resistance, and lowers the heat of hydration that drives early cracking in thicker pours; a 15 to 25% Class F replacement by weight of cementitious material is the 80% case; Class C fly ash up to 25% is acceptable where sulfate exposure is low but is less effective against sulfate attack and should not be the choice for S2/S3 soils; slag cement and silica fume are alternatives where specified by the mix designer. {note}
+
+```datasheet
+label: Supplementary Cementitious Material
+type: radio
+options:
+ - Class F fly ash, 15 to 25% replacement
+ - Class C fly ash, up to 25% replacement
+ - Slag cement, per mix design
+ - None
+default: Class F fly ash, 15 to 25% replacement
+```
+
+## Air entrainment is mandatory for exposed site concrete in freeze-thaw climates and is one of the most frequently omitted requirements; headwalls, curb aprons, and exposed wall faces take the full force of freeze-thaw cycling and deicing salts, and without entrained air (ASTM C260) the surface scales rapidly; the target air content is keyed to the nominal maximum aggregate size and freeze-thaw severity per ACI CODE-318-25 Table 19.3.3.1: 5.0 to 7.0% for 3/4 in. aggregate, 4.0 to 6.0% for 1-1/2 in. aggregate; interior-only, protected structures may be placed without entrained air; air content is verified in the field by ASTM C231. {note}
+
+### Concrete for surfaces exposed to freeze-thaw cycling shall be air-entrained to the target content for the nominal maximum aggregate size.
+
+```datasheet
+label: Target Air Content
+type: select
+unit: "%"
+options:
+ - "5.0 to 7.0 (3/4 in. max aggregate, freeze-thaw)"
+ - "4.0 to 6.0 (1-1/2 in. max aggregate, freeze-thaw)"
+ - "None - interior or protected, not freeze-thaw exposed"
+default: "5.0 to 7.0 (3/4 in. max aggregate, freeze-thaw)"
+```
+
+## Slump at the point of discharge is limited to control segregation, with a higher ceiling permitted only when a high-range water reducer is used; a conventional mix is limited to 4 in. slump at discharge; a high-range water-reducing admixture (HRWRA, ASTM C494 Type F or G) produces a flowable mix without adding water, permitting up to 8 in. slump for congested reinforcement or deep wall forms; the HRWRA path preserves the low w/cm, while adding water at the truck to gain workability does not and is prohibited. {note}
+
+### Slump at the point of discharge shall not exceed 4 in. without a high-range water-reducing admixture, or 8 in. with an approved Type F or G HRWRA.
+
+### Water shall not be added to the concrete at the point of discharge to increase slump.
+
+```datasheet
+label: Maximum Slump at Point of Discharge
+type: radio
+unit: in.
+options:
+ - 4 (no HRWRA)
+ - 8 (with approved Type F/G HRWRA)
+default: 4 (no HRWRA)
+```
+
+# Reinforcement and Cover {toc}
+
+## Reinforcement grade and minimum bar sizes follow standard practice; Grade 60 deformed bars (ASTM A615) are the standard choice, low-alloy A706 bars are specified where the structure is in a seismic design category that requires them or where reinforcement is to be welded, and procurement, fabrication, and placement submittals are covered by [[sync/concrete-reinforcement]] - this Standard sets only the grade and the cover required by the site exposure. {note}
+
+### Reinforcing bars shall conform to ASTM A615/A615M Grade 60 unless welding or seismic detailing requires ASTM A706/A706M low-alloy bars.
+
+### Walls less than 8 in. thick shall be reinforced with no smaller than #4 bars.
+
+```datasheet
+label: Reinforcing Steel Specification
+type: radio
+options:
+ - ASTM A615 Grade 60 (standard)
+ - ASTM A706 low-alloy (weldable / seismic)
+default: ASTM A615 Grade 60 (standard)
+```
+
+## Concrete cover is the durability margin for buried structures and is set by ACI 318, not by convenience; cover protects reinforcement from corrosion; ACI CODE-318-25 Table 20.5.1.3.1 requires 3 in. of cover for concrete cast against and permanently exposed to earth, 2 in. for formed surfaces exposed to weather or soil (for #6 bars and larger), and 1-1/2 in. for formed surfaces not exposed to weather; the cast-against-earth case - footings and slabs poured directly on subgrade with no form - is the condition most often shorted. {note}
+
+### Concrete cover for reinforcement shall be provided per ACI CODE-318-25 Table 20.5.1.3.1 for the cast condition of each surface.
