bridge preservation classification

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Nebraska Statewide Bridge Conference

April 16, 2013

Anwar S. Ahmad, P.E.

Bridge Preservation Engineer

Federal Highway Administration

Office of Bridges and Structures

Topics Bridge Preservation Overview

Bridge Preservation Program Implementation Strategies

Examples of Deck Preservation Techniques

What is Bridge Preservation?Actions or strategies that prevent, delay or reduce deterioration of bridges or bridge elements, restore the function of existing bridges, keep bridges in good condition and extend their useful life. Preservation actions may be preventive or condition‐driven.

This Definition was adopted by AASHTO SCOH in Sep. 2011

Bridge Preservation

Preventive Maintenance

Cyclical (Non‐Condition Based)

Activities

Condition Based Activities

Rehabilitation

Bridge Replacement

Bridge Preservation Classification

Why Bridge Preservation?

Public safety

Cost effective

Minimum traffic disruption

Lower user cost

Reduce the need to replace


Preventive maintenance (PM) is considered a component of preservation

PM includes cyclical and condition based activities

Bridge Preservation


Cyclical (Non‐Condition Based)

Activities

Condition Based Activities

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Examples of condition based PM activities include:

• Sealing or replacing leaking joints

• Sealing concrete cracks

• Complete, spot, or zone painting of steel elements

• Scour countermeasures installation


Cyclical PM Activity ExamplesCommonly

Used Frequencies

Clean/Flush bridge decks or entire bridge Annual

Seal decks with waterproofing penetrating sealant 3 to 5 Years

Lubricate bearing devices 2 to 4 Years

Clean/flush drainage system Annual

Clean/flush culverts 1 to 2 Years

Coat timber elements with wood preserver 1 to 2 Years

Rehabilitation Examples of Rehabilitation activities include:

• Deck repairs and installation of overlay

• Repairs and restorations of superstructure, substructure, and culverts

• Functional improvements such as adding a travel lane or raising vertical underclearance are not considered preservation.

Bridge Preservation


Rehabilitation

Replacement

Bridge replacement is an important activity, but not considered a preservation activity.

Examples of Preservation Activities

Seal or replace leaking joints or elimination of deck joints

Deck overlays


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Spot, zone, and complete coating of structural steel elements.


Installation of Cathodic Protection (CP) Systems.


Installation of scour countermeasures.

Removing large debris from channels.


Application of concrete sealants, coatings.

Bridge cleaning and/or washing service.


CopiescanmayorderedfromtheFHWAReportCenterEmail:[email protected]:(814)239‐1160OrContactAnwarAhmadEmail:[email protected]:(202)366‐ 8501

Copiesmaybedownloadedfromhttp://www.fhwa.dot.gov/bridge/preservation/guide/guide.pdf

Bridge Preservation Guide

Implementation Strategies for Bridge Preservation Program

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Program Goal

Example: Implement timely preservation treatments on structurally sound bridges, thereby extending their useful life.

Objectives & Measures

Example: Maintain 90 percent of bridges in a state of good repair.

Measure: Percent of bridges with element condition state ≤ 2.

Measure: Percent of bridges with NBI general condition rating ≥ 6.

Condition Assessments

Safety Inspection (NBIS)

Element Level Inspections

Work Activities

Identify Feasible and Cost Effective Activities & Treatments, and

Classify Activities Under Major Programs For Ease of Management.

For example, work activities can be classified under three programs: Preventive Maintenance, Rehabilitation, and Replacement/Improvement

PreservationImprovement

Preventive Maintenance RehabilitationBridge Cleaning/Washing Deck Repairs and Installation of Thin Bonded Overlay Bridge Replacement

Deck Joint Maintenance/Repairs Deck Repairs and Installation of Rigid Bonded Overlay Bridge Widening/Raising

Deck Joint Replacement Deck Repairs and Installation of Thin Bonded Overlay, and Cathodic Protection

Bridge Relocation

Deck Surface Repairs Deck Repairs and Installation of Rigid Bonded Overlay and Cathodic Protection

Culvert Replacement

Rail Maintenance/Repairs Superstructure Rehabilitation Culvert ExtensionCrack Sealing Superstructure Repairs and Painting

Deck Sealing Retrofitting Fatigue Prone Details/Fracture Critical Members

Installation of Thin Bonded Deck Overlay Substructure Rehabilitation

Installation of Rigid Bonded Deck Overlay Culvert Rehabilitation

Superstructure Maintenance/ Surface Repairs Culvert Lining/Sleeving

Superstructure Spot/Zone Painting Substructure Repairs and installation of Pile Jacketing

