Which of the following statements is/are true for the size of the aggregate to be used with cement? i. The nominal maximum size of the coarse aggregate should be as large as possible within the limits specified but in no case greater than ¼ of the minimum thickness of the member ii. For most work, 20 mm aggregate is suitable
- AOnly (i)
- BOnly (ii)
- CBoth (i) and (ii)Correct
- DNeither (i) nor (ii)
Solution
Concept
Nominal maximum size of coarse aggregates
Formula
NONE
Step-by-step solution
1. Standard concrete codes specify that nominal maximum size of coarse aggregate should not exceed 1/4 of the minimum member thickness. 2. For most general structural works, 20 mm size aggregate is considered standard and suitable. 3. Therefore, both statement i and statement ii are correct. Answer: C
Explanation
Standard design codes specify that the nominal maximum size of coarse aggregate should not exceed one-fourth of the minimum thickness of the structural member. Additionally, 20 mm aggregates are standard practice and widely considered suitable for most routine concrete work. Because both statements accurately state standard engineering guidelines, option C is correct.
Why the other options are wrong
A) Statement (ii) is also true as 20 mm aggregate is suitable for most general concrete works. B) Statement (i) is also true because nominal maximum aggregate size should not exceed 1/4 of the member's minimum thickness. D) Both statements (i) and (ii) are true according to standard concrete design rules.
Shortcut
Aggregate rules: Max aggregate size ≤ 1/4 member thickness; 20 mm is standard for most works.
Common mistake
Selecting option A or B by assuming one of the standard recommendations for aggregate sizing is incorrect.
Correct answer: C) Both (i) and (ii)