Select the incorrect statement regarding the comparison between Flexible and Rigid pavements
- AFlexible pavements have a low initial cost but high maintenance cost.
- BRigid pavements have a long design life than flexible pavements.
- CFlexible pavements can be opened to traffic shortly after construction.
- DRigid pavements are designed based on the California Bearing Ratio (CBR) of the soilCorrect
Solution
Concept
Comparison of Flexible and Rigid Pavements
Formula
N/A
Step-by-step solution
1. Evaluate the given statements comparing flexible and rigid pavements. 2. Recall that the California Bearing Ratio (CBR) method is used for flexible pavements, not rigid pavements. 3. Select Option (d) as the incorrect statement.
Explanation
Option D is incorrect because the California Bearing Ratio (CBR) method is used to design flexible pavements, not rigid pavements. Rigid pavements are designed based on the elasticity of concrete and the modulus of subgrade reaction.
Shortcut
To remember pavement design methods, use the phrase "Flexible CBR, Rigid Subgrade": - Flexible = CBR: Flexible pavements are designed using soil strength (California Bearing Ratio - CBR). - Rigid = Subgrade / Slab: Rigid pavements rely on concrete slab stiffness and the modulus of subgrade reaction (k-value).
Common mistake
A common mistake is failing to notice the word "incorrect" in the question prompt and selecting a true statement such as option A or B. Another common error is assuming that the California Bearing Ratio (CBR) method applies to all pavement types, overlooking that CBR is specifically used for flexible pavement design while rigid pavements are designed using slab theory and modulus of subgrade reaction (k-value).
Correct answer: D) Rigid pavements are designed based on the California Bearing Ratio (CBR) of the soil