Complete Superstructure Painting

Substructure Maintenance/ Surface Repairs

Culvert CleaningChannel Debris Removal

Installation of Scour Countermeasures

Pile Jacketing

Work Activities Examples

FundingDetermine needs and funding levels

Identify unmet needs

Determine funding and resource needs for meeting your program goal and objectives

Compare the unmet needs and targeted needs with allocated funds (authorized budget)

Develop short and long‐term plans

Seek or make adjustments to budget

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Work Plan Select and rank candidate projects

Classify projects based on work groups as discussed earlier (PM, Rehab, Improvement)

Conduct LCCA

Update your projects estimates

Group projects based on type and location (Site specific, Multiple sites, Corridor, Region‐wide, etc.)

Examples of Deck Preservation Techniques

Cyclical cleaning

Cyclical sealing and waterproofing

Installation of overlay

Deck Cleaning Sweeping

Pressure washing

Sealing and Waterproofing

Penetrating Sealers: These sealers include silanes which are absorbed into the concrete and react with it to form a hydrophobic (water repellant) surface

Surface Preparation

Follow the manufacturer's cleaning instructions

Power sweeping should be used to remove dirt and debris.

Shot blasting, sand blasting, or power washing must be used to remove grease, oil, and surface contaminants.

Surface Preparation: Shot‐blasting

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Application

Sealer is applied by spray or pour application in accordance with manufacturer‘s recommendations.

Sealer is applied at the appropriate coverage and number of coats according to the manufacturer’s recommendations.

Sealer is allowed to cure for a sufficient time prior to opening to traffic (2 to 6 hours)

Crack Sealer: Non‐moving Crack Being Filled

The resin poured into the crack and distributed by brush

Sealing Application

Material is poured out on concrete and moved along the deck using solvent resistant rollers on extension polls.

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Deck Overlay

Hydraulic cement overlays include:

Latex modified with Type I/II cement (LMC)

Latex modified with very early strength cement (LMC‐VE)

Silica Fume with Type I/II cement (SF)

Thin Epoxy Polymer Overlay

Hydraulic cement overlays Surface Preparation

Remove deteriorated concrete (milling, or hydrodemolityon, or saw cut and jackhammer)

Clean surface with shot blasting

Complete a final cleaning within 24 hours prior to overlay.

An hour before overlay, water‐soak the surface and cover with plastic

Leave surface wet and covered until overlay is placed

Prepared Surface

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Broom overlay mortar over surface, screed consolidates and strikes‐off overlay

Mobile mixer discharges concrete.Fogging increases relative humidity

Curing: wet burlap is placed on overlay as soon as practical

Curing: polyethylene is placed on wet burlap as soon as practical

Finished Product

Polymer overlays are placed on bridge decks to reduce infiltration of water and chloride ions and to improve skid resistance and surface appearance.

2 layers of epoxy and broadcasted aggregate placed on a dry, shot blasted surface.

Test patches done to verify materials, surface preparation, mixing and placing of materials are acceptable.

Overlay is 1/4 to 3/8 in thick.

Polymer overlay resins are typically epoxy, methyl methacrylate or polyester based

Thin Epoxy Polymer Overlay

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Ensure that the surface is clean and dry prior to application.

Pour polymer on the deck surface.

Work polymer into deck with a regular squeegee.

Cast aggregate over polymer.

After a couple hours, remove the unbounded aggregate.

Apply a second layer of polymer and aggregate.

Properly dispose contaminated material.

Procedure

Surface Preparation by Shot Blasting

drywall mud mixer

Mixing must be complete so that 1 or 2 parts A and 1 part B make contact and cure properly.

50‐ml gel sample is taken from each batch

Test Patch

• Shot blasted surface, duct tape, epoxy layer one, and broadcast aggregate

• The next day the overlay is cored at 3 locations for bond testing

Test Patch

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Spreading Epoxy

• 2 layers of epoxy & broadcasted aggregate 0.25‐in thick

Broadcasting Aggregate

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Spreading 2nd Layer of Epoxy and aggregates

Bridge preservation should be integrated in all core phases of bridge’s life…….. “cradle to grave”

Building an effective bridge preservation program entails a proactive and balanced approach

Implementing an effective bridge preservation program calls for appropriate tools and resources

Achieving optimum results is accomplished by applying the appropriate treatments/strategies at the right time

Summary

Anwar S. Ahmad, P.E.Bridge Preservation Engineer

Federal Highway AdministrationTelephone: (202) 366‐8501

Email: [email protected]

Thank You

bridge preservation classification

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