Question

Select the incorrect statement

• A. Lean mixes bleed more as compared to rich ones
• B. Bleeding can be minimized by adding pozzolana finer aggregate
• C. Bleeding can be increased by addition of calcium chloride
• D. None of the above

Hint:

Bleeding can be controlled by reducing water content and increasing fines in the concrete mix.

Answer 1

The Correct Option is D

Bleeding tendency can be judged using two key parameters: the effective water-cement ratio, and the total specific surface area of solids in the mix (more surface area holds more water on the particles instead of letting it rise).

1. Lean mixes bleed more: lean mixes generally need a relatively higher water content for workability, raising the effective water-cement ratio and increasing bleeding, so this statement holds.
2. Pozzolana or finer aggregate reduces bleeding: fine pozzolanic material adds a large amount of extra specific surface area to the solids, which holds more of the mixing water and lowers bleeding, so this statement holds.
3. Calcium chloride increases bleeding: this admixture is documented to raise bleeding despite accelerating setting, an accepted effect distinct from its influence on water-cement ratio or surface area, so this statement holds too.
4. None of the above: with all three parameter-based checks holding up, there is no incorrect statement among them.

So the incorrect statement is none of the above; the three given statements are all correct.

Answer 2

A third way to confirm this is to ask, for each statement, what we would expect to observe if it were actually false, and check whether that expectation matches accepted concrete practice.

1. Lean mixes bleed more as compared to rich ones: if this were false, rich mixes (more cement, usually lower water-cement ratio for the same workability) would need to bleed more than lean ones; but richer mixes are consistently observed and specified in practice as having a lower tendency to bleed, so the statement as given holds true, not false.
2. Bleeding can be minimized by adding pozzolana finer aggregate: if this were false, adding fine pozzolanic material would need to increase or not affect bleeding; but pozzolanic replacement is a standard, widely used practice specifically recommended to control excessive bleeding, so the statement holds true.
3. Bleeding can be increased by addition of calcium chloride: if this were false, calcium chloride would need to have no effect on, or reduce, bleeding; but it is documented as an accelerator that is associated with a bleeding increase, so the statement again holds true.
4. None of the above: since the counterfactual check for each of the three statements confirms they all hold as stated, there is no false statement to select, so this option is the one that must be correct.

Testing what would have to be true for each statement to be false, and finding none of those counterfactuals holds in practice, confirms all three given statements are accurate.

Therefore, the correct answer is None of the above.