BRIDGE DECK SURFACE PREPARATION USING TOTAL SURFACE HYDRODEMOLITION WITH LATEX MODIFIED CONCRETE OVERLAY
Description. This work shall consist of bridge deck surface preparation using hydrodemolition for selective removal of unsound concrete at variable depths in the structural deck slab and for providing a rough and bondable surface for the new Latex Modified Concrete (LMC) overlay. This item also includes water control, shielding, all removal and disposal of concrete and debris, additional trim work, cleaning and other preparatory work at the site necessary to prepare the bridge deck for the placing and finishing of a new LMC overlay.
Materials. All material shall be in conformance to the agency specifications.
Types of Repair Work Associated with the Total Surface Hydrodemolition Process.
Mechanical Scarification. Prior to the scarification, the depth of the rebar shall be verified in the field. The original bridge deck surface shall be scarified to a depth as specified on the contract plans (1/2” minimum) with a mechanical milling machine capable of accurately and automatically establishing profile grades. Areas adjacent to the curb, scuppers, joints or other locations inaccessible to the milling machine shall be hand chipped. For decks with an existing wearing surface, all wearing surface material or existing concrete overlay, shall be completely removed either as a separate operation to the milling of the original deck, or in conjunction with it, provided adequate grade control can be maintained.
If mechanical milling results in the snagging of reinforcing steel, the operation shall be stopped immediately, and the depth of removal adjusted. Damaged or dislodged reinforcing steel as a result of contractor negligence during the operation shall be repaired or replaced at the contractor’s expense.
All construction debris, wearing surface material, or residual materials from the scarification process shall be completely removed from the bridge deck prior to the commencement of total surface hydrodemolition.
Total Surface Hydrodemolition. This work shall consist of providing a highly rough and bondable surface, and selective removal of all unsound concrete in the structural bridge deck slab during the initial pass of the hydrodemolition equipment. The work shall include the removal and disposal of all concrete and debris as created by the process, and include shielding, deck washing, water control, and any other incidental concrete removal that may be required to prepare the deck for the placement of the overlay.
Full Depth Repair. This work shall consist of removal and replacement of the bridge deck in the required areas as identified in the plans or determined in the field. Predetermined areas of full depth repair may be done prior to hydrodemolition. Additional areas may require full depth repair following hydrodemolition as directed by the engineer. Concrete deck repair material used for full depth repair shall be placed to an elevation that is approximately one-half of the original slab thickness.
Removal Requirements. Removal requirements beyond the use of hydrodemolition equipment shall be in accordance with the state’s normal patching procedures, except that only pneumatic hammers no heavier than the nominal 35-pound class will be allowed, operating at no more than a 45 degree angle
from the horizontal, and in areas that are inaccessible to hydrodemolition equipment, or in previously patched or debonded concrete areas that require removal.
Total Surface Hydrodemolition Equipment. The hydrodemolition equipment shall consist of a water supply system, a high pressure water pumping system, and a demolition type unit. The demolition unit shall be a robotic, computerized, and self-propelled unit, utilizing a high pressure water jet stream that is capable of removing concrete to the desired depths specified with a single pass of the unit, including the selective removal of all unsound concrete. It shall also be capable of cleaning rust and concrete particles from all exposed reinforcing steel. The resulting concrete surface profile shall be one that is highly rough and bondable. All water used in conjunction with the hydrodemolition process shall be potable water, except that stream or lake water may be used if properly filtered prior to use.
Only individuals who have experience on jobs of similar size and type over the past three years shall operate the hydrodemolition equipment.
The contractor shall take steps to prevent damage to existing reinforcing steel. All equipment shall be operated in a manner that does not damage the slab, reinforcing steel or superstructure components. Any damage caused by the contractors equipment or negligence shall be repaired at the contractors expense. Only those vehicles directly required to perform the hydrodemolition work, clean up, or corresponding overlay construction shall be allowed on the bridge deck. Contamination of the deck by construction equipment or any other source shall be prevented.
The demolition unit must provide shielding to ensure containment of all dislodged concrete within the removal area in order to protect the traveling public and work crew from flying debris on, adjacent to, and below the work site.
Vacuum Clean-up Equipment. The vacuum equipment shall be equipped with fugitive dust control devices and capable of removing wet and dry debris, along with standing water, in the same pass.
Water Control Plan. Prior to the beginning of hydrodemolition, the contractor must submit a plan to the engineer for the control and filtering of all water discharged by the operation. All drains, joints, and other locations where discharge water could exit the deck must be blocked, in order to direct runoff to a central collection and filtering location, as designed by the contractor. The contractor shall be responsible for compliance with all environmental laws and regulations regarding the discharge of runoff water into the environment. Specific details shall be provided by the contractor detailing the method of water and debris collection, filtering, treatment, and legal disposal.
The contractor is responsible for the disposal of all concrete and debris, and securing any applicable permits which may be required.
Equipment Calibration. The robotic hydrodemolition equipment shall be calibrated on a representative sample of sound deck concrete, as directed by the engineer, in order to demonstrate the ability to cut to the desired depth, as indicated on the plans. The minimum allowable water pressure shall be 13,000 psi and the maximum water pressure shall not exceed 20,000 psi. The calibration must accomplish the desired surface roughness, profile, and cutting depth as indicated on the contract plans.
The equipment shall then be moved to an area of deteriorated deck, as directed by the engineer, in order to demonstrate the ability to remove all unsound material. The equipment shall selectively
remove all unsound concrete, avoid the removal of unnecessary sound concrete, and provide a highly rough and bondable surface.
