Section BC 1905: Concrete Quality, Mixing and Placing
1905.1 General.
The required strength and durability of concrete shall be governed by compliance with the proportioning, testing, mixing and placing provisions of Sections 1905.1.1 through 1905.13 of this code and ACI 318.
1905.1.1 Strength.
Concrete shall be proportioned to provide an average compressive strength in accordance with Section 1905.3, and shall satisfy the durability criteria of Section 1904. Concrete shall be produced to minimize the frequency of strengths below f 'c in compliance with Section 1905.6.3.3. For concrete designed and constructed in accordance with this chapter, f 'c shall not be less than 2,500 psi (17.22 MPa). No maximum specified compressive strength shall apply unless restricted by a specific provision of this code or ACI 318.
1905.1.2 Cylinder tests.
Requirements for f 'c shall be based on tests of cylinders made and tested in accordance with Section 1905.6.3.
1905.1.3 Basis of f 'c.
Unless otherwise specified, f 'c shall be based on 28-day tests. If other than 28 days, test age for f 'c shall be as indicated in construction documents. If at any time during the concrete operations, the concrete is not in conformance with ASTM C 94 or is otherwise compromised, it shall be rejected. If it is placed, the location of the load shall be recorded and a pair of cylinders shall be molded from the load per ASTM C 31 and included in the average f 'c.
1905.1.4 Lightweight aggregate concrete.
Where design criteria in ACI 318, Section 19.2.4, provides for use of a splitting tensile strength value of concrete (f 'ct), laboratory tests shall be made in accordance with ASTM C 330 to establish the value of f 'ct corresponding to the specified value of f 'c.
1905.1.5 Field acceptance.
Splitting tensile strength tests shall not be used as a basis for field acceptance of concrete.
1905.2 Selection of concrete proportions.
Concrete proportions shall be determined in accordance with ACI 318 and the provisions of Sections 1905.2.1 through 1905.2.4 of this code.
1905.2.1 General.
Proportions of materials for concrete shall be established to provide:
1. Workability and consistency to permit concrete to be worked readily into forms and around reinforcement under the conditions of placement to be employed, without segregation or excessive bleeding.
2. Resistance to special exposures as required by Section 1904.
3. Conformance with the strength test requirements of Section 1905.6.
1905.2.2 Different materials.
Where different materials are to be used for different portions of proposed work, each combination shall be evaluated.
1905.2.3 Basis of proportions.
Concrete proportions shall be established in accordance with Section 1905.3 or Section 1905.4, and shall comply with the applicable requirements of Section 1904.
1905.2.4 Mass concrete.
For areas of high-strength mass concrete, including but not limited to, 8,000 psi (55 158 kPa) or greater and the least dimension being equal to or greater than 36 inches (914 mm), as indicated on the construction documents, a thermal control plan complying with ACI 301, Section 8.1 and acceptable to the registered design professional of record shall be submitted by the contractor.
1905.3 Proportioning on the basis of field experience and/or trial mixtures.
Concrete proportioning determined on the basis of field experience or trial mixtures shall be done in accordance with ACI 318, Sections 26.4.3 and 26.4.4, and Sections 1905.3.1 through 1905.3.5 of this chapter.
1905.3.1 Required strength.
If the required f 'cr is obtained for trial batch mixes prior to the date specified, the trial mix design may be approved by the registered design professional of record for the structural design.
(Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023)
Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.
1905.3.2 Performance and approval.
Concrete mix designs shall be performed by an approved agency or by a concrete producer approved by the department as an approved fabricator authorized in accordance with Section 1704.2.2, and approved in accordance with the requirements of Sections 1905.3.2.1 through 1905.3.2.3.
1905.3.2.1 Certification.
All mix designs submitted for review and approval in accordance with Section 1905.3.2.2 shall be certified by the director of the approved agency or the quality control manager of the approved concrete producer that performed the tests used to substantiate the mix design. In addition all mix designs shall be signed by an owner or officer of the concrete production facility.
