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SynC · Historical revision

Cast-in-Place Concrete

Revision7
EditedAug 26, 2026
StatusSuperseded
Contents

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Historical revision. This is editorial revision 7, kept so citations to it stay resolvable. It is not the current text of this standard — see the current revision.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs

1 Scope

NOTE This standard covers the constituent materials, mixture proportioning and qualification, ready-mixed production and delivery, placement, consolidation, weather protection during placement, and evaluation and acceptance of structural cast-in-place concrete. (1.1)
NOTE Cast-in-place concrete is not one material but a family of proportioned mixtures, each engineered for the structural demand on a member, the exposure that member will meet in service, and the way the concrete will be delivered and placed into it. Two mixtures that both satisfy a 4000 psi design strength can behave completely differently in a freeze-thaw environment, in sulfate-bearing soil, or in a congested column cage, because strength and durability are governed by different parameters of the same mixture. (1.2)
NOTE The failure modes this standard controls are largely irreversible. Concrete is hidden inside formwork until stripping, it acquires its properties through reactions that cannot be interrupted and resumed, and a defective element usually cannot be corrected without demolition. Mixture qualification, delivery limits, consolidation, and field testing are therefore not administrative overhead; they are the last points at which defective work can still be stopped. (1.3)
1.4 Concrete and its constituent materials shall comply with ACI 301, and where structural performance is established by design, with ACI 318.
NOTE The work of the following standards is coordinated with, but not specified by, this standard. (1.5)
  • Formwork design, form materials and ties, release agents, shoring and reshoring, and form and shore removal — Concrete FormworkConcrete Formwork and AccessoriesResolves to the current adopted revision.sync/concrete-formwork.
  • Reinforcing bar supply, fabrication, placement, support, splicing, and concrete cover — Concrete ReinforcementConcrete ReinforcementResolves to the current adopted revision.sync/concrete-reinforcement.
  • Curing methods and duration, surface finishing, floor flatness and levelness, and surface-defect acceptance — Concrete Curing And FinishingConcrete Curing and FinishingResolves to the current adopted revision.sync/concrete-curing-and-finishing.
  • Joint type selection, joint layout and spacing, joint preparation and sealing, and waterstops — Concrete Joints And WaterstopsConcrete Construction Joints and WaterstopsResolves to the current adopted revision.sync/concrete-joints-and-waterstops.
  • Embedded plates and anchor rods, bar supports, dovetail slots, and under-slab vapor retarder placement — Concrete AccessoriesConcrete Accessories and EmbedsResolves to the current adopted revision.sync/concrete-accessories.
  • Assessment and repair of hardened, deteriorated, or defective concrete — Concrete Repair And RestorationConcrete Repair and RestorationResolves to the current adopted revision.sync/concrete-repair-and-restoration.
  • Subgrade preparation and structural design of slabs on grade — Slab On GradeSlab-on-GradeResolves to the current adopted revision.sync/slab-on-grade.
NOTE Plant-cast precast and prestressed concrete, post-tensioned concrete, shotcrete, concrete masonry, site paving and flatwork outside the building line, equipment pads, and mass concrete for dams and similar hydraulic structures lie outside this standard. (1.6)

2 Referenced Standards

2.1 Materials, production, delivery, placement, and testing shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ACI 214R Evaluation of Strength Test Results of Concrete
ACI 301 Specifications for Concrete Construction
ACI 305R Guide to Hot Weather Concreting
ACI 306R Guide to Cold Weather Concreting
ACI 309R Guide for Consolidation of Concrete
ACI 318 Building Code Requirements for Structural Concrete and Commentary
ASTM C31/C31M Making and Curing Concrete Test Specimens in the Field
ASTM C33/C33M Concrete Aggregates
ASTM C39/C39M Compressive Strength of Cylindrical Concrete Specimens
ASTM C42/C42M Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
ASTM C94/C94M Ready-Mixed Concrete
ASTM C138/C138M Density, Yield, and Air Content of Concrete (Gravimetric)
ASTM C143/C143M Slump of Hydraulic-Cement Concrete
ASTM C150/C150M Portland Cement
ASTM C157/C157M Length Change of Hardened Hydraulic-Cement Mortar and Concrete
ASTM C172/C172M Sampling Freshly Mixed Concrete
ASTM C173/C173M Air Content of Freshly Mixed Concrete by the Volumetric Method
ASTM C231/C231M Air Content of Freshly Mixed Concrete by the Pressure Method
ASTM C260/C260M Air-Entraining Admixtures for Concrete
ASTM C330/C330M Lightweight Aggregates for Structural Concrete
ASTM C494/C494M Chemical Admixtures for Concrete
ASTM C595/C595M Blended Hydraulic Cements
ASTM C618 Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete
ASTM C803/C803M Penetration Resistance of Hardened Concrete
ASTM C805/C805M Rebound Number of Hardened Concrete
ASTM C989/C989M Slag Cement for Use in Concrete and Mortars
ASTM C1017/C1017M Chemical Admixtures for Use in Producing Flowing Concrete
ASTM C1064/C1064M Temperature of Freshly Mixed Hydraulic-Cement Concrete
ASTM C1074 Estimating Concrete Strength by the Maturity Method
ASTM C1077 Agencies Testing Concrete and Concrete Aggregates for Use in Construction
ASTM C1157/C1157M Performance Specification for Hydraulic Cement
ASTM C1218/C1218M Water-Soluble Chloride in Mortar and Concrete
ASTM C1231/C1231M Use of Unbonded Caps in Determination of Compressive Strength of Hardened Cylindrical Concrete Specimens
ASTM C1240 Silica Fume Used in Cementitious Mixtures
ASTM C1260 Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)
ASTM C1293 Length Change of Concrete Due to Alkali-Silica Reaction
ASTM C1567 Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate
ASTM C1602/C1602M Mixing Water Used in the Production of Hydraulic Cement Concrete
ASTM C1610/C1610M Static Segregation of Self-Consolidating Concrete Using Column Technique
ASTM C1611/C1611M Slump Flow of Self-Consolidating Concrete
ASTM C1621/C1621M Passing Ability of Self-Consolidating Concrete by J-Ring
ASTM C1778 Reducing the Risk of Deleterious Alkali-Aggregate Reaction in Concrete
ASTM C1866/C1866M Ground-Glass Pozzolan for Use in Concrete

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review and acceptance before concrete is ordered for the affected element:
  • Concrete mixture design for each mixture class, identifying every cementitious material, aggregate, admixture, and water source, the batch weights, the water-cementitious materials ratio, the design air content, the design slump or slump flow, and the exposure classes the mixture is proportioned to satisfy
  • Documentation establishing the required average compressive strength for each mixture, consisting of the production strength record and its calculated standard deviation, the trial mixture results, or both
  • Product data and certificates of conformance for each cementitious material, aggregate source, and admixture
  • Qualification data for any mixing water source other than potable water, including the solids content of reclaimed water
  • Aggregate gradation analysis and alkali-aggregate reactivity evaluation for each aggregate source
  • Placement plan for each element that cannot be placed continuously from a single position, identifying the placement sequence, the location of construction joints, the placement rate, the consolidation equipment, and the anticipated concrete and ambient temperatures
  • Hot-weather and cold-weather concreting plans covering the measures selected in the datasheet and the temperature-monitoring method
Action Submittals Requiredcheckbox
☑ Concrete mixture design for each mixture class
☑ Required average strength documentation for each mixture
☑ Cementitious material certificates of conformance
☑ Aggregate gradation and reactivity evaluation
☑ Admixture product data and certificates
☐ Mixing water qualification for non-potable sources
☑ Concrete placement plan
☐ Hot-weather concreting plan
☐ Cold-weather concreting plan
3.1.2 Concrete shall not be placed in any element until the mixture design for that element has been reviewed and accepted.
3.1.3 A submittal that omits a required item shall be returned without review, and the review period shall restart on resubmittal.

