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.... . -, . . Do not core hardened concrete for determining pay adjustments when the 28-day acceptance cylinder strength test results are less than 500 psi [3.5 MPa] or 10%, whichever is greater, below the specified minimum strength. When the Contractor submits acceptable core samples to the Engineer for testing, the Engineer will determine payment reductions based upon th~ results of the strength tests. Both the Contractor and the Department shall accept the results of strength tests of the drilled cores, subject to 346-11.5 and 346-11.6, as final and in lieu of the cylinder strength test results for determining pay adjustments. 346-11.3 Coring for Determination of Pay Adjustments: Obtain the cores In accordance with 346-10.3. 346-11.4 Core Conditioning and Testing: The Department will test the cores In accordance with 346-10.4. 346-11 .5 Core Strength Representing Equivalent 28-Day Strength: For cores tested no later than 42 days after the concrete was cast, the Engineer will accept the core strengths obtained as representing the equivalent 28-day strength of the lOT of concrete in question. The Engineer will calculate the strength value to be the average of the compressive strengths of the three individual cores. The Engineer will accept this strength at its actual measured value. 346-11.6 Core Strength Adjustments: For cores tested later than 42 days after the concrete was cast, the Department will establish the equivalency between 28-day strength and strength at ages after 42 days based on test data developed by a Department approved testing laboratory to relate strength at the actual test age to 28-day strength for the particular class of concrete and design mix represented by the cores. Obtain such data at no additional expense to the Department. When such data is not available and cannot be produced, as determined by the Department, the Department will determine the equivalent 28-day strength by adjusting the tested core strengths according to the following relationship: 346-11.6.1 Portland Cement Concrete without Pozzolan or Slag: Equivalent 28-Day Strength, f' c (28) = 1/F (Average Core Strength) x II . ..., I . ,., . ,., . ,., . ., . 1 . II . II r"""I 100, . where: ro, F = 4.4 + 39.1 (In x) -3.1 (In X)2 (Type I Cement) F = -17.8 + 46.3 (In x) -3.3 (In X)2 (Type II Cement) F 48.5 + 19.4 (In x) -1.4 (In x)2(Type III Cement) . ., x number of days since the concrete was placed In = natural log 346-11.6.2 Pozzolanic-Cement Concrete: Equivalent 28-day compressive strength f'e (28), where: ....., . . . ( 8.31 )"276 f'e (28) == 0.490 x f'e (t)x e f (Type I Cement) f'e(28) = 0.730xf'e (t)xee':9)"'14 (Type II Cement) f'e (28) = 0.483 x f'e (t)x )5.~8r91 (Type III Cement) II . I' .., . r'I 09/09 01000-107 03-4122.F .