1905.3.2.2 Review and approval.
All mixes shall be approved by the registered design professional of record and filed with the department prior to use in construction.
1905.3.2.3 Distribution.
Copies of the approved mix design(s) shall be maintained at the construction site by the contractor and made available to the department upon request. A copy of the approved mix design(s) shall be provided by the contractor to the licensed concrete testing laboratory performing the acceptance testing of the concrete at the construction site.
1905.3.3 Test records and trial mixtures.
Field strength test records or trial mixtures used to determine f 'cr shall not be more than 24 months old measured from the date of batching, provided the materials are the same as those proposed for use and the concrete producer provides a written statement confirming the materials are the same as those proposed for use.
Exceptions:
1. Coarse aggregates may be acquired from an alternative source provided the nominal maximum size and the volume of coarse aggregate used remain unchanged.
2. Fine aggregates may be acquired from an alternative source provided the volume of fine aggregate used remains unchanged.
1905.3.4 Materials.
The type and source of the materials used in the concrete shall be identified in the proposed concrete mix design. In order for materials in field strength test records or trial mixtures to be considered the same as those proposed for use, the materials shall, at a minimum, comply with the following:
1. Cementitious materials. Cementitious materials shall be used in the same quantities for each individual component and shall be of the same type and shall be from the same source and mill. Upon request, the concrete producer shall provide mill certificates for the cementitious materials proposed for use and cementitious materials represented by the field strength test records or trial mixtures to the registered design professional of record and the department.
2. Aggregates. Coarse and fine aggregates shall be the same nominal maximum size and shall be used in the same volume for each individual component. The aggregate supplier shall attest that the aggregates proposed are not alkali-silica reactive. The aggregate supplier is permitted to rely on New York State Department of Transportation approval of the supplier's aggregate source.
3. Admixtures. Admixtures shall meet the requirements of the same admixture type in accordance with ASTM C 494 or ASTM C 260 and there shall be no change in air content or water content from the previously specified mix.
Exception: Addition or removal of retarding or accelerating admixtures as described in Section 1905.3.5 is acceptable.
4. Additional testing. Differences or changes in materials that are proposed for use, not meeting the requirements of Items 1 through 3 above, shall require new testing demonstrated by either field strength test records or trial mixtures.
Exception: Field changes to concrete proportions specified in Section 1905.3.5.
1905.3.5 Field changes to concrete proportions.
Based on test data and observations during the course of construction, the following changes described in Sections 1905.3.5.1 and 1905.3.5.2 are permitted without requiring additional trial mixtures or field strength test records, provided:
1. There are no changes to the type and source of materials described in Sections 1905.3.3 and 1905.3.4, except as permitted in Sections 1905.3.5.1 and 1905.3.5.2;
2. Documentation of these changes are maintained by the concrete producer and the concrete contractor;
3. The changes described in Section 1905.3.5 cannot be used for the submission of an initial mix design to demonstrate that a previously prepared mix design meets strength or air content requirements that differ from the required concrete properties without new field strength test records or new trial mix designs;
4. Where required in Section 1905.3.5, documentation of these changes shall be submitted for acceptance to the registered design professional of record for the structural design by the concrete producer prior to use;
5. Copies of the revised mixtures shall be maintained at the construction site and provided to the licensed concrete testing laboratory performing the acceptance testing of concrete in accordance with Item 4 of Table 1705.3 of this code; and
6. The documentation required by Items 2 and 5 above shall be made available to the commissioner upon request.
1905.3.5.1 Changes that do not require prior approval of the registered design professional of record for the structure.
The following admixture modifications to concrete proportions can be made without requiring prior acceptance by the registered design professional of record:
1. Air-entraining admixtures. Air-entraining admixture dosages can be increased or decreased as needed to obtain the air content specified in the construction documents
2. Water reducing admixtures. Water reducing admixture dosages can be increased or decreased to produce the specified workability, provided that the design water is not exceeded and the changes do not segregate the concrete mix.
