How can water-based release agents solve the problem of formwork sticking in high-grade concrete during high-temperature curing?
Publish Time: 2025-08-27
In modern large-scale infrastructure construction, high-grade concrete is widely used in key components such as precast bridges and shield tunnel segments to meet structural requirements for high strength and durability. However, the production of this type of concrete often faces a thorny technical challenge: "formwork sticking" is highly susceptible to occur under high-temperature steam curing conditions. This phenomenon occurs when the concrete adheres tightly to the mold surface. During demolding, this can lead to honeycombing, rough surfaces, chipped corners, and even extensive damage on the component surface, seriously affecting its appearance and structural performance. While traditional oil-based release agents are somewhat effective, they also have drawbacks such as mold contamination, interference with subsequent painting, and environmental concerns. Water-based release agents, with their unique formulation and mechanism of action, are becoming an ideal solution for solving the formwork sticking problem in high-grade concrete during high-temperature curing.1. Causes of Formwork Sticking: High Temperature Accelerates Hydration and Interfacial BondingHigh-grade concrete has a low water-binder ratio, high cement content, and a high concentration of reactive mineral admixtures. Under high-temperature steam curing (typically 60–80°C), the cement hydration reaction is significantly accelerated, leading to rapid development of early strength. This rapid hardening process creates an extremely dense transition layer in the interfacial zone (ITZ) between the concrete and the steel formwork, making it difficult to effectively isolate moisture, resulting in strong physical adsorption and chemical bonding between the two. Furthermore, high temperatures cause moisture within the concrete to migrate to the formwork surface and evaporate, further exacerbating interfacial bonding and ultimately causing "hair pulling" or "tearing" during demolding.2. Mechanism of Action of Water-Based Release Agents: Building a Stable Isolation BarrierThe core function of a water-based release agent is to form a uniform, continuous, and stable barrier between the concrete and the formwork, preventing direct contact between the two and enabling "destructive demolding." The key to solving the problem of formwork sticking lies in the following:Efficient Film-Forming Technology: High-quality water-based release agents utilize composite film-forming materials such as synthetic wax, modified silicone oil, and polymer emulsion. After spraying, the water evaporates rapidly, and the film-forming components self-assemble on the mold surface to form a dense, smooth, and low-surface-energy protective film. This film is chemically stable and does not react with the cement paste, effectively preventing cement particles from penetrating the mold surface and reducing interfacial adhesion.High-Temperature Stability: The film-forming materials in the water-based release agent have been specially modified for high-temperature curing environments, resulting in excellent thermal stability. Even in steam environments exceeding 80°C, the film will not soften, decompose, or dissolve, maintaining its integrity and barrier properties, ensuring continuous protection from pouring to demolding.Dual Penetration and Sealing: Some high-performance water-based release agents contain trace amounts of penetrating components that can slightly penetrate the mold's micropores, enhancing adhesion and preventing the film from being washed away by the impact of pouring. They also form a sealing film on the surface, preventing direct contact between concrete moisture and the mold, reducing the "capillary adsorption" effect.3. Synergistic Enhancement of Environmental Protection and Construction AdvantagesWater-based release agents use water as a carrier and do not contain harmful solvents such as benzene and toluene. They have no pungent odor during spraying, are friendly to worker health and the environment, and comply with green factory and sustainable construction requirements. They are easy to clean and do not form grease deposits on molds, reducing mold maintenance frequency and extending mold life. Furthermore, water-based products are easily automated for spraying and highly compatible with precast component assembly lines, ensuring uniform and controllable coating thickness on each mold and avoiding localized sticking caused by uneven coating.4. Practical Application Results and Quality AssuranceApplications at multiple high-speed rail precast beam yards and urban rail transit shield segment plants have demonstrated that the use of high-quality water-based release agents has achieved a near 100% demolding success rate for high-grade concrete components, significantly improving surface finish and significantly reducing defects such as bubbles, sand spots, and color variations. More importantly, the concrete surface remains free of residual oil residue after demolding, facilitating subsequent anti-corrosion coating or joint surface treatment, enhancing overall project quality and durability.Through its scientific formula design and stable film-forming properties, the water-based release agent effectively solves the problem of high-grade concrete sticking to the formwork during high-temperature curing. It not only ensures the appearance and structural quality of precast components, but also promotes the green and intelligent development of the precast concrete industry.
