Deflection due to Strengthening of slabs

Deflection due to Strengthening of slabs

The strengthening of slab is taken up only after the strengthening of beams is completed. A reinforced structural concrete topping over the existing slab can be used which provides a composite construction of old and new slabs, with additional depths to slab and beam.

To ensure a good bond between new and old concretes, mechanical anchorage consisting of steel bolts inserted in holes drilled into the slab at suitable intervals may be provided. The spaces surrounding the holes are filled with epoxy grout.

A shear connector is embedded for half of its length in old concrete and the remaining half which is projected will subsequently b embedded in new concrete.

Before applying topping the surface of old floor slab should be thoroughly scabbled and cleaned. Additional reinforcement may be required over the supports, because the old reinforcement at supports acquires a position which is near to the neutral axis of compositors section.

After the preparation of old concrete surface, epoxy bond coat is applied on it and while this coat is still touch-dry 25 to 50mm thick M20 grade concrete topping is laid. The thickness of topping is governed by the strength and thickness of old floor slab.

However application of topping increases the dead weight on the slab. With suitable treatment the top layer of topping maybe utilized as floor finish etc, After curing the beam and slab for 14 to 21 days props can be removed.