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OCR for page 38
28 cations for the surface preparation. The corresponding · Use a primer to enhance the bond between the con- number for existing bridge decks is 80%. crete deck and the membrane, where required by · The two major products used in conjunction with the specifications or the manufacturer. waterproofing membranes are primers applied to the · Install reinforcing membrane over cold joints and concrete deck and tack coats applied to the membrane cracks. before placing the protective surface layer of asphalt. · Make a complete seal with the curb up to the depth · Although several types of defects have been observed of the asphaltic concrete overlay. with waterproofing systems, the three predominant · Begin placement of preformed membranes on the ones are lack of adhesion between the waterproofing low point of the deck and provide adequate lap membrane and the concrete deck, lack of adhesion between adjacent strips. between the waterproofing membrane and the asphalt · Stagger membrane overlaps in the transverse direction. surface, and moisture penetration through the mem- · Repair any blisters that appear in the membrane brane. All types of defects were more prominent with before the overlay is placed. membranes applied to existing bridge decks than with · Prohibit or minimize traffic on the membrane and membranes applied to new bridge decks. allow only rubber-tired vehicles until the overlay · Unit costs showed a wide range of values for mem- is placed. branes installed on either new or existing bridge decks. · Specify a minimum and maximum time between membrane application and the first layer of overlay The literature review found that only a few articles about placement. research and use of waterproofing membranes have been · Use a tack coat to enhance the bond between the published since NCHRP Synthesis 220 in 1995. In addi- membrane and the overlay. tion, the methods reported in 1994 to evaluate waterproof- ing membrane systems in the field still exist today, but no 4. Quality Control method has emerged as being universally acceptable. · Conduct adhesion bond testing for spray-applied The review of state and provincial specifications identi- membranes. fied the following installation practices for waterproofing · Perform leak testing after the overlay is placed. membranes: No standard tests exist to evaluate the overall perfor- 1. Pre-installation mance of waterproofing membrane systems, no reliable methods exist to assess the quality of the installed systems, · Require a manufacturer's representative to be pres- and no proven techniques exist to determine any deteriora- ent when work is performed. tion of the membrane system during its service life. Conse- · Require that all work be performed by the manu- quently, it is not surprising that agencies with no experience facturer's certified personnel. in installing membranes are reluctant to start using them. On the other hand, agencies with experience believe they 2. Surface Preparation provide a reliable bridge deck protection strategy. · Ensure that the concrete surface is free of protru- Most Canadian provinces and many European and Asian sions and rough edges. countries that utilize waterproofing membranes believe that · Use abrasive blasting to remove all contamination they are essential for the protection of bridge decks. from the deck, including all material from any pre- vious membrane. · Do not use water to clean the deck. FUTURE RESEARCH · Clean surface with brooms, vacuum, or compressed air to remove all loose material before applying the The information collected for this synthesis suggests a need membrane system. to conduct a more in-depth investigation of systems used · Reinforce or repair cracks before placing the in the United States and Canada. This investigation would membrane. include site visits and meetings with owners who have installed membranes successfully and believe in their use as 3. Installation of Waterproofing System a deck protection strategy. It could be conducted as a state pooled fund research project by those states interested in · Specify a minimum deck and/or air temperature enhancing their use of waterproofing membranes. before applying the membrane. · Specify a dry deck and application only in dry Standard test methods should also be developed to evalu- weather. ate the overall performance of proprietary waterproofing
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29 membrane systems, assess the quality of installed systems, The waterproofing membrane is only one component of and identify deterioration of the membrane system during its waterproofing systems that may include primers, adhesives, service life. Waterproofing membrane systems could then be protection board, tack coat, and bituminous concrete layers. included in the AASHTO National Transportation Product The performance of the system is determined by the com- Evaluation Program. plex interaction of material factors, design details, and quality of construction. Research is required to define performance A TRB Maintenance Research Master Planning Work- requirements for waterproofing systems, to be followed by shop was held in January 2000 to develop a 3-, 5-, and development of a suite of quantitative prequalification tests 10-year phased master plan of maintenance research needs and quality assurance procedures, the findings to be embod- (Transportation Research Circular E-C022 2000). Before ied in a performance specification. The specification should the meeting, the TRB Highway Maintenance Committees cover the material requirements for the membrane, adhesives, prepared 60 research needs problem statements. The end and protection board (if used), together with requirements for result of the workshop was a series of recommended research installation. The performance specification could also include projects and synthesis topics. TRB Committee A3C15-- provisions for life-cycle costing so that systems that offer Corrosion developed and submitted the following research superior performance can compete on an equitable basis with problem statement to the workshop: systems that have low initial cost but a short service life. Performance Specification for Bridge Deck Water- Objectives: Develop a performance specification for proofing Membrane Systems Problem: Waterproofing bridge deck waterproofing membrane systems based on a membranes can be an effective method of protecting both quantitative definition of performance requirements, objec- the concrete and embedded reinforcement in new and exist- tive prequalification tests, and a life-cycle cost analysis. The ing bridge decks. Except for a few states, membranes are objective is to encourage competition between a wide range used only sporadically in the United States, often to pro- of products and processes, all of which will perform satis- vide only a short extension of service life on existing decks. factorily in the field. NCHRP Synthesis Report 220, Waterproofing Membranes for Concrete Bridge Decks, noted that North American prac- Cost: $350,000. tice has changed little in the past 20 years. The vast majority of membranes installed in the United States are preformed Duration: 36 months. products, and the market is dominated by three products introduced in the 1970s. A 1995 FHWA scanning tour of The statement was not selected by the workshop partici- bridge technology in Europe observed the broad range of pants for the master plan. However, based on the information materials and widespread use of waterproofing systems in provided in this synthesis, the need for a performance specifi- protecting bridge decks in aggressive environments. cation for bridge deck waterproofing systems still exists today.