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SPECIAL PROVISIONS - SP20I6 BOOK Last Revision by CO Special Provisions: 2/08/17 Created August 20, 2015 Page 42 SP 0202-101 G.5.c Field Control Strength Cylinders The Engineer will use field control cylinders to determine when the sequence of construction operations is dependent upon the rate of concrete strength development. The Engineer will cast field control cylinders to determine when the concrete attains the required strength for all desired field control limitations. The Engineer will perform the following for field control strength cylinders: (1) Cast up to three (3) field control cylinders per structure. The Contractor is responsible for any additional field control cylinders. (2) Mark field control cylinders for identification of the represented unit or section of concrete in accordance with 2461.3.G.5.a(2). (3) Cure the cylinders in the same location and under the same conditions as the concrete structure or unit involved meeting the requirements of the Concrete Manual, (3.1) For High -Early (HE) Concrete as defined in Table 2461-7, the Engineer will allow the Contractor to cure field control cylinders using insulated cylinder storage compartment. Provide insulated storage compartments and any equipment necessary to continually monitor temperatures of both the newly poured concrete structure and the insulated cylinder storage compartment. Maintain the insulated storage compartment at a temperature no greater than 5 °F above the newly poured concrete structures temperature. When the temperature exceeds 5 °F or the temperature monitoring system fails, the Engineer will not accept field control cylinder results. (4) Complete the MnDOT Concrete Cylinder Identification Card including the results for air content, slump (if required), concrete, and air temperature testing from the same load. During the Departments normal laboratory operating hours, the Engineer will perform compressive strength testing on the field control cylinders. If Project scheduling requires testing outside of the Departments' laboratories normal operating hours or the Department's nearest laboratory is greater than 30 miles from the project; Provide certified and calibrated hydraulic cylinder -testing machine within 30 miles of the project and at a location approved by the Engineer. Test the field control cylinders in the presence of the Engineer in accordance with ASTM C39. The Engineer will allow the Contractor to submit a strength -maturity relationship curve for use in lieu of field control cylinders in accordance with 2461.3.G.6, "Estimating Concrete Strength by the Maturity Method." S-32.33 MnDOT 2461.3.G.5.e, 2461.3.G.5.e(1), 2461.3.G.5.e(2), 2461.3.G.5.e(3), and 2461.3.G.5.e(4) shall be deleted and replaced with the following: G.5.e Concrete Compressive Strength The Concrete Engineer defines a single strength test as the average (28-day) strength of three (3) cylinders fabricated from a single sample of concrete and cured in accordance with the Concrete Manual If 1 of the set of 3 cylinders shows a strength variability of greater than 10% outside of the initial calculated three cylinder average strength, the Engineer will average the remaining two cylinders and report as the 28-day compressive strength. If 2 or more of the set of 3 cylinders shows a strength variability greater than 10% outside of the initial calculated average strength, the Engineer will use all three cylinder results to calculate the 28-day compressive strength. The Engineer will consider concrete acceptable in accordance with Table 2461-17 provided both the single strength test and the moving average of 3 consecutive strength tests are met for a required f c.