Concrete cylinders testing and fracture type 3

[gosai]

Does anyone can explain type of fracture of concrete cylinders and relationship of testing procedure. Which fracture type related to correct test procedure and which fracture is not?Thanks to all in advance

 

[Ron]

Generally you look for a cone-shear failure as representing proper specimen preparation and testing.

If you get a shear-only failure, that means that you have stress concentration on the loading.

 

[SirAl]

Agree with Ron. Theoretically you should see a conical failure as lateral strain on the top and bottom of the specimen is restricted by friction against the loading plates which would result in bulging of the mid area of the specimen.

 

[concretemasonry]

If you see non-symetrical shears instead of conical, that would be an indication of poor sample preparation (non-parallel surfaces), improper placement of the samples (off-center) or some testing machine problem.

We had historically had photos of all concrete block prism failure modes and found that the platen thickness were not great enough for larger size (12"x16" or greater top areas). Because of the lack of rigidity, the platen deformed and concentrated the loading. This ultimately lead to greater platen thickness for block prism testing to qualify for ASTM.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[gosai]

Thanks Ron, SirAl and Concretemasonry for answering my question.
Is there any book or article available on type of fracture of cylinder?

Thanks

 

[Ron]

See ASTM C39 for a graphic of the different break types.