For different tests we get different value of characteristic compressive strength.IS456 -2000 recommand 15cm Cube strength where as ASTM Recommand the cylindrical strength.
http://theconstructor.org/concrete/compressive-strength-of-concrete-cubes/1561/
http://theconstructor.org/concrete/compressive-strength-test-on-concrete-cylinders/2234/
i found grade of concrete is based on 15cm cube compressive strength.as the lamda(l/d)value obtained from strength reduced so that the cylindrical strength is 0.8 of 15 cm cube strength.and 10 cm cube strength is 1.1 strength of 15cm cube sterngth. for structural concrete the strength is 0.67 fck based on lamda. so we conclude that the actual strength of concrete is at the plastic strain 0.0035 as it is a brittle material.and constant.
15 cm cube strength after 28 days of curing is compressive strength. Also only 5% results are expected to fail and 95% results indicate the compressive strength of particular grade of concrete.
As per IS code the compressive strength of 150mm cube is tested, and the characteristic strength of cube is tested at the age of 28 days, not more than 5% result of the strength beyond the limit. ratio between the cylindrical strength and cubical strength is equivalent to 0.8 for up to M40 or M50 grade of concrete, where as if the grade of concrete is M80 or above this ratio will increase, and for concrete above M100 grade the ratio become unity.
As per RILEM, the strength of two different shape of concrete can not be compared, and the same is written by A M Neville in his book Properties of Concrete.
It is roughly taken as 95% of design mix strength at mean target strength.
- Badges
- Science topic