Concrete creep is defined as: Due to sustained load on the member of structure such as beam column causes deformation is called as creep of concrete. generally long term pressure can make the concrete change is its shape. The deformation generally occurs in the direction of force applied. Some of the few examples are concrete tends to compress and Beam tends to bend. It does not fail the concrete or break apart. Elastic strain is experienced by concrete when a a load is applied and this load produces the creep strain when the load sustained.
Factors Affecting Creep
- Aggregate
- Age of concrete
- Mix Proportions
1 to 3 times the value of instantaneous elastic strain is equal to magnitude than creep strain. Creep of concrete depend upon various factors age and strength of concrete, magnitude of the applied stress, proportion of aggregate,amount of cement ,paste ,size and shape of concrete specimen ,volume to surface ratio, amount of Steel reinforcement.
1. Influence of Aggregate
Aggregate is not the direct influencer of the creep but when the paste is prepared it is resposible for creep. The aggregate is when which is the influence of the the creep of concrete through restraining effect on the magnitude of creep. Aggregate do not creep under load but paste does creep under load. The Restraining effect is more when the aggregate is stronger and hence magnitude of creep will be less if the volumetric content of aggregate is increased by 65 to 75% then the the aggregate will able to decrease the by 10%.
Modulus of elasticity is one of the prime factor influencing creep it can be shown as more the modulus of elasticity less is the creep. Also as well lightweight aggregate produces higher creep then the normal weight aggregate.
2. Influence of Mix Proportions:
The paste content and amount of paste can be factors influencing the amount of creep. The structure of paste is good then the creep will be less. So you can say that is water cement ratio is more the creep will be more. Of concrete it is not directly proportional to creep of concrete also you can say that the factor which affecting water cement ratio will also affect creep of concrete.
3. Influence of Age:
8 of the concrete is one of the prime factor affecting the the creep of concrete. The age of member at which it is loaded may have significant effect on the creep of concrete. While the example of that is that young age jel creeps more because it is not stronger enough under load while quality will improve with the time. Also the moisture content in the concrete is different at the different age it also affect the creep of concrete.
Effects of Creep on Concrete and Reinforced Concrete
- Deflection can be increased with the time due to creep in the the reinforced concrete beam.
- Buckling can be occured due to increase of deflection because of cream in the ecentrically loaded column.
- Stress concentration which is caused due to shrinkage,temperature changes and moment of support can be relieved by creep at the column and beam junction. Creep property can be used as to reduce the internal stresses in the concrete structure.
- Creep of concrete is more dangerous to the mass concrete structures,where the temperature in the interior and the surface is different so it can cause cracking in the interior of the dam therefore all precaution needs to be taken to see that increase in temperature will not affect the the interior of the mass structure.
- Prestress can be lost due to creep of concrete in the prestressed concrete structure.
- The design load experienced by the member due to rapid construction techniques is very large at the early age of the member so this can cause deflection and low elastic modulus. Both of the factors are are structural integrity of the creep so it should be handled carefully.
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