Method of Statement for Replacing the Bar Screen Area Roof Slab – Civil Engineering

2. Relevant Process/Specification:

Tender specifications

3. Procedure:

Installation of Crash Deck:

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The crash deck for the roof slab of bar screen area shall be installed as per the approved scaffolding drawing.

All the base jacks shall be tightened till the crash deck supported fully the existing roof slab and channel.

Provide all the cross bracings and jacks as shown on the scaffold drawings.

Protection for Equipments and Services:

Adequate protection and supports shall be provided for the existing electrical panel and equipments.

All the electrical cables, pipes, etc. shall be properly supported by using scaffoldings system.

Where necessary plywood covering shall be provided for the cable tray and equipments

The existing crane rails shall be removed and the stop end shall be provided at the end of channel in order to keep the crane operation for channels B, C and D. On completion of reconstruction of slab, the existing rails shall be reinstated till it is being replaced with new ones.

Isolation of Roof Slab from Other Channels:

The perimeter of roof slab of the bar screen area shall be cut by saw for a depth of 30mm at top.

This isolation is to arrest the vibration transfer to the nearby slab, while demolishing the slab.

Concrete Slab Breaking:

After the completion of isolation cut, start the slab breaking by jack hammers from the isolation cut.

Extreme care shall be taken to minimize the jerking or impact on the slab while breaking the slab.

Cracks shall not be allowed to propagate to the nearby slabs at the time of demolition.

Concrete debris shall be removed from time to time and not to allow pile up on top of the crash deck.

All the rebars shall be cut and removed while breaking the slab except wherever lap length required rebar shall be left for lap length. The rebars in wall shall be refurbished and connected to the new slab rebars.

Concreting Of Slab:

The crash deck shall be used as the bottom shutter of the slab.

Reinforcement steel shall be place as per the “As Built” drawing and lap length for the adjacent slab shall be bent and kept upright.

Pockets will be provided in the slab while casting for fixing new rails

High strength concrete grade 40 micro silica concrete as per the approved design mix shall be used for concreting in order to achieve early deshuttering

The top surface of the concrete shall be finished with broom finish.

Curing and Deshuttering:

Water curing shall be carried out for the period of 7 days by water pending method.

Deshuttering shall do after 7 days of curing provided the cube strength attained is 75% of the designed strength of the concrete.