Innovative Waterproofing Solutions for Blind-Side Applications Using Prefabricated Modified-Bituminous Sheet Membranes Jean-François Côté; Rémi Saucier, TP; and Henry Staresina Soprema Inc. 1688 J-b. Michaud st., Drummondville, QC, Canada J2C 8e9 Phone : 819-478-8166 • fax : 819-478-8044 • e-mail: soprema@soprema.ca 3 0 t h RC I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 C ô t é e t a l . • 1 7 3 Abstract Blindside waterproofing provides challenges that can be addressed using prefabricated polymer-modified-bitumen sheet membranes. Benefits of a fully adhered system—such as preventing lateral water migration on the interior side of the membrane—will be presented, along with ways of taking advantage of the concrete curing process for an intimate bond between the concrete and membrane. Blindside waterproofing systems based on modified-bituminous sheets and accessories meet the expectations of designers for soil conditions and contaminants, as well as gas permeability of membranes, while providing contractors with an ease in installation and detailing. They allow a cost-effective solution to accomplish watertight structures. Speakers Jean-François Côté — Soprema Inc. JEan-FrançOiS CôTÉ joined Soprema in 1999 as a research chemist and has been the company’s director of strategic development since 2009, coordinating the activities related to product and systems development. He is cochair of the aSTm D08-04 subcommittee and is an active member of various technical committees, including those of the asphalt roofing manufacturers association (arma), the Single Ply roofing industry (SPri), the Canadian Standards association (CSa), and Underwriters laboratories of Canada (UlC). Henry Staresina — Soprema Inc. HEnrY STarESina is Soprema’s technical specialist for building envelope solutions. He has been a part of the Canadian construction industry since 1980. Hank has been involved with a number of high-level manufacturers, providing him with a vast knowledge of industry practices. He serves on the board of directors of the Building and Concrete restoration association and is past president of the Sealant Waterproofing association of Ontario. 1 7 4 • C ô t é e t a l . 3 0 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 3 0 t h RC I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 C ô t é e t a l . • 1 7 5 INTRODUCTION Blindside (or preapplied) waterproofing is the practice of installing waterproofing prior to the installation of concrete structure. Construction in dense urban areas (see Figure 1) requires more and more use of this type of waterproofing. Waterproofing zero-clearance property line construction projects can provide challenging scenarios but also have significant advantages. Blindside work remains less dangerous than working in a confined trench area and allows the installer quicker application due to freedom of movement and accessibility. The use of modified-bitumen prefabricated sheet membranes in blindside applications is relatively new. Previous attempts with spray-applied bituminous products or hot-rubberized asphalts were not very successful. But by extending cutting-edge, proven technologies in prefabricated polymermodified- bitumen sheet membranes to waterproofing needs, trained installers can efficiently accomplish watertight structures in scenarios previously thought difficult or impossible. impermeability of modified- bitumen sheets to gases such as methane has contributed to the renewed interest of this type of material for below-grade waterproofing. Experience accumulated in application and forensic examination over the last 10-plus years has allowed the refining of waterproofing sheet configuration, system installation, and proper detailing. CONCRETE ADHESION When performing traditional, postapplied waterproofing, great care is usually taken to ensure sufficient adhesion of the waterproofing membrane to the foundation walls. The same applies to preapplied (blindside) installation, but in such cases, the installation of the waterproofing membrane occurs long before concrete is poured. The first contact between membrane and structural concrete happens when the concrete is still fluid. The right conditions must be met so that, once cured, the concrete will remain tightly bound to the membrane-exposed surface. Over the life of the building, degradation of the materials surrounding the building (rotting of wood used for lagging being only one example) can lead to differential settlement or even soil collapse next to the building foundation. Under such circumstances, the waterproofing membrane must remain adhered to the structural concrete to continue offering its expected performance. if adhesion of the membrane to the surrounding materials is greater than between membrane and concrete, major failures may occur. The chemical reaction of hydration that happens during concrete curing is exothermic (it generates heat that increases concrete temperature). The amount of heat generated is dependent on many factors, including the quantity of concrete, which can be related to slab or wall thickness. Typical wall thicknesses and depths of concrete pours will use large volumes of concrete and generate significant tempera- Innovative Waterproofing Solutions for Blind-Side Applications Using Prefabricated Modified-Bituminous Sheet Membranes Figure 1 – Blindside waterproofing project in an urban setting. ture increase at the point of contact with the membrane. This will soften the sheet’s exposed surface and enhance adhesion between concrete and the membrane. These large quantities of concrete will also put significant pressure on the interface with the membrane and allow the sheet’s rough exposed surface to build a mechanical bond with the concrete. if water is able to find its way through a breach in the membrane, proper adhesion of the membrane will greatly facilitate remedial work. On the exterior side of the membrane, water may be permanently present and may even generate hydrostatic pressure from the outside in. if the membrane is not well adhered to the concrete, water will be pushed between the membrane and the concrete to large distances from the point of entry. This may allow water to enter the building and will make it more difficult to