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rl <br />t <br />n <br />k ;I <br />n <br />C� <br />n <br />L <br />u <br />C <br />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 />required) moist storage facilities for specimens, affording protection to the <br />specimens against injury or loss through his operations, and furnishing 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 />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 />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 />06/07 <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 />03300 -7 03 -4197 <br />