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1 D. Concrete Compressive Strength: <br /> 2 <br /> 3 1. Whenever the 28-day compressive strength shown on the plans is 3,500 pounds per <br /> 4 square inch or greater, the concrete shall be considered to be designated by <br /> 5 compressive strength. <br /> 6 <br /> z 2. When the concrete is designated by compressive strength the mix proportions shall be <br /> 8 determined and concrete shall be furnished which contains not less than 564 pounds <br /> 9 and not more than 800 pounds of cement per cubic yard of concrete and which <br /> 10 conforms to the strengths shown on the plans or as specified. , <br /> 11 <br /> 12 3. Batch proportions shall be adjusted as necessary to produce concrete having the <br /> 13 specified cement factor. <br /> 14 t <br /> 15 E. Fly Ash: <br /> 16 <br /> 17 Up to 15 percent by weight of fly ash may be substituted for the Portland Cement required <br /> 18 herein. <br /> 19 <br /> 20 F. Aggregate Sizing: <br /> 21 <br /> zz 1. Coarse aggregate maximum grading shall be either 1-1/2 inch or 1 inch. Grading shall <br /> 23 be as set forth in Section 90 of the State Specifications. <br /> 24 <br /> 25 2. Where the spacing of reinforcing bars is such as to result in minimum clearances, or in , <br /> 26 other locations where in the opinion of the Engineer difficulties may be experienced in <br /> 27 pouring concrete with 1-1/2" maximum size aggregate, concrete with 1" maximum size <br /> 28 aggregate shall be used. In this event the air content shall be increased by 1/2%. <br /> 29 <br /> 30 G. Submittal of Proposed Mix Design: <br /> 31 <br /> 32 1. The proposed mix design, with samples of rock aggregate and any admixtures to be f <br /> 33 used, shall be submitted for review at least 14 days prior to pouring concrete. <br /> 34 <br /> 35 2. The grading or proportioning of the fine and coarse aggregates in the mix shall be , <br /> 36 changed whenever necessary or desirable, in the opinion of the Engineer, to secure the <br /> 37 required economy, workability, density, impermeability or strength, and no additional <br /> 38 compensation because of such changes shall be allowed. <br /> 39 <br /> 40 3.02 MEASURING MATERIALS <br /> 41 <br /> 42 Materials shall be measured by weighing except as otherwise specified or where other <br /> 43 methods are specifically authorized by the Engineer. Scales shall be approved by the <br /> 44 Engineer and have been certified by the local Sealer of Weights and Measures within one <br /> 45 year of use. Each size of aggregate and the cement shall be weighed separately. The , <br /> 46 accuracy of all weighing devices shall be such that successive quantities can be measured <br /> 47 to within one percent of the desired amount. Cement in standard packages (sacks) need not <br /> 48 be weighed, but bulk cement and fractional packages shall be weighed. <br /> 49 <br /> 50 3.03 CONCRETE MIXING & DELIVERY <br /> 51 <br /> 52 A. All concrete shall be machine mixed at the site, or delivered to the site by transit mixers <br /> CONCRETE <br /> 042894 03100-6 , <br />