Major Maintenance and Rehabilitation of Concrete Bridge Decks
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 0
Major Maintenance and Rehabilitation of Concrete Bridge Decks • Large Percentage of All Bridge Decks (over 90%) • Two Main Mechanisms of Deterioration Ø freeze thaw damage Ø corrosion of rebar – delamination of concrete • Prevention of Freeze Thaw Damage Ø proper concrete mix design/air entrainment Technical Standards Branch Class A Bridge Inspection Course 1
Major Maintenance and Rehabilitation of Concrete Bridge Decks • Prevention of Corrosion Damage Ø prevent moisture/chloride entering concrete Ø ensure concrete around rebar remains passive Ø use non-corrosive rebar • Deck Durability – New Construction Ø membrane and ACP Ø epoxy coated rebar Ø stainless steel/stainless steel clad rebar Ø corrosion inhibitors Technical Standards Branch Class A Bridge Inspection Course 2
Major Maintenance and Rehabilitation of Concrete Bridge Decks Deck Rehabilitation - Timing • Optimum timing gives best life cycle cost • Too early Ø existing deck protection still working Ø no significant damage to deck Ø future life of deck/bridge not shortened if rehabilitation delayed • Too late Ø significant corrosion damage to deck Ø rehabilitation costs have significantly increased Ø high chlorides or other factors have significantly shortened life of deck/bridge • Great deal of experience and judgement to determine optimum timing Technical Standards Branch Class A Bridge Inspection Course 3
Major Maintenance and Rehabilitation of Concrete Bridge Decks Methods/Options for Rehabilitation • Concrete Overlays Ø provides durable long lasting wearing surface Ø less permeable – reduces moisture in deck Ø reduces rate of corrosion • Membrane/ACP Ø waterproofs deck surface Ø stops additional moisture getting in deck Ø significantly reduces corrosion Ø membrane/ACP not as long lasting wearing surface as concrete Technical Standards Branch Class A Bridge Inspection Course 4
Major Maintenance and Rehabilitation of Concrete Bridge Decks Methods/Options for Rehabilitation • Thin Polymer Overlays Ø membrane without protection of ACP Ø does not add significant dead load Ø existing concrete deck in good condition Ø need very good bond with concrete Ø subject to damage from snow plows, vehicle wear, UV rays Technical Standards Branch Class A Bridge Inspection Course 5
Major Maintenance and Rehabilitation of Concrete Bridge Decks Methods/Options for Rehabilitation • Cathodic Protection Ø electric potential over deck surface prevents additional corrosion Ø use when existing corrosion activity very high Ø need power source at site Ø generally needs to be used with concrete overlay Ø monitoring and maintenance required to ensure system is working Technical Standards Branch Class A Bridge Inspection Course 6
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlay • High Density Concrete Ø started using in mid-1970’s Ø low water/cement ratio – low slump Ø site batched with mobile mixer Ø placed with special finishing machine Ø very good durability Ø less permeable than normal concretes Ø still relatively high permeability Technical Standards Branch Class A Bridge Inspection Course 7
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlays • Latex Modified Concrete Ø also started using in mid-1970’s Ø latex used to replace some of the water in mix Ø also site batched Ø low permeability/high slump Ø difficult to finish and cracks easily Ø can be used for thin overlays < 40 mm Ø section of overlay can become loose if bond problem Technical Standards Branch Class A Bridge Inspection Course 8
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlays • Pyrament Cement Concrete Ø cement with high fly ash content – 35% Ø on market in early 1990’s Ø pre-bag mix – water added at site Ø fast setting, high strength, low permeability Ø hard to finish – shrinkage cracks Ø AAR problems – reduced bond Technical Standards Branch Class A Bridge Inspection Course 9
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlays • Silica Fume Concrete Ø started using in late 1980’s Ø small amount of silica fume in mix (7. 5%) Ø early use – pre-bag mix – water at site Ø presently mostly transit mix Ø low permeability – good durability Ø little more difficult to finish Ø more sensitive to shrinkage cracks Technical Standards Branch Class A Bridge Inspection Course 10
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlays • Silica Fume Concrete with Steel Fibres Ø steel fibres added to mix Ø increases tensile strength Ø reduces/controls shrinkage cracks Ø holds overlay together if debonded Ø presently most commonly used overlay by AT Technical Standards Branch Class A Bridge Inspection Course 11
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Concrete Overlays • Modified Silica Fume Concrete Ø small amount of fly ash in mix Ø fog curing immediately behind finishing machine Ø seven day wet curing Ø increase strength – reduces cracks Ø can be used with and without steel fibres Ø will be more widely used by AT in future Technical Standards Branch Class A Bridge Inspection Course 12
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Membrane/ACP • Hot Applied Rubberized Membrane/Protection Board/ 2 -40 mm Layers ACP (90 mm) Ø used on new construction Ø dead load limits use for rehabilitation • Sheet Membrane with 50 mm ACP Ø repair any damage to deck Ø requires fairly smooth surface Ø bond with concrete and joints between sheets main concerns Ø top of sheet rough surface to protect from and provide bond with ACP Technical Standards Branch Class A Bridge Inspection Course 13
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Membrane/ACP • Polymer Membrane with 50 mm ACP Ø requires relatively smooth surface Ø good bond with concrete decks Ø bond with ACP problem unless some aggregate in top layer Ø aggregate can affect permeability of membrane Technical Standards Branch Class A Bridge Inspection Course 14
