Which method of testing concrete tensile strength (apart from flexure test performed on beams) is the best in your opinion? Which method gives the results of the lowest standard deviation/coefficient of variance?
The split-cylinder test or WST (wedge splitting test ) or other?
Splitting cylinder test often gives low variation coefficient (CoV). For cylinder 150x300, CoV of fct,sp is about 0.07 for 3 samples. It is, however, noted that to calculate the uniaxial tensile strength from fct,sp we need a conversion factor, which scatters and depends on the aggregate size.
To get the realistic uniaxial tensile strength fct from fct,sp it is suggested to use splitting test with core drilling concrete. You can find more statistic information about splitting tensile strength in the following paper:
Article Uncertainties of concrete parameters in shear capacity calcu...
In my experience the slower the experiment is executed (load speed, deformation speed) the lower the COV will be.
In my project "CC" the 4-point-bending-test (deformation controlled) delivered the lowest COV (4,05%), the splitting tensile strength (cube) had a COV 5,77%. Here you will find the COV of all tests: (each 6 specimen)
Preprint Modeling the stiffness degradation of concrete based on phys...
Splitting tensile test, this splitting tensile stregth divided by 1.5 gives the tensile strength
It will depend on many external as well as internal factors. However, my experience favors split tensile test may be cylinder or cube.
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