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Guidelines Sealing Concrete Bridge Decks

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Guidelines Sealing Concrete Bridge Decks Powered By Docstoc
					                                                                                      August 29, 2005
                                                                                 Deck and Rail Sealing



  Guidelines for Sealing Concrete Bridge Decks
               and Concrete Rails
Background to Preventive Bridge Deck and Railing Sealing
       HSOP and Preventive Bridge Maintenance
       Deck sealing and concrete rail sealing are two of the seven preventive bridge
maintenance (PBM) activities in the 2005 Highway System Operations Plan (HSOP). The other
five PBMs are: seal cracks every five years, seal poured deck joints every eight years, repair or
replace all torn strip seals, flush all bridge decks annually, and spot paint critical areas.

        The initial target of these two PMBs is to seal all concrete bridge rails and bridge decks
which do not have a dense overlay and are in deck condition states (CS) 1 and 2 on a four to
seven year rotating schedule, depending on the type of sealer applied. Decks in CS 3 should be
crack sealed prior to applying a deck sealant and those in CS 4 and CS 5 should be brought to CS
2 or 1 prior to deck sealing. (Contact the Materials and the Bridge Office for assistance in
selecting crack sealing materials if deck is in CS 4.)

        We anticipate that future sealing programs will more closely conform to the best
practices of other agencies and product manufacturer recommendations for applying penetrating
sealers and that we will move to a two to four year sealing cycle on all concrete bridge decks.

       Purpose of Sealing Bridge Decks & Railings
       Sealers are used on highway Portland Cement Concrete bridge decks and railings to
reduce the rate of chloride attack on the reinforcing steel, thereby extending the service life and
reducing life-cycle structure costs of the bridge deck. Additionally, by reducing moisture in the
concrete, the severity of freeze-thaw deterioration and spalling due to rebar corrosion, is reduced.

        By applying sealers to existing concrete surfaces, the permeability of the concrete is
reduced by up to one order of magnitude. The permeability of the concrete is one of the most
important factors which will affect the rate of deterioration of rebar corrosion, alkali-aggregate
reaction, carbonation, and the effects of freeze-thaw cycles. All of these can occur
simultaneously. Even on dense concrete overlays, sealing small and micro cracks will prevent
intrusion of water and chlorides.

        History of Sealing Bridges
        One county in Wisconsin has reported more than a 60% reduction in deck-spalling after
four years of their program using Siloxane sealers on concrete decks, which do not have dense
overlays, using both a two year (for county bridges) and four year recoating cycle (for state
bridges). Alberta’s Ministry of Transportation has 19 years of continuous use of Silane sealers
and reports extended life on their dense concrete decks using a three year coating cycle.
Montana and South Dakota has been using High Molecular Weight Methyl-methacrylate crack
sealing with reported good success in extending the life of their bridge decks.




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                                                                                 Deck and Rail Sealing

       All agencies report that repetitive applications of penetrating sealers require less sealant
material with each application and the sealer effectiveness appears to improve.

       Types of Sealers
       Penetrating Sealers: Penetrating sealers are products that are adsorbed onto the surface of
       the concrete and react with the concrete to form a hydrophobic (water repelling) surface.
       The pores and cracks in the concrete are not blocked and while liquid water is repelled,
       water vapor can pass. This unique property allows the concrete to dry out while repelling
       water from all surfaces.
               Silanes – Low molecular weight penetrating sealer, which allows for maximum
               penetration of pores and fine cracks. Silane has excellent vapor transmission
               properties.

               Siloxanes – Higher molecular weight penetrating sealer which has about half the
               penetrating ability of Silane. It has good vapor transmission properties. (Suitable
               for sealing less dense concrete and coarser cracks.)

       Polymer Coatings: Polymer Coatings (colored or clear) are products that bond to the
       outer surface of the concrete and form a film. The waterproofing properties of the
       coating are generally independent of the concrete, although adherence to the concrete is
       necessary for the coating to function.
               High Molecular Weight Methyl-methacrylate –Of higher molecular weight than
               Siloxane, it has good crack penetrating properties, but fills rather than coats pores
               and so has poor vapor transmission. The coating is rapidly removed from wearing
               surfaces and relies on its penetrating ability rather than sealing the concrete
               surface to provide water proofing ability. A blotter seal is usually applied to
               remove surface residue and provide friction for traffic. Caution: use high
               molecular weight methyl-methacrylate to reduce flammability. Best application is
               for extensive fine cracking.

