Bridge Maintenance and Repair

Preventative Maintenance Objectives Preserve investment - Cost of replacement higher than initial cost - Repair costs increase with time Safety and avoidance of catastrophic failure Maximize life of bridge

PREVENTATIVE MAINTENANCE IS COST EFFECTIVE!

General Methods - Concrete removal and replacement of deteriorated concrete filling cracks coating and sealing concrete surface

General Methods - Steel protect it from exposure to electrolytes painting galvanizing

General Methods - Timber control moisture content of the wood

Bridge Seats and Caps Runoff through deck joints contains debris and de-icing chemicals de-icing chemicals that accumulate on substructure cap can result in: corrosion of reinforcing steel and spalling concrete corrosion of bearing assembly (i.e. “frozen bearing”)

Bridge Seats and Caps (cont’d) Proper maintenance regular cleaning of substructure caps and deck joints with high pressure pump provide drainage troughs below deck joints surface protective coatings on bearing systems

Substructure - Concerns Material deterioration wet/dry and freeze/thaw cycles abrasion by water/ice at waterline steel corrosion concrete spalling decay and vermin attack on timber Ground settlement

Substructure - Concerns (cont’d) Impact damage Other damage pressure exerted on the piers and abutments by the earth

Substructure - Maintenance Material deterioration protective coatings preservatives Foundation settlement and earth pressure subsurface drains struts regrading soil profile

Substructure - Maintenance (cont’d) Impact damage guard rails and energy dissipaters fenders or steel plates on abutments and piers

Superstructure - Concerns Usually very difficult to access, so problems are frequently overlooked Deterioration occurs with time salt and chemicals - cracks in concrete corrosion - frozen bearings carbonation and sulfation Impact damage high loads ice and drift

Superstructure - Maintenance Inspection Good protection system coatings - preservatives sealers - patching paints - crack filling Pressure washing and cleaning Strengthening

Deck Most susceptible to deterioration de-icing salts, acid rain ultraviolet rays mechanical abrasion Requires a lot of maintenance and repair Protects rest of structure

Concrete Decks De-icing salt is main menace causes reinforcement to corrode concrete spalls potholes

Concrete Decks (cont’d) Design and construction features to control deterioration optimum cover for reinforcement good drainage - silica fume smaller skews - low w/c ratio thicker slabs - good consolidation air-entrained concrete - low shrinkage

Concrete Decks (cont’d) Main preventative maintenance goal is to control salt and moisture penetration keep deck clean and drains operating properly add drains in low spots monitor deck for chloride contamination fill cracks asphalt sealing polymer overlays concrete sealers bituminous concrete overlays with waterproof membrane

Curbs & Railings Deteriorate with time Replacement can be minimized cracking and spalling - corrosion salt damage - collision Replacement can be minimized appropriate sealers, coatings and paint galvanized steel

Deck Drains Can cause hazardous traffic situations Can lead to deterioration of deck and other bridge elements and erode the soil backfill

Deck Drains (cont’d) Typical problems include: ponding of water on bridge deck poor drainage allows de-icing salts to deposit on deck and other bridge elements plugged downspout will burst in freezing weather Regular cleaning is best maintenance

Approach Road Approach bump Guardrail Drainage connection to bridge rail transition stiffness (standard drawing S-1471 & S-1472) Drainage trough drains

Approach Road (cont’d) Erosion of headslopes and ditches Signing vertical clearance load limit delineators

Streams and Channels Erosion control Slope protection Bank protection Rip-rap Drift Beaver dams

Bridge Major Maintenance and Rehabilitation Total deck replacement Partial-depth deck replacement Delamination repair Deck overlays Cathodic protection Deck joint replacement Bearing replacement

Culvert Major Maintenance and Rehabilitation Strutting Culvert liners Culvert end treatment repair and replacement Cathodic protection

Repair Materials Concrete silica-fume concrete fibre reinforced concrete latex modified concrete corrosion-inhibiting concretes

Repair Materials (cont’d) Polymers polymer concretes polymer overlays Specialty products patching materials grouts sealers

Approved Products Standard testing procedures Certified laboratories Testing paid by manufacturer Approved products list concrete sealers concrete patching & grouting paints

Concrete Sealers Type 1a - relatively dry deck RMC < 55% Type 1b - outdoor exposure deck RMC < 70% Type 1c - outdoor exposure deck RMC < 80% Type 2a - one component coating RMC < 70% Type 2b -two component coating RMC < 70% Type 3 - pigmented coating RMC < 70%

Concrete Patching Materials Type NH poured horizontal patches, 3 day curing Type OH-V trowelled overhead or vertical patch Type LTH low temperature poured horizontal patch Type HEH high early strength poured horizontal patch

Paints Type B2 Type B3 Type B5 & B6 Type 8 Truss / River / Little experience Type B3 Girder / River / Much experience Type B5 & B6 Freeway / Overpass Type 8 Submerged pipe piles