Dear Friends ,
Let us solve the query of one of the readers today.
This is the query :
In fact , there are two queries here :
- When do we use Plain Concrete in a footing ?
- 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 :
Now have a look at the base of a pit . This is how the surface shall be at the base of the excavation :
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 :
Next step is to lay the Rebars of the Footings :
Parallely , the shuttering for the footing is also fixed on the Levelling course.
Now we do casting of the Footing so that it becomes the RCC footing .
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 :
So what do we do in such a case ?
We have dewatering pumps and take out the water before laying the Levelling course :
There might be a case like this also :
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 :
These boulders , when laid in the base of a pit , shall look like this :
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 .
Blog Stats as on date :