Lec 3 - Testing of Concrete | Platen Effect | Concrete Technology

#Concrete_Technology_Lectures
@DCBA online
In this lecture you will learn an important property of hardened concrete that is compressive strength. You will learn testing of concrete and the specifications for testing of concrete. You will also learn about the platen effect.

[@DCBAonline]

Please note at 1:29 point number 3 of cylinder, the dia to size of aggregate should not be less than 3, the same is shown at 0:47 as well.

[@umairuddinshaikh8579]

Amazing sir👍,
During testing of cube which load value to be taken, whether first crack or highest value given by CTM??

[@RiteshSingh1909]

My doubt finally cleared in these most lucid manner. I have a question.. Since lateral resistance is being mobilised in cube, does that means the strength that we are finding is being over-stated but in reality the true strength of the specimen would be less? It would be very much appreciated to get a reply by you. Thankyou

[@DCBAonline]

Yes

[@RiteshSingh1909]

If incase we are testing compression test on opc 53 cement (which probably works on the same principle as that of concrete compression test ) and we found the value to be 53. This value here is being over stated again due to same reasons... Then can companies sell this cement in the name of grade 53 opc cement which doesn't represent the true strength but is over stated? How does IS code cope up this error of stating grades then .. What is the factor of safety code employs to counter this?

[@DCBAonline]

You'll get a strength probably more than 53 in that case. If its less than 53 its not permitted. In design however there are lot of safety factors that IS Code already recommends right from concrete mix design where TMS is greater than required strength to the partial material safety factor taken in LSM.

[@_.Light._]

Awesome . I have one doubt. If we are testing 2 cubes, 1st with steel plates+ cube and 2nd without plates+ cube,
Which one will give more strength?

[@DCBAonline]

Cubes with steel plates would be always better as they also dissipate the load evenly and avoid localised failures, also by applying lubrication platen effect is taken care of.

[@SumitPaudel]

The compressive strength of cencrete can be tested using cube......but why cylinders are necessary?? only cube test is sufficient or not to find its compressive strength??

[@DCBAonline]

Cylinders give more appropriate results, they are slender than cube and also exhibit platen effect due to which the strength of cylinder is lesser than strength of cube. This also creates a safety margin and is almost near to true condition on site.

[@SumitPaudel]

@@DCBAonline Thanks alot sir...

[@saurabhvidhate8533]

Sir you say diameter of mould to size of aggregate ratio should be less than 3.
And diameter of mould is 15cm and size of aggregate is 2cm.right? Then ratio (15/2)=7.5
So sir how can we say it should be less than 3.???

[@DCBAonline]

Ya its a mistake it should not be less than 3; you can see that at 0:47 i have told it should not be less than 3

[@kartiksinghal7345]

Sir in case of platen effect whether
Cube will expand or contract like cone as you have shown un in the figure

[@DCBAonline]

In figure it is not shown as contracting, the figure shows that part of cube which remains intact.

[@kartiksinghal7345]

@@DCBAonline sir at your video's
14:29 minute the contracting cube you have shown i am talking about that figure

[@DCBAonline]

That is not contracting that is the outer surface which has fallen and this shape is achieved.

[@kartiksinghal7345]

@@DCBAonline thank you sir for clearing my doubt and sorry for your inconvenience sir
Sir i am regularly watching your concrete technology videos that are very useful