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305-ConcreteLab-20101104

# 305-ConcreteLab-20101104 - CEEn 305B Civil Engineering...

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CEEn 305B Civil Engineering Materials—Concrete, Masonry, and Asphalt Department of Civil and Environmental Engineering Brigham Young University INSTRUCTIONS FOR CONCRETE LABORATORY ACTIVITY: MIXTURE DESIGN The purpose of this laboratory activity is to familiarize you with the Portland Cement Association (PCA) absolute volume method for concrete mixture design with a particular focus on maximizing concrete strength. Because this is a design activity, no single right answer exists. The procedure is specified in American Concrete Institute (ACI) 211 (Standard Practice for Selecting Proportions for Concrete). 1. Follow the PCA absolute volume method for concrete mixture design described in Chapter 7 of the textbook to produce a concrete mixture having maximum strength. Use the following values and constraints in the design process: a. Materials retained on the following sieves will be available for the mixture design: 1/2, 3/8, No. 4, No. 8, No. 16, No. 30, No. 50, No. 100, and pan. b. The aggregates should be considered “subangular.” c. The coarse aggregate gradation must satisfy that given for Size No. 6 described in American Society for Testing and Materials (ASTM) C33 in Table 5.5 of the textbook. d. The fine aggregate gradation must satisfy the ASTM C33 requirements given in Table 5.4 of the textbook. An example calculation of fineness modulus for a fine aggregate is given in Table 1. Table 1. Example Fineness Modulus Calculation for Fine Aggregate Sieve Size Weight Percent Cumulative Percent Retained (lb) Retained (%) Retained (%) 3/8 in. 0 0 0 No. 4 0.9 1.8 1.8 No. 8 4.6 9.2 11 No. 16 9.7 19.4 30.4 No. 30 9.9 19.8 50.2 No. 50 12 24 74.2 No. 100 8.1 16.2 90.4 No. 200 2.7 5.4 95.8 Pan 2.1 4.2 100 Total 50 100 258 Fine Aggregate Fineness Modulus = 258/100 = 2.58

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e. The nominal maximum size of aggregate is 0.75 in. f. The dry-rodded coarse aggregate density is 95 pcf. g. The absorption values for the coarse and fine aggregates are 2.0 percent and 1.0 percent, respectively. h. The values of bulk saturated-surface-dry (SSD) specific gravity for the coarse and fine aggregates are 2.65 and 2.70, respectively. i. The slump must be at least 2 in. j. The cement content cannot exceed that allowed in a “6-bag” mix (564 lb/yd 3 ). k. No air entrainment is required, and no admixtures are permitted. l. The design batch weight should be approximately 40 lb. 2. Record the weigh-outs for the prepared mixture design in Table 2. The design weight of free water should be determined from Table 7.8 in the textbook and adjusted for aggregate shape. The teaching assistant will provide information about the existing water contents of the coarse and fine aggregates before the concrete mixing and casting activity. Therefore, the adjusted weights for both the aggregate and the water will be calculated later. Table 2. Weigh-Outs Sieve Size Adjusted Combined Coarse Aggregate Fine Aggregate Combined Weight Retained (lb) 1/2 in.
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• Spring '11
• Guthrie
• Teaching assistant, unit weight, fine aggregate, Department of Civil and Environmental Engineering Brigham Young University, unit weight bucket

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