Which of the following statements is/are true for Class F fly ash? i. It contains of fly ash normally produced from the burning of anthracite or bituminous coal ii. This class of fly ash has both pozzolanic and varying degree of self-cementitious properties
- AOnly (i)Correct
- BOnly (ii)
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Characteristics of Class F fly ash
Formula
NONE
Step-by-step solution
1. Class F fly ash is produced from burning anthracite or bituminous coal. Answer: A
Explanation
Class F fly ash is derived from burning anthracite or bituminous coal and possesses predominantly pozzolanic properties with minimal self-cementing capability. Self-cementing properties are characteristic of Class C fly ash derived from sub-bituminous coal. Since only statement i is accurate for Class F fly ash, option A is correct.
Why the other options are wrong
C) Both statements cannot be true as statement (i) is excluded. D) Statement (ii) is true because Class F fly ash exhibits self-cementitious properties.
Shortcut
Class F comes from anthracite/bituminous coal (pozzolanic); Class C comes from lignite (pozzolanic + self-cementitious).
Common mistake
Selecting option C by assuming Class F fly ash has self-cementitious properties, which are characteristic of Class C fly ash.
Correct answer: A) Only (i)