The concrete slump recommended for columns, is A. 25 to 50 mm B. 25 to 75 mm C. 75 to 125 mm D. 50 to 100 mm

The correct answer is: A. 25 to 50 mm

The slump is a measure of the consistency of concrete. It is determined by how much the concrete slumps when it is placed in a cone and then released. A slump of 25 to 50 mm is recommended for columns because it provides a good balance of workability and strength.

A slump of less than 25 mm would make the concrete difficult to place and compact, while a slump of more than 50 mm would make the concrete more likely to crack.

Here is a brief explanation of each option:

• Option A: 25 to 50 mm. This is the recommended slump for columns. It provides a good balance of workability and strength.
• Option B: 25 to 75 mm. This is a higher slump than is recommended for columns. It would make the concrete more difficult to place and compact, and it would be more likely to crack.
• Option C: 75 to 125 mm. This is an even higher slump than option B. It would make the concrete very difficult to place and compact, and it would be very likely to crack.
• Option D: 50 to 100 mm. This is a range that includes both the recommended slump (25 to 50 mm) and a higher slump (75 to 125 mm). It is not clear which slump would be appropriate for columns, so it is not the best answer.