METHOD OF STATEMENT FOR STRUCTURAL DEFECTS RECTIFICATION WORKS

This project is located at B Connaught Drive to proposed rectification works of structural defects which mentioned during the building inspection by Singapore Metro Consulting .

The works involves minor structural reparation works including of spalling of concrete, reparation of R.C column and PU grouting works.

The location of this project is shown in Figure 1.

REPARATION SPALLING OF CONCRETE

CONTRUCTION PROCEDURES

1. Obtain all the necessary approvals / permits from the relevant Authorities prior to carrying out physical works on site.
2. Prior to start work, ensure that all the existing services are diverted or protected (if diversion is not necessary or to be carried out on later stage) and ensure that it will not be affected by the proposed works.
3. Mobilize all the necessary plants and equipment to be used in the construction site.
4. Mark up the defective concrete area
   
5. Removal of loose concrete cover
   – Using high pressure water jet, 1100 bar (large area)
   – With hammer drill (medium area)
   – Hammer and chisel (small patch repairs)
6. Extent of Concrete Removal – remove concrete minimum 15 mm behind main bars
7. Cleaning Reinforcement – to remove all the tie wires, rust, mortar / Concrete and other loose material
8. Application of Corrosion Protection coats( as approved by PE) – apply two 1 mm thick layers (total 2 mm minimum)*To allow time for the 1st coat to harden before applying 2nd coat. To allow application to dry before applying repair mortar.
   
9. Apply a bonding agent to the affected surface to ensure proper adhesion
   
10. Patch the hacked area using polymer modified non-shrink cement mortar
11. Curing protection by plastic sheeting
    
12. Paint (3layers as 2primiers and 1finish coat) over the patched area to match the rest of area.
13. Dispose off debris and prepare area for permanent works construction.
14. Reinstate all the affected works, where necessary.

REPARATION OF R.C COLUMN

CONTRUCTION PROCEDURES

1. Obtain all the necessary approvals / permits from the relevant Authorities prior to carrying out physical works on site.
2. Prior to start work, ensure that all the existing services are diverted or protected (if diversion is not necessary or to be carried out on later stage) and ensure that it will not be affected by the proposed works.
3. Mobilize all the necessary plants and equipment to be used in the construction site.
   
4. Mark up the defective concrete area
   
5. Removal of loose concrete cover- with hammer drill and hammer and chisel
   – Remove tire wires, nails etc.
   – Remove only defective concrete as instructed.
   – Do not reduce structural integrity.
6. Extent of concrete removal – remove concrete minimum 15 mm behind main bars
7. Roughen surface (2 mm minimum), cut sides minimum 90° to avoid undercutting and maximum 135° to reduce debonding around edges. Substrate shall be sound with no loose material.
   
8. Cleaning Reinforcement – to remove all the tie wires, rust, mortar / Concrete and other loose material
   
9. Recovering the damaged main column bars along the damaged length
10. Welding the added bar and column bars to each other along the lap length
11. Application of Corrosion Protection coats( as approved by PE) – apply two 1 mm thick layers (total 2 mm minimum)
    – Hopper spray for large applications
    – Brush for small applications
    – Inspect bars after to ensure full coverage
    – Use two brushes simultaneously to ensure full application behind bars

To allow time for the 1st coat to harden before applying 2nd coat. To allow application to dry before applying repair mortar.