Tag Archives: PCC

Footings : Levelling Course & Water Logging :

Dear Friends ,

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

This is the query :

1

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 :

14

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

8

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 :

12

Next step is to lay the Rebars of the Footings :

15

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

13

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

16

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 :

9

So what do we do in such a case ?

Simple.

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

10

There might be a case like this also :

6

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 :

17

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

18

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 :

 

Advertisements

Rate analysis for Stone Masonry :

Readers,

When I was standing in a car park , waiting for someone to complete the shopping ,

I got a Whatsapp message from one of my students , asking me for the Rubble masonry rates. He said he wanted to submit the quotation on the same day. There was no use of just giving him a rate which I remember because it has to match with the material and labour rates and profit margin expected by this person.

So , I had to make a rate analysis for the Rubble masonry .

I asked him to message me the basic rates which he promptly did.

I next 15 minutes , I completed the rate analysis and send back the entire analysis to him .

Thought I shall also share the same calculations with you for your quick reference.

 

RANDOM RUBBLE MASONRY USED IN THE COMPOUND WALL . [ REAR PORTION ]
RANDOM RUBBLE MASONRY USED IN THE COMPOUND WALL .
[ REAR PORTION ]
Part A : The data :

Cement: 300/bag

Aggregate:  2400/brass

Rubble : 1500/brass

Labour  :2000/brass

Sand 5500/ brass

You already know that : I brass = 100 Cft

Desired  Profit 25%

 

Specifications :

Rubble masonry Width 18″

for wall compound ht 3′ from ground level

 in cement mortar in ratio : ( 1:6 )

 

Material for 1 cum:

Cement : 300*(0.45*1.52*28.8)/7= Rs.844

Sand:   5500*0.3529*6*(0.45*1.52)/7= Rs.1138

Rubble: 2400*0.3529*1.25 = Rs.1058

Labour : 2000*0.3529= Rs.706

 

Total:                        Rs.3756

Profit:Add@ 25%:     Rs.937

                   Total:  Rs.4693 Rs/cum.

Or             Rs.133 per Cft.

 

PCC 1:4:8

Material for 1 cum:

Cement : 300*(1.52*28.8)/13 = Rs.1010

Sand:   5500*0.3529*4*1.52/13 =Rs.908

Aggregate: 2400*0.3529*8*1.52/13  = Rs.792

 Sub total:                     Rs. 2710

For Labour Add 40%    Rs.1084

Total :                            Rs. 3794

Profits Add25%               Rs.949

Total :  Rs. 4743 per Cum

Rs.   134 per  Cft.

  

Note :

1.You shall observe that the rate for Rubble masonry in cement mortar in CM 1 :6 and the rate for plain cement concrete in proportion 1:4:8 are  almost equal

2. The material wastage is a point on which I need to elaborate.

As such when we consider the factor 1.52 in the material calculations by dry mix method, we are already considering 2 % material wastage . In case you want a higher allowance for wastage , you may take the factor as 1.57 so that material wastage is 7%.