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following before the first structural concrete placement:
  • Name, address, and ASTM C1077 qualification documentation for the proposed testing agency, identifying the registered professional engineer providing technical direction
  • Certifications held by each technician who will perform field sampling and testing, with the certifying body and the expiration date for each
  • Batch plant qualification records for every plant that will supply the project
  • Sample delivery ticket demonstrating that each item required by ASTM C94/C94M will be reported
Informational Submittals Requiredcheckbox
☑ Testing agency name and qualification documentation
☑ Field testing technician certifications
☑ Batch plant qualification records
☐ Sample delivery ticket format

3.3 Closeout Submittals

3.3.1 The Contractor shall submit the following before concrete work is accepted:
  • Complete set of field test reports organized by mixture class and placement date, including compressive strength results, fresh concrete test results, and concrete temperature records
  • Delivery tickets for all concrete incorporated in the work
  • Record of every load rejected, every water addition made at the point of discharge, and every corrective action taken
  • Record of the placement dates, ambient conditions, and protection measures for each element placed under hot-weather or cold-weather provisions
  • Record of every defect reported to the Engineer of Record and the disposition directed for it
Closeout Submittals Requiredcheckbox
☑ Field test reports organized by mixture and date
☑ Delivery tickets for concrete incorporated in the work
☑ Record of rejected loads and corrective actions
☐ Hot-weather and cold-weather placement records
☑ Defect reports and directed dispositions

4 Quality Assurance

4.1 Concrete Producer and Batch Plant Qualification

4.1.1 Concrete shall be furnished by a ready-mixed concrete producer whose plant, equipment, and delivery vehicles conform to ASTM C94/C94M.
4.1.2 Each supplying plant shall hold a qualification on one of the bases indicated in the datasheet, and the Contractor shall furnish evidence of that qualification before the first delivery.
Acceptable Bases for Batch Plant Qualificationcheckbox
☑ National Ready Mixed Concrete Association plant certification
☑ State department of transportation plant approval
☐ Producer quality program audited by an independent agency
4.1.3 Where more than one plant supplies the project, every plant shall batch from the same accepted mixture design for a given mixture class.
4.1.4 The delivery ticket shall identify which plant produced the load.
NOTE Supplying a large continuous placement from two plants is ordinary practice and is not itself a defect. The risk it introduces is that the two plants draw from different aggregate stockpiles and different cement silos, so the concrete satisfies the same specification while differing in setting time, finishing window, and color across a single monolithic surface. (4.1.5)

4.2 Testing Agency Qualifications

4.2.1 The testing agency performing acceptance testing shall conform to ASTM C1077 and shall be under the technical direction of a professional engineer registered in the jurisdiction of the project.
4.2.2 Field sampling and testing shall be performed by technicians holding current certification for each test method they perform.
4.2.3 The party indicated in the datasheet shall engage and pay the acceptance testing agency.
Acceptance Testing Agency Engaged Byradio
● Owner
○ Contractor
4.2.4 The testing agency shall transmit each test result to the Engineer of Record and to the Contractor within 24 hours of the test.
4.2.5 The Contractor shall give the testing agency at least 24 hours notice of each placement, safe access to the point of discharge, and protected space on site for the initial curing of standard-cured specimens.
NOTE Acceptance decisions rest with the Engineer of Record regardless of which party engages the testing agency. The agency reports results; it does not accept or reject work, and its presence transfers no part of the Contractor's responsibility for furnishing conforming concrete. (4.2.6)

4.3 Pre-Placement Conference

4.3.1 A pre-placement conference shall be held before the first structural concrete placement.
4.3.2 The conference shall be attended by the Contractor's superintendent, the concrete producer's technical representative, the testing agency's project manager, the finishing subcontractor, and the Engineer of Record.
4.3.3 The conference agenda shall cover the accepted mixture designs, the placement sequence and joint locations, the consolidation method and equipment, the hot-weather and cold-weather plans, the curing plan required by Concrete Curing And FinishingConcrete Curing and FinishingResolves to the current adopted revision.sync/concrete-curing-and-finishing, the field testing plan, and the procedure for handling a rejected load in the middle of a placement.

4.4 Mixture Qualification

4.4.1 The required average compressive strength shall be established for each mixture on a basis indicated in the datasheet, in accordance with ACI 301.
Permitted Basis for Establishing Required Average Strengthcheckbox
☑ Production strength record with calculated standard deviation
☑ Trial mixtures proportioned across a strength range
☐ Conservative overdesign without a strength record
4.4.2 Where a production strength record is used, the record shall satisfy the number of tests, the recency, and the similarity-of-materials conditions of ACI 301, and the standard deviation shall be computed in accordance with ACI 214R.
4.4.3 Where fewer test results are available than the record basis requires, the required average strength shall be increased by the applicable modification factor of ACI 301.
4.4.4 The Contractor shall proportion each mixture to the required average compressive strength, not to the specified compressive strength.
NOTE The specified compressive strength is a design value: the strength the structure was analyzed for and the floor below which the material is presumed deficient. Production concrete varies from batch to batch, so a mixture proportioned to average exactly the specified strength would fall below it in roughly half of all tests. The required average strength is the target that shifts the whole distribution up far enough that the acceptance criteria are met at the variability the producer can actually demonstrate. (4.4.5)
NOTE A production strength record reflects the variability of the producing plant under working conditions, while trial mixtures reflect laboratory batching and curing. Where the two disagree, the record is the closer predictor of what will arrive at the point of discharge. (4.4.6)
NOTE Acceptance of a mixture design confirms only that the submitted proportions satisfy this standard. It transfers to the Engineer of Record no responsibility for batching, delivery, placement, or the strength actually produced. (4.4.7)

5 Exposure Classes and Durability Basis

NOTE ACI 318 assigns every concrete member four exposure classes — freezing and thawing, sulfate, contact with water, and corrosion protection of reinforcement — and from those classes fixes the maximum water-cementitious materials ratio, the minimum specified compressive strength, the air content, the cementitious materials permitted, and the allowable chloride ion content. The classes are the controlling input to every mixture on the project, not a durability footnote appended to a strength requirement. (5.1)
NOTE Specifying strength alone is the most common durability defect in structural concrete. A mixture can reach 4000 psi comfortably at a water-cementitious materials ratio of 0.55 and still scale apart in three winters of deicing salt, because resistance to freezing and thawing comes from entrained air and low permeability rather than from strength. (5.2)
5.3 The Engineer of Record shall assign the exposure classes for each member and shall record them in the datasheet.
Freeze-Thaw Exposure Classselect
F0 — not exposed to freezing-and-thawing cycles
F1 — exposed to freezing-and-thawing cycles with limited exposure to water
F2 — exposed to freezing-and-thawing cycles with frequent exposure to water
F3 — exposed to freezing-and-thawing cycles with frequent exposure to water and to deicing chemicals
Sulfate Exposure Classselect
S0 — negligible water-soluble sulfate in soil and in water
S1 — moderate sulfate concentration in soil or water, including seawater exposure
S2 — severe sulfate concentration in soil or water
S3 — very severe sulfate concentration in soil or water
Contact-with-Water Exposure Classselect
W0 — concrete dry in service
W1 — concrete in contact with water where low permeability is not required
W2 — concrete in contact with water where low permeability is required
Corrosion-Protection Exposure Classselect
C0 — concrete dry or protected from moisture in service
C1 — concrete exposed to moisture but not to an external source of chlorides
C2 — concrete exposed to moisture and to an external source of chlorides
5.4 The sulfate exposure class shall be assigned from testing of the site soil and groundwater reported in the geotechnical investigation, using the concentration limits of ACI 318 Table 19.3.1.1.
5.5 Where a member is subject to more than one condition within a category, the more severe class of that category shall be assigned.
5.6 The maximum water-cementitious materials ratio, the minimum specified compressive strength, the cementitious material restrictions, and the maximum water-soluble chloride ion content for each mixture shall satisfy ACI 318 Table 19.3.2.1 for the exposure classes assigned to the members that mixture serves.
5.7 The water-soluble chloride ion content of the hardened concrete shall be determined in accordance with ASTM C1218/C1218M at the age required by ACI 318.
NOTE Assigning a severe exposure class where the condition does not exist is not a cost-free conservatism. An F3 assignment forces entrained air into the mixture, and entrained air in an interior floor slab that will be hard-troweled is a recognized cause of surface blistering and delamination. (5.8)

