Concrete Scarification Prior to a Concrete Overlay
The purpose of this work is to perform the final one inch of concrete removal of the existing surface using hydrodemolition to provide a bonding surface that is free from micro-fractures and fractured or damaged coarse aggregate and is very rough with an amplitude of ± .5 inch. During the hydrodemolition, 100% of the original surface must be removed.
This section includes all labor, materials, equipment and supervision necessary to remove existing concrete as indicated on the drawings and in the specifications, including, but not limited to:
- Removal of concrete by means of hydrodemolition.
- Removal of concrete inaccessible to the hydrodemolition machine with conventional chipping hammers including shadows under the reinforcing steel.
- Containment, collection, treatment and disposal of hydrodemolition waste water and water used for clean up.
- Collection of debris from the demolition operation using a vacuum system and disposal of all debris.
- Final preparation of surface prior to placement of concrete.
Submit the following items:
- Hydrodemolition equipment specifications. Include robot size and weight, supply water requirements, water consumption.
- Location and layout of the temporary water supply including materials to be used and any permits required to secure the use of the water.
- Vacuum system including type, manufacture, capacities, filtration systems.
- Location and layout of the system to be used to contain the wastewater.
- Certification of the hydrodemolition operator’s qualifications.
- Equipment to be used for final wash down of the hydrodemolished surface.
- Methods to insure the safety of all personnel.
Work shall be performed by organizations that have successfully performed at least five verifiable projects similar to this project within the last five years.
Work shall be under the immediate control of a person experienced in hydrodemolition who has supervised three verifiable projects of similar type and size. Supervising person shall be present during all operations.
An individual trained and certified in the proper use and safety of the equipment and having a minimum of two years experience with the equipment on jobs of similar type and size shall operate the hydrodemolition system.
Chipping hammers used for detail chipping shall not exceed 15 lbs.
Final wash-down shall be done using a minimum of 8,000 psi and 8-gpm water blaster.
Wastewater shall be tested, as required, to insure compliance with the wastewater discharge requirements established by the governing authority.
All water used for hydrodemolition and final clean up shall be potable.
Concrete removals shall be performed with engineer approved high-pressure hydrodemolition equipment. Equipment shall be capable of removing concrete to the depth specified on the drawings and shall be capable of removing rust and laitance from exposed reinforcement designated to remain in place. The equipment shall be capable of operating at a minimum of 35,000-psi water pressure with flow rates not exceeding 32 gallons per minute. The equipment shall be capable of removing concrete to within one inch of vertical surfaces.
Hydrodemolition contractor shall supply all necessary equipment, parts and manpower to maintain pre-established production rates and assure adherence to construction schedule. Contractor shall maintain, on the job site, an inventory of common wear parts and replacement accessories for equipment adequate to ensure that routine maintenance tasks can be performed without delay to the hydrodemolition schedule.
Equipment shall be capable of performing one inch deep concrete removal as shown on the drawings at a minimum production rate of 2,300 square feet per eight-hour.
Vacuum equipment shall be of sufficient capacity to collect all debris from the hydrodemolition operation no later then two hours following the hydrodemolition operation. The vacuum equipment shall be capable of removing wet debris and water. Water collected during the vacuuming operation shall be discharged to the contractor’s wastewater collection system.
Testing and Acceptance of the Hydrodemolition Equipment
A trial area will be designated by the engineer to demonstrate that equipment, personnel and methods of operation are capable of producing results satisfactory to the engineer. The trial area shall consist of approximately 50 square feet.
The equipment shall be adjusted to remove an average of one inch of concrete from the existing surface to provide a bonding with an amplitude of ± .5 inch. During the hydrodemolition, 100% of the original surface must be removed.
If in the sole opinion of the engineer the hydrodemolition equipment does not produce satisfactory removal of the concrete or the unit does not meet the minimum production requirements of the project, then the engineer may require that the equipment be removed from the project and replaced with equipment that will meet the requirements of the specifications.
The hydrodemolition equipment shall be adjusted, as required, to maintain the quality and depth of cut demonstrated in the test area and to compensate for variations in the compressive strength of the concrete and other factors that may effect the actual depth of removal during the hydrodemolition operation.