               Epoxy – Penetrating abilities vary by product, but primarily is used to provide a
               barrier coating to ingress of water. Most epoxies designed for use as a bridge
               deck sealer have good elastic properties to span and cover cracks as they move.
               Some epoxy sealers are formulated to also have good penetrating capabilities.
               When applied in traffic areas, epoxies are always applied with additional friction
               materials, usually an aggregate chip. (Use only in coordination with the Materials
               and the Bridge Offices.)

       Bituminous Coatings: These thin surface coatings are primarily intended for use as a
       surface restorer for asphalt pavements, but polymer modified binders have elastic and
       water proofing properties that need to be evaluated for use as bridge deck sealers. (Use
       only in coordination with the Materials and the Bridge Offices.)
               Chip seals – Only polymer modified binders and proper chip embedment are
               expected to give satisfactory performance.




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             “Ultrathin Bonded Wearing Course” (Novachip) – A highly polymerized asphalt
             emulsion is sprayed and then immediately a thin layer of hot-mix asphalt is
             applied, which causes the emulsion to foam. This provides a quick setting and
             tough surface coating.

Selecting Concrete Sealers
     Sealer service life
     Service life is dependent on the specific manufactured product, the application of the
     sealer, and the severity of service it experiences. The following ranges assume good
     application and for polymer and bituminous coatings, low to moderate traffic levels.
             Penetrating Sealers
             Silanes – 3 to 5 years
             Siloxanes – 3 to 5 years

             Polymer Coatings
             High Molecular Weight Methyl-methacrylate – 4 to 10 years
             Epoxy – 10 to 20 years


             Bituminous
                   Chip seals - 3 to 5 years
                   “Ultrathin Bonded Wearing Course” 5 to 7 years.


     Matching Bridges to Sealers
     Approved penetrating sealers may be found at Alberta’s Ministry of Transportation web
     site: http://www.tu.gov.ab.ca/Construction/DoingBusiness.asp . Under Technology
     Development, select Alberta Transportation Product List, then Bridge Concrete Sealers.
     Use Type 1 sealers for concrete bridge decks and Type 2 sealers for concrete railing.
     Refer to Montana Department of Transportation’s specification and approved product list
     for High Molecular Weight Methyl-methacrylate:
     http://www.mdt.mt.gov/bridge/net/external/special-provisions/Br201.40.doc

     Type of Deck
            Dense Concrete Overlays – Sealing is not required for dense concrete decks in
            Condition State 1
            . Dense concrete decks in CS 2 should be sealed using Silane.

             Concrete Decks without dense overlays – Seal using either Silane or Siloxane if in
             CS 1 or CS 2.

     Condition of Deck
            Condition State 1: Deck has little or no deterioration (no notable spalls,
            delaminations, or patches). The wearing surface may have superficial cracking,
            scale or wear. The underside of the deck may have isolated leaching cracks, but
            there is no notable rust staining or water saturation.


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                       Seal using Silane every four years
                       Option: use Siloxane on bridge decks without dense overlays.
               Condition State 2: Deck has minor deterioration (isolated spalls, delaminations,
               or patches) – the percentage of unsound deck is less than 2% of the total deck
               area. The wearing surface may have minor cracking, surface scale, or wear. The
               underside of the deck may have minor leaching cracks –there may be isolate
               water saturation, or rust staining.
                       Seal using Silane every four years
                       Option: use Siloxane on bridge decks without dense overlays.
               Condition State 3: Deck has moderate deterioration (spalling, delaminations, or
               patches). – the percentage of unsound deck is between 2% and 10% of the total
               deck area. No full depth failures are present (structural underpinning is not
               required). The wearing surface may have cracking, surface scale, or wear. The
               underside of the deck may have leaching cracks, water saturation, or rust staining.
                       Crack seal before deck sealing with Silane or Siloxane, or
                       Crack seal using High Molecular Weight Methyl methacrylate and sand
                       blotter. (Best application is for decks with many cracks.)
               Condition State 4: Deck has extensive deterioration (spalling, delaminations, or
               patches) – the percentage of unsound deck is between 10% and 25% of the total
               deck area. Isolated full-depth failures may be present (or imminent) – structural
               underpinning may be required. The wearing surface may have extensive and
               significant cracking or scaling. The underside of the deck may have extensive
               and significant leaching cracks – there may be extensive water saturation or rust
               staining.
                       Crack seal and repair prior to deck sealing. Select sealant depending on
                       condition of deck – contact Bridge Office and Concrete Office.
                Condition State 5: Deck has severe or critical deterioration. The percentage of
                unsound deck is greater than 25% of the total deck area. Full-depth failures or
                impending failures may be prevalent. Immediate structural underpinning may be
                required. Wearing surface may have severe spalls requiring immediate repairs.
                       Repair prior to sealing deck.