6 Concrete Mixture Classes

NOTE A mixture class is a distinct proportioned mixture with its own strength, exposure, and workability requirements, and each class carries its own qualification, submittal, and strength record. Classes multiply for real reasons: a mat foundation and an interior column can share a specified strength while needing different aggregate sizes, different delivery temperatures, and different admixtures. (6.1)
6.2 The mixture classes required for the project shall be as indicated in the datasheet.
Mixture Classes Requiredcheckbox
☑ Footings, foundations, and grade beams
☐ Below-grade walls
☐ Slabs on grade
☐ Elevated slabs and decks
☐ Columns and structural walls above grade
☐ Exterior structural concrete exposed to weather
☐ Structural lightweight concrete
☐ Lean concrete fill and mud mats
6.3 The specified compressive strength for each mixture class shall be as indicated in the datasheet.
Specified Compressive Strength — Footings, Foundations, and Grade Beamsrange
psi
2500300035004000450050006000700080001000012000
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
Specified Compressive Strength — Below-Grade Wallsrange
psi
2500300035004000450050006000700080001000012000
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
Specified Compressive Strength — Slabs on Graderange
psi
25003000350040004500500060008000
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
Specified Compressive Strength — Elevated Slabs and Decksrange
psi
300035004000450050006000700080001000012000
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
Specified Compressive Strength — Columns and Structural Walls Above Graderange
psi
3000350040004500500060007000800010000120001400016000
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
Specified Compressive Strength — Lean Concrete Fill and Mud Matsrange
psi
50010001500200025003000
NOTE Specified compressive strength is an output of the structural analysis of a member, so it is recorded on the structural drawings rather than chosen when the specification is written. A template that asserts a strength invites a project to accept a number nobody designed for. (6.4)
6.5 Where the exposure classes assigned to a member require a higher minimum compressive strength than the structural design, the higher value shall govern.
6.6 Each mixture class shall carry a unique designation, and that designation shall appear on the mixture design submittal, on every delivery ticket, and on every test report for that mixture.
6.7 Where a limit on drying shrinkage is indicated in the datasheet, the mixture design submittal shall demonstrate compliance by testing in accordance with ASTM C157/C157M at the drying age stated on the submittal.
Maximum Drying Shrinkagerange
%
0.020.030.0350.040.0450.050.060.08
6.8 Where a minimum cementitious materials content is indicated in the datasheet, each mixture shall meet or exceed it.
Minimum Cementitious Materials Contentrange
lb/cy
400800
NOTE Drying shrinkage is what makes a slab curl at its joints and crack between them, and it is driven mostly by the volume of water and paste in the mixture rather than by its strength. Limiting it is a mixture-level control that competes directly with workability, which is why it is specified where slab performance governs and left unspecified where it does not. (6.9)
NOTE A minimum cementitious materials content buys finishability: a lean mixture screeds and floats badly and leaves an open, dusting surface. It also works against the shrinkage and heat limits above, so the three constraints are set together or one of them silently loses. (6.10)

7 Maximum Water-Cementitious Materials Ratio

NOTE The water-cementitious materials ratio is the strongest single control on the permeability of concrete, and permeability governs nearly every durability mechanism that attacks it: chloride ingress to the reinforcement, sulfate attack on the paste, freeze-thaw damage, and the moisture supply that drives alkali-silica reaction. It is also the parameter most easily destroyed on site, because a water addition small enough to look harmless moves the ratio further than most engineers expect. (7.1)
7.2 The maximum water-cementitious materials ratio for each mixture shall be the lesser of the value indicated in the datasheet and the value required by ACI 318 Table 19.3.2.1 for the exposure classes assigned to that mixture.
Maximum Water-Cementitious Materials Ratiorange
0.320.360.380.40.420.450.480.50.550.60.65
7.3 Free water contributed by aggregate moisture, by ice batched as part of the mixing water, by liquid admixtures, and by any water added at the point of discharge shall be included in the calculation of the water-cementitious materials ratio.
NOTE Mixtures proportioned below a water-cementitious materials ratio of roughly 0.40 produce very little bleed water. The finishing window shortens, and early curing stops being good practice and becomes the difference between a sound surface and a plastic-cracked one. (7.4)

8 Cementitious Materials

8.1 Hydraulic Cement

8.1.1 Hydraulic cement shall be limited to the types indicated in the datasheet, and each shall conform to the specification under which its type is designated.
Permitted Hydraulic Cement Typescheckbox
☐ Portland cement Type I under ASTM C150/C150M
☑ Portland cement Type II under ASTM C150/C150M
☑ Portland cement dual-certified as Type I and Type II under ASTM C150/C150M
☐ Portland cement Type III under ASTM C150/C150M
☐ Portland cement Type V under ASTM C150/C150M
☑ Portland-limestone cement Type IL under ASTM C595/C595M
☐ Portland-slag cement Type IS under ASTM C595/C595M
☐ Portland-pozzolan cement Type IP under ASTM C595/C595M
☐ Ternary blended cement Type IT under ASTM C595/C595M
☐ Hydraulic cement under the performance requirements of ASTM C1157/C1157M
8.1.2 Cementitious materials for sulfate exposure classes S1, S2, and S3 shall satisfy the cement type and supplementary cementitious material requirements of ACI 318 Table 19.3.2.1 for the assigned class.
8.1.3 Where a cement of high early strength is used, the mixture design submittal shall state the resulting increase in early heat of hydration, and the Contractor shall include the corresponding thermal-control measures in the placement plan.
8.1.4 A single cement source and type shall be used for all concrete of a given mixture class unless a change is accepted in writing by the Engineer of Record.
NOTE High-early-strength cement reaches a given strength sooner because it is ground finer and hydrates faster, and the same reaction releases its heat sooner. In a thin section placed in cold weather that is an advantage; in a thick element, or in warm weather, it raises the peak temperature, shortens the finishing window, and increases the risk of thermal cracking. (8.1.5)
NOTE Portland-limestone cement replaces part of the clinker with finely ground limestone and is produced and specified as a cement rather than as a supplementary cementitious material. A mixture using it is not thereby a blended mixture, and the supplementary cementitious material limits below apply only to what is added at the batch plant. (8.1.6)

