Metropolitan Transit Authority engineers have identified reinforced concrete as the optimal material for constructing subway tunnel walls in coastal c...
GMAT Information and Ideas : (Ideas) Questions
Metropolitan Transit Authority engineers have identified reinforced concrete as the optimal material for constructing subway tunnel walls in coastal cities. Unlike traditional concrete, this specialized material incorporates steel mesh and chemical additives that enhance its performance in challenging underground environments. The key advantage of reinforced concrete for subway construction lies in its exceptional resistance to water infiltration and salt corrosion. This resistance prevents structural degradation that typically occurs when seawater seeps through tunnel walls, ensuring long-term safety and reducing maintenance costs.
According to the text, what makes reinforced concrete advantageous for subway tunnel construction in coastal cities?
It incorporates innovative steel mesh technology developed specifically for transit systems.
It costs significantly less than traditional concrete materials over the project lifecycle.
Its exceptional resistance to water infiltration and salt corrosion prevents structural degradation.
It allows engineers to complete tunnel construction projects ahead of schedule.
Step 1: Decode and Map the Passage
Part A: Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'Metropolitan Transit Authority engineers have identified reinforced concrete as the optimal material for constructing subway tunnel walls in coastal cities.' |
|
| 'Unlike traditional concrete, this specialized material incorporates steel mesh and chemical additives that enhance its performance in challenging underground environments.' |
|
| 'The key advantage of reinforced concrete for subway construction lies in its exceptional resistance to water infiltration and salt corrosion.' |
|
| 'This resistance prevents structural degradation that typically occurs when seawater seeps through tunnel walls, ensuring long-term safety and reducing maintenance costs.' |
|
Part B: Passage Architecture and Core Elements
Main Point: Reinforced concrete is the optimal material for coastal subway tunnels because of its exceptional resistance to water infiltration and salt corrosion.
Argument Flow: The passage establishes that engineers prefer reinforced concrete for coastal subway tunnels, explains how this material differs from regular concrete through added components, identifies water and salt resistance as the key advantage, and concludes by explaining how this resistance prevents the structural problems that would otherwise occur from seawater exposure.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- The passage is very clear about this - it directly states that the key advantage of reinforced concrete for subway construction lies in its exceptional resistance to water infiltration and salt corrosion
- The text then explains that this resistance prevents structural degradation that typically occurs when seawater seeps through tunnel walls
- So the right answer should mention the water and salt resistance as the key advantage, possibly connecting it to preventing structural problems that would otherwise occur in coastal environments
It incorporates innovative steel mesh technology developed specifically for transit systems.
✗ Incorrect
- Claims the advantage is innovative steel mesh technology developed specifically for transit systems
- The passage mentions steel mesh as a component, but does not call it innovative or developed specifically for transit
- Missing the actual key advantage the passage emphasizes
It costs significantly less than traditional concrete materials over the project lifecycle.
✗ Incorrect
- Claims the advantage is lower costs over the project lifecycle
- While the passage mentions reducing maintenance costs, this is presented as a consequence of the resistance, not the primary advantage itself
- This represents a trap where students might focus on the cost benefit mentioned at the end rather than the key advantage explicitly identified in the passage
Its exceptional resistance to water infiltration and salt corrosion prevents structural degradation.
✓ Correct
- Directly matches the passage statement about exceptional resistance to water infiltration and salt corrosion
- Includes the connection to preventing structural degradation, which the passage explicitly states as the result of this resistance
- This is exactly what the passage identifies as the key advantage
It allows engineers to complete tunnel construction projects ahead of schedule.
✗ Incorrect
- Claims the advantage is faster construction completion
- The passage never mentions construction speed or project timelines
- Completely unsupported by the text