Traditional pebble-dash finish with wooden nail anchoring and textured paint overlay protection process

Abstract

This invention discloses a traditional process for anchoring wooden nails and applying textured coatings to pebble-dash finishes, applicable to the field of historical building restoration. The process includes preliminary survey and assessment, layered controlled cleaning, graded anchoring of hollow areas, reversible coating application, and post-construction monitoring and maintenance. The core innovation lies in the addition of bamboo nail pre-stress control and coating layer color difference calibration. A neutral paint stripping system is used to non-destructively remove the surface coating. For minor hollow areas, modified bamboo nails (tung oil-nano silica anti-corrosion) are used to apply 6-10 N·m pre-stress anchoring. For severe hollow areas, local replacement replicates the original process. Custom-matched textured coatings are used, and layered color difference calibration ensures visual consistency. This process achieves minimal intervention to protect historical information, improves the effectiveness of hollow area reinforcement and coating reversibility, controls water consumption to suit the continued use of buildings, and is suitable for the restoration of pebble-dash walls with a yellow mud mortar bonding layer.

Description

Technical Field

[0001] This invention belongs to the technical field of cultural relic building restoration, specifically involving the traditional water-brushed stone veneer wooden nail anchoring and textured coating surface protection process. Background Technology

[0002] Pebble-dash finishes, with their natural stone texture, dignified and beautiful colors, and durability, have been widely used in modern historical buildings. However, after long-term natural erosion and human modification, these finishes generally face multiple problems: First, cement-based putty and paint applied during later repairs cover the original pebble-dash surface, and current technology makes it difficult to completely remove them while protecting the original finish, resulting in the loss of historical information; second, traditional pebble-dash techniques and material ratios have largely been lost, and large-scale removal and reconstruction not only damage the original finish but also makes it difficult to replicate the old craftsmanship in the new finish; third, the yellow mud mortar bonding layer used in the early days loses its adhesive strength after long-term aging, causing large-scale hollowing, and conventional grouting reinforcement technology cannot effectively penetrate due to the yellow mud layer, resulting in poor reinforcement effects; fourth, historical buildings are often in continuous use (such as government office buildings and historical exhibition halls), and traditional pebble-dash repair techniques require a large amount of water, which can easily cause wall leakage and cannot meet normal usage needs.

[0003] In existing restoration techniques, some solutions use methods such as air chisels and sandblasting to remove surface coverings. However, these physical methods are prone to damaging the original pebble-dash particles and compromising the integrity of the finish. For the issue of hollow areas, existing techniques mostly rely on grouting reinforcement or overall replacement. Grouting has poor penetration into the yellow mud mortar bonding layer, while overall replacement has the drawbacks of over-repair and severe damage to historical information. In terms of surface protection, conventional coatings are mostly not reversible, making them difficult to remove without damage during subsequent repairs, and they cannot accurately replicate the texture and color of the original pebble-dash. Summary of the Invention

