Previous Year Question
In rural road construction, the use of which of the following is preferred for ensuring environmental sustainability or to reduce carbon footprint?
Copper slag
Cold mix asphalt technology
Geotextiles
Hot mix asphalt technology
Portland cement
Select the correct answer using the code given below:
1, 2 and 3 only
2, 3 and 4 only
4 and 5 only
1 and 5 only
Correct Answer: A
Detailed Solution
The environmental impact of rural road construction can be reduced by using local and waste materials, low-temperature technologies and materials that extend road life.
The use of copper slag is appropriate. It is an industrial by-product generated during the smelting of copper.
After testing and compliance with prescribed quality standards, it may be used as a partial substitute for natural sand or stone aggregates.
The use of copper slag can reduce the extraction of natural construction materials from quarries and the burden of disposing of industrial waste.
Depending on its technical suitability, it may be used in road-base layers, embankments, concrete or bituminous mixtures.
Environmental safety requires testing its chemical composition, leaching of metals, particle size and structural performance.
The use of cold mix asphalt technology is appropriate. It generally uses bitumen emulsion to prepare the mixture.
It does not require aggregates and bitumen to be heated to the high temperatures used in hot mix asphalt.
Lower temperatures reduce fuel consumption, carbon dioxide emissions, smoke and workers’ exposure to hot fumes.
This technology can be particularly useful for small works, maintenance and remote rural areas where large hot mix plants are not readily available.
The use of geotextiles is appropriate. These are permeable, fabric-like engineering materials placed between soil and different road layers.
Geotextiles can perform the functions of separation, filtration, drainage, reinforcement and erosion control.
They help stabilise weak subsoil, prevent the intermixing of road layers and extend the service life of the road.
This may reduce the requirement for natural aggregates, repeated repairs and the consumption of energy and materials over the road’s life cycle.
Hot mix asphalt technology is not preferred for reducing the carbon footprint because it requires heating bitumen and aggregates to high temperatures.
High temperatures require more fuel and increase CO₂, smoke and other air emissions.
Portland cement is also not preferred solely for reducing the carbon footprint because its production involves limestone calcination and high-temperature kilns.
Portland cement may be used for road stabilisation and concrete works, but it has high embodied carbon.
Therefore, copper slag, cold mix asphalt technology and geotextiles are preferred for environmental sustainability and reducing the carbon footprint.