1905.3.5.2 Changes that require prior approval of the registered design professional of record for the structure.
The following modifications to concrete proportions can be made only with prior acceptance by the registered design professional of record. Any added materials and the final mix proportions shall be indicated in a revised mix design submitted to the registered design professional of record prior to use:
1. Retarding and accelerating admixtures. Retarding and accelerating admixtures may be added to concrete mixtures or the dosage may be modified as needed to maintain practical set times.
2. Pigment. Pigment dosage may be adjusted to maintain uniform concrete color.
3. Fibers. Synthetic, glass or natural fibers may be added to the mix within the manufacturer recommended range. Any loss in workability shall be compensated with a water reducer.
Exception: Steel fibers may not be added to a concrete mixture without the performance of a new mix design.
4. Corrosion inhibitor. Corrosion inhibiting admixtures may be added, provided the corresponding adjustment of mix water remains within the limits of the required water/cementitious material ratio. The added materials and the revised design mix shall be submitted for review by the registered design professional of record for the structure prior to use.
5. Cementitious content and water-cementitious material ratio (w/cm). The cementitious content may be increased by a maximum of 12 percent, or the w/cm ratio may be decreased while maintaining the same cementitious content, but the w/cm and air content shall not be increased. Aggregate quantities shall be adjusted, as required, to maintain the mix proportion and yield.
6. Hydration control. Admixture may be added for the purpose of delaying hydration and maintaining a workable mix.
7. Source of aggregate. Change to the source of aggregate may be approved by the registered design professional of record without providing additional test data only when the original aggregate source is no longer producing the required aggregates or the quality of the aggregates produced no longer meets the requirements of ASTM C 33 or the New York State Department of Transportation, provided:
7.1. The new aggregate source is approved by the New York State Department of Transportation;
7.2. A modulus of elasticity is not specified;
7.3. The volume of both the fine and coarse aggregates remains the same and the nominal maximum size of coarse aggregates is unchanged;
7.4. Lightweight aggregate shall not be substituted for dense, nor dense aggregate for lightweight, where lightweight aggregates are defined as having a specific gravity less than 2.5; and
7.5. The registered design professional of record is informed of the reason necessitating the change of aggregate.
8. Cementitious materials. Any change to cementitious materials shall require an additional laboratory testing trial batch. The new cementitious material shall maintain the same air and water cementitious ratio (w/cm) as the original mix and meet the strength requirements of ACI 301, Table 4.2.3.3 b. Approval of the registered design professional of record and submittal of data from either a three- or seven-day compressive strength test shall be required prior to the placement of concrete.
1905.4 Proportioning without field experience or trial mixtures.
Concrete proportioning determined without field experience or trial mixtures shall be done in accordance with ACI 318, Section 26.4.4.1(b). This method of proportioning shall not be permitted for:
1. Load-carrying structural concrete where the total volume of concrete on a given project exceeds 50 cubic yards (38 m3); or
2. Structural or non-structural concrete mix proportions that will be exposed to exposure classes S1, P1, or C2.
1905.5 Average strength reduction.
As data becomes available during construction, it is permissible to reduce the amount by which the average compressive strength (f 'c) is required to exceed the specified value of f 'c in accordance with ACI 318, Section 26.4.4.1(c). A new mix design shall be submitted to the registered design professional of record for approval prior to use.
1905.6 Evaluation and acceptance of concrete.
The criteria for evaluation and acceptance of concrete shall be as specified in ACI 318, Sections 26.12 and 26.13, and Sections 1905.6.1 through 1905.6.5 of this code.
1905.6.1 Acceptance testing.
Concrete shall be tested in accordance with the requirements in Sections 1905.6.2 through 1905.6.5. Concrete sampling and testing for acceptance shall be deemed a special inspection performed by a licensed concrete testing laboratory as an approved agency. An approved agency shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field conditions, prepare specimens required for testing in the laboratory and record the temperature of the fresh concrete when preparing specimens for strength tests. All field sampling and testing, including the testing of aggregates, concrete mixes, and strength testing of specimens, shall be subject to special inspection by an approved agency. All testing laboratories shall be approved agencies and shall employ qualified special inspectors to perform all required field and laboratory tests. Test results shall be promptly distributed by the testing laboratory to the registered design professional of record, concrete producer, owner and contractor to allow for corrective action where the concrete is found to be non-compliant with the mix design or non-compliant with the requirements otherwise specified in this code. Unless more prompt action is required, test results shall be reported no more than 7 business days after the date the respective tests were performed.
