715 - Cleaning and Coating Existing Structural Steel
GENERAL
MDOT has two standard painting systems. New structural steel is completely shop painted with a three-coat system, referred to as Type 4S. Existing structural steel is blast cleaned and field coated with a similar three-coat system, referred to as Type 4. The following guidelines should be strictly followed in inspecting these systems.
Health and Safety
Exposure assessments, exposure monitoring, hygiene facilities and training involved with the removal of lead-based coatings from existing structural steel bridges.
The Contractor will provide the equipment and the training necessary to insure the safety of the personnel that are required to do the work and inspection required for the removal of lead-based coatings from existing structural steel bridges.
The equipment and the training will, as a minimum, provide employees with respirators including fit testing, respirator training and a respirator program. Protective clothing and equipment, change areas, showers, eating facilities and hand washing facilities are also required.
MDOT employees must take the required training from the Contractor. Employees that have not had the training cannot work on the project.
MDOT employees must also have a blood test to determine existing lead levels and a breathing test to insure that they can safely use the required respirators. The blood test and the breathing test are furnished by MDOT.
MATERIALS
Type 4S - Shop Painted Steel
Requirements
See Section 716 of the Standard Specifications for Construction.
At delivery, the shop coating on all steel components should be inspected.
If there is any evidence of faulty painting, damage from transportation or handling, the Contractor should be notified and the damage documented.
The pay item for repair of damaged coating covers all damage repair, but the Contractor should separate the shipping damage caused by the fabricator from the bridge erection damage. We do not try to referee this separation, but good documentation may eliminate future claims.
All shop painted steel must be handled with padded slings, chains or hooks and must be stored on cushioning pads above the ground so that no mud or water is deposited on the beams.
Special attention must be given to cleaning all bolted surfaces of dirt or mud before erecting the pieces.
After bridge erection is complete, the field repair of coating will be done in accordance with the requirements of the specifications.
Special attention should be given to the requirements for cleaning surfaces to be painted and the minimum temperature and maximum humidity requirements.
The Construction and Technology Support Area, Bridge Construction Section maintains a recommended procedure guide for damaged coating repair that depends on the exact system and paint manufacturer being used. Contact the Bridge Construction Engineer or the staff painting technician for a current copy before beginning the work.
Procedures for Field Repair of Shop Coated (New) Structural Steel
All adhering scale, dirt, grease or other foreign material will be removed by appropriate means.
All rusted or uncoated areas are to be cleaned to a near-white finish. A strip & clean wheel (abrasive embedded in an adhesive coated wheel) can be used to clean the rusted areas. This wheel, used on a power drill, will feather the edges of the existing coatings surrounding the repair areas.
The area around the repair will be cleaned and primed using the original coating system. The primer will be spray applied.
Before the intermediate coating is applied, the primer that was oversprayed on the existing coating around the repair area must be wiped off.
The intermediate coating is spray applied; this coating must be the same as the original coating system.
The topcoat will be spray applied and be part of the original coating system.
The curing times between applications of the three different coatings will be the same as the Type 4 coating system.
Type 4 - Field Painted Steel
Requirements
Abrasive blast cleaning of existing steel structures requires environmental controls.
Special attention should be given to the provisions in the proposal for removal of lead-based paint from bridges.
Any violation of requirements could lead to citations and severe penalties from DEQ or the Department of Consumer and Industry Services.
The inspector should be especially cautious of the handling and storage of spent blasting materials that have been designated as hazardous waste by the Environmental Protection Agency (EPA) toxicity test.
All portions of the structure that could be damaged by abrasive blasting and/or coating operations will be protected by covering or shielding.
During the abrasive blasting operations, provisions will be taken by the Contractor to protect existing land traffic, water traffic and pedestrians. This provision will be some type of barrier system.
During the coating operations, the Contractor will take whatever measures are necessary to prevent paint spray from reaching vehicles on the roadway, waterway or other private property. The required measures will probably include tarping around the area being coated.
The Contractor will select a blasting abrasive from the Qualified Products List for low dusting abrasive.
The Contractor will select a complete coating system from the MDOT Materials Source Guide. Color number will be as called for in the proposal or on the plans. The Contractor will provide the Engineer with product data sheets before any coating is started.
Sealing the Perimeter of Beam Plates - See Section 713 of the Standard Specifications for Construction.
Steel Preperation
Cleaning Requirements
The top of the bottom flange will be scraped to remove accumulated dirt and debris.
Areas of oil and grease on surfaces to be sandblasted will be cleaned with clean petroleum solvents before sandblasting operations begin.
Abrasive Blasting
A method to contain all spent material, dust and other debris generated during the blast cleaning or subsequent vacuuming of the structure in preparation for coating must be used. The containment design, the air flow (negative pressure) equipment and dust filtering equipment is the Contractor’s responsibility.
Procedure
The containment will consist of tarpaulins or other approved sheet material. The tarpaulins will be made of an airtight material and will be tightly and continuously secured at the seams.
