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During cube casting, concrete is placed in three layers and each layer is compacted by hand tamping with a steel bar. The bar specification and the tamp count per layer are:
Answer & Solution
Correct answer: A.
1. The tamping bar is a 16 mm diameter steel rod, 0.6 m long, with a bullet-pointed lower end.
2. Each of the three layers receives at least 35 evenly distributed tamps.
3. Alternative compaction is by table or immersion vibrator.
4. After the final layer the surface is finished with a mason's trowel.
5. The 12 mm, 20 mm and 10 mm options do not match the IS specification.
_Source: IGNOU ET-522 Concrete Technology, Block 2 Unit 9 "Testing of Concrete"._
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