Category Archives: PCC

Footings : Levelling Course & Water Logging :

Dear Friends ,

Let us solve the query of one of the readers today.

This is the query :

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In fact , there are two queries here :

  1. When do we use Plain Concrete in a footing ?
  2. Ground Water seepage during excavation ?

Let us solve these queries one by one.

First query is about the Plain cement Concrete .

Please have a look at the section of the Footing as given in the RCC drawing :

The PCC is marked here with Red :

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Now have a look at the base of a pit . This is how the surface shall be at the base of the excavation :

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It shall be very clumsy to lay the rebars on such a muddy surface. Right ? Thats why we provide a certain thickness of plain cement concrete here . This concrete is also known as the ” LEVELLING COURSE “.

So the Levelling course is a layer of Plain cement concrete which is given so that we get a good working surface for laying the footing properly. 

Now have a look at the leveling course laid on a site :

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Next step is to lay the Rebars of the Footings :

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Parallely , the shuttering for the footing is also fixed on the Levelling course.

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Now we do casting of the Footing so that it becomes the RCC footing .

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Hope the first query is clarified.

Now second query pertains to the Water logging during excavation.

You can have a condition like this on the site :

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So what do we do in such a case ?

Simple.

We have dewatering pumps and take out the water before laying the Levelling course :

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There might be a case like this also :

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So now , may be we shall have to wait for a dry spell so that this water either gets absorbed in the soil below or is evaporated.

In a situation , when the excavated pit is not completely dried, it shall not be possible to lay the plain cement concrete in the mud.

What do we do then ?

In such a case , we shall have to do Boulder solling so that we get a good ,

solid working surface .

Look at the stake of Boulders which are also known as Rubble or Stone :

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These boulders , when laid in the base of a pit , shall look like this :

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After this , the levelling course is laid in plain cement concrete. This is followed by the RCC footing.

Hope both the queries are clarified now.

Thank you for asking the queries .

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What is self-compacting concrete?

Answer by Joe Fernandes:

Self-compacting concrete is a flowing concrete mixture that is able to consolidate under its own weight. The highly fluid nature of SCC makes it suitable for placing in difficult conditions and in sections with congested reinforcement. Use of SCC can also help minimize hearing-related damages on the worksite that are induced by vibration of concrete. Another advantage of SCC is that the time required to place large sections is considerably reduced.

What is self-compacting concrete?