Upon approval by the engineer that the equipment settings do selectively remove all unsound concrete and provide a highly rough and bondable surface, the calibration will be approved, and the settings recorded. If the equipment does not demonstrate the ability to produce the desired result, as determined by the engineer, the equipment shall be removed from the project and the contractor shall provide other equipment for calibration. No additional contract time or compensation will be allowed for the mobilization of different equipment to the work site. The operating parameters shall be recorded as follows:
|Water Pressure Gauge|
|Machine Staging Control (Step)|
|Nozzle Travel Speed|
Upon approval of the calibration, the contractor shall perform total surface hydrodemolition over the entire top surface of the bridge deck with a single pass of the unit.
The calibration and production settings shall be maintained and provided in writing to the engineer. The settings shall be maintained throughout the operation, unless the desired results are not being attained, in which case re-calibration shall be performed. Calibration shall be required on each bridge, or when different equipment is brought to the site for use. The engineer shall also periodically verify the calibration settings and the desired results are being attained.
Removal of Slurry and Debris. The contractor shall clean up the slurry and rubble from the hydrodemolition operation in a timely manner, and before it dries on the deck and reinforcing steel. Vacuum clean up shall follow as closely as possible behind the hydrodemolition process. The deck shall then be blown dry to remove excess water. Following the cleaning, the surface shall be free of all debris, loose material, slurry, or cement paste.
Reinforcing Steel. Any reinforcing steel damaged by the contractors operation shall be replaced at no additional cost. Replacement may include the removal of additional concrete to adequately anchor reinforcing steel to the appropriate lap splice length. Where the bond between exposed reinforcing
steel and sound concrete has not been compromised, the clearance requirement around existing reinforcing steel will be waived. Partially exposed reinforcing steel is acceptable.
Sounding. After the initial pass of hydrodemolition and appropriate cleaning, sounding will be done after the deck is clean, dry and frost free. Any unsound deck concrete that remains shall be removed at the contractor’s expense with the use of pneumatic hammers.
Removal of Remaining Unsound Material. Where existing patches have debonded, or previous unsound overlay material is found below the top mat of reinforcing steel, that material shall be removed by force account with the use of pneumatic hammers or hydrodemolition.
Overlay Construction Preparation.
Final Cleaning Prior to Placement of New Concrete. This work shall all be performed in conjunction with the installation of the Bridge Deck Overlay. After completion of hydrodemolition and associated clean-up of debris, but not more than 24 hours prior to placement of the overlay, the entire deck surface shall be thoroughly cleaned by either abrasive blasting or high pressure water blasting (7500 psi minimum). All horizontal and vertical surfaces to which the overlay is to bond, including exposed reinforcing steel, shall be blasted clean. Upon cleaning, the deck surface shall be thoroughly saturated to the point that the surface does not dry out, and any excess water removed with compressed air. Clean polyethylene sheeting shall then be used to cover the deck completely until such time as the overlay is poured. If the deck is allowed to dry out it shall be reblasted at the contractor’s expense.
Concrete Wearing Surface Requirements with Total Surface Hydro-demolition. Installation of the LMC overlay shall be in conformance with agency specifications. The overlay shall not be placed on areas of full depth concrete until the repair material has cured. Where hydrodemolition has left variable depth areas below the plan elevation of the overlay, the entire area shall be poured monolithically with the overlay material. Any standing water on the deck shall be removed prior to placement of concrete overlay material. Hand vibrators shall be used in areas where concrete is being placed around reinforcement, deeper areas within the pour, and along curb lines and construction joints.
See Latex Modified Concrete Deck Overlay specifications for more details regarding surface preparation, materials, equipment, and other details related to the wearing surface installation.
Method of Measurement.
Surface Milling for scarification into the existing bridge deck, and including overlay material, shall be measured by the square yard, for the entire surface area of the deck.
Hydrodemolition of the bridge deck will be measured by the square yard for the entire surface area of the deck.
Full depth patching will be measured by the square foot. The volume of patching material used in Bridge Deck Patching, Full Depth, will not be measured for payment.
Basis of Payment
The milling operation for the scarification into the existing bridge deck, and existing overlay, if applicable, shall be paid for at the contract unit price per square yard for Surface Milling, based on the depth as specified in the plan documents. The cost of removal in areas adjacent to the curb or otherwise inaccessible areas to the power operated mechanical milling machine will be included in the contract unit price. All equipment, labor and materials necessary to perform the work in accordance with the specifications shall be included in the cost of Surface Milling, plus any other incidental work necessary to complete this item.
Hydrodemolition of the bridge deck will be paid for at the contact unit price per square yard, for Hydrodemolition, regardless of the number of passes of the equipment. The cost for all equipment, labor and materials necessary to perform the work, including blocking drains, initial equipment calibration, any re-calibration, filtering of discharge water, equipment shielding, hand chipping along curb areas, removal of remaining unsound concrete, deck washing, and clean-up, collection and disposal
of all debris, slurry, and water produced by the operation, shall be included in the cost for Hydrodemolition, along with any other incidental work necessary to complete this item.
Full depth patching will be paid for at the contract unit price per square foot for Bridge Deck Patching, Full Depth. All equipment, labor and materials necessary to perform the operation, including the cost of cleaning the removal area and the patching material used for full depth patching, shall be included in the cost of Bridge Deck Patching, Full Depth, along with any other incidental work necessary to complete this item.
Payment for bid items for total surface hydrodemolition will be made under:
Pay Item Pay Unit
Surface Milling………………………………………………………………………………………..SQ YDS
Bridge Deck Patching, Full Depth…………………………………………………………….SQ FT
No Bridge Deck Patching, Partial Depth pay item is required. This work and material is included within the pay item “Bridge Deck Overlay, Additional,” within the state specification for Latex Modified Bridge Deck Concrete Overlay.