Pick up the INCORRECT statement from the following regarding preliminary tests on concrete:
Try it first: pick an option, then read the explanation.
Correct answer: D. Concrete ingredients should be kept at a temperature of 37° ± 2° C
Detailed Explanation: Temperature for Preliminary Concrete Tests
Why D is INCORRECT (= the answer): IS 516 (Method of Tests for Strength of Concrete) specifies that during preliminary (trial) mix testing, the concrete materials and the testing environment should be maintained at 27°C ± 2°C, not 37°C. This represents normal ambient temperature in India and ensures reproducibility of results.37°C would be abnormally hot — at this temperature, cement hydrates faster, water demand increases (higher evaporation), and early strength development accelerates. Test results at 37°C would NOT represent typical site conditions, making the specification incorrect.
Checking All Statements
| Statement | Verdict | Reason |
|---|---|---|
| A. Same proportions as site mix | Correct | Trial mix must replicate actual site mix for valid results |
| B. Cement mixed by hand for uniformity | Correct | Manual blending of cement before batching ensures uniformity |
| C. Store mix in air-tight containers | Correct | Prevents evaporation and contamination during testing |
| D. Ingredients at 37° ± 2°C | INCORRECT | Should be 27° ± 2°C per IS 516 |
- Correct temperature for preliminary concrete tests: 27°C ± 2°C per IS 516.
- 37°C would cause accelerated hydration and give non-representative test results.