The containment will extend from the deck bottom to ground level and will be fastened securely to prevent lifting or opening by wind.
Ground cloths will be placed under the enclosed area and will extend at least 10 feet (3 m) beyond the containment edges. The ground cloth will be continuous within the containment with all seams and overlaps adequate to hold all spent material.
The containment will have air-moving equipment attached which will be capable of creating a negative pressure condition within.
Spent Material
Spent material includes spent abrasive, bag house dust, shower water, and solvents.
The spent material will be collected daily and stored in suitable waste disposal containers located at the structure.
The waste containers must be kept covered with a waterproof cover. The waste containers will not be disposed of until authorized by the Engineer.
Spent material collected and stored on the structure site will be sampled and tested by the Contractor in accordance with the EPA toxicity (TCLP) test.
Spent material that is classified as a hazardous waste by this test will be disposed of at a licensed hazardous waste disposal facility.
Spent material that is nonhazardous will be disposed of at a Type II landfill.
Solvent - see proposal for Solvent Reuse Determination Procedures.
Structural Steel Surface Abrasive Blasting Requirements
Near-white finish (SSPC-SP10). Visual standards are in paint inspection kit.
Fins, tears, slivers, burrs and sharp edges that appear during abrasive blasting operations will be removed by grinding and the area reblasted.
The profile produced by the abrasive blasting will be within the range of 1.0 mils to 2.8 mils (25 ųm to 70 ųm).
Abrasive and a paint residue will be removed from an abrasive blasted surface with a good commercial vacuum cleaner with a brush-type cleaning tool.
The steel surface will be kept dust free and primed within 8 hours.
Structures Over Waterways (Containment)
A floating boom will be stretched across the waterway at a 200 feet (60 m) limit or closer, if necessary. The boom is used to collect the spent residue floating downstream.
The Contractor will provide a barge in the water directly underneath the area being abrasive blasted to collect the spent residue. If the waterway is too shallow for a barge, the Contractor will provide some type of temporary platform. Tarpaulins will be draped from the abrasive blasting area to the barge or collection platform. Also, the surface of the platform or barge will be covered with ground cloths. This containment will direct the falling, spent residue onto either the barge or collection platform and prevent spillage into the water.
The Contractor will collect all the surface water scum within the 200 feet (60 m) limit, all the spent residues on the barge and/or temporary collection platform and all the spent residues on the ground cloths. This collection of spent residue is to be done on a daily basis.
CONSTRUCTION
Coating System
Coating will be done in three steps consisting of an organic-rich primer, an intermediate coat and a urethane top coat. The top coat color will be specified in the proposal.
Organic Zinc-Rich Primer
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Mix with high-shear mixer according to manufacturer’s instructions. |
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A thoroughly mixed coating will be strained to prevent clogging of spray equipment. |
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Zinc primer will be continuously agitated during application process. Application of the primer must be done with spray painting equipment. |
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Temperature:
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Humidity:
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Zinc primer will be spray-applied only, according to paint manufacturer’s instructions. |
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Primer Coating thickness: 4 mils (100 ųm) minimum; 10 mils maximum |
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Minimum cure times will meet the requirements of subsection 915.04A of the Standard Specifications. |
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Follow the manufacturer’s recommended cure time except that there shall be no more than 21 days between zinc-primer coating and the intermediate coating. If the 21 days are exceeded, the Contractor must reblast and repaint at his/her own expense. |
Intermediate Coat
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Primed surface will be cleaned by vacuuming with a good commercial vacuum cleaner with a brush-type cleaning tool. |
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Mix with high-shear mixer according to manufacturer’s instructions. |
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Thoroughly mixed coating will be strained to prevent clogging of spray equipment. |
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Application of the intermediate coating must be done with spray painting equipment. |
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Temperature:
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Humidity:
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Coating thickness:
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Minimum cure times will meet the requirements of subsection 915.04A of the Standard Specifications. |
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Follow the manufacturer’s recommended cure time except that there shall be no more than 21 days between the application of the intermediate coating and the topcoat. |
Urethane Topcoat
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Intermediate coating will be cleaned by vacuuming with a good commercial vacuum cleaner with a brush-type cleaning tool. |
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Mix with high-shear mixer according to manufacturer’s instructions. |
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Thoroughly mixed coating will be strained to prevent clogging of spray equipment. |
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Application of the topcoat must be done with spray equipment. |
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Temperature:
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Humidity:
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Coating thickness:
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Minimum cure times will meet the requirements of subsection 915.04A of the standard specifications. |
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After completion of coating operations, the completion date (month and year) and the number of coating system types (four) will be stenciled on the structure in 4 inch (100 mm) numbers. Use black urethane spray paint for stenciling. (subsection 715.03.D.4 of the Standard Specifications for Construction for locations). |
Paint Warranty
See Proposal for Paint Warranty.
Pin and Hangers
See Section 713 of the Standard Specifications for Construction.
MEASUREMENT AND PAYMENT
-Reserved-