Category Archives: basement

OH BASEMENT ? NO ISSUES…

Dear Readers ,

Good evening to all .

We heartily welcome the newly joined followers.

Today let us work out the quantities for a RCC basement.

Here is the full question.

13

12

7

11

10

9

8

6

5

4

3

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LEARN BASEMENT IN EASY STEPS

Dear friends ,

Hurrey !

Its 4 th July 2016.

Hearty congrats to you !

Today we are completing exactly 20 months since inception of this blog.

This is our performance ;

Whole credit goes to you for your support.

We shall learn about Mat foundation today.

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Box type waterproofing

Dear Readers ,

Some days back , we had a discussion regarding the construction of the  basements.

There we also reviewed , how exactly is the water proofing carried out.

We also saw what is meant by box type water proofing.

For quick reference , here is the link : Box type water proofing 

Going further , on the same topic, you can see this video where the author is explaining to the students ,

the importance of the box type water proofing .

[ This is in Marathi ]

here is the link for the video :Box type waterproofing

Would look forward for your suggestions

Thank you so much for your active participation in the blogging process.

Box type Water proofing

Background :

During previous post , we considered the various elements to be constructed for an elevator or lift.

We also saw that in the Lift pit , we need to do the box type of water proofing.

{ Refer the post :PROVISION FOR ELEVATOR }

The water proofing is also needed for the basement portion.

basic purpose is quite obvious. To prevent the basement from getting flooded by water.

This might happen during the rainy season or in case if the  water level is already at a higher level , then this might be a perennial issue.

This article explains the basic steps to be taken during the box type of water proofing .

A series of photographs right from mass excavation up to the base raft have been demonstrated for clarity of the steps.

IMAG3986
YOU SHALL WONDER TO THIS SCENARIO. THIS IS A MASS EXCAVATION DONE FOR THE BASEMENT OF A BUILDING. THE MASS EXCAVATION WAS COMPLETED FAST WITHOUT PROPER PLANNING.AS A RESULT , YOU CAN SEE THAT THIS PIT IS FLOODED WITH RAIN SURFACE WATER . IN MY OPINION , THE EXCAVATION SHOULD BE TAKEN UP ONLY WHEN THE BASIC INFRASTRUCTURE SUCH AS CEMENT GODOWN , APPROACH AND MATERIALS ARE AVAILABLE AT SITE .
IMG02772-20130107-1219
DE-WATERING HAS BEEN COMPLETED FOR THE ENTIRE PIT.IT HAS BECOME DRY NOW.THE EXCAVATION BOTTOM HAS BEEN DRESSED TO RECEIVE FURTHER TREATMENT.
17122010013
RUBBLE SOLING HAS COMPLETED . THIS IS NECESSARY ESPECIALLY IF THERE IS A LARGE LEVEL DIFFERENCE AT THE PIT BOTTOM. THIS IS AN ECONOMICAL AND STRUCTURALLY BETTER SOLUTION TO SPENDING ON PLAIN CEMENT CONCRETE. FILLING MURRUM IS ALSO A GOOD OPTION BUT IT TAKES MORE TIME TO COMPACT AND CONSOLIDATE THE MURRUM IN LAYERS.
20122010040
PLAIN CEMENT CONCRETE IN MIX M10 HAS BEEN COMPLETED OVER THE RUBBLE SOLING.
26122010065
FLAG STONES ( 15 TO 20 MM THICK ) ARE LAID OVER THE PCC. FLAG STONE IS A NATURAL STONE ( SEDIMENTARY/METAMORPHIC ) AND IS RESISTANT TO WATER SEEPAGE. YOU CAN SEEN THAT AN OPEN JOINT OF 15 TO 20MM IS KEPT IN BETWEEN THE STONES. THIS IS FOR ENSURING THAT A WATERTIGHT JOINT CAN BE PREPARED BETWEEN THE STONES.
20150304_104633
THIS IS THE BASE PORTION OF THE RAFT WHICH CORRESPONDS TO THE ELEVATOR AREA. YOU CAN SEE A CENTRAL PIT WHICH IS EQUAL TO THE LIFT SHAFT/DUCT. THE REINF. ARE FOR THE LIFT RCC WALL .
20150310_125424
HERE YOU CAN SEE THE FOLLOWING : 1. WATER PROOF CEMENT PLASTER FINISHING HAS BEEN COMPLETED OVER THE PCC. 2.THE BASE RAFT REINFORCEMENT HAS BEEN LAID IN POSITION 3.BOX FOOTINGS & COLUMN REINFORCEMENT ALSO HAS BEEN PLACED IN POSITION.
20150310_085750
THIS IS A PANORAMIC VIEW OF THE BASEMENT . THE BASE RAFT IS NOW READY FOR CASTING. IN THIS PIC YOU CAN ALSO SEE THE PERIPHERAL RCC WALL FOR THE BASEMENT.
IMG_20150304_095619
THIS PHOTOGRAPH SHOWS THE POSITION AFTER THE BASE RAFT HAS BEEN CAST.

