UPSC Prelims 2020 · GS Paper I
Question 78: Environment and Ecology
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 :
AnswerUPSC’s answer is (a).
Green technologies promoted in rural road building include copper slag as an industrial-waste substitute for aggregate, cold mix asphalt (which needs no heating and uses less energy than hot mix), and geotextiles, which reduce the thickness of aggregate needed. Hot mix asphalt and Portland cement carry a larger carbon footprint.
- 1. Copper slag reuses industrial waste in place of aggregate.
- 2. Cold mix needs no heating, so it uses less energy.
- 3. Geotextiles reduce the aggregate needed.
- 4. Hot mix asphalt is energy intensive.
- 5. Portland cement has a high carbon footprint.
How you could have got this
- If you were sure statement 1 is correct, (b) and (c) go: each of them leaves 1 out.
What you needed to know: Copper slag reuses industrial waste in place of aggregate.
- Then, if you were sure statement 2 is correct, (d) goes: it leaves 2 out.
What you needed to know: Cold mix needs no heating, so it uses less energy.
Only (a) is left. You didn’t need statements 3, 4 or 5.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Right: copper slag, cold mix and geotextiles.
- (b) Wrong: includes hot mix asphalt, which is energy intensive.
- (c) Wrong: hot mix asphalt and Portland cement have a larger carbon footprint.
- (d) Wrong: includes Portland cement and leaves out cold mix and geotextiles.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper I, Series A. The paper on upsc.gov.in.