        Concrete rails – Seal using either Siloxane (preferred) or Silane if more compatible with
concurrent deck sealing.
        Bridge seats and Ends of Concrete Beams (to be coated if easily accessible) – Silane is
preferred for prestressed concrete, Siloxane for other concrete. (Use system compatible with
concurrent deck sealing to minimize material preparation and handling.)
        Adjacent concrete components or structures which are in the “spray zone” during winter
chemical applications may be sealed using same products recommended for concrete rails,
bridge seats and beam ends and at the same time, to minimize the number of operations, lane
closures and mobilizations.

Selection of Bridge Decks for Sealing
Using Pontis bridge data, the Bridge Office will send out a list of bridge decks prioritized
according to rating system presented in Appendix C. Recognizing that the Pontis data is not
always current, the district should use this list only as a starting point to determine which decks


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they will add to their work plan to seal for the season. (Please contact the Bridge Management
Unit with discrepancies between actual and reported conditions.)

Documentation
Prior to application of any sealer complete the Bridge Deck Sealer Evaluation Form in Appendix
A and send a copy to: Jim Lilly at the Bridge Office, MS 610. Additional documentation will be
required for use of materials other than Silane, Siloxane and HMWM (see the following section
on Research for new products.)

Work should be charged to activity 2836 DECK AND RAILING SEALING – Square Feet, to
track Deck and Rail Sealing.

Research
At this time, all products other than Silane, Siloxane and High Molecular Weight Methyl-
methacrylate should be considered research products. Evaluation of these materials, such as
epoxy, bituminous and other deck sealer, should be done in coordination with the Materials, the
Maintenance, and the Bridge Offices. As a minimum, for research products, chloride and
moisture determination and deck soundness using ground penetrating radar (GPR) and chain
dragging, in addition to the information required in standard Bridge Deck Sealer Evaluation
Form, should be made for all decks prior to placing any of these research coatings. More
extensive photo-documentation should be made for future comparisons.

Some deck sealers may provide enhanced anti-icing capabilities, improve friction and or reduced
noise properties. Evaluation of these products should include comparisons of crash rates, skid
testing numbers, and noise evaluations before and after application of these products. Adequate
documentation of these values should be available prior to application of the product(s).




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Appendix A
                   Bridge Deck Sealer Evaluation
Bridge Number:                                         Location:
Owner:                                                    TH:
Deck Area:                                                County
   Total (SF):                                            District
   Sealed (SF)                                         Deck Type:
Girder Type:                                             Dense Concrete Overlay
Bridge Length (LF):                                      Concrete Deck without overlay
  Total                                                  Other: _________________
  Main Span                                            Deck Width (LF)
Year Constructed                                             Total
Rehabilitated:                                               Sealed
 Year                                                  Deck condition NBI prior                post
 Type                                                         Pontis: CS prior                 post
Description of top of deck prior to sealing:           ADT:
(photos)


Description of Bottom of Deck prior to sealing:
  Visible Cracks (photos)
        Number
        Location
        Efflorescence (bleed through)




Product used for sealing:                              Moisture:
  Manufacturer:                                          Dry surface Yes     No
Temperature at application:               F              Weather Humid        Dry
Gallons Applied                                          Last Rain:
Square Feet Per Gallon                                         Less than 3 days
                                                               3 to 5 days
Comments:                                                      Greater than 5 days
 Chloride content
 Problems mixing or applying sealers
 Photographs (Attach copies of top & bottom of deck)




