Which of the following statement(s) is/are true regarding water-cement ratio? (i) Lower water-cement ratio increases the strength of concrete. (ii) Higher water-cement ratio improves durability.
- AOnly (i)Correct
- BOnly (ii)
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Water-cement ratio and concrete durability
Formula
fc = A / Bw/c
Step-by-step solution
1. Abrams' Law establishes that compressive strength is inversely proportional to water-cement ratio; lower w/c yields higher strength; statement (i) is true. 2. Higher water-cement ratios create surplus capillary pores upon hydration water consumption, increasing matrix porosity and permeability. 3. Higher permeability allows chemical ingress, carbonation, and freeze-thaw damage, substantially degrading concrete durability; statement (ii) is false. 4. Therefore, only statement (i) is true. Answer: A
Explanation
According to Abrams' Law, the compressive strength of fully compacted concrete increases as the water-cement ratio decreases because less surplus water creates fewer capillary pores in the paste. Conversely, higher water-cement ratios increase porosity and matrix permeability, allowing water and aggressive chemical agents to penetrate more readily and reducing structural durability.
Why the other options are wrong
B) Higher water-cement ratio drastically lowers durability by creating interconnected capillary porosity. C) Statement (ii) is false. D) Statement (i) is correct according to Abrams' fundamental law of concrete strength.
Shortcut
Abrams' Law: Lower w/c = Higher strength + Lower permeability + Higher durability.
Common mistake
Believing higher water content improves durability due to better workability or flow.
Correct answer: A) Only (i)