Bridgedeck Waterproofing FAQ

Information about methods and materials.

What is it? How it works? Which products?

What To Know

  • Protection. A bridge is an expensive asset and are vulnerable to corrosion of the rebar. Since all bridges bounce, it is likely any concrete deck will be cracked. This crack will allow water intrusion to the reinforcing steel in the deck and cause corrosion; unless there is a waterproofing membrane.

  • The oldest most common method is sheet membrane. Sheet membranes that are self adhered to the deck are most common. These membranes work by placement on the deck and are melted in place once the asphalt pavement is placed and rolled on top. The membranes should not have any release films on them when used. Although simple in design, they are the most prone to problems when installed by an inexperienced crew.

    Liquid rubber membranes have probably been used the longest for bridgedecks. The have evolved to specially blended formulations of asphalt with polymer additives and fillers. Asphalt rubber or hot liquid rubber membranes are more fail safe than other systems. Upon placement you will immediately know if there are water issues on the deck and bond issues. They will fill voids better, are not as succeptable to tenting like sheet membranes, it is difficult to trap are, they flow into cracks and ensure a tight seal along edges. Liquid systems must use a protection board system. A protection board is more robust than a sheet membrane and will provide better protection while paving.

    Chemically Cured systems such as PMMA and PUMA are the latest and most expensive type systems. They involve an application of fast curing flexible and durable coating. This type of coating is much more resistant to puncture and abrasion. The drawback to chemically cured systems is often they are sensitive to moisture. Cure times will vary. They can sometimes be placed without the use of protection boards. They can be applied vertically with ease

  • Sheet membranes have the advantage of being easily transported, installed with minimal equipment, have built in protection, and depending on the membrane, can be cheaper than other options.

    They can reduce transport costs to remote locations.

    Sheet membranes are suited for smooth bridge deck surfaces.

    Do not use sheet membranes on rough surfaces. Sheet membranes require the person or company responsible for the finished system to closely monitor the paving operations. Sheet membrane systems are soft and prone to damage easier, the many seams can create problems with moisture, the system rarely works well without heat from the asphalt pavement melting the system together.

    There are some torch on type sheet membranes. These can be less prone to damage than peel and stick but have added open flame issues. Liability insurance coverage can be difficult to obtain.

  • Hot rubber is a well known time tested and passed system. It works on both smooth and rough surfaces. It will adhere better than sheet membrane systems and generally provide longer service life. Although liquid hot rubber systems are soft and easily prone to damage, the protection board does the job to exceed durability of sheet membrane systems.

    Hot rubber requires indirect melting systems with temperature control to provide the basic quality control on the waterproofing product.

    Hot rubber is not ideal for vertical applications.

  • Chemically cured waterproofing systems for bridges are becoming more common to protect the ever growing infrastructure life cycle costs. These membranes are more expensive than asphalt based products. They have greater durability, can require less components, can sometimes be faster, do not require open flame, have greater bonding capacity. They will also have better thermal range but usually don't have the movement range compared to asphalt systems.

    These membranes do not have seams nor are they easily affected by exposed edges like asphalt systems due to their strong bond capacity.

    Environmental factors can play an important role in these membrane systems.

    Chemically cured membranes provide better quality assurance for multi phase projects, high possible damage locations,

  • Concrete that hasn't cured long enough to reduce vapour transmission will lead to a failure of the membrane system. Curing times will vary depending on the system.

    A moisture test should be done. At minimum a poly test and primer bond test will indicate if moisture is an issue. Generally 14 days after pour is sufficient to achieve low enough moisture in the deck to achieve a bond. Sometimes this is extended to 21 days. Cure times to achieve a dry surface are extended in cool moist conditions.

Important Details

  • All decks should be clean and free of all dust, oils, and any bond breaker. New decks are preferrably shot blasted to a CSP 2-3 profile.

    Alternatively, minor concrete laitenance / dirt can be removed using a 4,000-6,000 psi surface cleaner or turbo nozzle.

    All pitting greater than the membrane allowance should be filled.

    All sharp / protruding points should be removed.

    Weep holes should be cleaned, plugged or sleeved prior to waterproofing work.

  • Be mindful of standing water on decks. Although some standing water can occur, it is not helpful in assisting the membrane to do it's job. Keep all pooling water below membrane terminations and be mindful of ice effects. (Pavement is pourous and not waterproof).

