Creep is defined as the long term deformation under a sustained load. Water within the hardened cement paste is forced to more as a result of the applied load. This movement of moisture is the primary cause of creep deformation. Some movement also occurs due to the propagation of microcracks.
The movement due to creep can be greater than the elastic strain on loading. Creep can continue over a long period of time (more than 30 years in some cases) after the application of the load.
Many of the factors that affect shrinkage and modulus of elasticity also affect the creep is a similar way.
Following are the cases, which affect creep in concrete:
- When the aggregate volume is increased, creep will be less as the aggregate is more rigid than the cement paste.
- When the water/cement ratio is increased, the higher water/cement ratio will result in a more porous and weaker cement paste which will deform more under a given load.
- When the natural aggregate is replaced by a lightweight artificial aggregate, the lightweight aggregate will be more porous and less rigid than the natural aggregate.
- If the applied load is increased, the creep also increases.