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PGSF WMVD Storm and Combined Sewer - Construction Package 2 Cast-in-Place Concrete <br />Project No. 180162 03 30 00 - 10 <br /> <br />2. Trial Mix Design: <br />a. Mixes verified by this method shall have the samples produced for testing, <br />manufactured at the batch plant which will supply concrete to the project, using <br />materials proposed for the Work and material combinations listed above. Testing, <br />data, and reporting shall conform to ACI 318 and the following: <br />1) Required compressive strength used as the basis for selecting concrete <br />proportions (f’cr) shall be the specified concrete strength (f’c) + 1000 psi for <br />specified concrete strengths less than 3,000 psi and f’c + 1200 psi for <br />specified concrete strengths between 3000 psi and 5000 psi. <br />2) Make at least three different trial mixtures for each class of concrete <br />qualified by the Trial Mix Design. Each trial mixture shall have a different <br />w/cm ratio or different cementitious materials content that will produce a <br />range of compressive strengths encompassing f’cr. <br />3) Design trial mixtures to produce a slump within ¾ inch of the maximum <br />specified and an air content within 0.5 percent of the maximum specified. <br />4) For each w/cm ratio or cementitious materials content, cast and cure at least <br />twelve standard test cylinders in accordance with ASTM C192. Four cylinders <br />from each batch tested at age 7-days, 14-days, and 28-days or as required to <br />comply with ACI 318. <br />5) From results of the cylinder tests, plot a curve showing the relationship <br />between w/cm ratio and compressive strength. <br />6) From the curve of w/cm ratio versus compressive strength, select the w/cm <br />ratio that will produce f’cr. This is the maximum w/cm ratio to be used unless <br />a lower w/cm ratio is specified above. <br />3. Field Experience Data: <br />a. When sufficient test data for a particular mix design is available which is identical <br />or substantially similar to that proposed for use, Contractor may substitute use of <br />this data in lieu of a trial mix design. Field data, reports, and analysis shall <br />conform to ACI 318, except as modified herein. <br />1) Historical mix design proportions for which data are submitted may vary from <br />the specified mix within the following limits: <br />a) f’c as specified or up to 500 psi above <br />b) w/cm ratio as specified or lower <br />c) pozzolan content within 5 percent of that specified <br />d) maximum coarse aggregate size may not vary smaller, but gradation of <br />coarse aggregate may vary <br />e) slump after introduction of admixtures +0/-1 inch. <br />b. Use of historical Field Experience Data does not allow modification of the project <br />mix specifications herein without review and acceptance by the Engineer.