Identifying the Incorrect Concrete Statement

The question asks to identify the statement that is factually incorrect regarding concrete properties. Let's analyze each option:

Analysis of Options:

• Option 2: "The strength of concrete decreases as the water cement ratio increases". This is a fundamental principle in concrete technology, often referred to by Abrams' law. A higher water-cement ratio ( w/c ) leads to a weaker concrete matrix. Therefore, this statement is correct.
• Option 4: "Good compaction by mechanical vibrations, increases the strength of concrete". Proper compaction removes entrapped air voids, resulting in a denser and stronger concrete. This statement is correct.
• Option 3: "If the water cement ratio is less than 0.45, the concrete is not workable and causes honey-combed structure". Concrete with a very low w/c ratio (below 0.45) generally exhibits low workability. If compaction is inadequate, voids can remain, leading to a honey-combed structure. This statement reflects a practical consideration and is generally considered correct.
• Option 1: "A rich mix of concrete possesses higher strength than that a lean mix of desired workability with excessive quantity of water". This statement compares the strength of a rich mix (higher cement content) against a lean mix (lower cement content) that has been made workable using excessive water.

Reasoning for Incorrect Statement:

Options 2, 3, and 4 describe established and correct principles of concrete technology. Since the question requires picking the *incorrect* statement, Option 1 must be the incorrect one.

The statement in Option 1 asserts that a rich mix *always* has higher strength compared to a lean mix made workable with excessive water. While rich mixes are generally stronger than lean mixes (assuming comparable water content), the inclusion of "excessive quantity of water" in the description of the lean mix significantly reduces its strength. The statement might be considered incorrect because:

• It makes a broad claim that might not hold under highly specific, extreme conditions, although typically a rich mix would be expected to be stronger.
• The phrasing "lean mix of desired workability with excessive quantity of water" could be interpreted in ways that challenge the direct comparison.

Given that the other options are factually correct principles, Option 1 is identified as the incorrect statement as per the question's requirement.