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C. Concrete Strength: Establish required average strength for each type of concrete trial mixtures,as <br /> specified in ACI 301. <br /> 1. For trial mixtures method,employ independent testing agency acceptable to Architect for preparing and <br /> reporting proposed mix designs. <br /> 3.9 CONCRETE MIXES <br /> A. Mix and deliver concrete in accordance with ASTM C94.Prepare design mixes for each type and strength of <br /> concrete by the laboratory trial batch as specified in ACI 301. <br /> B. Exposure Classification: Geographical exposure classification shall be in accordance with Figure 1904.2.2 of the <br /> IBC. Uncertainty of classification due to a project location near a border of a classification shall be referred to <br /> Owner's Construction Manager for clarification. <br /> C. Exterior Pavement and Slabs on Grade: <br /> 1. Compressive Strength and Water-Cementitious(W/C) Ratio: Strength at 28 days and W/C ratio shall be as <br /> follows unless otherwise indicated on the Drawings: <br /> 2. Negligible exposure classification:3,500 psi with a maximum water-cementitious ratio of 0.53. b. <br /> Moderate exposure classification:4,000 psi with a maximum water-cementitious ratio of 0.48.c. <br /> Severe exposure classification:4,500 psi with a maximum water-cementitious ratio of 0.45. <br /> 3. Slump Range:4"+/-1"at the point of placement. <br /> 4. Air Entrainment for exterior concrete only shall be as follows: <br /> a. Nominal Max Size /Average Air Content (%)+/-1.5%by Exposure Classification <br /> NOM MAX SIZE Negligible Moderate Severe <br /> 3/8 4.5 6.0 7.5 <br /> 1/2 4.0 5.5 7.0 <br /> 3/4 3.5 5.0 6.5 <br /> 1 3.0 4.5 6.0 <br /> 1-1/2 2.5 4.0 5.5 <br /> D. Interior Concrete and Exterior Structural Concrete: <br /> 1. Compressive Strength: Strength at 28 days shall be 3500 psi unless otherwise shown or specified. <br /> 2. Maximum Water-Cementitious Material Ratio(Cement Quantity Includes Fly Ash or slag): <br /> a. Exterior Structural Concrete:0.50 by wt. <br /> b. Interior Concrete: 0.45 by weight <br /> 3. Slump for Conventionally Placed Concrete: Not to exceed 4 inches+/-1 inch. <br /> 4. Slump for Pumped Concrete: Not to exceed 5 inches at the point of placement. <br /> 5. Air Content:As listed below <br /> a. Negligible Exposure&Interior Slabs:Max 34.0 percent entrapped air only. <br /> b. Moderate Exposure:5.0 percent. <br /> c. Severe Exposure:6.0 percent <br /> 6. Concrete to be Placed by Pumping Methods <br /> a. The minimum quantity of constituent materials passing the No. 50 sieve (fine aggregate and <br /> cementitious materials)shall be 600 pounds per cubic yard. <br /> b. The particle size distribution of the combined fine and coarse aggregate shall be uniform from the <br /> largest to the smallest particles. <br /> E. Admixtures: <br /> 1. Use water-reducing admixture or mid - range water-reducing admixture in concrete as required for <br /> placement and workability. Unless otherwise permitted herein, chemical admixtures shall be dispensed at <br /> the batch plant. <br /> 2-26-18 <br /> 033000-6 <br />