1905.6.2 Frequency of testing.
The frequency of conducting strength tests of concrete shall be as specified in Sections 1905.6.2.1 through 1905.6.2.4.
1905.6.2.1 Minimum frequency.
For the first 250 cubic yards of each class of concrete placed each day, samples for strength tests of each such class shall be taken: (i) not less than once a day; (ii) not less than once for each 50 cubic yards (38 m3) of concrete; and (iii) not less than once for each 5,000 square feet (465 m2) of surface area for slabs or walls. After the first 250 cubic yards (191 m3), samples for strength tests of each class of concrete placed each day shall be taken once for each additional 150 cubic yards (115 m3). For structural concrete exposed to exposure class C2, additional field testing of the concrete for water content per AASHTO T 318 shall be required. At the discretion of the registered design professional of record, the frequency of testing may be reduced, but not less than once for each 150 cubic yards (115 m3).
1905.6.2.2 Minimum number.
On a given project, if the total volume of concrete is such that the frequency of testing required by Section 1905.6.2.1 would provide less than five strength tests for a given class of concrete, tests shall be made from at least five randomly selected batches or from each batch if fewer than five batches are used.
1905.6.2.3 Small volume.
When the total volume of concrete is less than 50 cubic yards (38 m3) on a given project, testing may be waived by the registered design professional of record.
1905.6.2.4 Strength test.
A strength test shall be the average of the strengths of two 6" x 12" or two 4" x 8" cylinders made from the same sample of concrete and tested at 28 days or at the test age designated for the determination of f 'c. Consideration shall be given to specifying an f 'c at 56 days or later for concrete utilizing pozzolans in the mix proportions. At the discretion of the registered design professional of record or the approved agency performing the testing, additional pairs of test cylinders may be taken at the time of sampling for testing at a later date. The additional cylinders may be tested at a later date should the strength at the specified date not meet the required f 'c.
1905.6.3 Standard-cured specimens.
Standard-cured specimens shall comply with the provisions of Sections 1905.6.3.1 through 1905.6.3.9.
1905.6.3.1 Mix design.
The special inspector shall verify that the proportions indicated on the batch ticket for the concrete delivered to the construction site are as per the approved concrete mix design prior to concrete placement (see Table 1705.3 of this code). Concrete that does not meet the requirements of the approved concrete mix design shall be rejected.
(Am. L.L. 2023/077, 6/11/2023, eff. 6/11/2023)
Editor's note: For related unconsolidated provisions, see Appendix A at L.L. 2023/077.
1905.6.3.2 Sampling.
Samples for strength tests shall be taken in accordance with ASTM C 172.
1905.6.3.3 Cylinders.
Cylinders for strength tests shall be molded and standard-cured in accordance with ASTM C 31.
1905.6.3.3.1 On-site curing.
The contractor shall be responsible for providing the specified field storage curing facility and for monitoring the temperature of the cylinders as defined in ASTM C 31.
1905.6.3.3.2 Final curing.
Cylinders shall be placed in final curing conditions meeting the requirements of ASTM C 511. Cylinders shall be transported to final curing conditions by the licensed concrete testing laboratory within 48 hours of casting the cylinders.
1905.6.3.3.3 Compressive Strength Testing.
The cylinders shall be tested in accordance with ASTM C 39.
1905.6.3.4 Evaluation of results.
The strength level of an individual class of concrete shall be considered satisfactory if both of the following requirements are met:
1. Every arithmetic average of any three consecutive strength tests equals or exceeds f 'c.
2. No individual strength test (average of two cylinders) falls below f 'c by more than 500 psi (3.45 MPa) when f 'c is 5,000 psi (34.50 MPa) or less, or by more than 0.10 f 'c when f 'c is more than 5,000 psi (34.50 MPa).