8.2 Supplementary Cementitious Materials

8.2.1 Supplementary cementitious materials shall be limited to the materials indicated in the datasheet.
Permitted Supplementary Cementitious Materialscheckbox
☑ Class F fly ash under ASTM C618
☐ Class C fly ash under ASTM C618
☐ Natural pozzolan under ASTM C618
☑ Slag cement under ASTM C989/C989M
☐ Silica fume under ASTM C1240
☐ Ground-glass pozzolan under ASTM C1866/C1866M
☐ No supplementary cementitious materials permitted
8.2.2 The maximum content of each supplementary cementitious material, and of all of them combined, shall be as indicated in the datasheet, expressed as a percentage by mass of the total cementitious materials.
Maximum Fly Ash Contentrange
%
050
Maximum Slag Cement Contentrange
%
080
Maximum Silica Fume Contentrange
%
015
Maximum Total Supplementary Cementitious Material Contentrange
%
080
8.2.3 Where concrete is assigned to exposure class F3, the content of each supplementary cementitious material and the total of all of them shall not exceed the limits of ACI 318 for that class.
8.2.4 The mixture design submittal shall state the age at which each mixture containing supplementary cementitious materials attains its specified compressive strength.
NOTE Supplementary cementitious materials react with the calcium hydroxide released by cement hydration rather than with water directly, so they build strength later and, in exchange, produce a denser and markedly less permeable paste. The practical consequences are a slower early strength gain that shifts formwork and loading schedules, a longer curing period, and substantially better long-term performance wherever chloride or sulfate ingress is the governing durability demand. (8.2.5)
NOTE Silica fume has a surface area roughly two orders of magnitude greater than portland cement. That is why it reduces permeability so sharply at low replacement rates, and also why a silica fume mixture bleeds almost nothing and will crack in the plastic state if the surface is left unprotected between screeding and curing. (8.2.6)

9 Aggregates

9.1 Aggregate Type and Size

9.1.1 Aggregate for each mixture class shall be of the density class indicated in the datasheet.
Aggregate Density Classselect
Normalweight aggregate conforming to ASTM C33/C33M
Structural lightweight aggregate conforming to ASTM C330/C330M
Sand-lightweight combination of normalweight fine and lightweight coarse aggregate
9.1.2 The nominal maximum size of coarse aggregate shall be as indicated in the datasheet.
Nominal Maximum Coarse Aggregate Sizerange
in
0.3750.50.7511.52
9.1.3 The nominal maximum aggregate size shall not exceed one-fifth of the narrowest dimension between form faces, one-third of the depth of a slab, or three-quarters of the minimum clear spacing between individual reinforcing bars, bundles of bars, or tendons, whichever of these is least.
9.1.4 Where the nominal maximum size indicated in the datasheet exceeds any of those limits at a specific member, the Contractor shall notify the Engineer of Record before placement, and the Engineer of Record shall direct either a smaller aggregate for that member or a revision to the member.
9.1.5 Coarse and fine aggregate for normalweight concrete shall conform to ASTM C33/C33M.
9.1.6 Fine aggregate shall have a fineness modulus between 2.3 and 3.1, and the fineness modulus of the aggregate supplied shall not vary from the value used in the mixture design by more than 0.20.
9.1.7 Aggregate from more than one source shall not be combined within a single mixture class unless that combination was used in the trial mixtures or the strength record that qualified the mixture.
NOTE Larger aggregate reduces the paste volume needed for a given workability, which lowers water demand, drying shrinkage, and cost. Smaller aggregate travels through congested reinforcement and into thin sections that larger stone bridges across. The governing constraint is almost always the bar spacing at the most congested member in the class rather than at the average member. (9.1.8)
9.1.9 The equilibrium density of structural lightweight concrete shall be as indicated in the datasheet.
Equilibrium Density — Structural Lightweight Concreterange
pcf
9095100105110115120125
Per drawings — concrete mixture schedule on the structural drawings (deferred by default)
9.1.10 Lightweight aggregate shall be pre-wetted before batching to the moisture condition assumed in the mixture design.
NOTE Lightweight aggregate is porous, and dry aggregate keeps absorbing mixing water after batching. A load then leaves the plant at its design slump and arrives stiff, which is the single most common reason lightweight concrete draws a request for a water addition it does not actually need. Pre-wetting removes the mechanism. (9.1.11)

9.2 Alkali-Aggregate Reactivity

9.2.1 Each aggregate source shall be evaluated for alkali-silica and alkali-carbonate reactivity in accordance with ASTM C1778 before the mixture design is submitted.
9.2.2 The basis on which reactivity is addressed for each aggregate source shall be as indicated in the datasheet.
Alkali-Aggregate Reactivity Basisselect
Documented field service record of the aggregate source in comparable exposure
Expansion testing of the aggregate under ASTM C1260 or ASTM C1293
Expansion testing of the aggregate and cementitious combination under ASTM C1567
Prescriptive mitigation by supplementary cementitious materials without expansion testing
Prescriptive mitigation by limiting the alkali content of the cementitious materials
Chemical mitigation by lithium-bearing admixture
9.2.3 An aggregate that exceeds the expansion limits of ASTM C1778 for the project exposure shall not be used unless the mixture incorporates a mitigation shown effective for that aggregate by ASTM C1567 testing or by an equivalent documented service record.
NOTE Alkali-silica reaction is slow, self-propagating, and effectively unrepairable. Reactive silica in the aggregate forms a gel that swells as it takes up water, cracking the concrete from the inside over years to decades. No test performed on the fresh concrete detects it, so the only available control is qualification of the aggregate and of the cementitious combination before the first placement. (9.2.4)

10 Mixing Water

10.1 Mixing water shall be potable, or shall conform to ASTM C1602/C1602M.
10.2 Wash water and water reclaimed from concrete production operations may be used only where the producer demonstrates conformance to ASTM C1602/C1602M and reports the solids content of the reclaimed water on the mixture design submittal.
10.3 Water shall not be used as mixing water in concrete containing reinforcement or other embedded metal where its chloride ion content would cause the concrete to exceed the water-soluble chloride ion limit required for the assigned corrosion-protection exposure class.
10.4 Ice used to reduce the temperature of the concrete shall be batched as part of the mixing water and shall be completely melted before discharge.
NOTE Water is the only constituent of concrete that is commonly available on site in unlimited quantity and at no cost, which is exactly why its control is written into so many separate requirements: the mixture design, the batching record, the delivery ticket, and the discharge policy each constrain the same quantity from a different direction. (10.5)

11 Chemical Admixtures

11.1 Chemical admixtures shall be limited to the types indicated in the datasheet.
Permitted Chemical Admixture Typescheckbox
☑ Air-entraining admixture under ASTM C260/C260M
☑ Type A water-reducing admixture under ASTM C494/C494M
☐ Type B retarding admixture under ASTM C494/C494M
☐ Type C accelerating admixture under ASTM C494/C494M
☑ Type D water-reducing and retarding admixture under ASTM C494/C494M
☐ Type E water-reducing and accelerating admixture under ASTM C494/C494M
☑ Type F high-range water-reducing admixture under ASTM C494/C494M
☐ Type G high-range water-reducing and retarding admixture under ASTM C494/C494M
☐ Type S specific-performance admixture under ASTM C494/C494M
☐ Admixture for flowing concrete under ASTM C1017/C1017M
☐ Viscosity-modifying admixture
☐ Shrinkage-reducing admixture
☐ Corrosion-inhibiting admixture
☐ Chloride-bearing accelerating admixture
11.2 The producer shall certify each admixture as compatible with the cement, the supplementary cementitious materials, the other admixtures, and the aggregate of the mixture in which it is used.
11.3 Admixture dosages shall remain within the range used to qualify the mixture, and a dosage outside that range shall require a revised mixture design submittal.
11.4 Admixtures containing intentionally added chlorides shall not be used in prestressed concrete, in concrete containing aluminum embedments, or in concrete in contact with galvanized steel.
11.5 Unless chloride-bearing accelerating admixtures are permitted in the datasheet, accelerating admixtures shall be non-chloride formulations.
11.6 Where chloride-bearing accelerating admixtures are permitted, the mixture design submittal shall demonstrate that the total water-soluble chloride ion content of the concrete remains within the limit required for the assigned corrosion-protection exposure class.
NOTE A water reducer lets a mixture reach its target slump at less water, which lowers the water-cementitious materials ratio without changing the cement content. That is the mechanism by which most durability requirements are met economically, and it is why a load that arrives stiff is corrected at the plant by dosage rather than on site by water. (11.7)
NOTE Retarders extend the time to initial set, which is what keeps successive lifts knitting together in hot weather or over a long haul. Accelerators shorten it, which is what allows finishing to start at a workable hour in cold weather. Both shift the finishing window rather than the final strength, and both interact with supplementary cementitious materials, so dosage is established by trial rather than from a catalog. (11.8)