Major Maintenance and Rehabilitation of Concrete Bridge Decks Thin Polymer Overlays • Flexible Epoxy Overlays Ø two components - must be mixed properly Ø can be multi-layer system Ø very low permeability Ø requires very good preparation of concrete surface § rough texture but clean Ø very sensitive to weather conditions § concrete internally dry Ø even flexible epoxy is a relatively brittle material Technical Standards Branch Class A Bridge Inspection Course 15
Major Maintenance and Rehabilitation of Concrete Bridge Decks Thin Polymer Overlays • MMA Overlays Ø more flexible, thicker material Ø single layer Ø somewhat more expensive than epoxy Ø also requires very good concrete surface preparation Ø works better on more flexible decks • Urethane Overlays Ø use in parking garages Ø not durable enough for highway traffic Technical Standards Branch Class A Bridge Inspection Course 16
Major Maintenance and Rehabilitation of Concrete Bridge Decks Cathodic Protection Systems • Conductive Titanium Wire Mesh in Overlay Ø requires concrete overlay Ø must eliminate all shorts between mesh and deck Ø requires monitoring • Under Deck Conductive Coating Ø do not require concrete overlay Ø still must eliminate all shorts Ø requires monitoring Ø long-term performance not proven Ø coating system appears to dry out and become non-conductive with time Technical Standards Branch Class A Bridge Inspection Course 17
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 18
Major Maintenance and Rehabilitation of Concrete Bridge Decks Lateral Connection Between Girders • AT has a number of concrete girder types that are placed side by side and connected together by grout-keys or connector bolts • These grout keys have not stood up well over time • During rehabilitation of these girder bridges the lateral connections are usually upgraded and supplemented (underslung beams, lateral post-tensioning) Technical Standards Branch Class A Bridge Inspection Course 19
Major Maintenance and Rehabilitation of Concrete Bridge Decks Typical Shear Key – PM Girders Technical Standards Branch Class A Bridge Inspection Course 20
Major Maintenance and Rehabilitation of Concrete Bridge Decks Girder Shear Keys Technical Standards Branch Class A Bridge Inspection Course 21
Major Maintenance and Rehabilitation of Concrete Bridge Decks Lateral Connection Between Girders • Short Span Girders with Bolted Connector Pockets (HC, VS, SM) Ø reinforced concrete overlay (nominally 150 mm) Ø hair pin bars and grouting • Longer Span Girders (FC, VF, FM) – Continuous shear keys Ø lateral stressing Ø underslung beams Ø combination of both Technical Standards Branch Class A Bridge Inspection Course 22
Major Maintenance and Rehabilitation of Concrete Bridge Decks Lateral Stressing and Underslung Beam – FC Girders Technical Standards Branch Class A Bridge Inspection Course 23
Major Maintenance and Rehabilitation of Concrete Bridge Decks Bridge Deck Joints • Pre – 1975 Bridges Ø lots of simple spans Ø lots of non-waterproof joints • Existing Practice Ø continuous spans, eliminate deck joints where possible Ø joints waterproof or with drainage systems Technical Standards Branch Class A Bridge Inspection Course 24
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Deck Joints • Strip Seal Joints Ø waterproof Ø a rubber/neoprene seal attached to metal extrusion Ø moderate thermal movements (up to approx. 75 mm) Ø make sure installation fills all voids behind extrusions Ø work well but seals must be replaced from time to time Technical Standards Branch Class A Bridge Inspection Course 25
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Deck Joints • Finger Plate Joints Ø non-waterproof Ø sliding finger plates with plumbing/drainage system Ø works for large thermal movements (> 75 mm) Ø careful to fill all voids behind plates when installing Ø mis-alignment of fingers due to dead load creep and abutment rotation Ø plumbing/drainage systems need to be cleaned out from time to time Technical Standards Branch Class A Bridge Inspection Course 26
Major Maintenance and Rehabilitation of Concrete Bridge Decks Types of Deck Joints • Small Movement Joints Ø small movements due to live load deflection, etc. Ø compression seals Ø types of caulking materials Technical Standards Branch Class A Bridge Inspection Course 27
Major Maintenance and Rehabilitation of Concrete Bridge Decks Specifications for Bridge Construction • • • Link to Specifications for Bridge Construction Section 4 - Cast in Place Concrete Section 15 - Polymer Overlays Section 16 - Bridge Deck Waterproofing Section 20 – Deck Overlays and Concrete Rehabilitation • https: //www. transportation. alberta. ca/4753. htm Technical Standards Branch Class A Bridge Inspection Course 28
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 29
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 30
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 31
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 33
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 34
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 38
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 40
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 41
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 42
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 43
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 45
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 46
Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 47
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 57
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 59
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 65
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Technical Standards Branch Class A Bridge Inspection Course 73
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Major Maintenance and Rehabilitation of Concrete Bridge Decks Questions Technical Standards Branch Class A Bridge Inspection Course 88
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