In rural road construction, the use of which of the following is preferred for ensuring environmental sustainability or to reduce carbon footprint? Select the correct answer using the code given below:

Answer: (a) 1, 2 and 3 only

Slag, cold mix and geotextiles cut the carbon footprint (PMGSY guidelines).

Statement by statement

1. ✓ YES Copper slag replaces mined aggregate.

2. ✓ YES Cold mix asphalt needs no heating — less fuel and CO₂.

3. ✓ YES Geotextiles (jute, coir) strengthen roads and reduce material use.

4. ✗ NO Hot mix asphalt needs heating — more fuel, more emissions.

5. ✗ NO Portland cement is carbon-heavy.

The idea

A road has three big sources of carbon: fuel burnt to heat bitumen, the making of cement, and the quarrying and transport of stone. A material or method is “green” if it avoids one of these.

Copper slag: an industrial waste → replaces quarried stone → Cold mix: bitumen emulsion laid without heating → no fuel burnt → Geotextiles: jute or coir fabric → stronger base with less material → Hot mix: heated to about 150°C → fuel burnt → Portland cement: made by heating limestone → high CO₂

The trap

Hot mix is standard on highways, so it feels “preferred”. For low carbon, cold mix wins.

Also know

Rural roads under the Pradhan Mantri Gram Sadak Yojana also use fly ash and waste plastic mixed in bitumen. Coir and jute geotextiles add a use for natural fibres.