investigate the source and location of the breach. a well-adhered membrane will block water from traveling in any direction between membrane and concrete. PRODUCT DESIGN AND INSTALLATION SBS-modified-bitumen prefabricated sheets are delivered to job sites in rolls. They are typically manufactured by saturating and coating a reinforcing mat with an asphaltic waterproofing compound. The reinforcing mat provides the sheet with its mechanical resistance. it must be robust and allow the membrane to bridge cracks and resist puncture, among other things. The asphaltic compound is typically highly flexible within a large temperature range and is hydrophobic in nature, which is expected from a durable waterproofing material. The surface of the modified-bitumen sheets that will be in contact with poured concrete (referred to as “exposed surface”) is designed to grab firmly to the fluid concrete and remain adhered to it long after its cure. in order to allow better compatibility between the hydrophobic asphaltic compound and the water-filled concrete slurry, the asphaltic compound of the exposed surface may be formulated with adhesiveenhancement additives. a rough exposed surface, providing a larger effective contact area, also contributes to increased adhesion to concrete through mechanical grab. The surface materials must also allow the sheet to be exposed up to several weeks without degradation due to ultraviolet radiation. Depending on the area where they will be used (horizontally under the slab or vertically around the foundation walls), the sheets will exhibit slight differences. For example, both sides of the reinforcing mat may be coated with the same asphaltic compound or with two different compounds. This allows versatility in sheet installation and lap seaming techniques. a schematic view of a typical SBS-modified-bitumen prefabricated sheet is presented in Figure 2. Horizontal Sheets The sheets must simply be laid (but not adhered) on the prepared subgrade. Adhesion of the sheets to any of the underlying materials (especially the nonstructural ones) is generally avoided so that the best adhesion of the system is achieved between the exposed surface of the sheets and the poured concrete, as mentioned in the Concrete adhesion section above. Therefore, the bottom face of the sheet is covered with a nonadhering material or even a bond breaker. in areas where the membrane will be exposed to pedestrian and light mechanical equipment traffic, it may be required to protect its exposed surface from constructionrelated abuse. areas intended to be used as storage of steel re-bars will also call for some extra protection. When site conditions require the use of two plies of waterproofing, a monolithic membrane will be formed by heat-welding the plies together. Vertical Sheets Sheets intended for vertical installation have their bottom face compounded with a self-adhesive bitumen formulation (covered with a release film). Their exposed surface will, however, be identical to that of the horizontal sheets to ensure proper concrete adhesion. installation of the waterproofing membrane on the vertical portions is also quite straightforward. They are very conveniently self-adhered on the vertical surfaces surrounding the building footprint. Soldier piles and wood lagging that were installed at the time of excavation are actual examples of these surfaces. The self-adhesive performance should be sufficient to ensure the sheets will remain in place until the concrete has cured. if a drainage board or other material is intended to be used on the interior face of the wall-retaining system, the sheets simply have to be adhered to this drainage board. The essential point here is to ensure that the exposed surface of the waterproofing sheets will be in contact with poured concrete. The sheets installed on vertical surfaces may not be exposed to as much abuse as those on the horizontal. But they must be manufactured with a reinforcing mat that will allow them to withstand the continued action of gravity before and during concrete pouring, without stretching and deforming over time. 1 7 6 • C ô t é e t a l . 3 0 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 Figure 2 – Schematic layered view of an SBS-modified-bitumen prefabricated sheet. Numbers represent the following: 1 – exposed surface, 2 – top-side asphaltic compound, 3 – reinforcing mat, 4 – bottom-side asphaltic compound, 5 – sheet underside (nonadhering material or release film). LAP SEAMING To ensure a successful end result, the waterproofing must be installed so the membrane is continuous and watertight. laps must be properly sealed, which is an easy task with modified-bitumen sheets since they offer various lap-sealing options. Heat Welding laps can be sealed by melting the selvedges of two adjacent sheets together, with either a propane burner or a heat gun. This seaming technique has been used for decades in the roofing industry. if both sides of the reinforcing mat are coated with heat-fusible modified bitumen, which is usually the case with horizontally installed sheets, a trained applicator can perform lap seaming so that only the faces forming the lap are melted by the heat source. This ensures that the exposed surface of the sheet, which will adhere to concrete, is not altered during lap seaming and remains receptive to the concrete bonding. Upon cooling down to ambient temperature, the lap area becomes monolithic and is immediately watertight. Furthermore, lap seams are generally stronger than the rest of the sheet. Adhesion laps can also be adhered with lap cement or be self-adhered, with the option of heat-sealing a portion of the lap. Such an option requires the edge of the sheet to be equipped with a 1-in.