When concrete structures are not permanently saturated with water, it begins to lose moisture and begin to shrink by the time the curing process stops.

The 7 primary structural effects of shrinkage are as follows.

1. Joint

The shrinkage of the concrete between the moving joints causes the joints to open up or widen. The joints must therefore be designed to accommodate the widening caused by shrinkage.

2. other material

Where other materials, such as ceramic tiles, are fixed on top of the concrete surface, shrinkage of the concrete results in relative movement between the different materials. The resulting stresses can cause failure at the interface.

3. hoof

If the shrinkage is stopped, the concrete is put under stress and when the tensile stress equals the tensile strength, the concrete cracks.

shrinkage cracks in concrete
shrinkage cracks in concrete

Structural designers may design structures to reduce restraint, press concrete to prevent tensile stress, or use reinforcement to control cracking.

4. pressure loss

Due to the shrinkage, the compressive force decreases. When calculating prestressing forces, designers take this into account to ensure that the residual stress is structurally sufficient.

5. Repairs

If concrete is used to fill a cavity in the old concrete, the shrinkage of the new concrete is inhibited by the surrounding old concrete. Repair concrete and mortar must be specially prepared (by incorporating a polymeric material) to prevent cracking caused by this restraint.

6. bond strength

As the concrete shrinks, the reinforcing bars hold the concrete more firmly in place. This increases the friction between the concrete and the steel and therefore improves the bonding strength, especially for plain bars.

7. deflection

Contraction increases the deflection of the flexural members. This is because the lighter reinforced compression region is free to shrink more than the heavily reinforced tension region.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.