In rural road construction, the use of which of the following is preferred for ensuring environmental sustainability or to reduce carbon footprint ? 1. Copper slag 2. Cold mix asphalt technology 3. Geotextiles 4. Hot mix asphalt technology 5. Portland cement Select the correct answer using the code given below :
- (a) 1, 2 and 3 only ✓ UPSC's answer
- (b) 2, 3 and 4 only
- (c) 4 and 5 only
- (d) 1 and 5 only
Why the answer is (a)
• PMGSY promotes 'green technologies' in rural roads to cut carbon footprint and use waste.
• Copper slag (1), an industrial waste, replaces natural aggregate; cold-mix asphalt (2) is laid at ambient temperature, saving the fuel and emissions of heating bitumen; geotextiles (3) stabilise soil and reduce material use.
• Hot-mix asphalt (4) requires heating to ~160 °C and Portland cement (5) is highly carbon-intensive — neither is preferred for sustainability.
• Hence 1, 2 and 3 only, option (a).
Why the other options are wrong
- (b) 2, 3 and 4 only
- Hot-mix asphalt is energy-intensive, not preferred.
- (c) 4 and 5 only
- Hot mix and Portland cement have high carbon footprints.
- (d) 1 and 5 only
- Portland cement is carbon-intensive; cold mix and geotextiles are the green choices.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.