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

Step 1: Understand bleeding in concrete.
Bleeding is the phenomenon where excess water rises to the surface of freshly placed concrete.
Step 2: Examine each statement.
(A) Lean mixes have less cement and more water, hence bleeding is more — correct.
(B) Addition of pozzolanic or finer materials reduces bleeding by filling voids — correct.
(C) Calcium chloride accelerates setting and can increase bleeding — correct.
Step 3: Identify the incorrect statement.
Since all the given statements (A), (B), and (C) are correct, none of them is incorrect.
Step 4: Conclusion.
Hence, the correct answer is (D) None of the above.

Answer 2

Instead of simply confirming each statement is a known fact, we can check each one against the underlying physical mechanism of bleeding — the settling of solid particles (cement and aggregate) under gravity while excess mixing water is displaced upward through the voids between them.

1. Lean mixes bleed more as compared to rich ones: A lean mix has proportionally less cement (and hence less total surface area available to hold water by adsorption) relative to the water present, and typically uses a higher water-cement ratio for workability. With less solid surface area to retain the mixing water, more water is left free to rise to the top, so lean mixes do bleed more — this statement is correct.
2. Bleeding can be minimized by adding pozzolana finer aggregate: Fine pozzolanic material adds a large amount of additional fine solid surface area into the mix, which physically obstructs the upward channels through which bleed water would otherwise travel, and also adsorbs some of that water onto its surface. Both effects reduce the amount of water that reaches the surface, so this statement is correct.
3. Bleeding can be increased by addition of calcium chloride: Calcium chloride is an accelerator that speeds up the early hydration reactions; faster early stiffening changes how quickly the paste's internal structure sets, and in practice this accelerated, non-uniform early stiffening is associated with an increase, not a decrease, in the amount of bleeding observed, so this statement is also correct.
4. None of the above: Since each of the three preceding statements independently checks out against the physical mechanism of bleeding, there is no incorrect statement among them, making "none of the above" the only logically remaining choice for "the incorrect statement."

Examining the particle-settling and water-displacement mechanism behind bleeding confirms all three specific statements are technically accurate.

Therefore, the correct answer is None of the above.