+
+```datasheet
+label: Minimum Concrete Cover
+type: select
+unit: in.
+options:
+ - 3 (cast against and permanently exposed to earth)
+ - 2 (formed, exposed to weather or soil)
+ - 1.5 (formed, not exposed to weather)
+default: 2 (formed, exposed to weather or soil)
+```
+
+# Formwork {toc}
+
+## Formwork must resist the fluid pressure of fresh concrete and hold dimensional tolerance; fresh concrete behaves as a fluid until it sets, exerting lateral pressure on the forms that increases with placement rate and wall height; ACI 347R gives the design loads, lateral pressure formulas, and stripping criteria; job-built plywood forms and modular panel systems are both acceptable for routine site structures, but walls over 8 ft tall, or any form where the lateral pressure exceeds code-default assumptions, require a formwork design stamped by a licensed engineer; OSHA 29 CFR 1926.703 sets the federal safety requirements for formwork, shoring, and form removal. {note}
+
+### Formwork shall be designed and constructed per ACI 347R to resist the lateral pressure of fresh concrete at the planned placement rate.
+
+### Formwork for walls over 8 ft tall, or where lateral pressure exceeds code-default assumptions, shall be designed and stamped by a licensed engineer.
+
+### Formwork, shoring, and form removal shall comply with OSHA 29 CFR 1926.703.
+
+### Formed surfaces shall be constructed to the dimensional tolerances of ACI 117.
+
+```datasheet
+label: Formwork System
+type: radio
+options:
+ - Job-built plywood forms
+ - Modular steel or aluminum panel forms
+ - Proprietary headwall / vault form system
+ - Engineer-designed formwork (walls over 8 ft or high pressure)
+default: Modular steel or aluminum panel forms
+```
+
+## Formwork stripping shall be governed by strength or temperature, never by calendar days alone; specifying a stripping time as a flat number of hours invites failure because a 24-hour stripping rule that is fine in summer is far too early on a cold-weather pour where the concrete has not gained enough strength to hold its own shape; early stripping causes surface spalling, sloughing, and form blowouts; ACI 347R Table 3 ties minimum stripping time to ambient temperature and gained strength; vertical surfaces may be stripped after a minimum of 12 hours at 50 °F or above, but never before the concrete has reached the strength that lets it carry its own weight and the stripping forces. {note}
+
+### Vertical formwork shall not be stripped until the concrete has reached the strength required by ACI 347R Table 3 for the placement temperature, and in no case earlier than 12 hours after placement at 50 °F or above.
+
+### On cold-weather placements, formwork shall not be stripped until the concrete has reached a minimum of 70% of the specified f'c.
+
+# Jointing and Waterstops {toc}
+
+## Construction joints in below-grade structures shall be waterstopped because an unstopped cold joint is the most common leak path in site concrete; a construction joint is the planned interface between two placements, and below grade that interface is a direct path for groundwater infiltration into a vault or junction chamber and for exfiltration out of a water-conveying structure; a waterstop cast into the joint blocks that path; a flat PVC dumbbell waterstop, minimum 6 in. wide, is the standard for accessible joints; a hydrophilic swellable rubber strip (typically 3/4 in. by 3/8 in.) is the alternative for joints too tight or congested to place a PVC stop, and it expands on contact with water to seal the joint. {note}
+
+### Construction joints in below-grade structures shall receive a continuous waterstop.
+
+### PVC dumbbell waterstop shall be a minimum of 6 in. wide.
+
+### PVC dumbbell waterstop shall be continuous and spliced by heat-welding, not overlapping.
+
+### Where joint geometry prevents PVC placement, a hydrophilic swellable rubber waterstop strip shall be used in lieu of PVC.
+
+### Construction joint surfaces shall be roughened and cleaned, and an approved bonding agent shall be applied before the adjoining placement.
