Category: LIBRARIES

A Primary Mission of the Council is to promote effective means of surface preparation in the maintenance industry using water and water/abrasive blasting techniques.

Costs for hazardous waste disposal are more than double that of non-hazardous waste disposal costs.1 This, combined with the liability involved with hazardous waste disposal has brought other options to the forefront in the bridge painting industry.

Two relatively new solutions to the hazardous waste problem in bridge painting are the use of admixture blended abrasives and liquid applied pretreatments.

The liquid pretreatment is a liquid material that is sprayed on the painted surface at a specified thickness, allowed to dry, then blasted off with the underlying lead-based paint.

The manufacturer of the admixture guaranteed their product by refunding the cost of the admixture if the waste produced tests hazardous for lead.

When using these products, there are additional costs involved, including the price of materials and additional labor needed to use them.

pretreatment As can be seen from the previous example, both the admixture and liquid pretreatment can reduce maintenance painting costs.

The other factor, availability, refers to the location of the jobsite to a distribution center for the materials.

Liquid pretreatment can be purchased and shipped rather easily, similar to paint.

Both the admixture blended abrasive and liquid pretreatment cost more than expendable abrasive, however, those increases are less than the disposal cost savings realized.

2. The use of admixture blended abrasives did not seem to affect the contractors productivity with the Torbo® Wet Abrasive Blasting System.

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A Primary Mission of the Advisory Council is to promote effective means of surface preparation in the maintenance industry using water and water/abrasive blasting techniques.

The Abrasive Injected Water Blasting (AIWB) process involves introducing an abrasive into a high pressure water stream where it is delivered to the surface to be blasted.

AIWB will impart a profile on the substrate and is capable of cleaning to an SSPC-SP-5, though flash rusting may occur.

This equipment is useful in spot repair requirements for highway structures where localized corrosion and/or damaged paint areas require repair.

While performing the spot repair requirements, AIWB is also capable of feathering transition areas of intact paint, which surround areas prepared to bare metal.

In addition, the surrounding areas of intact paint are sweep-blast to remove delaminated coating.

The observed structures were part of a multiple bridge maintenance painting contract for Virginia Department of Transportation’s Northern Virginia District.

Due to the nature of this repair work, (i.e. spot prepare corroded areas, and overcoat), production rates during a given shift were dependant upon the amount of old coating that was removed.

The water consumed per square foot was also dependent on the amount of coating deterioration on the structure, shown in Table 1.2.

During this eight hour demonstration shift the contractor utilized two Carolina Equipment & Supply Aqua Miser D-44 AIWB units with one blaster per unit to remove all coatings down to bare metal.

This cost model calculated cost for maintenance painting of structures with varying extents of coating deterioration for a comparison between abrasive injected water blasting and hand/power tool cleaning surface preparation methods.

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Slurry blasting and surfaces.

This slurry material is forced through the blast hose to the nozzle using compressed air, similar to the method used to move dry abrasive through hoses in conventional abrasive blasting operations.

However, the Torbo® system allows the blast operator to control the following directly at the nozzle: abrasive mixture quantity, air pressure and nozzle on/off.

The use of this slurry media reduces airborne dust, which could possibly reduce the containment requirements compared to dry abrasive blasting.

The depth of the profile is dependent on the size and type of abrasive used as well as the air pressure.

A wide variety of abrasives may be used such as sand, plastic, glass, slag, bicarbonates and other manmade abrasives.

The contractor performing the work was PbX and consisted of a crew of five men: one foreman, two blasters, and two helpers.

This was done using the Torbo® Wet Abrasive Blasting System, which allowed the blasters to turn off the abrasive and use only low-pressure fresh water.

The abrasive admixture is a proprietary additive used to render lead in waste nonleachable.

For the I-40 bridge painting project, abrasive consumption was reduced from an assumed average of 10 lb/ft2 for once-through dry abrasive blasting to 3 lb/ft2, a 70% decrease.

VII: The Use of Admixture Blended Abrasives and Liquid Applied Pretreatments in the Removal of Lead-Based Paint, Corrpro Companies, Inc.

To compare the two surface preparation technologies, a cost model built for this FHWA study was used.

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