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Why Bond Strength Matters when Sealing and Lining Vertical Buried Assets
Michael Caputi, Vice President of Epoxytec
Applied Polymer Lining – Why Bond Strength Matters
When a true monolithic watertight solution for vertical structures is required, it is important to select a technology that is bonded. Vertical structures would include assets such as manholes, wet wells, and lift stations. Great adhesion is not just limited to how well the liners bond to the host, but also to other system liners which require seamless transition (i.e.- manhole liners to pipe liners).
Bonded systems will reduce risk of an annulus occurring, thereby stopping hydrostatic pressure and water migration with the correct distribution of resistance. In the event of an annulus formation, water pressure undergoes redirection and accumulates at an alternative point. This point tends to exacerbate abnormal pressure, typically manifesting at weakly bonded edge terminations (if a high-bonding material has not been used). Technologies lacking strong adhesion and surface tolerance features are often not designed with an emphasis on optimal bonding, necessitating the implementation of internal seals or end seals at their termination points when remedied later. This should be avoided, as it introduces an additional technology and potential failure mechanism. Instead, select a material with superior edge termination and capability for interface bonding with a variety of construction materials, such as to concrete, clay, brick, steel, PVC, and ductile iron, as well as CIPP. This is the only way to ensure true monolithic sealing with both horizontal and vertical lining fused together over the long term.
Fortunately, bonded systems represent the optimal technology for vertical structures when a comprehensive inflow and infiltration (I&I) mitigation solution is needed. These systems hold back pressure without the risk of annulus formation and exhibit robust bonding capabilities with various construction materials and adjacent pipe lining materials, such as CIPP. Consequently, they deliver a vacuum-verified, true monolithic, watertight system from manhole to manhole.
Various technologies claim to be a bonded system, but it is crucial to delve into the actual bond strength data for a comprehensive evaluation. Ensuring not only high adhesion on both dry and wet conditions, but also compatibility with manhole-specific environments and other construction materials is paramount.
For this type of assessment, testing standards such as those defined by the University of Houston’s CIGMAT program and the US EPA Environmental Technology Verification testing protocol play a valuable role. These entities conduct thorough bond strength tests, not only on dry concrete but also on wet (SSD – Saturated Surface Dry) concrete. Selecting materials with high adhesive properties and favorable surface acceptance helps raise the safety factor to prevent bonding-related failure. Additionally, they extend their assessments to include various substrates like brick, providing a more realistic and comprehensive understanding of how these technologies perform in diverse conditions. This level of testing contributes significantly to validating the effectiveness and reliability of bonded systems in real-world scenarios.
When designing bonded lining systems, the most effective designs commonly incorporate epoxy-amine resins. Epoxy stands out among its counterparts, such as polyurethanes or polyurea, due to its exceptional versatility in navigating manhole environments, in terms of both wet tolerance and optimal substrate acceptance. Additionally, epoxy systems facilitate rapid and efficient self-repairs, with its exceptional ability to tie into itself, and to tie into other materials and liners.
Systems designed with elevated film builds and robust strengths fall under the category of “Ultra-High-Build, High-Strength Epoxy” or simply “Structural Epoxy.” These formulations are frequently specified for diverse applications, including manhole, lift station, and wet well lining systems and SIPP applications, and may also find utility in certain conditions at water treatment plants and wastewater treatment plants when humid or moist conditions cannot be avoided.
Key Attributes of a Fully Sealed Monolithic Solution
When selecting vertical lining technologies requiring a fully sealed monolithic solution from manhole to manhole, consider the following key attributes:
- Adhesion to Various Construction Materials: The liner must exhibit high bond strength to a diverse range of construction materials, including CIPP, clay, brick, concrete, and steel.
- High Film Thickness: The liner should feature a substantial wall thickness, measured as Dry Film Thickness (DFT), to enhance durability and longevity.
- High Flexural and Tensile Strengths: The product must possess elevated flexural and tensile strengths, as compressive strength is less critical for applied and bonded lining applications.
- Vacuum Test Compatibility: The product should be capable of undergoing vacuum testing to ensure a reliable and airtight seal.
- H2S Resistance: The product must exhibit adequate resistance to hydrogen sulfide (H2S), a common corrosive gas found in wastewater environments.
- Repairability and Maintainability: The product should be designed for ease of repair and maintenance without the need for complex equipment, ensuring cost-effective and straightforward upkeep.
- High Bond Strength with Zero Annulus Design Intention: The product must demonstrate high bond strength with respect to the host substrate, and its design should intentionally prevent the formation of an annulus, ensuring a seamless and watertight connection.
- Resistance to Root Intrusion, Hydrostatic Pressure, and Water Infiltration: In the event of small, inadvertent unbonded areas, the product’s “structural” spanned high strength film should resist root intrusion, hydrostatic pressure, and water infiltration, ensuring continued structural integrity and preventing leaks.