+
+```datasheet
+label: Waterstop Type (Below-Grade Construction Joints)
+type: radio
+options:
+ - PVC dumbbell, 6 in. wide
+ - PVC dumbbell, 9 in. wide
+ - Hydrophilic swellable rubber strip (3/4 in. x 3/8 in.)
+default: PVC dumbbell, 6 in. wide
+```
+
+### Construction joint locations shall be as indicated, coordinated with the waterstop layout. [[drawing: construction joint locations]]
+
+# Penetrations and Embedded Hardware {toc}
+
+## Pipe and conduit penetrations shall be cast in, not cored after the pour, and their locations shall be coordinated against the civil, mechanical, and electrical drawings before placement; a penetration cast into the form - a sleeve, a knockout, or a blockout - is clean, located, and detailed for sealing, while the same penetration drilled after the pour through a reinforced wall is expensive, cuts reinforcement, and weakens the structure; sleeve and knockout locations must be reconciled against every trade's drawings before the pour because a missed penetration discovered after stripping is a core-drilling problem that never performs as well as a cast-in opening. {note}
+
+### Pipe and conduit penetrations shall be cast in place using sleeves, knockouts, or blockouts; coring after placement shall not be used except where specifically accepted by the Engineer.
+
+### Penetration locations shall be coordinated against the civil, mechanical, and electrical drawings and verified at the pre-pour inspection.
+
+### Cast-in pipe sleeve locations and inverts shall be as indicated. [[drawing: pipe sleeve schedule and inverts]]
+
+```datasheet
+label: Pipe Penetration Method
+type: radio
+options:
+ - Cast-in sleeve (steel or PVC)
+ - Cast-in knockout / blockout
+ - Cored after placement (Engineer accepted only)
+default: Cast-in sleeve (steel or PVC)
+```
+
+## The annular space between a pipe and its sleeve shall be sealed because an unsealed annular gap is the primary infiltration path through a vault wall; a pipe passing through a sleeve leaves a ring-shaped gap, and left open that gap is the main way groundwater enters a vault or escapes a water-carrying structure; the closure must be designated explicitly - a non-shrink grout pack for fixed pipes, or a modular mechanical link-seal where the pipe needs to articulate or where a positive, gasketed seal is required; leaving the annular closure unspecified guarantees a leak. {note}
+
+### The annular space between each pipe and its sleeve shall be sealed by non-shrink grout or a modular mechanical link-seal as scheduled.
+
+```datasheet
+label: Pipe Sleeve Annular Seal
+type: radio
+options:
+ - Modular mechanical link-seal
+ - Non-shrink grout pack
+ - Hydrophilic sealant and backer rod
+default: Modular mechanical link-seal
+```
+
+## Cast-in anchor hardware and conduit stubs shall be set before the pour because adding them afterward requires core drilling that never matches cast-in performance; anchor bolts for frames and grates, lifting inserts, conduit brackets, grounding electrode conductors, and conduit stubs into vaults all perform best when cast into the concrete with the reinforcement, and drilled-and-epoxied or cored-and-grouted retrofits are weaker and leak-prone; anchor bolts conform to ASTM F1554 - Grade 36 for general anchorage, Grade 55 where higher strength is required; grounding and conduit elements must be coordinated with the electrical drawings and set before the pour. {note}
+
+### Anchor bolts shall conform to ASTM F1554 Grade 36 or Grade 55 as required by the connection design and shall be cast in place.
+
+### Cast-in conduit stubs and grounding electrode conductors shall be positioned and secured before placement, coordinated with the electrical drawings.
