目的 设计并制备一种低温固化磷酸盐无机阻气涂层,以提升混凝土表面防护涂层的施工性能。方法 磷酸盐无机涂层因其优异的附着力、耐高温性、无毒环保、成本低廉及安全性高等优点,在结构表面防护领域备受青睐。本研究成功制备了一种磷酸盐无机阻气涂层（AHPM）。该涂层以磷酸二氢铝（(25±2)%）为胶黏剂、氧化铝（(48±2)%）为填料、改性氧化镁（(2±1)%）为固化剂,并辅以防沉剂（1.8%）和消泡剂（0.2%）制备而成。将AHPM均匀涂覆于混凝土基底后,在200 ℃热处理条件下完成固化。为定量评价涂层阻气性能,创新性地提出了涂层-混凝土双介质气体渗透模型。通过线性拟合不同测试气压下测得裸混凝土试块及涂覆特定厚度AHPM涂层的混凝土试块的气体渗透率数据,结合达西定律计算得出无机阻气涂层本身的气体渗透率。结果 该磷酸盐无机涂层成膜性良好、制备工艺简单、表干时间短、有效使用期长。经200 ℃热处理10 min后完成固化,涂层展现出以下优异性能：与混凝土基底的结合强度高（>5 MPa）、阻气性能优异（渗透率为6.89×10-18 m2）、高温烧失率低（2.42%）。这表明该涂层在高温下性能稳定,适用于高温环境下的防护应用。结论 基于磷酸盐无机阻气涂层的固化机理分析及实验结果,可以确定：在200 ℃加热条件下,涂层发生脱水缩合反应实现完全固化。固化后形成由铝磷酸盐相构成的固体三维铝磷酸盐（P—O—Al）网络结构。该结构显著提升了涂层的黏接强度、结构密封性、耐水性及热稳定性。
Abstract
Elevated temperature environments readily induce significant concrete deterioration, manifested through accelerated cracking, exacerbated spalling, and structural integrity degradation resulting from thermal expansion mismatch. To ensure the protective efficacy of concrete structures under high-temperature exposure, functional surface coatings are frequently employed for performance enhancement. Phosphate-based inorganic coatings have garnered considerable attention within high-temperature protection applications due to their exceptional adhesion, superior thermal stability, environmental compatibility, economic viability, and inherent safety. In this study a low-temperature curing aluminum-magnesium phosphate-based inorganic gas barrier coating (designated AHPM) is designed and synthesized to improve application convenience and efficiency for concrete protective coatings. The optimized coating composition comprises: aluminum dihydrogen phosphate binder ((25±2) wt%), alumina reinforcing filler ((48±2) wt.%), modified magnesium oxide curing agent ((2±1) wt.%), supplemented with fumed silica anti-settling agent (1.8wt.%) and silane-based defoamer (0.2wt.%). Application involved uniform manual brushing onto concrete substrates, followed by a brief thermal curing at 200 ℃ for 10 minutes to achieve full polymerization. An innovative dual-medium (coating-concrete) gas permeability model is developed. Leveraging Darcy's law, the intrinsic gas permeability coefficient of the AHPM coating itself (6.89×10-18 m2) is quantitatively determined. This involves linear fitting of gas permeability data obtained from both uncoated concrete specimens and coated concrete composite specimens tested under multiple pressure differentials, followed by computational derivation of the coating's specific permeability. Comprehensive analysis confirms that the formulated AHPM coating exhibits outstanding film-forming characteristics, straightforward manufacturability, rapid surface drying kinetics within minutes, and extended service life under thermal cycling. Scanning Electron Microscopy (SEM) characterization verifies that the AHPM coating cured at 200 ℃ possesses a continuous, crack-free, pore-free, smooth, and planar surface morphology, indicative of excellent film quality. The coating exhibits a densely packed internal microstructure, demonstrates thorough interfacial wetting with the concrete substrate, and achieves remarkably high bonding strength (5 MPa) exceeding typical requirements. FT-IR analysis shows that when the temperature exceeds 100 ℃, a new Al—O peak appears at 748 cm-1, and the intensity approaches its maximum when the temperature rises to 200 ℃. This peak indicates a crosslinking reaction between polyphosphate (P—O—P) and Al2O3 filler, generating aluminum phosphate (P—O—Al). The crosslinking reaction is almost complete, and at this point, the coating has formed a stable three-dimensional network structure crosslinked by P—O—Al bonds. This network tightly combines phosphate, alumina fillers, and SiO2 - encapsulated magnesium oxide curing agents. This crystalline structure provides a fundamental theoretical basis for the coating's high interfacial bond strength and superior resistance to water ingress. Furthermore, the coating exhibits minimal high-temperature mass loss (2.42%), collectively validating its exceptional performance stability and reliable protective functionality under thermal stress. Integrating mechanistic analysis with experimental findings, the curing mechanism of the AHPM coating is elucidated as follows: Thermal energy initiates a dehydration-polycondensation reaction chain. Progressive temperature elevation facilitates the sequential removal of both free water and chemically bound water molecules. The incorporation of MgO elevates the system pH dramatically, thereby accelerating phosphate precipitation and polymerization. Concurrently, Mg²+ cations function as pivotal crosslinking nodes, facilitating the formation of a robust three-dimensional aluminum phosphate (P—O—Al) network structure via ionic and covalent bonding between phosphate anions and metal cations. Completion of the dehydration-polycondensation process culminates in the formation of a solid-state mixed phase comprising crystalline aluminum phosphate and magnesium aluminate compounds. This resultant coherent microstructure critically enhances the coating's adhesive strength, structural impermeability, and thermal resilience.
关键词
磷酸盐 /
阻气涂层 /
机理 /
低温固化 /
高温防护
Key words
phosphate /
gas barrier coating /
mechanism /
low temperature curing /
high temperature protection
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