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