Cylinder versus cube test view

View: the statement is correct. Many research laboratories are shifting to cylinders because they give a more reliable measure of the real strength of the material.

Reasons in favour of cylinders

1. Less platen restraint. A cylinder of height/diameter = 2 has a central zone not confined by the end friction, so failure is closer to uniaxial compression. The cube (h/d = 1) lies completely within the restraint zone and gives a strength 20 to 25% higher.
2. Uniform stress and a well-defined failure mode.
3. The same cylinder is used for splitting tension, modulus of elasticity and Poisson's ratio, and gives consistent results.
4. Better for high-strength concrete and for comparing results among laboratories (ASTM and Eurocode specify cylinders; $f_{ck,cyl}\approx 0.8f_{ck,cube}$).
5. Cores drilled from structures are cylinders, so the same shape allows direct comparison.

Limitations

• Cylinders need capping (sulphur, neoprene pads) or grinding, are heavier, and the test is more sensitive to the end condition and to care in moulding.

For quality control on sites in Nepal and India, the 150 mm cube remains the standard (IS 456 and IS 516) for simplicity, but for research and international use the cylinder is rightly preferred.