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24 CHAPTER THREE TESTING AND RESEARCH LABORATORY TESTING then exposed to a saturated sodium chloride solution for 28 days. A sample of the concrete directly below the membrane At the request of the New England Transportation Consor- is then obtained from each block and chloride ion concentra- tium, the U.S. Army Cold Regions Research and Engineer- tion determined. The measured chloride ion concentration is ing Laboratory conducted laboratory studies to develop then compared with the background chloride ion concentra- standardized procedures for the evaluation of bridge deck tion of the reference concrete block. membranes (24 ). They reported that although there are ASTM tests to evaluate various engineering properties of tape, rubber, roofing, plastics, and geomembranes, there EVALUATING FIELD INSTALLATIONS is no group of standards or ways to interpret them that all manufacturers follow when reporting performance data Manning (5) described various methods to evaluate water- for their products. The intent of the work was to recom- proofing systems in the field, including visual inspection, mend tests to compare membranes. Six sheet products electrical methods, embedded devices, physical sampling, were tested to measure adhesion, tensile strength and elon- ultrasonic methods, and air permeability methods. These same gation, puncture resistance, and water vapor permeability. techniques still exist today, though many have been improved Liquid membranes were not included in the scope of the through the use of electronics and automation to make them study. Conclusions based on testing and analyses included more practical to use on large areas of bridge decks. the following: One of the challenges of detecting defects is that the defect · A membrane does not have to be perfectly adhered to has to be large enough to be detected using the selected the deck to avoid blistering. method. If the defect is small, it is like looking for a needle · High bond strength matters less than continuity of in a haystack. If the defect is large, it may be detected by bond. visual observation of surface defects such as delaminations · The smallest void size that can originate a blister is or water leakage through the deck. about the size of a quarter. · Elongation rather than strength is a more appropriate Seven agencies responding to the survey reported that property to judge a membrane's ability to span a crack. they had used the following nondestructive test methods to · Puncture resistance is an important property of a good assess the condition of the in-place waterproofing systems: sheet membrane. · ASTM E96 Procedure B (Water Method) is an accept- · Visual inspection, able method to measure water vapor permeability. · Electrical conductivity or electrical resistance, · Ground-penetrating radar (GPR), The authors stated that even though laboratory tests can · Chain drag or hammer sounding, and help rank membranes according to individual properties, · Leak testing. exposure to the complex combination of natural forces is essential for proving a material's durability. Visual Inspection The European Organisation for Technical Approvals has Visual inspection requires observation of the top and bottom a report that describes a method for determining the resis- surfaces of the bridge deck from a relatively close position, tance of liquid-applied bridge deck waterproofing member such as walking on the deck surface. With this method, the to chloride ion penetration following the indentation of the condition of the membrane cannot be directly observed. The membrane by simulated hot asphalt (25). In this method, most direct method would be observation of the deck under- three heated concrete blocks with the membrane applied side after a period of rain to check for wet spots or efflores- are indented at four locations using a heated 8-mm (0.3-in.) cence. Rust stains or spalled concrete may also be evident, diameter truncated cone applied at a specified rate until a but by the time these are visible, active corrosion has been maximum force is applied. The surface of the membrane is ongoing for some time.
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25 In Denmark, where more than 85% of the bridge deck (27 ). That synthesis reported that GPR is a noninvasive and area has a bitumen overlay and waterproofing membrane, nondestructive tool that has been used successfully in trans- invasive inspections are sometimes performed on bridge portation structures for applications such as profiling asphalt decks. An area of wearing course and membrane approxi- thickness, detecting air-filled voids, and determining rein- mately 0.8 x 0.8 m (30 x 30 in.) is removed so the condi- forcement spacing and depths in concrete. However, no pub- tion of the structural concrete deck can be inspected (15). A lished papers about the use of GPR to evaluate waterproofing similar procedure is followed in Sweden when deterioration membranes were identified for this synthesis. is observed at the deck surface. Kansas reported on the use of GPR on a bridge with a Visual inspection of the asphalt surface may offer some waterproofing membrane. Based on the results, Kansas indications of the condition of the membrane. Wide cracks, decided to rehabilitate the bridge deck. The deterioration radial crack patterns, wet spots, and gaps at curbs or barriers levels found in the concrete during the rehabilitation work may be signs of potential problems. were much higher than expected, and near full-depth patch- ing was needed throughout most of the deck. The final reha- Electrical Methods bilitation cost was almost as high as the estimated cost for complete deck replacement. Virginia's standard specifications require that the water- proofing effectiveness of the membrane system be deter- Chain Drag and Hammer Soundings mined in accordance with Virginia Test Method T 39. In this test method, the electrical resistance between the top surface Chain drag and hammer soundings are simple techniques of the asphalt and the top mat of reinforcement is determined to detect delaminations in bridge decks. In both methods, using an ohmmeter. The specification requires a minimum the change in sound from dragging chains across a deck or resistance of 500,000 ohms. Areas having a lower resistance striking a local area with a hammer is used to identify areas are to be repaired if determined by the engineer to be detri- of delaminations. The method is labor-intensive and is not mental to the effectiveness of the system. If more than 30% foolproof. of the deck area is determined to be detrimental to the effec- tiveness of the system, the membrane is to be replaced. Leak Testing Washington State has a similar procedure, Test Method Leak testing involves ponding the deck top surface with T 413. The scope of the method indicates that it may be used water and checking underneath for leaks. This method may for either membrane alone or membrane-pavement combina- not be feasible on some bridge decks owing to longitudinal tion. The use of the method has been discontinued because of or transverse slopes. Oregon requires leak testing as soon difficulty in training staff to use it and because membranes as the deck is ready for traffic. No water leakage is allowed. rarely failed the test. Interestingly, McKeel (26 ) commented on Virginia's T 39 method that a great deal of judgment is Missouri reported that it has recently started to do leak necessary to perform the test and it is advisable to use the testing on newly constructed adjacent box beam bridges. In same crew as much as possible. Manning (5) also points out some instances, it has flooded the deck before waterproof- that low resistivity readings are not necessarily associated ing to establish which joints leak or after the membrane and with defects in the membrane but may be the result of mois- asphalt overlay have been placed and prior to bridge open- ture in the surface layers. ing. Missouri reported that the best way to perform the test is during a rainstorm. This approach does not delay the project ASTM D3633, Standard Test Method for Electrical Resis- or impact traffic but is dependent on the weather. tivity of Membrane-Pavement Systems, is similar to Virgin- ia's T 39 method and Washington State's T 413 method and Bond Testing may be used to measure the electrical resistance between the saturated top surface of the system and the reinforcing steel The New Hampshire special provisions for liquid-spray bar- embedded in the concrete. rier membranes requires that the prepared substrate and the completed membrane be tested for adequate tensile bond Ground-Penetrating Radar strength in accordance with ASTM D4541, Standard Test Method for Pull-Off Strength of Coatings Using Portable GPR consists of transmitting pulses of radio frequency Adhesion Testers. At least one test is specified for every 55 energy into the deck and recording the reflected signal. yd2 of deck area, with a minimum of three tests per structure Reflections occur from each interface where there is a or deck construction phase. When the bond strength of the change in the dielectric constant, such as at voids, cracks, substrate is less than 100 psi, the engineer may request addi- or steel reinforcement. The use of GPR for evaluating sub- tional surface preparation. Illinois has a similar specifica- surface conditions was the subject of NCHRP Synthesis 255 tion and specifies a minimum tensile adhesion value of 100