Permits & Development - Encroachment(EP)/Driveway(DW) Permits - 2007_EP-07-301 thru EP-07-400_ - EP-07-352

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compressive strength at the maximum curing age specified or allowed below 85 percent,the concrete represented by that test will be rejected,unless the Contractor,at the Contractor's expense, obtains and submits evidence acceptable to the Engineer that the strength and quality of the concrete placed in the work are acceptable. If the evidence consists of tests made on cores taken from the work, the cores shall be obtained and tested in conformance with the requirements in ASTM Designation: C 42. • No single compressive strength test shall represent more than 250 m3. • If a precast concrete member is steam cured,the compressive strength of the concrete will be determined from test cylinders that have been handled and stored in conformance with Method 3 of California Test 540. The compressive strength of steam cured concrete will be evaluated on the basis of individual tests representing specific portions of production. If the concrete is designated by 28-day compressive strength rather than by cementitious material content, the concrete shall be considered to be acceptable whenever its compressive strength reaches the specified 28-day compressive strength provided that strength is reached in not more than the maximum number of days specified or allowed after the member is cast. • When concrete is specified by compressive strength, prequalification of materials, mix proportions, mixing equipment, and procedures proposed for use will be required prior to placement of the concrete. Prequalification shall be accomplished by the submission of acceptable certified test data or trial batch reports by the Contractor. Prequalification data shall be based on the use of materials,mix proportions,mixing equipment,procedures,and size of batch proposed for use in the work. • Certified test data, in order to be acceptable, shall indicate that not less than 90 percent of at least 20 consecutive tests exceed the specified strength at the maximum number of cure days specified or allowed,and none of those tests are less than 95 percent of specified strength. Strength tests included in the data shall be the most recent tests made on concrete of the proposed mix design and all shall have been made within one year of the proposed use of the concrete. • Trial batch test reports, in order to be acceptable, shall indicate that the average compressive strength of 5 consecutive concrete cylinders, taken from a single batch, at not more than 28 days (or the maximum age allowed) after molding shall be at least 4 MPa greater than the specified 28-day compressive strength,and no individual cylinder shall have a strength less than the specified strength at the maximum age specified or allowed. Data contained in the report shall be from trial batches that were produced within one year of the proposed use of specified strength concrete in the project. Whenever air-entrainment is required,the air content of trial batches shall be equal to or greater than the air content specified for the concrete without reduction due to tolerances. • Tests shall be performed in conformance with either the appropriate California Test methods or the comparable ASTM test methods. Equipment employed in testing shall be in good condition and shall be properly calibrated. If the tests are performed during the life of the contract,the Engineer shall be notified sufficiently in advance of performing the tests in order to witness the test procedures. • The certified test data and trial batch test reports shall include the following information: A. Date of mixing. B. Mixing equipment and procedures used. C. The size of batch in cubic meters and the mass,type,and source of all ingredients used. D. Penetration or slump (if the concrete will be placed under water or placed in cast-in-place concrete piles) of the concrete. E. The air content of the concrete if an air-entraining admixture is used. F. The age at time of testing and strength of all concrete cylinders tested. • Certified test data and trial batch test reports shall be signed by an official of the firm that performed the tests. • When approved by the Engineer,concrete from trial batches may be used in the work at locations where concrete of a lower quality is required and the concrete will be paid for as the type or class of concrete required at that location. • After materials, mix proportions, mixing equipment, and procedures for concrete have been prequalified for use, additional prequalification by testing of trial batches will be required prior to making changes that, in the judgment of the Engineer,could result in a strength of concrete below that specified. — • The Contractor's attention is directed to the time required to test trial batches and the Contractor shall be responsible for production of trial batches at a sufficiently early date so that the progress of the work is not delayed. • When precast concrete members are manufactured at the plant of an established manufacturer of precast concrete members,the mix proportions of the concrete shall be determined by the Contractor, and a trial batch and prequalification of the materials,mix proportions,mixing equipment,and procedures will not be required. 90-10 MINOR CONCRETE 90-10.01 GENERAL • Concrete for minor structures, slope paving, curbs, sidewalks and other concrete work, when designated as minor concrete on the plans,in the specifications,or in the contract item,shall conform to the provisions specified herein. Contract No. 10-OM7104 90