[0004] The purpose of this invention is to provide a traditional process for anchoring wood nails and applying textured coatings to protect the surface of terrazzo finishes, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A traditional process for anchoring wood nails and protecting textured paint overlays on pebble-dash veneers is characterized by five steps: preliminary investigation and defect assessment, layered controllable paint cleaning, graded hollow anchoring reinforcement, reversible textured paint overlay protection, and post-construction monitoring and maintenance. Furthermore, a bamboo nail pre-stress control process is added to the graded hollow anchoring reinforcement, and a layered color difference calibration process is added to the reversible textured paint overlay protection. The details are as follows: S1. Preliminary Investigation and Defect Assessment: Infrared thermal imaging detection technology combined with ultrasonic rebound method is used to generate a 1:1 scale wall hollow distribution map to accurately determine the hollow area, separation distance and bonding strength; X-ray fluorescence spectroscopy is used to analyze the composition and particle size of the original water-brushed stone, and a spectrophotometer is used to collect the original surface color parameters according to CIELAB standards; infrared spectroscopy analysis is used to determine the chemical composition of the later covering layer. S2. Layered Controllable Paint Cleaning: A neutral paint stripping system is selected, which is composed of neutral paint stripper, modified cellulose corrosion inhibitor, and penetrant in a mass ratio of 100:3:5, with a pH value of 6.0-8.0 and a density of 1.00-1.02 g / cm³. A three-step cleaning method is adopted: "segmented softening - directional peeling - low-pressure rinsing and drying." The cleaning unit is divided into 2m×2m sections. The high-pressure cleaning pressure is controlled at 0.3-0.5MPa, the water temperature is 30-50℃, and the moisture content of the wall surface after cleaning is ≤15%. S3, graded hollow anchoring reinforcement: Treatment of severe hollow areas: The "cutting and limiting - local replacement - original process replication" scheme is adopted. First, a regular cut is made along the edge of the hollow area. After the hollow area is removed, a layer of yellow mud, straw and lime mortar bonding layer, plain cement slurry and cement stone ballast finishing layer are laid according to the original structure to replicate the original T-shaped joint. Treatment of minor and potential hollow areas: Modified bamboo nails are used for anchoring. After drying and undergoing tung oil-nano silica composite anti-corrosion treatment, the bamboo nails are inserted into the pre-drilled holes. A torque wrench is used to apply a pre-tension stress of 6-10 N·m. Then, tung oil putty is filled, compacted, and smoothed. The anchoring points are arranged at a spacing of 900 mm × 900 mm, and the spacing is increased to 600 mm × 600 mm in areas of stress concentration. S4. Reversible Textured Coating Topcoat Protection: The base layer is pretreated with reversible elastic putty, and a custom-made white marble textured coating that matches the spectrum of the original water-brushed stone is applied. First, a primer and the first textured coating are sprayed. The color difference is detected by a spectrophotometer and local touch-up coating is applied for calibration. Then, the second textured coating is sprayed. Low-tack masking tape is pasted according to the original joint size. The tape is removed when the coating is semi-dry to form joints. Finally, the topcoat is sprayed. S5. Post-construction monitoring and maintenance: Embed miniature temperature and humidity sensors in concealed parts of the wall to build a wireless wall health early warning system; use a breathable protective film for 7 days of maintenance, and then regularly test color difference, bonding strength and breathability every 1-6 months thereafter.

[0006] In step 1, the spectrophotometer has a measurement accuracy ΔE ≤ 0.01, and at least 10 typical sampling points are selected to collect color parameters and take the average value; the ultrasonic rebound method is used to detect the bonding strength with an accuracy error ≤ ±0.02MPa.

[0007] In step 3, the modified bamboo nail has a three-section square structure with a width ≤ 5 mm and a total length of 60 mm. The nail head is a 30° wedge shape, and the cross section of the nail tail is 20-25% larger than that of the nail body. The bamboo nail is dried at 105℃ with forced air until the moisture content is below 4%, then immersed in tung oil-nano silica composite preservative solution for 24 hours, and naturally air-dried until the moisture content is below 12%. The compressive strength is ≥ 8 MPa.

[0008] In step 4, a diamond drill bit is used for drilling. The hole diameter is 0.5mm larger than the width of the bamboo nail, the hole depth is 60mm, and it penetrates into the substrate by no less than 30mm. The verticality deviation of the drilling is ≤2°. The tung oil putty is prepared by mixing tung oil, gypsum, and fine sand in a mass ratio of 4:3:3. The fine sand particle size is 0.1-0.2mm.

[0009] In step 4, the marble-textured coating is prepared by mixing base material, aggregate, and additives in a mass ratio of 40:55:5. The base material is water-based acrylic resin, the aggregate is 0.1-0.3mm marble powder and 1-2mm marble particles in a mass ratio of 3:2, and the additives contain 0.3-0.5% benzotriazole UV absorber and 0.2-0.3% fluorinated anti-fouling agent. After layer color difference calibration, the overall color difference value of the coating is ΔE≤3.

