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1 <br /> Bureau of the National Ready-Mixed Concrete Association, as well as ACI <br /> Standard 304 and ASTM Specification C94. <br /> D. The re-tempering of concrete or mortar which has partially hardened, that is, <br /> mixing with or without additional cement, aggregate, or water, will not be permitted. <br /> E. Attention is called to the importance of dispatching trucks from the batching plant <br /> so that they shall arrive at the site of the work just before the concrete is required, <br /> thus avoiding excessive mixing of concrete while waiting or delays in placing <br /> successive layers of concrete in the forms. <br /> 3.03 FIELD TESTS <br /> A. Sets of four field control cylinder specimens will be taken at random by the <br /> Engineer during the progress of the work, in conformity with ASTM Designation <br /> ' C31; the total number of specimens taken on the project may average one set per <br /> 150 cubic yards, and in general not less than one set of specimens will be taken on <br /> any one day when concrete is being placed. When average ultimate 28-day <br /> strength of control cylinders in any set falls below the required ultimate strength or <br /> below proportional minimum 7 day strengths where proper relation between 7 and <br /> 28 day strengths have been established by tests, proportions, water content, or <br /> temperature conditions shall be changed to secure the required strength. <br /> B. The Contractor shall cooperate in the making of such tests to the extent of allowing <br /> free access to the work for the selection of samples, providing heated (when <br /> 1 required) moist storage facilities for specimens, affording protection to the <br /> specimens against injury or loss through his operations, and fumishing material <br /> and labor required for the purpose of taking concrete cylinder samples, curing <br /> boxes and shipping boxes. All shipping of specimens will be paid for by the Owner. <br /> C. Slump tests will be made in the field by the testing laboratory. <br /> 3.04 INSPECTION AND CONTROL <br /> A. The preparation of forms, placing of reinforcing steel, conduits, pipes, and sleeves, <br /> batching, mixing, transportation, placing and curing of concrete shall be at all times <br /> under the inspection of the Engineer. <br /> B. The Contractor shall engage the services of an approved testing laboratory to <br /> 1 establish the basic mixtures of concrete as required by the specifications. <br /> C. The Owner will engage the services of a testing laboratory to test field control <br /> cylinder specimens and to conduct other tests as specified herein or as deemed <br /> required by the Engineer to insure the quality. <br /> 1 D. Air entrainment shall be measured by the testing laboratory or his representative at <br /> time of concrete deposit in accordance with ASTM Designation C231. <br /> 3.05 CONCRETE APPEARANCE <br /> A. Concrete for every part of the work shall be homogeneous structure which, when <br /> hardened, will have the required strength, durability and appearance. <br /> 1 <br /> 05/08 03300-7 05-4893 <br />