1905.6.3.5 Correction.
If either of the requirements of Section 1905.6.3.4 is not met, steps shall be taken to increase the average of subsequent strength test results. The requirements of Section 1905.6.5 shall govern if the requirement of Section 1905.6.3.4, Item 2 is not met.
1905.6.3.6 Field Testing.
Each time concrete is sampled for strength testing, the tests set forth in Items 1 through 5 shall be performed by the approved agency:
1. Temperature in accordance with ASTM C 1064.
2. Slump in accordance with ASTM C 143.
3. Unit weight in accordance with ASTM C 138.
4. Air content in accordance with ASTM C 173 or C 231. Testing in accordance with ASTM C 173 must be used for concretes made with lightweight aggregates, and other instances where ASTM C 231 is not applicable.
5. Water content per AASHTO T 318 when required by Section 1905.6.2.1 of this code.
1905.6.3.7. Mass concrete.
For mass concrete sections identified as requiring monitoring, install temperature devices that are capable of measuring the temperature of the concrete continuously and record temperature data in increments that do not exceed 30 minutes for a minimum period of seven days per ACI 301, Section 8.3 or as otherwise directed by the registered design professional of record. In lieu of monitoring a concrete placement for core and outside face temperatures, a computer simulated thermal study may be substituted, if approved by the registered design professional of record. The computer simulated thermal study shall be of the largest section placed for a specific concrete mix proportion and reflect the thermal properties for the specific cementitious materials and quantities in the mix. The thermal study shall include the maximum temperature at which concrete may be placed and the ambient temperature range for concrete placement.
1905.6.3.8 Results of Field Tests.
The approved agency shall immediately report the results of field tests performed to the contractor, and concrete truck driver, or other representative of the concrete producer. If at any time during the concrete operations, the concrete is not in conformance with ASTM C 94, this code, or is otherwise compromised, it shall be rejected. If it is placed, the location of the load shall be recorded and a pair of cylinders shall be molded from the load per ASTM C 31 and included in the average f 'c. The approved agency shall keep a written record of all field tests at the construction site and make the records available upon request. These results need not be used in calculating the arithmetic average of consecutive test results required by Section 1905.6.3.4.
1905.6.3.9 Reporting Requirements.
Field sampling and testing shall be deemed a special inspection, and the approved agency performing the field sampling and testing of concrete at the construction site shall be subject to the requirements of Section 1704.1.1.2 regarding reporting of deficiencies.
1905.6.4 Field-cured specimens.
Field-cured specimens shall comply with the provisions of Sections 1905.6.4.1 through 1905.6.4.4.
1905.6.4.1 When required.
Where required by the commissioner, the results of strength tests of cylinders cured under field conditions shall be provided to the department.
1905.6.4.2 Curing.
Field-cured cylinders shall be cured under field conditions in accordance with ASTM C 31.
1905.6.4.3 Sampling.
Field-cured test cylinders shall be molded at the same time and from the same samples as laboratory-cured test cylinders.
1905.6.4.4 Correction.
Procedures for protecting and curing concrete shall be improved when the strength of field-cured cylinders at the test age designated for determination of f 'c is less than 85 percent of that of companion laboratory-cured cylinders. The 85-percent limitation shall not apply if the field-cured strength exceeds f 'c by more than 500 psi (3.45 Mpa).
1905.6.5 Low-strength test results.
The investigation of low-strength test results shall be in accordance with the provisions of Sections 1905.6.5.1 through 1905.6.5.5.
1905.6.5.1 Precaution.
If any strength test of laboratory-cured cylinders performed in accordance with Section 1905.6.2.4 falls below the specified value of f 'c by more than the values given in Section 1905.6.3.4, Item 2, or if tests of field-cured cylinders performed in accordance with Section 1905.6.4 indicate deficiencies in protection and curing, steps shall be taken to assure that the load-carrying capacity of the structure is not jeopardized.