12 Fresh Concrete Properties

12.1 Air Content

12.1.1 Air-entraining admixture shall conform to ASTM C260/C260M.
12.1.2 The total air content of concrete assigned to exposure class F1, F2, or F3 shall be as required by ACI 318 Table 19.3.3.1 for the assigned class and the nominal maximum aggregate size of the mixture.
12.1.3 The air content tolerance at the point of discharge shall be as specified in ASTM C94/C94M.
12.1.4 Each mixture shall be proportioned to reach its specified compressive strength at the required air content, and the strength loss caused by entrained air shall be offset within the mixture design rather than by reducing air on site.
12.1.5 Where a mixture is assigned exposure class F0 and serves an interior floor slab that will receive a hard-troweled finish, air-entraining admixture shall not be used in that mixture.
NOTE Entrained air is a system of very small, closely spaced voids distributed through the paste. When pore water freezes and expands, the voids give it somewhere to go; without them the expansion works against the paste and each cycle removes a little more of the surface. Entrapped air from poor consolidation does nothing of the kind, because those voids are too large and too widely separated to relieve the pressure. (12.1.6)
NOTE Each percentage point of total air costs roughly three to five percent of compressive strength, which is how an air content run high for workability quietly erodes the strength margin the mixture was proportioned for. (12.1.7)
NOTE Air deliberately entrained in a slab that is then hard-troweled can be sealed beneath the densified surface and lift it away as a blister or a delamination, because the finishing operation closes the surface before that air has escaped. (12.1.8)

12.2 Slump and Slump Flow

12.2.1 The specified slump for each conventional mixture shall be as indicated in the datasheet, measured in accordance with ASTM C143/C143M at the point of discharge.
Specified Slump — Conventional Mixturesrange
in
110
12.2.2 The slump tolerance shall be as specified in ASTM C94/C94M.
12.2.3 Each mixture shall be proportioned to deliver its specified slump at the point of discharge under the haul time and ambient conditions anticipated for the placements it serves.
12.2.4 Whether self-consolidating concrete may be used shall be as indicated in the datasheet.
Self-Consolidating Concreteradio
○ Permitted for any structural element
○ Permitted for elements the Engineer of Record accepts in writing
○ Not permitted
12.2.5 Where self-consolidating concrete is used, its slump flow shall be as indicated in the datasheet, measured in accordance with ASTM C1611/C1611M.
Slump Flow — Self-Consolidating Concreterange
in
1832
12.2.6 Where self-consolidating concrete is used, static segregation shall be verified in accordance with ASTM C1610/C1610M and passing ability shall be verified in accordance with ASTM C1621/C1621M as part of mixture qualification.
NOTE Slump measures the workability of a conventional mixture, and only indirectly: it responds to water content, admixture dosage, aggregate gradation, temperature, and elapsed time since batching all at once. Its value on site is as a consistency check, because a load arriving well outside the qualified slump is a load whose proportions are not what was accepted, whatever the cause. (12.2.7)
NOTE Self-consolidating concrete fills and de-airs without vibration, using a high-range water reducer together with a viscosity-modifying admixture to make a mixture that flows and levels under its own weight while holding its coarse aggregate in suspension. It is measured by slump flow rather than slump, it exerts full hydrostatic pressure on the formwork, and it is unforgiving of a segregating mixture, so adopting it changes the formwork design and the quality control regime rather than only the placement method. (12.2.8)

12.3 Concrete Temperature at Delivery

12.3.1 Concrete temperature shall be measured in accordance with ASTM C1064/C1064M at the point of discharge and shall be recorded with every strength test sample.
12.3.2 The maximum concrete temperature at the point of discharge shall be as indicated in the datasheet.
Maximum Concrete Temperature at Dischargerange
°F
707580859095
12.3.3 The minimum concrete temperature at placement shall be as required by ACI 306R for the least dimension of the section being placed.
NOTE Concrete temperature drives the rate of hydration, so it sets the finishing window at one end and the rate of strength gain at the other. A high delivery temperature costs water demand, slump retention, and ultimate strength, and it raises the peak temperature the element will reach. A low delivery temperature slows setting until finishing runs into the night and, below freezing, stops hydration outright. (12.3.4)

13 Batching, Mixing, and Delivery

13.1 Concrete shall be batched, mixed, and delivered in accordance with ASTM C94/C94M.
13.2 Each load shall be accompanied by a delivery ticket reporting every item required by ASTM C94/C94M together with the mixture class designation, the batch plant, the batch time, and the quantity of water withheld at the plant.
13.3 The maximum elapsed time from the introduction of mixing water to the completion of discharge shall be as indicated in the datasheet.
Maximum Elapsed Time from Batching to Completion of Dischargerange
min
45607590105120
13.4 Discharge shall be completed before the drum has revolved 300 times at mixing and agitating speed following the introduction of mixing water.
13.5 The field water addition policy for the project shall be as indicated in the datasheet.
Field Water Addition Policyradio
● One addition permitted at the point of discharge within the water withheld from the accepted mixture
○ No water addition permitted after the load leaves the batch plant
13.6 Where a water addition is permitted, it shall be made in a single increment before any part of the load has been discharged.
13.7 A water addition shall not cause the mixture to exceed the maximum water-cementitious materials ratio required for its exposure classes.
13.8 Concrete to which water has been added shall be mixed at mixing speed for at least 30 revolutions before discharge resumes.
13.9 Every water addition shall be recorded on the delivery ticket with the quantity added and the name of the person who authorized it.
13.10 Water shall be added only on the authorization of the Contractor's superintendent, who shall verify the remaining withheld water on the delivery ticket before authorizing it.
13.11 A load to which water was added outside the field water addition policy shall be rejected and shall not be placed in the work.
13.12 The cost of a rejected load, of its disposal, and of any delay it causes shall be borne by the Contractor, except where the rejection is caused by an act of the Owner or by a change directed in writing.
NOTE The water withheld at the plant is not spare water. It is the difference between the mixture's design water and the water actually batched, held back so the load can be brought to its design slump at the site instead of arriving over-wet. Water added beyond it raises the water-cementitious materials ratio, and the loss of strength and durability that follows is permanent and invisible until a cylinder breaks low or the surface scales years later. (13.13)

14 Placement and Consolidation

14.1 Pre-Placement Verification

14.1.1 Concrete shall not be placed in any element until formwork for that element has been inspected and released in accordance with Concrete FormworkConcrete Formwork and AccessoriesResolves to the current adopted revision.sync/concrete-formwork.
14.1.2 Concrete shall not be placed in any element until reinforcement placement, support, and cover for that element have been verified in accordance with Concrete ReinforcementConcrete ReinforcementResolves to the current adopted revision.sync/concrete-reinforcement.
14.1.3 Concrete shall not be placed in any element until embedded items, sleeves, anchor rods, and waterstops have been set and secured in accordance with Concrete AccessoriesConcrete Accessories and EmbedsResolves to the current adopted revision.sync/concrete-accessories and Concrete Joints And WaterstopsConcrete Construction Joints and WaterstopsResolves to the current adopted revision.sync/concrete-joints-and-waterstops.
14.1.4 Debris, standing water, ice, snow, and loose material shall be removed from the interior of the forms and from the placement surface immediately before concrete is placed.
14.1.5 The subgrade or supporting surface beneath a slab on grade shall be in the moisture condition required by Slab On GradeSlab-on-GradeResolves to the current adopted revision.sync/slab-on-grade at the time of placement.
14.1.6 Concrete shall not be placed until the testing agency technician is present at the point of discharge.
14.1.7 The Contractor's superintendent shall record the completion of each pre-placement verification, and the record shall be available to the Engineer of Record before placement begins.

