Foundation, Concrete and Earthquake Engineering

What Should be the Suitable Height of Concrete Layer?

Many aspects of compaction and specially compaction by vibration of concrete have already discussed in previous posts. Vibrators have capacity to compact to certain depth below concrete layer. Depending on the type of vibrator the capacity of vibrator may vary. But there have standard practice to provide layer height of concrete to have a dense concrete having no air void without segregation. We will now know the usual practice of placing height of concrete layer.

It should keep in mind that the depth of layer depends on placement method and method and type of compaction. If hand compaction is used, the depth of concrete layer definitely much layer than that for machine vibration.
Vibrating Compaction of deep concrete mass in Salt River Project, Arizona
Here we are discussing about height of concrete layer that are compacted by vibrator. Generally concrete is placed at a thickness of less than 600 mm. But the thickness of initial placement of concrete should be less than 150 mm. When height of concrete layer increased, it helps performance of vibrator with increased super imposed load. But excess height results a way of entrapping air in concrete. Vibration of too deep concrete layer, results trapping air to come up by vibration. In some special cases like dam, heavy pile cap etc. sometimes the depth may be greater than 1 m but these heavy concreting works require powerful vibrator of adequate capacity. So too deep layer (greater than 600 mm) are avoided in normal practice.

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