1905.6 Evaluation and Acceptance of Concrete

The criteria for evaluation and acceptance of concrete shall be as specified in Sections 1905.6.2 through 1905.6.5.5.

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 noncompliant with the mix design or noncompliant with the requirements otherwise specified in this code. Unless more prompt action is required, test results shall be reported no less than 7 business days after the date of the respective tests were performed.

The frequency of conducting strength tests of concrete shall be as specified in Sections 1905.6.2.1 through 1905.6.2.4.

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 T318 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).

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.

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.

A strength test shall be the average of the strengths of two 6 inch by 12 inch (152 mm by 304.8 mm) or two 4 inch by 8 inch (102 mm by 203 mm) 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 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.

Standard-cured specimens shall comply with the provisions of Sections 1905.6.3.1 through 1905.6.3.9.

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 1704.4 of this code). Concrete that does not meet the requirements of the approved concrete mix design shall be rejected.

Samples for strength tests shall be taken in accordance with ASTM C 172.

Cylinders for strength tests shall be molded and standard-cured in accordance with ASTM C 31. The contractor shall be responsible for providing the specified field storage curing facility and for monitoring the temperature as defined in ASTM C 31.

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.

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.

The cylinders shall be tested in accordance with ASTM C 39.

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).

If either of the requirements of Section 1905.6.3.3 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 1905.6.3.6, Item 2, is not met.

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 1905.6.2.1.

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.

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.

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 1704.1.2 regarding reporting of deficiencies.

Field-cured specimens shall comply with the provisions of Sections 1905.6.4.1 through 1905.6.4.4.

Where required by the commissioner, the results of strength tests of cylinders cured under field conditions shall be provided to the department.

Field-cured cylinders shall be cured under field conditions in accordance with ASTM C 31.

Field-cured test cylinders shall be molded at the same time and from the same samples as laboratory-cured test cylinders.

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).

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.

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 1905.6.3.6, Item 2, or if tests of field-cured cylinders performed in accordance with Section 1905.6.4.4 indicate deficiencies in protection and curing, steps shall be taken to assure that the load-carrying capacity of the structure is not jeopardized.

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 1905.6.4.3, Item 2.

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.

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.

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 20, 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.

Steel fiber-reinforced concrete used in beams shall be subject to the requirements of ACI 318, Section 5.6.6. 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.