14.2 Depositing Concrete

14.2.1 Each mixture shall be proportioned for the placement methods indicated in the datasheet.
Placement Methods the Mixtures Must Accommodatecheckbox
☑ Boom or line concrete pump
☐ Crane and bucket
☑ Direct chute from the truck
☐ Belt conveyor
☐ Concrete buggy or motorized cart
☐ Tremie placement under water
14.2.2 Concrete shall be deposited as near as practicable to its final position.
14.2.3 Concrete shall not be moved laterally into position by vibration.
14.2.4 The maximum free fall of concrete without a drop chute, tremie, or elephant trunk shall be as indicated in the datasheet.
Maximum Free Fall Without a Drop Chuterange
ft
345681015
14.2.5 Concrete shall not be permitted to fall against reinforcement, form faces, or embedded items in a manner that separates the coarse aggregate from the mortar.
14.2.6 Pump lines shall be primed with mortar or a proprietary priming material, and the priming material shall be discharged outside the work rather than into a structural element.
14.2.7 Water used to clean pump lines, buckets, or chutes shall be discharged outside the forms.
NOTE Free fall by itself is not what causes segregation, because a vertical drop into open air lands as a coherent stream. Segregation happens when the stream strikes something on the way down, so the height that matters is the height above the last obstruction. A congested column cage makes a 4 ft drop worse than a 12 ft drop into an empty form. (14.2.8)

14.3 Lift Depth and Placement Rate

14.3.1 The maximum depth of a single lift in walls and columns shall be as indicated in the datasheet.
Maximum Lift Depth — Walls and Columnsrange
in
1218243036
14.3.2 The rate of placement in vertical elements shall not exceed the rate assumed in the formwork design accepted under Concrete FormworkConcrete Formwork and AccessoriesResolves to the current adopted revision.sync/concrete-formwork.
14.3.3 Each lift shall be placed and consolidated before the lift beneath it has reached initial set.
14.3.4 The vibrator shall penetrate the full depth of the lift being placed and shall extend approximately 6 in. into the lift beneath it.
NOTE Lift depth is governed from two directions at once. It cannot exceed the reach over which the vibrator can genuinely consolidate, and the rate at which lifts are stacked cannot exceed the lateral pressure the formwork was designed for. The two limits are set by different parties and are the pair most often reconciled only after a form blows out. (14.3.5)

14.4 Consolidation

14.4.1 All concrete other than self-consolidating concrete shall be consolidated by internal mechanical vibration in accordance with ACI 309R.
14.4.2 The vibrator head shall be sized so that its radius of action covers the section being consolidated at the insertion spacing used.
14.4.3 Insertion points shall be spaced at not more than 1.5 times the radius of action of the vibrator head, and the insertion pattern shall leave no part of the placement outside the radius of action of an insertion.
14.4.4 The vibrator shall be inserted vertically and rapidly, held until the surface takes on a uniform sheen and air bubbles stop rising, and withdrawn slowly enough that the concrete closes behind it.
14.4.5 The vibrator shall not be dragged horizontally through the concrete and shall not be used as a rodding tool.
14.4.6 The vibrator shall not be held in sustained contact with reinforcement, embedded items, or form faces.
14.4.7 Re-vibration of a lift is permitted while the vibrator still sinks into the concrete under its own weight, and shall not be performed after initial set.
NOTE Consolidation is the operation that converts a placed mixture into the material the design assumed. Entrapped air occupies roughly 5 to 20 percent of the volume of freshly placed concrete, and every part of it left behind is lost strength, lost bond to the reinforcement, and a path for water. Honeycombing, sand streaking, and surface voids are the same defect seen from outside. (14.4.8)
NOTE Re-vibration within the plastic period closes the settlement cracks and voids that form as concrete bleeds and subsides around reinforcement, particularly over the top bars of deep members, and it does not reduce strength while the concrete still responds to the vibrator. (14.4.9)
NOTE Self-consolidating concrete is designed to fill and de-air without vibration, so vibrating it can drive the coarse aggregate down through the paste and produce exactly the segregation the mixture was formulated to avoid. (14.4.10)

14.5 Continuity of Placement

14.5.1 Concrete shall be placed continuously within each element or between the joints shown on the joint layout accepted under Concrete Joints And WaterstopsConcrete Construction Joints and WaterstopsResolves to the current adopted revision.sync/concrete-joints-and-waterstops.
14.5.2 The Contractor shall establish the placement rate, the number of trucks, and the discharge sequence needed to cover each layer before the layer beneath it reaches initial set, accounting for haul time, ambient conditions, and admixture dosage.
14.5.3 Where placement is interrupted for a period that puts the preceding layer at risk of initial set, the Contractor shall immediately notify the Engineer of Record.
14.5.4 Where the parties disagree whether an interruption has produced a cold joint, the Engineer of Record shall make the initial determination and shall direct either that placement resume, that the interruption be treated as a construction joint prepared in accordance with Concrete Joints And WaterstopsConcrete Construction Joints and WaterstopsResolves to the current adopted revision.sync/concrete-joints-and-waterstops, or that the element be evaluated as defective work.
NOTE A cold joint is the plane left where a layer of concrete reached initial set before the next layer was placed against it. It differs from a construction joint only in that it was not planned, not located where the design can tolerate it, and not prepared, so it carries reduced shear transfer and, below grade, a leakage path. (14.5.5)

15 Hot and Cold Weather Concreting

15.1 Hot Weather Placement

15.1.1 Hot weather concreting measures shall be implemented whenever the concrete temperature at discharge would otherwise exceed the maximum indicated in the datasheet, or whenever the calculated rate of evaporation from the concrete surface would exceed the threshold indicated in the datasheet.
Evaporation Rate Threshold Requiring Protective Measuresrange
lb/ft²/hr
0.050.10.150.20.250.3
15.1.2 The rate of evaporation shall be calculated from the concrete temperature, the ambient temperature, the relative humidity, and the wind speed in accordance with ACI 305R.
15.1.3 The hot weather measures available on the project shall be as indicated in the datasheet.
Hot Weather Concreting Measurescheckbox
☐ Substitution of ice for part of the batch water
☐ Sprinkling or shading of coarse aggregate stockpiles
☐ Liquid nitrogen cooling of the mixed concrete
☐ Reduced haul time and reduced load size
☐ Retarding admixture dosed for the anticipated haul and placement time
☐ Placement during the cooler hours of the day
☐ Wind screens at the perimeter of the placement
☐ Fog misting above the placement surface
☐ Evaporation retardant applied between screeding and finishing
☐ Sunshades over the placement area
15.1.4 Where the measures indicated in the datasheet are insufficient to hold the concrete at or below its maximum discharge temperature, placement shall not proceed until additional measures are agreed with the Engineer of Record.
NOTE Plastic shrinkage cracking occurs when water evaporates from the surface of fresh concrete faster than bleed water rises to replace it. The surface goes into tension at a moment when the concrete has almost no tensile strength, and it tears. The cracks run roughly parallel, extend a substantial fraction of the depth, do not close on their own, and cannot be troweled out once the concrete has stiffened. (15.1.5)
NOTE Low-bleed mixtures reach the evaporation threshold under conditions that would be harmless for a conventional mixture, because there is less bleed water available to replace what evaporates. A low water-cementitious materials ratio, silica fume, and a high fines content all produce that condition. (15.1.6)