  • Prior to installation of a membrane some items must be done.

    1. Deck preparation must be complete. All washing must be done 48 hours prior to membrane installation.

    2. Paving direction should be known.

    3. Tie in points to vertical faces to be exposed (approach slabs faces, abutments) as detailed for membrane install.

    4. Deck must be dry.

    5. Weep holes plugged (spill containment)

    6. Paving crew scheduled immediately following.

    7. Heads up for material acquisition.

  • There are different ways to building decks and each has their own costs associated with them. Bridgedecks that have more details and joints will cost more.

    Cast in place decks are generally cheaper while precast panels are more expensive. The detail requirements are listed with the Provincial Standard Specifications, the Engineer drawings, or the membrane manufacturer.

  • We always like to see the medians on top the membrane and always on top if it is precast medians.

    Any precast barriers placed before the membrane will void the membrane warranty to damage from such a system.

  • Expansion joints, like median / parapets are weak points in the system if they crack. All expansion joints should have an impermeable barrier installed that is resistant to cracking. The material should have the movement range to meet the conditions expected, especially at low temperature. Each membrane system will have it's own, but similar details.

    Where the membrane can not be integrated with the joint, an impervious barrier should be installed as a joint header. The expansion joint and the membrane system will tie into the joint header.

Paving The Deck?

  • Mix designs are important, especially with softer asphalt / sheet membrane systems. The maximum aggregate size is often limited compared to a regular mix design. This reduced size is to limit puncturing of the membrane during the compaction process.

    It is more common to see 1/2" maximum aggregate sizes than 3/4" sizes.

    Check with the membrane manufacturuer to the mix design and aggregate size needed.

  • A minimum thickness recommended by Roaron Construction is 50mm or 2 inches. The suggested thickness for membranes is 100mm or 4". The thicker design does not really add strength but allows future maintenance without damaging the membrane. It will also reduce full depth potholing.

  • Monitoring the paving process by a qualified membrane installer is of utmost importance if the bridge builder wants to maintain any kind of warranty. Many paving companies do not know the ins and outs of the paving process. This quickly and easily leads to damage unless someone knowledgeable is on site to direct and correct if needed.

    Approximately 25% of paving works on bridges result in some incorrect practises.

  • Without proper mix placement temperatures, the system is vulnerable to slipping and cracking. Sheet membranes are dependent on the heat of the asphalt pavement to work. Without the heat from the asphalt, membrane systems fail to bond the individual components into a single system. This leads to premature failure.

  • Rolling on a bridgedeck or any suspended slab is different than on grade. Vibratory rollers are not permitted on decks. Compaction can be more difficult to acheive without vibratory so heavier rollers may be needed.

    During the initial roll, the melted membrane can cause shoving during rolling if the rollers are not dual drive or too heavy. Start with a breakdown roller then hit it with the heavier rollers.

  • A significant problem for membrane systems as heat from the asphalt pavement can create steam and act as a debonder to the system. Moisture under sheet membranes will cause the membrane system to fail. Moisture under protection sheets may cause bond issues and steam pockets created under the protection board may cause the asphalt to improperly compact and crack.

    Ensure paving is done before rain is present. Seal all edges on sheet systems if asphalt pavement can't be placed in time.

Common Questions

  • Generally, no. The membrane system installed will most likely have a top coarse in contact with the pavement which already is fully bondable to the asphalt pavement.

  • Most decks are done in a day, not including deck preparation. Excessive details and size may extend the installation to more than one day.

  • Yes. The priming materials are highly flammable. The membrane materials can be extremely hot. VOC's may impact some workers if caution isn't taken.

  • Once the membrane installation is complete, it is immediately ready.

  • We need free and clear access to the deck.  Once we are working, people can not cross the deck.  We may need access to the deck via vehicle if it is a medium to large deck.

    Most often we will require parking for 2 to 3 vehicles and 2 trailers on one side of the deck to be waterproofed.

  • Yes. Certain precautions should be taken and different approaches may occur based on the membrane system used.

DISCLAIMER

Not All Situations Are The Same

Information presented from this page are based from our experiences and knowledge. It is presented only as general information to assist in decision making and general procedures. This information may or may not provide accurate and/or appropriate solutions for any specific questions as each situation may vary and require different strategies. Use of the information provided does not hold Roaron Construction responsible for any liabilities, cost, wrong doing, or related expenses incurred from the use of information provided on this site.

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