Protect and/or relocate existing utilities within the work area that may be damaged during the demolition work. Provide temporary service until affected utilities are restored. Take adequate measures to protect existing sprinkler system.
Install temporary protection and other safety requirements prior to starting demolition. Contractor shall adequately shield the work area to prevent debris resulting from hydrodemolition operation from traveling beyond the boundaries of the work area.
Provide adequate lighting as required to perform the work of this section.
Remove the concrete in the areas designated on the drawings using hydrodemolition to the minimum depth specified in the drawings and in these specifications and as demonstrated and approved by the engineer in the hydrodemolition test cut area. Maintain the quality and depth of cut demonstrated in the test area throughout the project. If delaminations exist beyond the minimum removal depth, removals shall continue until all unsound and delaminated concrete has been removed.
Following hydrodemolition, the bulk debris shall be removed from the area using the vacuum system. Areas inaccessible to the hydrodemolition equipment shall be removed using hand-held pneumatic tools.
Clean the area to remove all loose debris and other materials scheduled to be removed during the demolition. Thoroughly clean the demolished area using an 8,000-psi water blaster using a minimum of 8 gpm held at a maximum of 12″ from the deck surface. The surface shall be vacuumed immediately following the high-pressure water cleaning to remove any debris or wastewater. Following the cleaning, the surface shall be free of all debris, loose material, slurry, cement paste and any other material that might interfere with the bond of the new concrete overlay.
Areas where pneumatic tools were used must be thoroughly cleaned using 8,000-psi water blast to remove rust and laitance from existing reinforcing.
Any areas contaminated by materials detrimental to a good bond as a result of the contractors operations shall require additional removals and/or cleaning until a clean surface is obtained, at no additional cost to the owner.
Wastewater Containment and Disposal
Wastewater containment shall be the sole responsibility of the contractor. All equipment needed, including piping, pumps, hoses, settling areas and pH adjustment equipment (if needed) required for the proper collection, clean up and disposal of wastewater from the work area shall be provided and maintained by the contractor. The system shall be designed by the contractor and approved by the engineer to meet the discharge requirements of the local governing authority.
The contractor shall obtain any permits required for the discharge of the wastewater.
All wastewater generated by the contractor’s operations including hydrodemolition and clean up water must be contained by the contractor and must pass through the contractor’s approved collection system. No water will be allowed to flow directly into the drainage system of the facility.
The contractor shall establish and maintain any testing program required by the local governing authority for the wastewater discharge.
The contractor shall remove daily from the site all concrete debris, sludge and other materials generated by his work and legally dispose of all such materials.
The owner shall designate the location from which the contractor shall obtain potable water. The contractor is responsible for supplying all material, equipment and tools necessary to tap into the water source.
During concrete removal do not damage existing reinforcement steel intended to remain in place.
Do not drive or place equipment in the work area that may damage the reinforcing steel to remain in place. Bars that are bent or damaged by the contractor shall be replaced by the contractor at no charge to the owner.
Following removal of debris, and prior to placement of new reinforcement steel, the entire surface shall be cleaned to remove any contamination or loose material remaining in the area.
All water from the hydrodemolition and cleaning process must be contained within the construction barrier limits of the work area. The remaining facility will be operating under normal conditions. Any water that escapes the work area will immediately and without any delay, be removed from occupied areas. The construction barriers shall then be resealed to eliminate the leak.
Following final preparation of the area, including all other work items that must be completed prior to placement of concrete, but before final inspection and placement of concrete, the area shall be thoroughly cleaned using an 8,000 psi minimum water blaster at 8 gpm using a rotating, multi-jet nozzle held at not more then 12 inches from the surface. Following the final cleaning the surface shall be clean and free from all dirt, debris, slurry or any other material that might interfere with the bond of the new overlay.
Inspection of Exposed Surfaces
After removals are complete, but prior to final cleaning, all exposed concrete surfaces and all reinforcement designated to remain in place will be inspected by the engineer for compliance with the plans and specifications. Where the engineer finds unsatisfactory surface preparation, the engineer will direct contractor to perform additional removals and/or cleaning. Engineer will re-inspect after additional removals. Overlay material shall not be placed until the engineer has approved the surface preparation.
Scarify Concrete Surface One Inch Using Hydrodemolition: ______ SY, ______$/SY