15.2 Cold Weather Placement

15.2.1 Cold weather concreting measures shall be implemented when the ambient temperature is at or below 40°F, or is forecast to fall below 40°F at any time during the protection period, in accordance with ACI 306R.
15.2.2 The cold weather measures available on the project shall be as indicated in the datasheet.
Cold Weather Concreting Measurescheckbox
☐ Heated mixing water
☐ Heated aggregate
☐ Non-chloride accelerating admixture
☐ Insulating blankets over concrete and forms
☐ Insulated formwork left in place through the protection period
☐ Heated enclosure with vented combustion heaters
☐ Heated enclosure with electric or indirect-fired heaters
☐ Ground thawing before placement on grade
15.2.3 Concrete shall not be placed on or against frozen subgrade, frozen formwork, frozen reinforcement, ice, or snow.
15.2.4 Fresh concrete shall be protected from freezing until it has attained at least the compressive strength indicated in the datasheet, verified by field-cured specimens or by the maturity method.
Minimum Compressive Strength Before Exposure to Freezingrange
psi
5001000150020002500300035004000
15.2.5 The concrete temperature shall be maintained at or above the minimum required by ACI 306R for the least dimension of the section throughout the protection period.
15.2.6 The rate at which the concrete surface is allowed to cool at the end of the protection period shall not exceed the limit given by ACI 306R for the least dimension of the section.
15.2.7 The Contractor shall record the concrete surface temperature and the ambient temperature at intervals not exceeding 12 hours throughout the protection period and shall make the record available to the Engineer of Record on request.
15.2.8 Where a combustion heater is operated inside an enclosure, its exhaust shall be vented to the exterior of the enclosure, and the Contractor shall monitor the carbon monoxide concentration inside the enclosure throughout heater operation.
NOTE Where a combustion heater exhausts into an enclosure, the carbon dioxide in that exhaust reacts with the fresh concrete surface to form a soft, chalky, dusting layer, and the same exhaust accumulates carbon monoxide to concentrations lethal to the crew working inside. Venting the exhaust to the exterior removes both mechanisms at once. (15.2.9)
NOTE Concrete that freezes before it reaches roughly 500 psi is permanently damaged. The mixing water expands as it freezes and disrupts the paste structure while that structure is still forming, and warming the element afterward does not restore what was broken. (15.2.10)
NOTE Below about 50°F, hydration slows sharply, so a mixture that would be ready to finish at noon in summer is often not ready until the middle of the night. That schedule effect, rather than the risk of freezing, is what most often drives the choice between an accelerator and a heated enclosure. (15.2.11)

16 Thermal Control of Thick Sections

NOTE A thick element generates heat faster than it can shed it. Cement hydration is exothermic, the interior is insulated by the concrete around it, and the core of a mat foundation can run far above the temperature at which it was placed while the surface tracks the weather. Two distinct problems follow: the core gets hot enough to damage its own paste chemistry, and the difference between core and surface puts the cooler outer concrete into tension against a restrained interior. (16.1)
16.2 The least dimension above which a placement is subject to thermal control shall be as indicated in the datasheet.
Least Dimension Above Which Thermal Control Appliesrange
ft
1.5234568
16.3 The Contractor shall submit a thermal control plan for every placement subject to thermal control, identifying the predicted temperature history, the sensor locations, the insulation or cooling measures, and the criterion for ending temperature monitoring.
16.4 The maximum in-place concrete temperature and the maximum difference between the core temperature and the surface temperature shall be as indicated in the datasheet.
Maximum In-Place Concrete Temperaturerange
°F
140150158160170180
Maximum Temperature Difference Between Core and Surfacerange
°F
20253035404550
16.5 Concrete temperature shall be monitored at the predicted hottest point of the element, at a point within 2 in. of the nearest exposed surface, and at the ambient air, and shall be recorded at intervals not exceeding 2 hours until the maximum temperature difference has passed and is falling.
16.6 Where a monitored temperature exceeds either limit, the Contractor shall immediately notify the Engineer of Record, who shall make the initial determination whether the affected concrete is acceptable, requires evaluation, or requires replacement.
16.7 Insulation removed from a thick element at the end of the monitoring period shall be removed in stages where necessary to keep the surface cooling rate within the limit of ACI 306R for the least dimension of the section.
NOTE Peak core temperature is limited because concrete cured above roughly 160°F can form ettringite later, after the paste has hardened, and the expansion that accompanies it cracks the concrete from within years after placement. The core-to-surface difference is limited for an unrelated reason: the outer concrete contracts as it cools while the hot core does not, and beyond about 35°F of difference the resulting tension exceeds what young concrete can carry. (16.8)
NOTE Supplementary cementitious materials are the primary tool for both limits, because a mixture with a large fraction of slag cement or fly ash releases the same total heat more slowly and reaches a lower peak. Insulation works on the difference rather than the peak, by keeping the surface warm instead of cooling the core. (16.9)

17 Field Testing and Acceptance

17.1 Sampling and Test Frequency

17.1.1 Concrete shall be sampled at the point of discharge in accordance with ASTM C172/C172M.
17.1.2 The frequency of strength testing by volume placed shall be as indicated in the datasheet, and shall in no case be less frequent than the minimum required by ACI 318 Section 26.12.2.
Strength Test Frequency by Volume Placedrange
cy
255075100125150
17.1.3 At least one strength test shall be made for each mixture class on each day that class is placed.
17.1.4 At least one strength test shall be made for each 5000 ft² of slab or wall surface area placed.
17.1.5 The number of specimens cast for each strength test shall be as indicated in the datasheet.
Specimens Cast per Strength Testrange
specimens
28
Default: 5 specimens
17.1.6 A strength test shall be the average compressive strength of at least two specimens tested at the acceptance age, and the remaining specimens of the set shall be allocated to early-age indication and to reserve.
17.1.7 Specimens for acceptance shall be made and standard-cured in accordance with ASTM C31/C31M and tested in accordance with ASTM C39/C39M.
17.1.8 Unbonded caps used in compression testing shall conform to ASTM C1231/C1231M.
17.1.9 The acceptance test age shall be as indicated in the datasheet.
Acceptance Test Agerange
days
3714285690
17.1.10 Where Concrete FormworkConcrete Formwork and AccessoriesResolves to the current adopted revision.sync/concrete-formwork requires strength verification before form or shore removal, the testing agency shall cast additional field-cured specimens for that purpose, and those specimens shall not be used for acceptance.
NOTE A strength test is the average of the specimens tested at the acceptance age, not an individual cylinder. A single low cylinder is ordinary scatter, and the acceptance criteria are written against the test average precisely so that specimen-handling variability does not condemn conforming concrete. (17.1.11)
NOTE Where a mixture develops much of its strength after 28 days, as mixtures with a high proportion of slag cement or fly ash do, an acceptance age later than 28 days measures what the structure will actually have and avoids rejecting concrete that is merely slow. The age has to be chosen before the first placement, because the structural schedule depends on it. (17.1.12)

