Access to Repair Areas for Inspection
1. The Contractor shall allow the Overseeing Organisation a minimum period of 3 hours of unhindered access to each area before work commences. This is to allow him time to inspect and test the concrete to identify repair areas. The Contractor shall notify the Overseeing Organisation at least 24 hours before inspection is required.
As repair work proceeds, the Overseeing Organisation will continue to carry out inspections and may undertake further testing to establish the limits of the concrete to be removed.
2. The Contractor shall allow in his programme for these periods of inspection and testing. High Pressure Water Jetting
3. If water for the Works is not available from a Public Utility Undertaking supply, the Overseeing Organisation's approval shall be obtained regarding the source of supply and manner of its use. When required by the Overseeing Organisation the Contractor shall arrange for tests of the water to be carried out in accordance with BS EN 1008. Water from the sea or tidal rivers shall not be used.
be selected:
a. Protection against ingress. b. Moisture control.
c. Concrete restoration. d. Structural strengthening. e. Increasing physical resistance. f. Resistance to chemicals.
g. Preserving or restoring passivity. h. Increasing resistivity.
i. Cathodic control. j. Cathodic protection. k. Control of anodic areas. Storage of Materials
3. All materials vulnerable to deterioration should be protected from the weather prior to use.
4. Proprietary repair products should be stored in accordance with the manufacturer’s recommendations.
176 Guidance for the Development ofStandard Specification andStandard Details for Local Highway Maintenance Contracts
Appendix 1 - Specification - October 2012 Removal of concrete
4. Weak, damaged or deteriorated concrete shall be removed prior to the application of repair products.
5. Existing concrete shall be removed to the extent instructed by the Overseeing Organisation. Removal of concrete additional to that described in the Contract may be instructed by the Overseeing Organisation if found to be necessary.
6. Concrete shall be removed from the area until sound concrete is reached. Where reinforcement becomes exposed, concrete shall be removed for a minimum distance of 25mm beyond the rear face of the reinforcement. Where corroded reinforcement is identified the area of concrete removed shall be extended to expose 100mm of uncorroded reinforcement.
7. Before cutting out, the Contractor shall determine the position and depth of the reinforcement with a covermeter. The perimeter of the concrete to be removed shall, except as described below, be saw cut perpendicularly to the face of the concrete to a depth of not less than 15mm or to within 10mm of the reinforcement, whichever is the lesser.
8. The edges of repair areas shall be inclined to avoid the entrapment of air when the concrete is poured.
9. Concrete shall be removed by the use of suitable light hand held mechanical tools or high pressure water jetting in accordance.
10. Any saw-cut edges produced shall be abraded by grit blasting or equivalent method. The surface of the concrete to receive repair concrete is to be such that the repair concrete will flow freely into all voids and be in intimate contact with the existing concrete.
11. The Contractor shall not damage concrete to be retained adjacent to, above or below repair and replacement areas. Any concrete damaged by the Contractor shall be rectified as directed by the Overseeing Organisation. The Contractor shall not damage the steel reinforcement. Any steel reinforcement damaged by the Contractor shall be rectified as directed by the Overseeing Organisation.
12. The profile of each area, after removal of the existing concrete, shall be as detailed on the Contract Drawings or as directed by the Overseeing Organisation for each area within a ±5mm tolerance.
Preparation of surface of concrete
13. Concrete surfaces shall be clean and dry and free of cement laitance, contaminants and loose friable material.
177 Guidance for the Development ofStandard Specification andStandard Details for Local Highway Maintenance Contracts
Appendix 1 - Specification - October 2012 14. The surface of the concrete shall be cleaned of all dust and abrasive particles. Filtered
oil-free air, or a similar accepted method, shall be used to remove any loose particles. 15. The surfaces shall then be saturated with potable water for a minimum of 4 hours and
repair material shall be placed within one hour after completion of wetting.
16. Bonding agents shall not be used between the substrate and the repair concrete unless required by manufacturer of proprietary repair product and approved by the Overseeing Organisation.
Preparation of surface of reinforcement
17. Exposed surfaces of reinforcement shall be cleaned to bright steel. The surfaces shall be free of embedded abrasive particles and corrosion products when viewed through a x10 illuminated magnifying glass.
Method :
Blast cleaning using dry air/abrasive system; or
Wet blast cleaning using a low pressure air/water/abrasive system. The equipment shall not allow the air/water pressure to exceed 14 bar and shall incorporate a metering device to allow the abrasive quantity introduced to be adjusted from zero to a maximum.
18. Within an hour of blast cleaning the treated reinforcement shall be pressure washed with clean water.
19. In locations where more than 10% of the cross sectional area of the bar has been lost the advice of the Overseeing Organisation must be sought before proceeding.