1905.6.5.2 Core tests.
Where calculations indicate that load-carrying capacity is significantly reduced, tests of cores drilled from the area in question in accordance with ASTM C 42 shall be permitted. In such cases, three cores shall be taken for each strength test that falls below the values given in Section 1905.6.3.4, Item 2.
1905.6.5.3 Condition of cores.
Cores shall be prepared for transport and storage by wiping drilling water from their surfaces and placing the cores in water-tight bags or containers immediately after drilling. Cores shall be tested not earlier than 48 hours nor later than seven days after coring unless approved by the registered design professional of record.
1905.6.5.4 Test results.
Concrete in an area represented by core tests shall be considered structurally adequate if the average of three cores is equal to at least 85 percent of f 'c and if no single core is less than 75 percent of f 'c Additional testing of cores extracted from locations represented by erratic core strength results is permitted.
1905.6.5.5 Strength evaluation.
If the criteria of Section 1905.6.5.4 are not met and the structural adequacy remains in doubt, the commissioner may order a strength evaluation in accordance with ACI 318, Chapter 27, for the questionable portion of the structure, or take other appropriate action. The registered design professional of record shall present to the commissioner a complete analysis showing the final safe load-carrying capacity of the questionable portion of the structure including any proposed remedial actions necessary for review and approval.
1905.6.6 Steel fiber-reinforced concrete.
Steel fiber-reinforced concrete used in beams shall be subject to the requirements of ACI 318, Section 26.12.5. The required testing and inspection of steel fiber-reinforced concrete shall be deemed a special inspection. Steel fibers shall not be used in place of required reinforcing bars.
1905.7 Preparation of equipment and place of deposit.
Preparation before concrete placement shall include the following:
1. Equipment for mixing and transporting concrete shall be clean.
2. Debris and ice shall be removed from spaces to be occupied by concrete.
3. Forms shall be properly coated.
4. Masonry filler units that will be in contact with concrete shall be well drenched.
5. Reinforcement shall be thoroughly clean of ice or other deleterious coatings.
6. Water shall be removed from the place of deposit before concrete is placed unless a tremie is to be used or unless otherwise permitted by the commissioner.
7. Laitance and other unsound material shall be removed before additional concrete is placed against hardened concrete.
1905.8 Mixing.
Mixing of concrete shall be performed in accordance with Sections 1905.8.1 through 1905.8.3.
1905.8.1 General.
Concrete shall be mixed until there is a uniform distribution of materials and shall be discharged completely before the mixer is recharged. Concrete delivered shall be proportioned in accordance with Section 1905.2.3. Modification to the approved concrete proportions shall be based upon standards acceptable to the commissioner.
1905.8.2 Ready-mixed concrete.
Ready-mixed concrete shall be mixed and delivered in accordance with the requirements of ASTM C 94 or ASTM C 685.
1905.8.2.1 Concrete Plants.
Concrete plants shall be certified by the National Ready Mixed Concrete Association (NRMCA), the Concrete Industry Board Concrete Producer Certification Program, or other program acceptable to the department, and shall comply with the rules of the department. Concrete producers shall have their plants inspected quarterly and have their scales and trucks certified. In fulfilling this certification requirement, the concrete producer may present certification by either a New York City government agency, or by the New York State Department of Transportation subject to the approval of the commissioner.
1905.8.2.2 Delivery Personnel.
Concrete ready-mix truck drivers shall be certified by the NRMCA and shall comply with the rules of the department.
1905.8.2.3 Batch Tickets.
Batch tickets shall accompany every load of concrete delivered to a site. The batch ticket shall contain the information specified in Items 1 through 7:
1. Plant name and location.
2. Contract number and project.
3. Mix designation as to type and strength.
4. Each material in the load along with quantities of each by weight, and admixture by ounces or gallons.
5. The total amount of mix proportion water approved, quantity of water added at the plant and in transit, and the remaining water that can be added on site.