[0010] In step 5, the reversible elastic putty is prepared by mixing acrylic emulsion, talc powder, and biodegradable cellulose ether in a mass ratio of 50:45:5. The repair thickness is 0.5-1mm, the flatness deviation after base layer pretreatment is ≤2mm, and the vapor permeability is ≥0.05g / (m·h·Pa).

[0011] In step 5, the monitoring range of the miniature temperature and humidity sensor is 15-25℃ temperature and 50-60% relative humidity, and the vapor permeability of the breathable protective membrane is ≥0.08g / (m·h·Pa). The periodic testing indicators include: color difference value ΔE≤3, bonding strength ≥0.3MPa, and vapor permeability ≥0.03g / (m·h·Pa).

[0012] Compared with existing technologies, this invention provides a traditional process for anchoring wooden nails and applying textured coatings to protect pebble-dash finishes, which has the following advantages: 1) Through layered controllable cleaning technology, the later coatings are removed without damaging the original water-brushed stone surface, while retaining the original putty layer and water-brushed stone particles; spectral matching and color difference precise control technology are adopted to make the textured coating and the original surface visually consistent with ΔE≤3, completely replicating the original surface appearance, and solving the problem of historical information loss caused by "replacing the old with the new" in traditional restoration.

[0013] 2) Modified bamboo nail anchoring technology is adopted. Through nano-silica modification and tung oil anti-corrosion treatment, the anti-corrosion performance of bamboo nails is improved by more than 300%, and the bonding strength with tung oil putty is increased by 2 times. The graded reinforcement scheme specifically solves the problem of hollowing of different degrees, avoids the defect of conventional grouting method ineffective penetration of yellow mud mortar bonding layer, and at the same time, compared with the overall replacement method, it reduces the damage to the original decoration by more than 80%.

[0014] 3) All repair materials are reversible. Elastic putty and textured paint can be removed without damage with acetone, leaving room for future technology upgrades. The paint contains UV absorbers and anti-fouling agents, improving its weather resistance to more than 15 years and its vapor permeability to 0.03g / (m·h·Pa), solving the problem of dampness on the wall caused by the strong sealing of traditional paints.

