NOTE 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. (1.1)

NOTE Typical applications covered by this Standard include the following. (1.2)

NOTE This Standard is a child of 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. (1.3)

NOTE Several adjacent standards own work that is easy to conflate with this Standard: building structural concrete belongs to Cast In Place Concrete; isolated mechanical and electrical equipment pads belong to Concrete Pads; site retaining walls carrying significant retained-soil surcharge belong to Retaining Walls; precast manholes, vaults, and box culverts supplied from a plant belong to Utility Manholes And Handholes; storm pipe, inlet sizing, and network layout belong to Storm Drainage; and the excavation and backfill operations around these structures belong to Earthwork. (1.6)

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 Utility Manholes And Handholes. (1.7)

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. (1.8)

NOTE 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. (3.1)

NOTE 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. (3.2)

NOTE Closeout submittals are delivered at completion and become part of the project record for the owner's future operation and maintenance of the structure. (3.3)

NOTE 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. (4.1)

NOTE 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 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. (4.3)

NOTE 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. (5.1)

NOTE 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). (5.3)

NOTE 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. (6.1)

NOTE 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. (6.2)

NOTE 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. (6.3)

NOTE 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. (6.4)

NOTE 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. (6.5)

NOTE 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. (6.6)

NOTE 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 Concrete Reinforcement - this Standard sets only the grade and the cover required by the site exposure. (7.1)

NOTE 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. (7.2)

NOTE 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. (8.1)

NOTE 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. (8.2)

NOTE 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. (9.1)

NOTE 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. (10.1)

NOTE 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. (10.2)

NOTE 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. (10.3)

NOTE 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. (11.1)

NOTE 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. (11.2)

NOTE 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. (11.3)

NOTE 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. (11.4)

NOTE 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. (12.1)

NOTE 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. (12.2)

NOTE 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. (13.1)

NOTE 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 Earthwork and, for drainage behind the wall, by Foundation Drainage. (13.2)

NOTE 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. (14.1)

NOTE 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. (15.1)