Submit copy to:
Jim Lilly
Bridge Office, MS 610


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Appendix B –
Application of Sealers
      Methods
              Deck and Railing Condition assessment
              Surface Preparation – In general, follow the manufactures recommendations for
      surface preparation. Preparation for penetrating sealers usually requires only that all dirt,
      sand, clay and other debris be removed from the concrete deck or railing. Preparation for
      the application of polymer coatings usually requires blasting of the concrete surfaces.
              Penetrating Sealers
                   Deck should be washed and / or power swept to remove all dirt, sand, clay
                     and other debris from the deck or rail and remain dry at least three days
                     prior to applying sealer. Normally it is the best practice to schedule this
                     operation in conjunction with the deck flushing program. The deck must
                     be very dry prior to applying the sealer.
                   Coverage rate of sealer should be based on manufacture’s
                     recommendations. Allow an additional 30% for variable concrete
                     conditions.
                   Check that the sealer is compatible to any previous sealer used on the
                     concrete surface.
                   Silane sealer should be kept in airtight drums and should be stirred to mix
                     the active ingredient prior to use. Product must be use within the
                     manufacturer’s specified shelf life.
                   Method of application may be by hand spraying using an airless or garden
                     type sprayer, or a vehicle mounted spray bars applicator may be use. In
                     the later case and constant rate sprayer will give better results.

                   Polymer Coatings
                      High Molecular Weight Methyl-methacrylate 1 (Use only High Molecular
                      Weight Methyl-methacrylate – HMWM) – Note: Handling and cleanup of
                      HMWM requires care. South Dakota and Montana use this product with
                      good success. If MnDOT crews select this product, they should work closely
                      with the product manufacturer until comfortable with handling the product.
                      There is no requirement that HMWM be used, as standard crack sealing prior
                      to deck sealing is always an option.
                       Material Delivery and Storage. Store sufficient quantities of all HMWM
                          materials at the site to perform the entire application before starting deck
                          surface preparation. Store containers of promoters and initiators in a
                          manner that prevents leakage or spillage from one to contact the
                          containers or material of the other. Note: that direct contact between
                          the promoter and initiator can result in a spontaneous explosion!
                          Store these materials in their original containers. These containers must
                          bear the manufacturer's label. The label must show the manufacture date,
                          the batch number, the trade name brand, the quantity, and the mixing ratio.
1
    Based on Montana Department of Transportation Specification -
http://www.mdt.mt.gov/bridge/net/external/special-provisions/Br201.40.doc


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    Include a Materials Safety Data Sheet (MSDS) with each shipment of
    resin. On delivery of the materials to the site, take two, one-half pint (0.25
    liter) samples of each lot number of base resin. Store one sample at the
    site. Provide the other sample to the Materials Lab at Maplewood, to
    verify the infrared signature of the resins against the earlier submittal from
    the manufacturer. Submit these samples at least three calendar weeks
    before starting the resin application to: Jim McGraw, MS 645, Materials
    Lab, Maplewood, MN. Do not send samples of the initiator or promoter
   Provide a clean, dry storage facility for the materials that will shelter them
    from the elements and preserve their fitness for use. The storage facility
    must have a thermometer that records extreme temperatures. Replace the
    materials if the temperature exceeds the range the manufacturer
    recommends or if the materials’ shelf life has expired. Repeat the FTIR
    sampling and testing in this case.
   Require all workers to handle the resins in compliance with the
    Manufacturer's Safety Data Sheets, especially with respect to the proper
    protective clothing.
   Deck Preparation
         o Surface Condition. The deck surface must appear dry to a visual
             inspection at the time of HMWM treatment.
         o Surface Preparation Equipment. Use shot blast equipment such as
             Blastrac, Wheelabrator Frye, or Turbo Blast, Turbo Blast
             Company to clean the deck surface. Determine the size and type
             of equipment based on specific job conditions. Select the size of
             shot or sand and travel speed of the equipment to provide a
             uniformly clean surface with a uniform profile.
   Sand blast areas that are not cleaned with the shot blast equipment.
         o Surface Preparation. Clean all concrete surfaces for HMWM
             treatment by blasting prior to the HMWM application. Remove all
             traces of curing compound, laitance, grease, dirt, dust, salt, oil,
             asphalt, paint, striping, coating, or other foreign materials.
   Protect the concrete surface from undue damage during the cleaning
    process. Provide a reasonably uniform surface color.
   Generally expose coarse aggregate with slight reveal (maximum reveal:
    1/8 inch - or 3 mm).
   HMWM Application. Apply resin to the entire deck at a rate of 100 to
    150 ft2/gal (3 to 4 m2/l). The application rates may vary depending on
    field conditions, temperature of deck and slight variations in specific
    gravity. Apply the resin to the deck within 5 minutes of complete mixing.
    Do not use material showing any visible increase in viscosity prior to
    application. Porous or tined concrete requires application rates at the
    lower end of this range. After application of the resin, continuously sweep
    excess resin to untreated areas of the deck. Stop this sweeping between 5
    and 10 minutes before the HMWM gels. Re-fill all cracks visible to the
    eye constantly after application until 5 minutes before gel formation by
    using brooms, brushes, or squeegees. The Engineer has the discretion of