17.2 Fresh Concrete Testing

17.2.1 At each sampling made for strength testing, the testing agency shall perform and record the tests indicated in the datasheet:
  • Temperature of the freshly mixed concrete in accordance with ASTM C1064/C1064M
  • Slump in accordance with ASTM C143/C143M, or slump flow in accordance with ASTM C1611/C1611M for self-consolidating concrete
  • Air content in accordance with ASTM C231/C231M for normalweight concrete, or ASTM C173/C173M for lightweight and other highly porous aggregate concrete
  • Density and yield in accordance with ASTM C138/C138M
  • Batch time, arrival time, and discharge time taken from the delivery ticket
Fresh Concrete Tests Required at Each Samplingcheckbox
☑ Temperature of the freshly mixed concrete
☑ Slump or slump flow at the point of discharge
☑ Air content by the pressure method
☐ Air content by the volumetric method
☑ Density and yield of the fresh concrete
☑ Batch and discharge times from the delivery ticket
NOTE The pressure method for air content is invalid on lightweight and other highly porous aggregate, because the pressure applied in the test compresses air held inside the aggregate pores and the meter reads that as entrained air. The volumetric method is the one that gives a true reading on those mixtures. (17.2.2)

17.3 Rejection of Fresh Concrete

17.3.1 A load shall be rejected at the point of discharge, and no part of it placed in the work, where any of the following conditions exists:
  • The slump or slump flow lies outside the specified value by more than the tolerance of ASTM C94/C94M
  • The air content lies outside the required value by more than the tolerance of ASTM C94/C94M
  • The concrete temperature is above the maximum or below the minimum required for the placement
  • The elapsed time or the drum revolutions exceed the limits of this standard
  • Water was added outside the field water addition policy
  • The delivery ticket does not identify the load as the accepted mixture class for the element being placed
17.3.2 The testing agency shall notify the Contractor and the Engineer of Record immediately when a rejection condition is identified.
17.3.3 The Contractor shall provide a replacement load without interrupting the placement.

17.4 Acceptance of Hardened Concrete

17.4.1 The strength of a mixture class shall be accepted when both of the following conditions of ACI 318 Section 26.12.3 are satisfied:
  1. Every arithmetic average of any three consecutive strength tests equals or exceeds the specified compressive strength.
  2. No individual strength test falls below the specified compressive strength by more than 500 psi where that strength is 5000 psi or less, or by more than ten percent of it where it exceeds 5000 psi.
17.4.2 Where a strength test falls below the specified compressive strength, the Contractor shall within 48 hours review and report to the Engineer of Record the batching records, the delivery tickets, the fresh concrete test results, and the curing history for the concrete that test represents.
17.4.3 Where a strength test fails either acceptance condition, the Engineer of Record shall direct the steps required by ACI 318 Section 26.12.4 to establish the adequacy of the concrete in the affected area.
17.4.4 Cores taken to evaluate a low strength test shall be obtained and tested in accordance with ASTM C42/C42M.
17.4.5 Concrete in the area represented by cores shall be accepted as structurally adequate where the average compressive strength of three cores is at least 85 percent of the specified compressive strength and no single core falls below 75 percent of it.
17.4.6 The Engineer of Record shall determine the number and location of cores and shall direct the repair of core holes in accordance with Concrete Repair And RestorationConcrete Repair and RestorationResolves to the current adopted revision.sync/concrete-repair-and-restoration.
17.4.7 The cost of investigating a low strength test shall be assigned as indicated in the datasheet.
Cost Responsibility for Investigation of a Low Strength Testradio
○ Contractor bears all investigation costs
● Owner bears the cost where the investigation establishes the concrete as adequate and the Contractor bears it otherwise
○ Owner bears all investigation costs
17.4.8 The Contractor shall not defer investigation of a low strength trend to the acceptance age where the early-age specimens have already shown it.
NOTE For a conventional portland cement mixture, the 7-day strength typically falls between 65 and 75 percent of the 28-day strength. A 7-day result well below that band is early warning that the acceptance test will fall short, while a mixture carrying a high proportion of slag cement or fly ash sits below the band legitimately and still reaches its specified strength at the acceptance age. (17.4.9)
NOTE Failure of the three-consecutive-test average and failure of a single test mean different things. A low running average says the mixture is centered too low and the proportioning or the plant control has to change; a single low test against a healthy average says one load or one set of specimens went wrong. Treating the two as the same event produces either an unnecessary coring program or an uncorrected mixture. (17.4.10)

17.5 Supplementary In-Place Testing

17.5.1 In-place test methods may be used to estimate strength for construction decisions before acceptance-age results are available, using rebound number in accordance with ASTM C805/C805M, penetration resistance in accordance with ASTM C803/C803M, or the maturity method in accordance with ASTM C1074.
17.5.2 An in-place method shall be correlated to standard-cured specimen results for the specific mixture before its results are relied upon.
17.5.3 In-place test results shall not be used as the basis for acceptance of concrete strength.
NOTE In-place methods measure a surface property or a temperature history and infer strength from a correlation. That correlation is mixture-specific and degrades with age, carbonation, surface moisture, and aggregate type, which is why these methods serve well for deciding when to strip a form and poorly for deciding whether a structure is adequate. (17.5.4)

18 Defective Work

18.1 The Contractor shall report to the Engineer of Record every defect discovered after form removal, including honeycombing, cold joints, voids, exposed reinforcement, and cracks, before any corrective work begins.
18.2 The Contractor shall not repair, patch, coat, or conceal a defect before the Engineer of Record has reviewed it and directed a disposition in writing.
18.3 Concealing a defect before review shall be grounds for rejection of the element.
18.4 The Engineer of Record shall make the initial determination whether a reported defect is cosmetic, repairable, or cause for removal and replacement.
18.5 Repairs directed by the Engineer of Record shall be executed in accordance with Concrete Repair And RestorationConcrete Repair and RestorationResolves to the current adopted revision.sync/concrete-repair-and-restoration.
18.6 Surface defects attributable to finishing or curing shall be evaluated and remediated in accordance with Concrete Curing And FinishingConcrete Curing and FinishingResolves to the current adopted revision.sync/concrete-curing-and-finishing.
18.7 The cost of removing and replacing concrete that fails to conform to this standard, and the cost of correcting the work of other trades disturbed by that removal, shall be borne by the Contractor, except where the nonconformance is caused by an act of the Owner or by a change directed in writing.
NOTE A defect found at form removal is evidence about a process, not only about one element. Honeycombing at the base of a wall says the lift depth or the vibrator reach was wrong and the next wall will look the same; a cold joint says the placement rate never matched the delivery rate. Reporting before repair is what preserves that evidence. (18.8)

19 Protection and Load Application

19.1 Curing of each placement shall begin and continue in accordance with Concrete Curing And FinishingConcrete Curing and FinishingResolves to the current adopted revision.sync/concrete-curing-and-finishing.
19.2 Construction loads shall not be applied to any element until the strength required by Concrete FormworkConcrete Formwork and AccessoriesResolves to the current adopted revision.sync/concrete-formwork for that loading condition has been demonstrated by field-cured specimens or by the maturity method.
19.3 Concrete surfaces shall be protected from impact, abrasion, staining by stored materials, and chemical spillage until the finish or covering scheduled for that surface is installed.
19.4 The condition of a completed concrete surface shall be documented before the operations of another trade begin over it, and damage caused by those operations shall be repaired at the expense of the party causing it.

20 Warranty

20.1 The Contractor shall warrant the concrete work against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
Warranty Periodrange
years
1235
20.2 The warranty shall cover strength deficiency, cracking attributable to the Contractor's means and methods, surface scaling within the exposure classes specified for the element, and delamination of concrete placed under this standard.
20.3 Where the parties disagree on the cause of a defect claimed under the warranty, the Engineer of Record shall make the initial determination.
20.4 Work repaired under the warranty shall carry a renewed warranty running from the date the repair is accepted, for the full original period or for the remainder of the original period, whichever ends later.
NOTE Distress arising from loading beyond the design basis, from exposure more severe than the exposure classes specified for the element, or from a mixture the Engineer of Record directed over the Contractor's written objection is a design matter rather than a construction defect. (20.5)