Use the ACI method to design a concrete mix for the following function situation

Question

Use the ACI method to design a concrete mix for the following function situation. The 28-day compressive strength should be 5,000 lb/in^2. The concrete will not be air entrained. The slump should be between 3 and 4 in. and the maximum aggregate size should not exceed 1 in. The properties of the materials are as follows: Cement: Type 1, specific gravity = 3.1 Coarse Aggregate: Bulk specific gravity (SSD) = 2.7; absorption capacity = 1.0% dry-rodded unit weight = 100 lb/ft^3; surface moisture 1% Fine Aggregate: Bulk specific gravity (SSD) = 2.6; absorption capacity = 2.0% fineness modulus = 2.6; surface moisture 2% What is the appropriate amount of mixing water, before adjustment for moisture in the aggregate, recommended for this mix? A. 275 lb/yd^3 B. 300 lb/yd^3 C. 325 lb/yd^3 D. 340 lb/yd^3 E. 365 lb/yd^3 What is the w/c recommended for this mix? A. 0.40 B. 0.44. C. 0.48 D. 0.52 E. 0.54 If the required mixing water is 300 lb/yd^3 and the w/c is 0.42, what is the approximate amount of cement recommended for this mix? A. 698 lb/yd^3 B. 714 lb/yd^3 C. 750 lb/yd^3 D. 812 lb/yd^3 E. 934 lb/yd^3 What is the approximate amount of course aggregate recommended for this mix (do not adjust for stockpile conditions)? A. 1, 578 lb/yd^3 B. 1, 623 lb/yd^3 C. 1, 797 lb/yd^3 D. 1, 863 lb/yd^3 E. 1, 881 lb/yd^3 If the required amount of water is 300 lb/yd^3, what is the approximated volume of water in 5 yd^3 of concrete? A. 4.8 ft^3 B. 9.6 ft^3 C. 24.0 ft^3 D. 28.0 ft^3 E. 32.0 ft^3 If the required amount of cement is 710 lb/yd^3, what is the approximated weight in 5 ft^3 of cement? A. 113.8 lb B. 121.3 lb. C. 129.9 lb. D. 131.5 lb. E. 142.0 lb.

Explanation / Answer

10. From table 6.3.3 of ACI 211.1 for 3-4 inch slump and 1 inch maximum nominal size aggregate for non-air entrianed concrete

Water required = 325 lb/yd3 (C)

11. From table 6.3.4(a)

w/c ratio for non-air entrained for 5000 lb/in2 compressive strength w/c ratio = 0.48 (c)

12. As per clause 6.3.5

Required cement = water content/ water-cement ratio = 300/0.42= 714 lb/yd3 (B)

13. From table 6.3.6 coefficient ,for a fineness modulus of fine aggregate 2.6 = 0.69

Volume of aggregate on oven dry rodded basis for yd3 = 0.69*27

Dry weight of coarse aggregate per yd3 = 0.69*27*100 = 1863 lb/yd3 (D)

14. Required amount of water = 300 lb/yd3

for 5 yd3 amount of water = 300*5 = 1500 lb

specific weight of water is 62.43 lb/ft3

so amount of water = 1500/62.43 = 24.0 ft3 (C)

15. Required amount of cement= 710 lb/yd3

1 yd3 = 27 ft3

so 5 ft3 = 5/27 = 0.185 yd3

for 0.185 yd3 amount of cement = 0.185*710

= 131.5 lb (D)

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