Growing columns in backyard ?

Overview:

Previously , we saw how the action went on from land procurement up to the construction of the basement. [ Read posts  :One ..two..three  and ..start & The building grows above plinth ]

We saw how the specimen cubes were cast and tested on 7th & 28th days from the date of casting.
We also spoke about the characteristic strength of concrete.

We went ahead and listed down all tasks that need to be executed in a building.

We also saw 4 different cases of multidisciplinary coordination.[Read post: Progress continued ..upwards ]

Now let’s go ahead and focus on the next activity ..the columns beams slab.

Background:

Basement roof slab has been cast.
Dowel bars are left protruding from the columns .

Further activities shall be undertaken as follows:

Columns above basement roof slab :

1.Dowel bars shall be lapped with new bars of the same diameter so that  the bars reach above the proposed slab .The dowel bars shall extend at least 45 times the bar diameter above the slab.
( If the bar diameter is 12 mm then we must verify that these extend for a minimum of                       45 x 12 = 540 mm above the slab level.Some situations may require that this lapping distance be maintained as 52 times bar diameter. This detail shall be provided in the RCC  drawings.
The lapping between the bars shall be tied together with the binding wire .
Binding wire is mild steel wire of 1.6 mm diameter . Some builders use galvanized binding wire which is resistant to rusting and hence improves the durability  of concrete.
Hand held portable machines are also available for tying the bars with binding wire .

LAPPING OF COLUMN BARS COMPLETED. STIRRUPS ARE BEING TIED UP.
LAPPING OF COLUMN BARS COMPLETED.
STIRRUPS ARE BEING TIED UP.

2.Stirrups shall be inserted in the main bars of the column and shall be fixed at the  spacing specified in the drawing.

COVER BLOCKS WITH BINDING WIRE FOR TYING WITH THE REINF.BARS
COVER BLOCKS WITH BINDING WIRE FOR TYING WITH THE REINF.BARS

Usually the doughnut shaped cover blocks are fixed in the stirrups so that the cover to the reinforcements is maintained.

COLUMN SHUTTERING IN PLACE. PROPERLY CLAMPED WITH SHIKANJA.
COLUMN SHUTTERING IN PLACE.
PROPERLY CLAMPED WITH SHIKANJA.

3.Form work for the column shall now be fixed on the starter.
Starter is a small piece of column which is cast before the main column is cast.
A wooden  box  of internal size exactly matching with  column size is placed in position. The center lines are checked.and concrete of the specified grade is poured in this mould .

STARTER ON THE TOP OF A TRAPEZOIDAL FOOTING
STARTER ON THE TOP OF A TRAPEZOIDAL FOOTING

The advantages of having a starter are:

a.It is easier to establish & verify the center line  of the starter than of that of the column.

b.It is sturdier to fix the column shuttering if the starter is already in place.
c.The chances of column form work becoming skew are eliminated.

4.After erecting the shuttering for column ,Bracing or supports are fixed ,the verticality is checked on two  sides ( adjoining faces ) with a plumb bob and alignment is checked with the help of a cotton or nylon thread.

5. The column shall be cast after all checks are completed with the approved concrete mix.

6.the column shuttering shall be removed next day and the curing shall be taken up. depending on the climate ( temperature and humidity ), the curing can be done either by spraying water at intermediate intervals or by wrapping column with hessian clothe and keeping it wet.

