How can we reduce laitance from concrete structures?

Laitance can be reduced by controlling the amount of water in the concrete mix during construction. If too much water remains in the concrete than various other issues can be found like greater shrinkage with the possibility of more cracks and reduced compressive strength overall.

The appearance of cement-sand particle on the surface of freshly places concrete is known as laitance.
Precautions to be taken:
1. Clay, silt, dust content should be removed before mixing the concrete.
2. Maintain W/C ratio.
3. Do not sprinkle water during finishing work of concrete.
4. Use well graded F.A. in mix.
5. Use water-reducing admixture little in concrete mix

When cement slurry come out on surface that’s call laitance. It is prevented by following steps

• reduce w/c ratio.
• proper vibration .
• concrete should mix around 20-25 rotation of mixture drum.
• concrete should not throw from more Hight.
• aggregate should have well graded.
• if higher workability we should add pozzolana material instead of higher w/c ratio.
• use of fibers in concrete….

reason of laitance in concrete.

1. higher w/c ratio
2. more vibration
3. improper gradation of mixing material
4. improper mixing of concrete
5. may be segregation occur during placing of concret

preventive steps are as follow-–

1. reduce/proper w/c ratio
2. take care of vibration, if more vibration done than slurry of cement come out on surface
3. concrete should mix around 20-25 rotation of mixture drum
4. concrete should not throw more than 1.5 meter
5. in concrete, aggregate should have well graded so we can get proper packing of partical..
6. if higher workability we should add pozzolana material instead of higher w/c
7. we can also use fiber as a admixture to reduce laitance.

Laitance arises in concrete primarily due to excessive water, improper mixing, curing, batching, and from improper finishing. Also, too much cement or fine sand helps to cause laitance.

So, to prevent laitance :

• Barely the required amount of water must be used and check must be done on atmospheric and surface water absorption.
• Reduction in the amount of fines will help. Reduction in cement or fine sand volumes.
• Proper and omplete curing must be done.
• Not much trampling on the concrete before maturity.
• Overworking of the surface must not be done.
• Proper finishing of the concrete surface should be done.

Laitance can be avoided by reducing or controlling water during the mixture of concrete. It too much water exists, then other issues also be happening like greater shrinkage and the possibility of more cracks in the structure.

If you want to remove laitance, then It is very easy to remove by acid etchings solution.