[0015] 4) Water consumption is controlled throughout the process, and low-pressure spray cleaning and segmented drying processes are adopted to prevent water from seeping into the base layer and causing leakage. All operations use low-noise and low-dust equipment, and the building can be used normally during construction, which solves the problem that traditional water-brushed stone repair requires a lot of water and affects the normal use of the building. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides, for example Figure 1 shown A traditional process for anchoring wood nails and protecting textured paint overlays in pebble-dash finishes includes five steps: preliminary investigation and defect assessment, layered controllable paint cleaning, graded hollow anchoring reinforcement, reversible textured paint overlay protection, and post-construction monitoring and maintenance. The graded hollow anchoring reinforcement incorporates a bamboo nail pre-stress control process, and the reversible textured paint overlay protection incorporates a layered color difference calibration process. Details are as follows: S1. Preliminary Investigation and Defect Assessment: Infrared thermal imaging detection technology combined with ultrasonic rebound method is used to generate a 1:1 scale wall hollow distribution map to accurately determine the hollow area, separation distance and bonding strength; X-ray fluorescence spectroscopy is used to analyze the composition and particle size of the original water-brushed stone, and a spectrophotometer is used to collect the original surface color parameters according to CIELAB standards; infrared spectroscopy analysis is used to determine the chemical composition of the later covering layer. S2. Layered Controllable Paint Cleaning: A neutral paint stripping system is selected, which is composed of neutral paint stripper, modified cellulose corrosion inhibitor, and penetrant in a mass ratio of 100:3:5, with a pH value of 6.0-8.0 and a density of 1.00-1.02 g / cm³. A three-step cleaning method is adopted: "segmented softening - directional peeling - low-pressure rinsing and drying." The cleaning unit is divided into 2m×2m sections. The high-pressure cleaning pressure is controlled at 0.3-0.5MPa, the water temperature is 30-50℃, and the moisture content of the wall surface after cleaning is ≤15%. S3, graded hollow anchoring reinforcement: Treatment of severe hollow areas: The "cutting and limiting - local replacement - original process replication" scheme is adopted. First, a regular cut is made along the edge of the hollow area. After the hollow area is removed, a layer of yellow mud, straw and lime mortar bonding layer, plain cement slurry and cement stone ballast finishing layer are laid according to the original structure to replicate the original T-shaped joint. Treatment of minor and potential hollow areas: Modified bamboo nails are used for anchoring. After drying and undergoing tung oil-nano silica composite anti-corrosion treatment, the bamboo nails are inserted into the pre-drilled holes. A torque wrench is used to apply a pre-tension stress of 6-10 N·m. Then, tung oil putty is filled, compacted, and smoothed. The anchoring points are arranged at a spacing of 900 mm × 900 mm, and the spacing is increased to 600 mm × 600 mm in areas of stress concentration. S4. Reversible Textured Coating Topcoat Protection: The base layer is pretreated with reversible elastic putty, and a custom-made white marble textured coating that matches the spectrum of the original water-brushed stone is applied. First, a primer and the first textured coating are sprayed. The color difference is detected by a spectrophotometer and local touch-up coating is applied for calibration. Then, the second textured coating is sprayed. Low-tack masking tape is pasted according to the original joint size. The tape is removed when the coating is semi-dry to form joints. Finally, the topcoat is sprayed. S5. Post-construction monitoring and maintenance: Embed miniature temperature and humidity sensors in concealed parts of the wall to build a wireless wall health early warning system; use a breathable protective film for 7 days of maintenance, and then regularly test color difference, bonding strength and breathability every 1-6 months thereafter.

[0019] In step 1, the spectrophotometer has a measurement accuracy ΔE ≤ 0.01, and at least 10 typical sampling points are selected to collect color parameters and take the average value; the ultrasonic rebound method is used to detect the bonding strength with an accuracy error ≤ ±0.02MPa.

[0020] In step 3, the modified bamboo nail has a three-section square structure with a width ≤ 5 mm and a total length of 60 mm. The nail head is a 30° wedge shape, and the cross section of the nail tail is 20-25% larger than that of the nail body. The bamboo nail is dried at 105℃ with forced air until the moisture content is below 4%, then immersed in tung oil-nano silica composite preservative solution for 24 hours, and naturally air-dried until the moisture content is below 12%. The compressive strength is ≥ 8 MPa.

[0021] In step 4, a diamond drill bit is used for drilling. The hole diameter is 0.5mm larger than the width of the bamboo nail, the hole depth is 60mm, and it penetrates into the substrate by no less than 30mm. The verticality deviation of the drilling is ≤2°. The tung oil putty is prepared by mixing tung oil, gypsum, and fine sand in a mass ratio of 4:3:3. The fine sand particle size is 0.1-0.2mm.

[0022] In step 4, the marble-textured coating is prepared by mixing base material, aggregate, and additives in a mass ratio of 40:55:5. The base material is water-based acrylic resin, the aggregate is 0.1-0.3mm marble powder and 1-2mm marble particles in a mass ratio of 3:2, and the additives contain 0.3-0.5% benzotriazole UV absorber and 0.2-0.3% fluorinated anti-fouling agent. After layer color difference calibration, the overall color difference value of the coating is ΔE≤3.

[0023] In step 5, the reversible elastic putty is prepared by mixing acrylic emulsion, talc powder, and biodegradable cellulose ether in a mass ratio of 50:45:5. The repair thickness is 0.5-1mm, the flatness deviation after base layer pretreatment is ≤2mm, and the vapor permeability is ≥0.05g / (m·h·Pa).

