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
(b) 2, 3 and 4 only
(c) 4 and 5 only
(d) 1 and 5 only
8. Ans: a
Explanation:
Copper slag is a by-product obtained during smelting and refining of copper. The waste copper slag can be used as abrasive tools, road construction, and ballast. One of the greatest potential applications for reusing copper slag is in cement and concrete production.
Asphalt is a mixture of aggregates, binder and filler, used for constructing and maintaining roads, parking areas, railway tracks, ports, airport runways, bicycle lanes, sidewalks and also play- and sport areas. Aggregates used for asphalt mixtures could be crushed rock, sand, gravel or slags. Nowadays, certain waste and by-products, such as construction and demolition debris, are being used as aggregates, which increases the sustainability of asphalt.
Hot Mix Asphalt (HMA)
Hot asphalt mixes are generally produced at a temperature between 150 and 180 °C. (more energy is involved and, consequently, more fumes are produced)
Warm Mix Asphalt (WMA)
A typical WMA is produced at a temperature around 20 – 40 °C lower than an equivalent Hot Mix Asphalt. Significantly less energy is involved and, consequently, less fumes are produced (as rule of thumb, a reduction of 25ºC produces a reduction of 75% of fumes emission). In addition, during the paving operations, the temperature of the material is lower, resulting in improved working conditions for the crew and an earlier opening of the road.
Cold Mix Asphalt
Cold mixes are produced without heating the aggregate. This is only possible, due to the use of bitumen emulsified in water, which breaks either during compaction or during mixing. Producing the coating of the aggregate. Over the curing time, water evaporates and strength increases. Cold mixes has the least emissions among all.
Geotextiles are permeable fabrics made from synthetic or natural fibers. They are designed to be placed in contact with soil or rock to improve their strength and stability. Moreover, they are commonly used to prevent soil erosion, filter water, and separate different layers of soil or rock.
Portland cement is a fine powder, gray or white in color, that consists of a mixture of hydraulic cement materials comprising primarily calcium silicates, aluminates and aluminoferrites.
Particulate matter (PM and PM-10), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), and CO2 are the primary emissions in the manufacture of portland cement. Small quantities of volatile organic compounds (VOC), ammonia (NH3), chlorine, and hydrogen chloride (HCl), also may be emitted. Emissions may also include residual materials from the fuel and raw materials or products of incomplete combustion that are considered to be hazardous.
Hence, option a is correct.
Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2020