As the cube size increases, the strength of concrete

Explanation:

• Larger Cube Size – Lower Strength:
  As the size of the concrete cube increases, the measured compressive strength decreases.
  This is due to a higher probability of internal flaws, stress concentrations, and heterogeneity in larger specimens.

• Size Effect:
  Known as the size effect in concrete strength, it results from non-uniform stress distribution and micro-cracking that become more prominent in larger specimens.

 Additional Information

• Standard Cube Sizes:
  The typical size for compressive strength testing is 150 mm cubes. For smaller elements, 100 mm cubes may be used.

• Why Smaller Cubes Show Higher Strength:
  Smaller specimens are more homogeneous and less likely to contain critical flaws, leading to higher strength readings.

• Code Considerations:
  IS 516 specifies correction factors when comparing strengths from cubes of different sizes to maintain consistency.

• Practical Implication:
  Structural elements often show lower in-situ strength than lab-tested small cubes, and design safety factors account for this discrepancy.