[0024] In step 5, the monitoring range of the miniature temperature and humidity sensor is 15-25℃ temperature and 50-60% relative humidity, and the vapor permeability of the breathable protective membrane is ≥0.08g / (m·h·Pa). The periodic testing indicators include: color difference value ΔE≤3, bonding strength ≥0.3MPa, and vapor permeability ≥0.03g / (m·h·Pa).

[0025] The following detailed description of the invention is based on a water-brushed stone wall renovation project of a government office building in Guangzhou. This embodiment incorporates key technologies such as pre-stress control and layered color difference calibration to ensure the stability and accuracy of the renovation results. Built in 1935, the office building features a traditional pebble-dash finish on its exterior walls. The finish consists of a 20mm thick layer of yellow mud mortar, a 5mm thick layer of neat cement slurry, and a 2mm thick layer of cement-stabilized stone. The stone chips are a mixture of translucent marble chips and gray stone chips (1-2mm in diameter), with T-shaped joints 2-3mm wide. Later, the walls were covered with cement-based putty and exterior paint, resulting in some areas showing signs of hollowing and cracking. The average bonding strength of the wall surface is only 0.12MPa, lower than the standard requirement of 0.3MPa. Repairs must be completed while ensuring normal office operations.

[0026] The implementation steps are as follows: 1) Preliminary Investigation and Defect Assessment: A full-area scan was conducted using an infrared thermal imager (resolution 0.05℃) combined with ultrasonic rebound testing to generate a 1:1 scale map of wall hollow areas, accurately marking 32 hollow areas. Of these, 25 were mild hollow areas (hollow area ≤50%, separation distance ≤15mm, bonding strength 0.15-0.25MPa), and 7 were severe hollow areas (hollow area >50%, separation distance >15mm, bonding strength <0.15MPa). X-ray fluorescence spectroscopy was used to analyze the composition of the original plywood. The main components were determined to be SiO (65%), CaCO (20%), and AlO (8%), with a particle size distribution range of 1.2-1.8 mm. The original surface color parameters were collected using a spectrophotometer (measurement accuracy ΔE≤0.01), and the average value of 10 typical sampling points was obtained, resulting in L*=85.2, a*=1.2, and b*=3.5. Infrared spectral analysis was performed on the later-applied coating and putty layers, which determined that the coating was acrylic and the putty was a cement-talc system, providing a basis for the selection of the cleaning system.

[0027] 2) Layered and controllable paint cleaning: Based on the preliminary component analysis, a customized neutral paint stripping system was selected (neutral paint stripper: modified cellulose corrosion inhibitor: penetrant = 100:3:5, pH = 7.2, density 1.01g / cm); a "segmented and step-by-step" cleaning strategy was adopted, dividing the wall surface into 2m×2m cleaning units to avoid moisture accumulation caused by applying chemicals to a large area at the same time. Step 1: Softening: Apply paint remover evenly to large areas of paint using a low-pressure sprayer (0.1 MPa), cover with a breathable PE film and let stand for 7 hours, checking the softening status every 2 hours. Step 2: Peeling: Gently peel the softened paint at a 45° angle along the texture of the pebble-dash finish using a soft polyurethane scraper, controlling the peeling rate to within 0.5 m / h. For irregularly shaped areas such as window frames and door frames, apply paint remover paste (65% solids content) locally, controlling the thickness to 2 mm, cover with a sealed PVC film and let stand for 12 hours, then peel manually using a bamboo scraper. Step 3: Residue Removal: Use 40℃ warm water for high-pressure cleaning (0.4 MPa, nozzle 30 cm from the wall, moving speed 0.3 m / s), using a soft nylon brush to remove residual paint, and finally rinse with deionized water under low pressure (0.1 MPa). Use a portable hot air dryer (50℃, wind speed 1.2 m / s) to assist drying, ensuring the wall surface moisture content is ≤15%. After cleaning, the original water-washed stone particles were found to be intact and undamaged, and the surface pores were not blocked, when inspected with a magnifying glass (10x magnification).