+
+```datasheet
+label: Cast-In Anchor Bolt Grade
+type: radio
+options:
+ - ASTM F1554 Grade 36
+ - ASTM F1554 Grade 55
+default: ASTM F1554 Grade 36
+```
+
+```datasheet
+label: Cast-In Hardware Provided
+type: checkbox
+options:
+ - Frame / grate anchor bolts
+ - Lifting inserts
+ - Conduit stubs and brackets
+ - Grounding electrode conductor
+default:
+ - Frame / grate anchor bolts
+```
+
+# Configurations {toc}
+
+## This Standard covers a family of cast-in-place site structures formed with job-built or modular forms; the configurations below share materials and execution but differ in geometry and in which features apply - a headwall needs wingwall flare and surface sealer, a vault needs a lid pocket and waterstopped joints, an apron needs integral curbs and energy dissipation; the structure type drives which of the optional features in this Standard are invoked. {note}
+
+```datasheet
+label: Structure Type
+type: select
+options:
+ - Headwall with wingwalls (culvert / outfall end)
+ - Utility vault (pull, splice, or meter)
+ - Trench-interceptor wall / channel liner
+ - Catch basin collar / adjustment ring
+ - Junction chamber
+ - Outfall apron with integral curbs
+ - Low wall integral to utility routing
+default: Headwall with wingwalls (culvert / outfall end)
+```
+
+## Headwalls and wingwalls are formed at the outlet end of a culvert or storm outfall with the wingwalls flared to retain the embankment and guide flow; a headwall caps the pipe end and supports the embankment while the wingwalls flare out from it to hold back the fill and direct the discharge; the flare angle is a hydraulic and grading decision, with 30° and 45° being the common values; headwalls are fully exposed and so invoke the air-entrainment and surface-sealer requirements of this Standard, and they are formed with job-built forms or reusable proprietary headwall form systems. {note}
+
+```datasheet
+label: Wingwall Flare Angle
+type: radio
+unit: degrees
+options:
+ - 30
+ - 45
+ - 90 (straight / U-type)
+default: 45
+```
+
+## Cast-in-place utility vaults are rectangular below-grade structures with a lid or frame pocket, pipe penetrations, and a floor sump; pull, splice, and meter vaults are box structures formed in place where a precast unit will not fit the configuration or the site constraints; they invoke the full below-grade feature set of this Standard - waterstopped construction joints, sealed pipe penetrations, and cast-in hardware for the lid frame and any grounding or conduit; a floor sump is provided so water that does enter can be pumped or drained rather than standing on equipment. {note}
+
+```datasheet
+label: Vault Floor Sump
+type: radio
+options:
+ - Cast-in sump with drain connection
+ - Cast-in sump, pumped
+ - No sump
+default: Cast-in sump with drain connection
+```
+
+## Outfall aprons with integral curbs dissipate flow energy at a storm outfall and are fully exposed concrete; an apron slab with integral curbs spreads and slows the discharge at a storm outfall so the receiving channel is not scoured; because the apron is wet, exposed, and salt-affected, it invokes air entrainment and a penetrating surface sealer; aprons are formed with standard curb and gutter forms. {note}
+
+# Curing and Surface Treatment {toc}
+
+## Curing controls the moisture and temperature that let concrete gain strength and durability; concrete that dries too soon loses strength and surface durability and is prone to shrinkage cracking; a minimum of 7 consecutive days of moist curing at 50 °F or above is required; where continuous moisture is impractical after stripping, a liquid membrane-forming curing compound (ASTM C309 Type 1-D or Type 2) is an accepted alternative, applied promptly after form removal to seal moisture into the concrete. {note}
+
+### Concrete shall be moist-cured for a minimum of 7 consecutive days at 50 °F or above.
+
+### Where membrane curing is used, a curing compound conforming to ASTM C309 Type 1-D or Type 2 shall be applied within 20 minutes of form stripping.
+
+```datasheet
+label: Curing Method
+type: radio
+options:
+ - Moist cure, 7 days minimum
+ - Membrane-forming compound (ASTM C309 Type 1-D / Type 2)
+ - Moist cure followed by membrane compound
+default: Moist cure, 7 days minimum
+```
+
+## Exposed site concrete shall receive a penetrating surface sealer because unprotected concrete in wet-dry and freeze-thaw cycling degrades quickly; headwalls, aprons, curbs, and exposed wall faces live in repeated wetting and drying and, in cold climates, freeze-thaw with deicing salts; unsealed, they carbonate and admit chlorides and the surface scales and spalls; a penetrating silane or siloxane sealer soaks into the surface and repels water without changing the appearance and is the standard protection for exposed site concrete; for below-grade vaults where watertightness is the priority, a crystalline waterproofing admixture batched into the mix is the alternative - it grows crystals that block water through the concrete body rather than at the surface. {note}
+
+### Exposed surfaces of headwalls, aprons, curbs, and walls shall receive a penetrating silane or siloxane sealer after curing is complete.
