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PGSF WMVD Storm and Combined Sewer - Construction Package 2 Cast-in-Place Concrete <br />Project No. 180162 03 30 00 - 24 <br /> <br />4) Testing of specimens for compressive strength shall be in accordance with <br />ASTM C39. Each test shall consist of two 6 x 12 inch (or three 4 x 8 inch) test <br />cylinders from each group of six (or nine) specimens. Test at the end of 7 <br />days and at the end of 28 days. The remaining cylinders shall be tested at the <br />end of 56 days if the 28-day strength reports below specification. <br />5) A strength test shall consist of the average strength of two 6 x 12 inch (or <br />three 4 x 8). If one cylinder shows evidence of low strength due to improper <br />sampling, casting, handling, or curing, the result of the remaining cylinders <br />may be used if approved by the Owner’s Representative. <br />6) The average of any three consecutive 28-day strength test results of the <br />cylinders representing each class of concrete for each structure shall be <br />equal to or greater than the specified strength. Not more than 10 percent of <br />the individual strength test results shall have values less than the specified <br />28-day strength for the total job concrete. No individual strength test result <br />shall be less than the specified strength by more than 500 pounds per <br />square inch. <br />7) Provide certified reports of the test results directly to the Owner’s <br />Representative and the Engineer. Test reports shall include sufficient <br />information to identify the mix used, the stationing or location of the concrete <br />placement, and the quantity placed. Slump, water/cement ratio, air content, <br />temperature of concrete, and ambient temperature shall be noted. <br />8) The 28-day strength test results shall be evaluated in accordance with ACI <br />214R. Quality control charts showing field test results shall be included with <br />the test results for each class of concrete in each major structure. Charts <br />shall be prepared in accordance with ACI 214R. Quality control charts shall <br />be maintained throughout the entire project and shall be available for the <br />Owner’s Representative’s inspection at any time. <br />9) If the 28-day test results fall below the specified compressive strength for the <br />class of concrete required for any portion of the work, adjustment in the <br />proportions, water content, or both, shall be made as necessary at the <br />Contractor’s expense. Report changes and adjustments in writing to the <br />Owner’s Representative. <br />10) If compressive test results indicate concrete in place may not meet structural <br />requirements, tests shall be made to determine if the structure or portion <br />thereof is structurally sound. Tests may include, but not be limited to, cores in <br />accordance with ASTM C42 and any other analyses or load tests acceptable <br />to the Engineer. Costs of such tests and/or anlysis shall be borne by the <br />Contractor. <br />b. Tests for Consistency of Concrete: <br />1) Measure slump in accordance with ASTM C143. Take samples for slump <br />determination from concrete during placement. Tests shall be made at the <br />beginning of concrete placement operation, whenever test cylinders are cast, <br />and at subsequent intervals to ensure that the specification requirements are <br />met. <br />2) For pumped concrete, measure slump in accordance with the Placing <br />Concrete by Pumping subparagraph of the Conveying and Placing article <br />above. <br />3) When high range water reducer is added at the site, slump tests shall be <br />taken before and after addition of the admixture.