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        requiring that decks with tined surfaces receive a separate pre-treatment
        for visible cracks. In this case, fill the cracks and keep them full until 5
        minutes before gel formation. This pre-treatment requires approximately
        one gallon per 100 lineal feet (1 liter per 8 meters) of crack.
       Application of Sand. Broadcast silica sand mechanically over the entire
        treated area of the bridge deck to obtain a visually uniform coverage of 1
        lb. per square yard (0.5 kg/m2). Apply the sand before the resin gels.
        Remove excess sand if the technical representative requires it.
       Limitation of Operations. Protect people and vehicles from injury or
        damage. Cover membrane and elastomeric material in deck joints, plug
        deck drain scuppers, seal cracks on underside of deck, and institute other
        protective measures to protect traffic, waterways, and bridge components.
        If materials or solvents harm the appearance or the function of bridge
        components, replace or repair the component.
       The following conditions govern work on each individual portion of a
        structure unless otherwise approved.
            o Initiate work on any portion of a structure only if the local weather
                 forecast predicts daytime temperatures favorable for HMWM
                 application and no rain is forecast for a period of 48 hours prior to
                 the scheduled HMWM application time.
            o Conduct the work in a continuous operation with the HMWM
                 application immediately following surface preparation.
            o Do not apply HMWM treatment if rain is likely within 4 hours
                 following the application.
            o Apply HMWM treatment only if the deck surface temperature and
                 the air temperature are 50º F (10º C) or above and 90º F (32º C) or
                 below and the weather forecast shows they will remain within that
                 temperature range for at least twelve hours after the end of the
                 work day.
            o Apply HMWM treatment only between 1 May and 1 September.
       Do not permit traffic on the treated surface until the sand cover adheres
        sufficiently so that no tracking will occur.

Epoxy
Epoxy products should be evaluated using the procedures outlined in Research” section.
        Product handling (To be developed)
        Application (To be developed)
        Safety considerations (To be developed)
        Cure time and time to return traffic (To be developed)

Bituminous Coatings
Bituminous coatings including chip seals, thin bonded surface coatings and thin hot-mix,
should be evaluated using the procedures outlined in “Research” section.
        Product handling (To be developed)
        Application (To be developed)
        Safety considerations (To be developed)


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Cure time and time to return traffic (To be developed)




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Appendix C
Sealing Prioritization
                                                           Deck Sealing Prioritization
Table A – Deck Condition Rating
Deck Condition Rating                         CS 1                   CS 2                  CS 3                   CS 4                  CS 5
                                                                                                      1
Deck Sealing Prioritization Points                     1                      2                     3              Repair first2         Repair first3

Table B - Average Daily Traffic
ADT                                               > 10,000                         2000 to 10,000                           < 2000
Deck Sealing Prioritization Points                             130                               70                                           10

Table C - Deck Type
Wearing Surface                                      Black Rebars           Coated Rebars
      No Overlay - Points                                  300                    150
      Dense Overlay >1” Points                             200                    100
1
  Crack seal first, then deck seal with Silane or Siloxane, or use High Molecular Weight Methylmethacrylate if cracks are tight (See note . 4 below)
2
 Normally consider an overlay in this condition. Check with Bridge Office and Maplewood Lab Concrete Office.
3
  Normally consider a deck replacement in this condition

Priority of bridge deck sealing is calculated according to the following: Values in (Table A x Table B) + value in Table C.




                                                        Crack Sealing Prioritization
Crack Condition Rating                     CS 1               CS 2                           CS 3            CS 4
Crack Sealing Prioritization                   N/A              Cracks are sealed                15                                 Repair
5
    Option is to deck seal with High Molecular Weight Methylmethacrylate if cracks are tight. Check with Bridge Office and Maplewood Lab Concrete Office.




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