UPSC CSE Prelims

Correct Option: A (1, 2 and 3 only) Explanation: Using suitable industrial by-products, cold-mix asphalt and geotextiles can lower energy use and virgin material consumption in rural roads; hot-mix asphalt and conventional cement typically have high embodied emissions. Statement / Pair / Item-wise Analysis: 1. Correct - Copper slag can substitute for some virgin aggregates when environmentally tested. 2. Correct - Cold-mix asphalt avoids high-temperature heating and can save energy. 3. Correct - Geotextiles improve road reinforcement and may reduce material demand. 4. Incorrect - Hot-mix asphalt requires energy-intensive heating in conventional paving. 5. Incorrect - Portland cement production involves high process and fuel CO2 emissions. Option-wise Analysis: A. Correct-includes all and only valid statements/items 1, 2, 3. B. Incorrect-includes incorrect item 4 (Hot-mix asphalt requires energy-intensive heating in conventional paving); omits correct item 1 (Copper slag can substitute for some virgin aggregates when environmentally tested). C. Incorrect-includes incorrect item 4 (Hot-mix asphalt requires energy-intensive heating in conventional paving); includes incorrect item 5 (Portland cement production involves high process and fuel CO2 emissions); omits correct item 1 (Copper slag can substitute for some virgin aggregates when environmentally tested); omits correct item 2 (Cold-mix asphalt avoids high-temperature heating and can save energy); omits correct item 3 (Geotextiles improve road reinforcement and may reduce material demand). D. Incorrect-includes incorrect item 5 (Portland cement production involves high process and fuel CO2 emissions); omits correct item 2 (Cold-mix asphalt avoids high-temperature heating and can save energy); omits correct item 3 (Geotextiles improve road reinforcement and may reduce material demand). Review note: Industrial by-products must satisfy leachate and engineering standards; use is not automatically benign.