+
+```datasheet
+label: Surface Protection
+type: radio
+options:
+ - Penetrating silane sealer (exposed surfaces)
+ - Penetrating siloxane sealer (exposed surfaces)
+ - Crystalline waterproofing admixture (below-grade vaults)
+ - None (interior / protected)
+default: Penetrating siloxane sealer (exposed surfaces)
+```
+
+# Installation and Backfill {toc}
+
+## Concrete placement shall follow the accepted mix, temperature, and slump requirements and consolidation shall be by mechanical vibration; placement is where the accepted mix design is either realized or undone, with concrete placed at the accepted slump and temperature, deposited so it does not segregate, and consolidated by internal mechanical vibration to remove entrapped air and fill the form against the reinforcement and embeds; over-vibration that drives entrained air out of a freeze-thaw mix is as harmful as under-consolidation. {note}
+
+### Concrete shall be placed within the accepted slump and temperature limits and consolidated by mechanical vibration without segregation.
+
+### Concrete shall be deposited in horizontal layers and shall not be allowed to free-fall in a manner that causes segregation.
+
+## Backfill against walls shall not begin until the concrete has reached minimum age or strength because premature backfill can crack or overturn a wall that has not yet reached working strength; a freshly poured wall has little strength to resist lateral load, and heavy compaction equipment working against the wall transmits lateral pressure that can crack the wall or push it off its footing before the concrete is strong enough to act as designed; within 3 ft of the wall, only hand compaction is permitted until the structure reaches full strength; backfill material and the earthwork operation itself are governed by [[sync/earthwork]] and, for drainage behind the wall, by [[sync/foundation-drainage]]. {note}
+
+### Machine compaction of backfill against structure walls shall not begin until the concrete is a minimum of 7 days old or has reached 75% of the specified f'c, confirmed by field-cured cylinders.
+
+### Within 3 ft of a wall, backfill shall be placed and compacted by hand methods only until the structure has reached its full specified strength.
+
+### Backfill shall be placed in balanced lifts on opposing sides of a structure to avoid unbalanced lateral loading.
+
+```datasheet
+label: Backfill Release Criterion
+type: radio
+options:
+ - 7 days minimum age
+ - 75% of f'c by field-cured cylinder
+ - Whichever is achieved first
+default: Whichever is achieved first
+```
+
+# Field Quality Control {toc}
+
+## Field acceptance rests on the measured properties of the fresh and hardened concrete sampled at the rate set under Quality Assurance; the field tests are the evidence that the concrete delivered and placed is the concrete that was accepted; slump, air content, and temperature are measured on the fresh concrete at the point of discharge; strength is measured on cylinders cured and broken under ASTM C39; a placement that fails an acceptance test is evaluated by the Engineer, who may require cores, additional curing, or removal. {note}
+
+### Fresh concrete shall be tested for slump, air content, and temperature at the point of discharge for each composite sample.
+
+### Compressive strength acceptance shall be evaluated per ACI 301-20, with the average of any three consecutive strength tests equaling or exceeding f'c and no single test falling more than 500 psi below f'c.
+
+### Concrete represented by strength tests that fail the acceptance criteria shall be evaluated by the Engineer, who may require core testing per ASTM C39 or corrective action.
+
+```datasheet
+label: Strength Acceptance Basis
+type: radio
+options:
+ - ACI 301-20 statistical acceptance (3-test average)
+ - Single-cylinder minimum per pour
+default: ACI 301-20 statistical acceptance (3-test average)
+```
+
+# Warranty {toc}
+
+## The warranty covers leakage at joints and penetrations, surface scaling, cracking beyond tolerance, and reinforcement corrosion staining traceable to insufficient cover or defective placement; the one-year period is the common default; the warranty does not relieve the Contractor of latent-defect liability under the Contract. {note}
+
+### The Contractor shall warrant the work against defects in materials and workmanship for the warranty period.
+
+### The warranty shall cover leakage at construction joints and penetrations, surface scaling, and cracking beyond the tolerances of ACI 117.
+
+```datasheet
+label: Warranty Period
+type: radio
+unit: year(s)
+options:
+ - 1
+ - 2
+ - 5
+default: 1
+```