As an element of building structure that combines protection and decoration, the durability of multi-functional stone railings is directly related to safety and aesthetics. Although traditional stone is naturally strong, it is prone to weathering, corrosion, structural damage and other problems when exposed to complex environments (such as rain, wind and sand, and pollutant erosion) for a long time. Surface treatment technologies (such as nano-coating and antique aging) optimize the surface properties of materials through physical, chemical or mechanical means, and build a multi-dimensional protection system from micro to macro levels, significantly improving the weathering resistance, anti-pollution performance and structural stability of multi-functional stone railings, thereby extending service life and reducing maintenance costs.
Nano-coating forms a dense protective film only tens of nanometers thick on the surface of the stone, blocking the penetration of moisture, salt and pollutants at the molecular level. Its core mechanism of action includes: 1) Super hydrophobicity - nanoparticles make the surface contact angle exceed 150°, water droplets roll in a spherical shape and cannot penetrate into the pores of the stone, thereby inhibiting physical weathering processes such as salt crystal expansion and freeze-thaw cycles; 2) Chemical inertness - nanomaterials such as titanium dioxide (TiO₂) can decompose organic pollutants (such as oil and moss), while forming an oxide layer to resist acid rain corrosion; 3) Self-repairing potential - microcapsule repair agents are embedded in some nano coatings. When microcracks appear on the surface, the repair agents are automatically released and fill the cracks to restore the protective function. Laboratory tests show that the water absorption rate of stone treated with nano coatings is reduced by 80%-95%, and the number of freeze-thaw cycles is increased from 50 to more than 200 times, significantly extending the outdoor service life.
The antique aging process uses physical or chemical means to create microcracks and concave-convex structures on the surface of the stone. Its durability improvement mechanism is reflected in: 1) Energy absorption - microcracks can absorb external energy such as earthquakes and vehicle impacts, reducing the risk of cracking caused by stress concentration; 2) Bond enhancement - the contact area between the rough surface and cement mortar increases by 30%-50%, significantly improving the structural stability; 3) Microbial inhibition - the acidic solution used in the antique treatment can reduce the pH value of the stone surface, inhibit the growth of microorganisms such as moss and lichens, and reduce biological corrosion. In a certain ancient bridge restoration project, the multi-functional stone railings treated with antique aging did not break during the 2018 typhoon "Mangosteen", while the damage rate of the untreated part reached 15%, verifying its impact resistance.
Single surface treatment has limitations, such as nano-coatings are prone to failure due to mechanical wear, and antique aging may accelerate local weathering. The composite treatment technology achieves a performance leap through the synergistic effect of "protective layer + strengthening layer": 1) Primer + topcoat - first apply a penetrating protective agent to fill the pores of the stone, and then cover it with a nano-coating to form a "protection-anti-fouling" double barrier; 2) Antique + protection - spray transparent fluorocarbon paint after antique aging, which not only retains the texture but also enhances weather resistance; 3) Data verification - the wear resistance of composite treated stone is increased by 3 times, the anti-ultraviolet aging time is extended to more than 15 years, and the life cycle cost (LCC) is 25%-40% lower than that of untreated stone.
Under different climates and pollution environments, surface treatment needs to be optimized in a targeted manner: 1) High humidity areas - hydrophobic nano-coatings are preferred to avoid long-term retention of moisture and cause stone alkali; 2) Industrial pollution areas - use coatings containing nano silver ions to inhibit microbial attachment and growth; 3) Cold areas - antique aging combined with anti-freeze-thaw additives to reduce the damage of ice expansion stress to stone. For example, a coastal project uses a combination of "antique texture + nano-hydrophobic coating" to successfully resist sea breeze and salt spray erosion, and no obvious signs of weathering have appeared in 5 years.
The thicker the nano coating, the better - too thick a coating is prone to cracks, and the optimal thickness is 50-100nm; 2) Myth 2: Antique aging will reduce the strength of the stone - the depth of microcracks needs to be controlled (≤0.5mm) to avoid damaging the stone matrix; 3) Surface treatment can replace structural reinforcement - surface treatment only enhances durability, and structural defects still require special repairs. Through standardized construction and quality inspection, performance degradation caused by technology abuse can be avoided.
Self-healing coating - develop nano-coatings containing microcapsule repair agents, which automatically release repair agents when cracks occur; 2) Bionic design - imitate the surface structure of lotus leaves to develop super-hydrophobic and self-cleaning stone surfaces; 3) Green materials - use waste stone powder and bio-based resins to prepare environmentally friendly protective agents to reduce carbon emissions. For example, the "photocatalytic nano-coating" developed by a research team can decompose air pollutants and has antibacterial function, giving multi-functional stone railings environmental purification capabilities.
The surface treatment technology of multi-functional stone railings significantly improves durability through micro-protection, mechanical strengthening, composite synergy and other mechanisms. Nano-coating and antique-style aging each have their own advantages, and in practical applications, they need to be selected in combination with environmental, cost and functional requirements. In the future, smart materials and sustainable technologies will promote the surface treatment of multi-functional stone railings to develop in the direction of high efficiency, environmental protection and adaptability, providing more reliable solutions for architectural heritage protection and modern engineering.
