Concrete Practice – choose the incorrect statement (workability, controlled concrete, and sand bulking) Identify the single incorrect statement among the following site-practice observations.

Introduction / Context:
Many site decisions hinge on correct understanding of fresh concrete behavior and aggregate characteristics. This item asks you to separate one false statement from a group of otherwise acceptable descriptions regarding workability, controlled concrete, and bulking of sand.

Given Data / Assumptions:

• No special water-reducers unless stated; observations refer to ordinary concretes.
• “Controlled concrete” implies that trial mixes and preliminary tests govern proportions.
• Bulking is the apparent volume increase of moist fine aggregate due to a water film.
• Lean mixes such as 1 : 6 : 12 are associated with mass concrete where high strength is not the primary goal.

Concept / Approach:

Workability generally increases with additional moisture (to a point), because more paste fluidity allows easier placement and compaction. Thus, claiming that workability decreases with an increase in moisture is incorrect. The other statements reflect accepted practice: controlled concrete is based on trials and tests; bulking depends on fineness with finer sands showing greater bulking; and very lean mixes like 1 : 6 : 12 are used for mass concreting purposes rather than structural RCC elements.

Step-by-Step Solution:

Verification / Alternative check:

Slump typically rises with water content; bulking curves show peak bulking for fine sands around 4–6% moisture; construction handbooks list lean mixes for mass works.

Why Other Options Are Wrong:

(b), (c), and (d) align with standard guidance; “All of the above” cannot be right because (a) is false.

Common Pitfalls:

Confusing “workability increases” with “strength increases”—they are not the same; ignoring that excessive water harms durability even though it may improve slump.

Final Answer:

Workability of the concrete mix decreases when moisture content increases