[0028] 3) Graded Hollow Area Anchoring Reinforcement: ① Severe Hollow Area Treatment: For 7 severely hollow areas, first, a 2mm thick EVA protective film and a wooden protective frame (50mm×50mm cross-section) were pasted onto the surrounding intact wall surface. A regular cut (5mm width) was made along the edge of the hollow area using an electric diamond cutter to avoid debris flying and damaging the surrounding finish during removal. The hollow finish was gently removed using a pneumatic scraper (0.8kW power, 300 impacts / min). After removal, the surface dust of the base layer was cleaned, and the pores of the base layer were blown away using a high-pressure air pump (0.6MPa pressure). Repair was carried out in layers according to the original structure: First, a 20mm thick layer of yellow mud, straw, and lime mortar was laid. The first layer (yellow mud: straw fibers: lime = 6:1:3, straw fiber length 30-50mm, moisture content 18%) is compacted with a wooden trowel and cured for 7 days (ambient temperature 20±2℃, relative humidity 60±5% during curing); a 5mm thick layer of neat cement slurry (water-cement ratio 0.45) is applied, and within 30 minutes after application, a 2mm thick layer of cement-aggregate finishing (cement:aggregate = 1:2.5, aggregate is semi-transparent marble aggregate + gray aggregate, particle size 1.2-1.8mm, matching the original finish) is laid, compacted with a steel trowel, and cured with water for 3 days, strictly replicating the original T-shaped joint structure, with joint width controlled at 2.5mm, and grouting with yellow mud mortar of the original ratio. ② Treatment of slight hollow areas and potential hollow areas: Modified bamboo nail anchoring reinforcement technology is adopted, and a pre-stress control process is added. Bamboo nail preparation: Select bamboo that is 3 years or older, cut off the middle part of the bamboo flesh (8-10mm in diameter), remove the bamboo green and bamboo yellow, and process it into a three-section structure of "nail head-nail body-nail tail" along the direction of bamboo fiber. The cross-section is square (4mm wide) and the total length is 60mm. The nail head is cut into a 30° wedge shape (15mm in length), and the nail tail has a cross-section of 5mm×5mm (25% larger than the nail body) to form a limiting structure. Place the bamboo nail in a 105℃ forced-air drying oven for 4 hours until the moisture content is below 4%. Then immerse it in tung oil-nano silica composite preservative solution (tung oil:nano silica = 100:2, nano silica particle size 50nm) for 24 hours. After taking it out, let it air dry naturally until the moisture content is below 12%. Test the compressive strength of the bamboo nail to be ≥8MPa. Anchoring Construction: Drill holes at the T-joint of the pebble-dash stone using a diamond drill bit (4.5mm diameter), with a hole depth of 60mm, ensuring that the hole penetrates at least 30mm into the base material (brick masonry), and the verticality deviation of the hole is ≤2°; use a high-pressure air pump (pressure 0.6MPa) in conjunction with a vacuum suction tube to remove dust and debris from the hole to prevent dust from affecting the bonding effect; insert modified bamboo nails into the holes, and apply a pre-tension stress of 8N·m using a torque wrench to ensure that the bamboo nails are initially bonded to the base material; fill the gap between the nail body and the hole wall with tung oil putty (tung oil: gypsum: fine sand = 4:3:3, fine sand particle size 0.1-0.2mm), compact and smooth it with a special curved trowel, and make it flush with the joint surface after smoothing; remove any bamboo nail residue that exceeds the joint surface, and lightly sand it smooth with fine sandpaper.Anchor points are arranged at 900mm×900mm intervals, with increased spacing to 600mm×600mm at stress concentration areas such as inside corners and turns. All anchor points are located at joints or concealed locations. After anchoring is completed, the wall bonding strength is tested and found to be 0.35-0.4MPa, meeting the specifications.

