Concrete Cube Test

Why is the concrete cube tested for weight before compression test?

Questions by jraman

Showing Answers 1 - 6 of 6 Answers

bhupi1588

  • Aug 10th, 2009
 

The main reason for calculating the weight on concrete block before testing in the compression machine is to check whether the weight is nearly same or approximately equal to the value which is calculated by the multiplication of density
and volume.  What I mean to say is that this is an approx way to see whether the concrete being used is correct or
not and now the exact results can be calculated by the concrete compression testing
machine which will give the strength the block can hold.

mass=density*volume


The weight should come to about 8 to 8.5 kg for a 150*/150*150 mm^3 concrete block.
If the value does not come as the given value then the concrete mixture is not correct
and the compressive testing is of no use as the concrete being taken cannot be used in building structures.


Thanks for the interest

bhupi1588

  • Aug 11th, 2009
 

The basic reason for the weight calculation is to check for density as if the prescribed density is not the same as the density as calculated from the weight calculated then the compression test is not useful to do as the concrete cannot be used for building structures as it is not fit for it.

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The concrete cube test is done to detect the maximum load that the proportiones cube with the ratio of water to cement,can bear before cracking and ultimately failing.

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sappy_shail

  • Nov 23rd, 2009
 

As a thumb rule, more the density, more will be the compressive strength. But it is not always true. The compressive strength depends on many factors. Density gives a general idea as to how much was the water in the mix and what would be the void ratio after hydration, given constant physical properties of other ingredients. What adds to strength is that there is max possible size of aggregate, there are other sizes so graded to fill in max voids between coarse aggregate, there is enough cementetious material to cover all other particles with cement paste and there is enough water which is actually slight less than required for complete hydration. Now you can understand why and to what extent density can be taken as mark of strength.

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It is not so simple. A very dense concrete is not necessarily strong in compression. You may like to know about open grading used for economical concrete.... new trend. The question in the first place is not an objective type one. It is still open to different interpretations. Less dense concrete may be due to more water, more entrapped air, less FA, open grade....etc...and all this may be to meet some properties during laying, economy in material or durability in longer run

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