COLUMNS BEING CURED WITH WET HESSIAN CLOTHES [ THE OWNER PROUDLY LOOKS ON ]
COLUMNS BEING CURED WITH WET HESSIAN CLOTHES
[ THE OWNER PROUDLY LOOKS ON ]
Author’s note :

Thank you for reading so far with total attention.

In the next article we shall speak about the entire process involved in the casting of the roof slab.

Till then , bye bye

Take care.

AUTHOR with Construction personnel at a site
AUTHOR with Construction personnel at a site

The Building grows….. above the plinth

Welcome back Readers.

In Previous articles we saw which are the overall phases from start to completion of any building.

We discussed about the Planning phase , the Pre-construction phase .

In the construction phase,  we covered up to  completion of the basement raft.

BASEMENT RAFT:  Just prior to pouring
BASEMENT RAFT:
Just prior to pouring
BASEMENT IS COMPLETE
BASEMENT IS COMPLETE

Now before we continue further , we take a small detour :

Know something about cubes testing :

Just to update you, the cubes were cast during the concreting of basement raft .The Clients had bought a set of 6 cube moulds for taking the specimen cubes on the site. Its a good thing to have own set of cube moulds so that the cubes can be cast whenever planned without any dependence on any external agency.

SPECIMEN CUBES BEING CAST AT SITE .  cube moulds 6 nos are being cast.
SPECIMEN CUBES BEING CAST AT SITE .
cube moulds 6 nos are being cast.

How to get the cube moulds :

These are generally available at any agency dealing in scientific instruments and are supplied as per

FPS units or as per  MKS units .

FPS: foot, Pound,second    MKS: Meter ,Kilogram, Second 

Mould Size in FPS units : 6″ x 6″x 6″

 Mould Size in MKS units : 150 mm x 150 mm x 150 mm.

Practically speaking ,there is no difference whatsoever as to which cubes you buy.

Since the laboratory is as such going to measure the top area of the cubes in exact dimensions.

Compressive strength = crushing load / Area of the cube.

The cubes cast at the basement raft were sent to local laboratory.for testing .

RECENTLY CAST SPECIMEN CUBES. [ The date of casting and location has not yet been marked ]
RECENTLY CAST SPECIMEN CUBES.
[ The date of casting and location has not yet been marked ]
Method of testing :

The cubes were immersed in curing pond till one day prior to the date of testing.

These were taken out 24 hours earlier and then tested.

CUBES  SUBMERGED IN CURING POND
CUBES SUBMERGED IN CURING POND

The tests were carried out on 7th day and 28th day from the date of casting.

SPECIMEN CUBE BEING TESTED IN THE COMPRESSION TESTING MACHINE.
SPECIMEN CUBE BEING TESTED IN THE COMPRESSION TESTING MACHINE.

That’s why you would have noticed that during finishing of the cubes, the casting date and the location is always mentioned on the cubes.

OBSERVE THE DATE OF CASTING ENGRAVED ON THE CUBES.
OBSERVE THE DATE OF CASTING ENGRAVED ON THE CUBES.

As a good practice , a cube testing register is maintained at site in which the date of casting, date of testing and test results are recorded. This register becomes an important record of the quality of concrete carried out.

Certain builders have a regular practice of getting the cubes tested in the In house laboratory as well in the external laboratory. The cube testing from an external laboratory acts as a third party check on the in house testing process.

You shall be probably wondering as to why 7th day test is carried out ?

The 7th day test shows 65% of the characteristic strength of the concrete.So, if we are working with

M20 grade concrete with characteristic strength of  20 x 10 = 200 kg /Sq.cm,

the 7th strength shall not be less 200 X 65% = 130 Sq. cm

By carrying out the 7th day testing we receive an early confirmation of the strength of the concrete and actions can be initiated in case it is called for at an early date .

Any way , the results of both the 7th day and the 28th day testing were as per the norms.

AUTHOR ON A CONSTRUCTION SITE
AUTHOR ON A CONSTRUCTION SITE

AUTHOR’S NOTE :

Friends.

This was just a small detour to talk about the cubes testing at site.

From next post , we shall continue with our journey above the plinth.

Till then,

Good bye