Skip to main content

Cube versus cylinder compression test

Short answer

Cubes (150 mm) are easy to mould and store, but platen restraint gives 20-25% higher strength. Cylinders (150×300 mm) with h/d=2 give truer uniaxial strength but need capping and are heavier. Steps: sample at placement, cast cubes in 3 layers, tamp, cure 28 days at 27°C, test loaded on side faces at 14 N/mm^2/min, fc = P/A, average three cubes.

State the merits and demerits of cube and cylinder as specimen for compression test. Write the steps for compression testing of concrete from sampling.

Merits and demerits

Cube (150 mm)Cylinder (150 × 300 mm)
MouldingEasy to cast, handle and store; used in India, Nepal, UKHeavier; casting and capping are more difficult
Platen restraintHigh (h/d = 1), so strength appears 20 to 25% higherLower (h/d = 2), so nearer to the true uniaxial strength
Stress stateNot uniform; complex stressMore uniform and close to uniaxial
SurfaceCast faces are smooth and parallel, no capping neededNeeds capping of ends
UseQuality control and acceptance (IS 456)Used in USA, Europe, research; also for modulus and splitting tests
Conversionfcyl≈0.8fcubef_{cyl} \approx 0.8 f_{cube}

Steps for compression testing from sampling

  1. Take the sample at the point of placing, as per the frequency of IS 456, Cl. 15.2 (1 sample for 1 to 5 m3^3, etc.).
  2. Fill 150 mm cube moulds in 3 layers, compact each layer by tamping (35 blows with a 16 mm rod) or by vibration, level the top, and mark the cube.
  3. Keep at 27 ± 2 °C, covered, for 24 hours; demould and cure in water until 28 days.
  4. Remove the cube from the water and wipe it. Place it between the platens so that the load acts on two opposite faces as cast (not on the top and bottom as cast), and apply the load at 14 N/mm2^2/min until failure.
  5. Calculate fc=P/Af_c = P/A, take the average of three cubes, and apply the acceptance criteria of IS 456, Table 11.

✓ Answer checked by Claude Sonnet 5.5

Related questions

All Concrete Technology and Masonry Structure chapter 5 questions →