-wide burn-off film. When assembling the lap, the section of the lap with the burn-off film needs extra attention. it is left hanging until the installer lifts it and heats it to melt/burn the plastic film and activate the adhesive compound. This ensures greater quality for the lap because of the reheating of the adhesive compound, which is beneficial— especially when installation occurs in colder weather. All lapseaming techniques above allow a small quantity of molten asphalt compound to bleed out from the seam area. This facilitates inspection of the seams by the work crew and quality assurance and control representative. An experienced installer and/or inspector will recognize (by the amount of asphalt compound bleeding out) whether the adequate amount of heat was provided to the lap during the seaming operation. See Figure 3. DETAILING Pile caps, tiebacks, and other details must be treated appropriately. in most cases where modified-bitumen sheets are used, details can be made using the same sheet material as the rest of the work. The detailing will be finished using a complementary sealing liquid compound, which can take the form of a bitumen-ure- 3 0 t h RC I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 C ô t é e t a l . • 1 7 7 Figure 3 – Lap seaming on a vertical portion using a heat gun. bitumen-urethane liquid membrane Prefabricated sheet membrane Figure 4 – Pile caps before and after installation of waterproofing. thane liquid membrane. This type of material has the advantage of being formulated with asphalt and other ingredients that will ensure there will be no worries about compatibility between the materials used around these sensitive areas. Figure 4 shows typical pile caps requiring waterproofing and one method of realizing this task. in this case, the prefabricated modified-bitumen sheet has been used on the flat portions, then complemented with the bitumen-urethane liquid membrane on the elevation surrounding the steel bars. The drawing and photograph in Figure 5 show a detail used to allow water capture from the vertical drainage boards onto which the waterproofing membrane has been installed. Such a water-management method can be inexpensive and uses readily available accessories. Drained water will be captured in the pipes (shown in Figure 5) and connected under the slab to the sump pit. Water will accumulate in the pit and be pumped out as needed. REPAIRS Despite all precautions taken to protect the membrane from damage until concrete is poured, slits, tears, or other defects that require repairs may be discovered. Damage to modified-bitumen sheets may be easily repaired by cutting a piece from an unused roll (the dimensions of which should be 6 in. greater in all directions from the damaged section) and applying said piece over the affected area. The preferred method of application is by heat welding the entire piece to the existing sheet. Upon cooling, the repair will be immediately watertight, and the installer can quickly allow the continuation of work. Monolithic and continuous repairs ensure watertightness and impermeability to gases that could be present in the soil, such as methane. MEASURING ADHESION There are several ways to quantify adhesion between the poured concrete and the surface of the waterproofing membrane. laboratory tests can be useful to report this quantitative property. Peel adhesion tests, such as those presented in the aSTm D903 standard, are one example of such tests. But the D903 standard limits its scope to the conditions of the peel test itself. It does not specify the preparation of the test specimen; this would be especially useful for a system in which uncured concrete is to be poured on the exposed surface of a waterproofing sheet. Specimen preparation during a laboratory test is critical to ensure that the conditions for assembly of the concrete-membrane interface are as close as possible to those encountered in the field. Pouring only an inch of concrete at room temperature on top of a sheet may not be representative of any real-life condition and could lead to unrealistic and unsatisfactory peel results. Proper wetting of the membrane surface by the concrete, whether obtained by vibration or other means, also has a significant impact on adhesion performance. Failure to replicate adequate wetting conditions when preparing laboratory specimens can also lead to abnormal peel-adhesion values. Concrete should be allowed to cure at least 14 days for any type of comparative peel testing, but performing peels as a function of cure time, starting as early as three days after pouring, can give information on adhesion build-up with time, as illustrated in Figure 6, where two sets of curing conditions are compared. in both cases, temperature was controlled inside the room where the concrete specimens were curing (15°C and 23°C), but relative humidity was controlled (at 50%) only in one set. When specimens are cured and condi- 1 7 8 • C ô t é e t a l . 3 0 t h R C I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 Figure 5 – Drawing of below-slab water management detail and actual view. Figure 6 – Comparative evolution of peel adhesion over time under two cure conditions. tioned in controlled laboratory settings, peel tests can be performed as per the D903 standard guidelines. The waterproof sheet is partially peeled back at a 180º angle from its position. The end of the piece is then clamped in a constant-rate-ofelongation recording device that will peel the sheet at a constant speed of 50 mm per minute, as shown in Figures 7 and 8. Peel tests between modified-bitumen sheets and poured concrete performed using D903 will typically generate numbers in the 3,000 to 4,500 n/m range. These values are sufficiently high when compared to those obtained when testing the bond of self-adhesive vertical sheets to a clean and smooth surface. They ensure that the sheet will remain preferentially adhered to the poured concrete under all circumstances. CONCLUSION Costs incurred for blindside installations have typically been much higher than conventional (post-applied) waterproofing. However, using new techniques and low-cost accessories, incremental costs can be significantly reduced. modified-bitumen sheet waterproofing membranes have proven to be effective in blindside applications and provide tangible benefits due to their ease of detailing and repair and compatibility with accessory materials; but, more importantly, they will bond to the poured concrete and remain firmly adhered. 3 0 t h RC I I n t e R n a t I o n a l C o n v e n t I o n a n d t R a d e S h ow • M a R C h 5 – 1 0 , 2 0 1 5 C ô t é e t a l . • 1 7 9 Figure 7 – Modified-bitumen sheet being peeled from concrete. Figure 8 – Modified-bitumen sheet after six D903 peel tests.
