Creep in Concrete

Creep in Concrete

Creep in Concrete

Definition:

Creep is the time-dependent component of strain in a material under sustained stress.

Causes of Creep:

• Internal movement of adsorbed water.
• Viscous flow or sliding between gel particles.
• Moisture loss over time.
• Growth of microcracks in the material.

Effects of Creep:

• Increased deflection in beams and slabs.
• Excessive deflection in slender columns, possibly leading to buckling.
• Loss of prestress, causing a reduction in induced stress from restrained shrinkage.

Factors Affecting Creep:

Creep increases when:

• High cement content is used.
• High water-cement (W/C) ratio is present.
• Low aggregate content is used.
• Air entrainment is high.
• Relative humidity is low.
• Temperature is high.
• Small section thickness is used.
• Loading occurs at an early age.
• Stress is proportional to one-third of the compressive strength (f'c/3).

Methods to Reduce Creep:

• Using high-strength concrete.
• Adding reinforcement to resist excessive deformation.
• Steam curing under pressure, which reduces shrinkage and moisture movement.