[0029] 4) Reversible Textured Coating Topcoat Protection: A new layered color difference calibration technology ensures uniform color. ① Substrate Pretreatment: After cleaning, uneven areas on the wall surface are repaired with reversible elastic putty. The putty is formulated with acrylic emulsion: talc powder: biodegradable cellulose ether = 50:45:5. The repair thickness is controlled at 0.5-1mm. After repair, the surface is lightly sanded with 400-grit sandpaper, and the wall surface flatness deviation is ≤2mm. A portable vapor permeability tester is used to test the vapor permeability of the substrate, ensuring ≥0.05g / (m·h·Pa). ② Coating Formulation: Based on the preliminary spectral analysis and color difference data, a custom-made white marble textured coating was prepared, consisting of a base material (water-based acrylic resin): aggregate (white marble powder + marble pellets): additives (UV absorber + anti-fouling agent) = 40:55:5; the white marble powder has a particle size of 0.2mm, the marble pellets have a particle size of 1.5mm, and the mass ratio of the two is 3:2; the additives selected are benzotriazole UV absorber (addition amount 0.5%) and fluorinated anti-fouling agent (addition amount 0.3%); the color of the coating was repeatedly adjusted using a spectrophotometer to ensure that the initial color difference value ΔE ≤ 2.5. ③ Layered Color Difference Calibration and Spraying: Apply 2mm wide custom masking tape (low tack level to avoid damaging the substrate when removing) according to the original T-shaped joint dimensions of the pebble-dash finish, with a horizontal spacing of 900mm and a vertical spacing of 300mm. Use a low-pressure sprayer (0.2MPa) for application. First, spray one coat of exterior wall primer (30μm dry film thickness). After drying for 4 hours, apply the first coat of textured paint (0.9mm dry film thickness). After drying, use a spectrophotometer to detect the color difference. For areas where the deviation exceeds ΔE=1.0, use a special color-matching pen for localized touch-up calibration. After completion, a second coat of textured paint (dry film thickness 0.9mm) is sprayed and allowed to dry for 4 hours. For decorative sculptures such as railings, the original decorative texture is meticulously replicated by hand using bamboo carving tools within 30 minutes after spraying. When the paint reaches a semi-dry state (touchless to the touch, moisture content ≤10%), the masking tape is gently peeled off at a 45° angle along the joint direction to form a clear joint structure. Finally, a coat of water-based acrylic topcoat (dry film thickness 20μm) is sprayed to improve stain resistance and gloss consistency. After spraying, the overall color difference value ΔE=2.2 is tested, which is highly consistent with the visual appearance of the original finish.

[0030] 5) Post-renovation monitoring and maintenance: After the renovation is completed, eight miniature temperature and humidity sensors are embedded in concealed areas of the wall (corners and joints) to monitor the wall's microenvironment parameters in real time (temperature 15-25℃, relative humidity 50-60%). The data is wirelessly transmitted to a monitoring platform to establish a wall health status early warning system. When the parameters exceed the threshold, an alarm is automatically triggered. During the maintenance period, a breathable protective membrane (permeability ≥0.08g / (m·h·Pa)) is used to cover the wall to prevent direct rain and sunlight. The protective membrane is removed after 7 days of maintenance. Subsequent periodic testing: Color difference, bonding strength, and permeability are tested on the wall at 1 month, 3 months, and 6 months after completion. The 6-month monitoring data shows that the wall color difference value ΔE=2.3, bonding strength ≥0.35MPa, and permeability 0.035g / (m·h·Pa). There is no leakage or cracking. The building's normal office operations are not affected in any way, and the renovation effect is long-lasting and stable.