6. Any deviations from the approved concrete mix design and variations permitted by Section 1905.3.5.
7. The time the water was added to the batch.
1905.8.2.3.1 Copies of batch tickets.
A copy of each batch ticket shall be given to the licensed concrete testing laboratory special inspector performing the acceptance testing at the delivery of each load. The licensed laboratory shall maintain copies of the batch tickets along with other inspection reports required by Section 1704.1, and make them available to the department upon request.
1905.8.3 Job-mixed concrete.
Job-mixed concrete shall comply with ACI 318, Section 26.5.
1905.9 Conveying.
The method and equipment for conveying concrete to the place of deposit shall comply with Sections 1905.9.1 and 1905.9.2.
1905.9.1 Method of conveyance.
Concrete shall be conveyed from the mixer to the place of final deposit by methods that will prevent separation or loss of materials that may alter the properties of the concrete delivered. Cylinders shall be made to determine the quality of concrete. Such cylinders shall be made at the truck or at the point of placement of the concrete as determined by the special inspection agency or the registered design professional of record.
1905.9.2 Conveying equipment.
The conveying equipment shall be capable of providing a supply of concrete at the site of placement without separation of ingredients and without interruptions sufficient to permit the loss of plasticity between successive increments.
1905.10 Depositing.
The depositing of concrete shall comply with the provisions of Sections 1905.10.1 through 1905.10.8.
1905.10.1 Segregation.
Concrete shall be deposited as nearly as practicable to its final position to avoid segregation due to rehandling or flowing.
1905.10.2 Placement timing.
Concreting operations shall be carried on at such a rate that the concrete is at all times plastic and flows readily into spaces between reinforcement.
1905.10.3 Unacceptable concrete.
Concrete that has partially hardened or been contaminated by foreign materials shall not be deposited in the structure.
1905.10.4 Retempering.
Retempered concrete or concrete that has been remixed after initial set shall not be used.
1905.10.5 Continuous operation.
After concreting has started, it shall be carried on as a continuous operation until placing of a panel or section, as defined by its boundaries or predetermined joints, is completed, except as permitted or prohibited by Section 1906.4.
1905.10.6 Placement in vertical lifts.
The top surfaces of vertically formed lifts shall be generally level.
1905.10.7 Construction joints.
When construction joints are required, they shall be made in accordance with Section 1906.4.
1905.10.8 Consolidation.
Concrete shall be thoroughly consolidated by suitable means during placement and shall be thoroughly worked around reinforcement and embedded fixtures and into corners of the forms.
1905.11 Curing.
The curing of concrete shall be in accordance with Sections 1905.11.1 through 1905.11.3.
1905.11.1 Regular.
Concrete (other than high early strength) shall be maintained above 50°F (10°C) and in a moist condition for at least the first seven days after placement, except when cured in accordance with Section 1905.11.3.
1905.11.2 High-early-strength.
High-early-strength concrete shall be maintained above 50°F (10°C) and in a moist condition for at least the first three days, except when cured in accordance with Section 1905.11.3.
1905.11.3 Accelerated curing.
Accelerated curing of concrete shall comply with ACI 318, Section 26.5.3.2(c), but concrete temperature shall not exceed 160°F (71°C).
1905.12 Cold weather requirements.
Concrete that is to be placed during freezing or near-freezing weather shall comply with the following:
1. Adequate equipment shall be provided for insulating or heating concrete materials and protecting concrete during freezing or near-freezing weather.
2. Concrete materials and reinforcement, forms, fillers and ground with which concrete is to be in contact shall be free from frost. The temperature of surfaces in contact with fresh concrete, including but not limited to forms and reinforcing steel, shall be raised above freezing.
3. Frozen materials or materials containing ice shall not be used.
1905.13 Hot weather requirements.
During hot weather, proper attention shall be given to ingredients, production methods, handling, placing, protection and curing to prevent excessive concrete temperatures or water evaporation that could impair the required strength or serviceability of the member or structure.
