How can water-based release agents ensure uniform film formation and zero residue in the complex curved surfaces and densely reinforced structures of tunnel boring machine (TBM) segments?
Publish Time: 2026-02-18
In modern urban rail transit and tunnel engineering construction, TBM segments, as the core prefabricated components of tunnel lining, have highly complex geometries—including not only internal and external curved surfaces, chamfers, and sealing grooves, but also densely packed embedded reinforcing bars, grouting holes, and connecting bolt holes. This structural characteristic places extremely high demands on the concrete release process: the release agent must be able to form a continuous, uniform, and ultra-thin functional film layer between irregular curved surfaces and reinforcement gaps, while achieving clean peeling and no oil residue after the concrete hardens, so as not to affect subsequent waterproofing sealing or structural bonding performance. Water-based release agents, with their environmental friendliness and controllable film-forming characteristics, are becoming the preferred solution for TBM segment production. The key to achieving uniform coverage and zero residue lies in the deep synergy of formulation design, construction technology, and material compatibility.1. Low Surface Tension and High Permeability: Overcoming Complex Geometric BarriersThe densely reinforced areas of tunnel lining segment molds are prone to a "masking effect." Traditional oil-based release agents, due to their high viscosity and poor flowability, struggle to penetrate the bottom of the reinforcing bars or narrow grooves, leading to localized sticking. High-quality water-based release agents, by adding nonionic surfactants and nanoscale film-forming aids, significantly reduce the surface tension of the liquid, giving it excellent wetting and spreading capabilities. During spraying, the liquid quickly climbs along the surface of the reinforcing bars, wraps around curved dead corners, and distributes evenly under gravity and capillary action, avoiding "beading" or "dry spots." Simultaneously, its water-based carrier has a moderate evaporation rate, providing sufficient leveling time for film formation, ensuring complete coverage of the entire mold surface—including deep grooves, sharp corners, and the inner walls of bolt holes.2. Molecular-Level Film-Forming Technology: Constructing an Ultra-Thin Isolation BarrierThe active ingredients of water-based release agents are typically modified wax emulsions, siloxane polymers, or fatty acid derivatives, which are formed into stable micelles with a particle size of less than 100 nm through a special emulsification process. After spraying and drying, these microparticles self-assemble into a dense release film only 0.5–2 micrometers thick. Despite its thinness, this film possesses high hydrophobicity and low surface energy, effectively preventing direct contact between cement slurry and the steel mold, and preventing hydration products from seeping into the mold's micropores and forming chemical bonds. More importantly, this film loses its adhesion after the concrete initially sets, naturally peeling off as the tunnel segments are lifted, leaving no oil stains or clogging pores, fully meeting the stringent cleanliness requirements of the shield tunnel segment joint sealing surface.3. Residue-Free Formula Design: Ensuring Compatibility with Subsequent ProcessesAfter demolding the shield tunnel segments, rubber waterstops must be installed immediately, and grouting is performed after assembly. If the release agent contains residual grease or silica, it will severely weaken the bond strength between the waterstop and the concrete, even leading to leakage risks. Therefore, high-end water-based release agents use fully water-soluble film-forming resins and biodegradable emulsion systems to ensure that the film-forming substances are completely transferred to the concrete surface or evaporate with steam during demolding, leaving no accumulated residue on the mold. Meanwhile, the product is free of mineral oil, silicone, and halogen components. Third-party testing has confirmed that it has no adverse effects on subsequent epoxy coatings, polyurethane sealants, and other materials, truly achieving "clean removal and strong bonding."4. Intelligent Construction Matching: Enhancing On-Site Application ReliabilityTo adapt to the pace of automated shield tunnel segment production lines, water-based release agents are often paired with high-pressure airless spraying systems. By adjusting nozzle pressure and spray speed, consistent film thickness is achieved. Some advanced systems also integrate humidity and temperature sensors to automatically compensate for the impact of environmental changes on drying rates, avoiding uneven film formation in the rainy season or sagging in winter. Furthermore, water-based products are easy to clean; mold maintenance only requires rinsing with water, significantly reducing the use of organic solvents and meeting green construction site standards.In summary, the success of water-based release agents in the challenging application scenario of shield tunnel segments stems from its core technical logic of "low-tension penetration + molecular-level film formation + zero interference residue." It not only solves the engineering pain point of demolding complex structures, but also supports modern tunnel engineering towards high quality and sustainability with its clean, safe and efficient characteristics—silently guarding the century-old safety of underground cities on the smooth arc surface of each ring segment.
