Search
The deterioration of concrete is inevitable; under the influence of external factors—such as climate, moisture, temperature extremes, chemical media, wind erosion, and abrasion—concrete structures undergo a series of physicochemical changes over time, leading to a gradual decline in their overall performance.
Enhancing concrete durability is a systematic undertaking that can be broadly categorized into two approaches: preventive measures implemented during the design and construction phases, and durability restoration measures applied during the service life of the structure. The former includes measures such as optimizing the mineral composition of cement clinker, utilizing chemical admixtures, designing appropriate and rational mix proportions, and improving density and impermeability. The latter primarily involves the application of repair techniques and surface protection methods.
The primary function of concrete surface protection materials is to prevent the penetration and diffusion of atmospheric oxygen, water, and saline media into the concrete, thereby retarding the deterioration of the concrete’s performance and the corrosion of its steel reinforcement. Given that concrete structures are widely utilized in applications such as beams, slabs, columns, flooring, interior and exterior walls, storage tanks, and underground pipelines, there exists a correspondingly vast array of concrete surface protection coatings.
Based on various classification criteria, concrete surface anti-corrosion materials primarily fall into the following categories:
(1) Based on the chemical composition of the binders used, they can be classified into three categories: organic, inorganic, and hybrid. Among these, the inorganic category includes various silicate cements, while the organic category consists primarily of various polymeric materials—including synthetic resins and synthetic rubbers—such as epoxy resins, acrylates, and silicones. The hybrid category refers primarily to mixtures of polymers and silicate cements, such as epoxy resin mortar and polymer-modified cement mortar.
(2) Based on their mode of action, they can be classified into: film-forming coatings, hydrophobic impregnation materials, pore-blocking surface treatment materials, and multifunctional surface treatment materials.
In terms of chemical composition, silane-based materials primarily include propyltrieth(meth)oxysilane, isobutyltriethoxysilane, amyltrieth(meth)oxysilane, octyltrieth(meth)oxysilane, and dodecyltriethoxysilane, among others. Based on their physical state, they can be classified into colorless transparent liquids, white emulsions, and white pastes [10]. Since my country’s first industry standard regarding silanes—JTJ 275-2000, *Technical Specification for Corrosion Prevention of Concrete Structures in Seaport Engineering*—explicitly stipulated the use of isobutyltriethoxysilane, and subsequent standards referenced the provisions of JTJ 275-2000, isobutyltriethoxysilane remained the most widely consumed silane impregnating agent in the domestic market for a considerable period. However, the consumption volume of isobutyltriethoxysilane has been declining year by year, primarily due to two factors: on one hand, the manufacturing process for isobutyltriethoxysilane is complex, resulting in a relatively high cost; on the other hand, practical applications have demonstrated that octyltriethoxysilane—as well as other types of silanes—can achieve comparable protective effects. Furthermore, the use of octyltriethoxysilane results in lower volatility; when emulsified to form a silane paste, it minimizes material loss during application on vertical and overhead surfaces [14, 15]. The standard *Silane Paste Materials for Surface Protection of Bridge Concrete* (JTT 991-2015) [16] establishes specific performance requirements for octylsilane paste materials.
The primary parameters used to evaluate the protective efficacy of silane-based materials on concrete include penetration depth, water absorption rate, chloride ion content, resistance to freeze-thaw cycles, resistance to sulfate attack, and resistance to acid rain. Additionally, field evaluation of silane-protected concrete typically employs the Karsten tube method to determine the average 2-hour water absorption coefficient of the concrete, thereby assessing its water absorption characteristics.
Silane-based materials are colorless, transparent, small-molecule substances that penetrate into the interior of concrete. Through hydrophobic action, they reduce the concrete’s water absorption rate as well as the migration rate of water and harmful substances, thereby achieving the objective of enhancing the concrete’s durability.
Surface protection of concrete serves as an economical and highly effective method for enhancing durability. Silane-based protection technology currently represents the most effective class of anti-corrosion materials available. However, silane-based technologies face several major challenges: (1) Product adulteration: Taking liquid silanes as an example—due to their colorless and transparent nature—it is a common market practice to substitute genuine silane impregnants with materials such as water glass or silane coupling agents. While water glass and silane coupling agents may provide a transient hydrophobic effect on the surface, they are incapable of preventing freeze-thaw damage or chloride ion ingress in concrete. A common issue with paste-form silane materials, conversely, is that their actual silane content often falls short of the stipulated 80% threshold. (2) Lack of established standards: There are currently no relevant standards governing fluorocarbon-modified silane materials. Consequently, designers often resort to using vague terminology—such as “tinted silane”—during the design phase, which results in poor operational feasibility during the actual implementation of engineering projects.