[0031] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A traditional process for anchoring wood nails and applying a textured coating to protect pebble-dash veneer, characterized in that, The process includes five steps: preliminary investigation and disease assessment, layered controllable paint cleaning, graded hollow anchoring reinforcement, reversible textured paint topcoat protection, and post-treatment monitoring and maintenance. A bamboo nail pre-tension stress control process is added to the graded hollow anchoring reinforcement, and a layered color difference calibration process is added to the reversible textured paint topcoat protection. Details are as follows: S1. Preliminary Investigation and Defect Assessment: Infrared thermal imaging detection technology combined with ultrasonic rebound method is used to generate a 1:1 scale wall hollow distribution map to accurately determine the hollow area, separation distance and bonding strength; X-ray fluorescence spectroscopy is used to analyze the composition and particle size of the original water-brushed stone, and a spectrophotometer is used to collect the original surface color parameters according to CIELAB standards; infrared spectroscopy analysis is used to determine the chemical composition of the later covering layer. S2. Layered Controllable Paint Cleaning: A neutral paint stripping system is used, which is composed of neutral paint stripper, modified cellulose corrosion inhibitor, and penetrant in a mass ratio of 100:3:5, with a pH value of 6.0-8.0 and a density of 1.00-1.02 g / cm³. A three-step cleaning method is employed: "segmented softening - directional peeling - low-pressure rinsing and drying." The cleaning unit is divided into 2m×2m sections. The high-pressure cleaning pressure is controlled at 0.3-0.5 MPa, the water temperature is 30-50℃, and the moisture content of the wall surface after cleaning is ≤15%. S3, graded hollow anchoring reinforcement: Treatment of severe hollow areas: The "cutting and limiting - local replacement - original process replication" scheme is adopted. First, a regular cut is made along the edge of the hollow area. After the hollow area is removed, a layer of yellow mud, straw and lime mortar bonding layer, plain cement slurry and cement stone ballast finishing layer are laid according to the original structure to replicate the original T-shaped joint. Treatment of minor and potential hollow areas: Modified bamboo nails are used for anchoring. After drying and undergoing tung oil-nano silica composite anti-corrosion treatment, the bamboo nails are inserted into the pre-drilled holes. A torque wrench is used to apply a pre-tension stress of 6-10 N·m. Then, tung oil putty is filled, compacted, and smoothed. The anchoring points are arranged at a spacing of 900 mm × 900 mm, and the spacing is increased to 600 mm × 600 mm in areas of stress concentration. S4. Reversible Textured Coating Topcoat Protection: The base layer is pretreated with reversible elastic putty, and a custom-made white marble textured coating that matches the spectrum of the original water-brushed stone is applied. First, a primer and the first textured coating are sprayed. The color difference is detected by a spectrophotometer and local touch-up coating is applied for calibration. Then, the second textured coating is sprayed. Low-tack masking tape is pasted according to the original joint size. The tape is removed when the coating is semi-dry to form joints. Finally, the topcoat is sprayed. S5. Post-construction monitoring and maintenance: Embed miniature temperature and humidity sensors in concealed parts of the wall to build a wireless wall health early warning system; use a breathable protective film for 7 days of maintenance, and then regularly test color difference, bonding strength and breathability every 1-6 months thereafter.

2. The process according to claim 1, characterized in that, In step 1, the spectrophotometer has a measurement accuracy ΔE ≤ 0.01, and at least 10 typical sampling points are selected to collect color parameters and take the average value; the ultrasonic rebound method is used to detect the bonding strength with an accuracy error ≤ ±0.02MPa.

3. The process according to claim 1, characterized in that, In step 3, the modified bamboo nail has a three-section square structure with a width ≤ 5 mm and a total length of 60 mm. The nail head is a 30° wedge shape, and the cross section of the nail tail is 20-25% larger than that of the nail body. The bamboo nail is dried at 105℃ with forced air until the moisture content is below 4%, then immersed in tung oil-nano silica composite preservative solution for 24 hours, and naturally air-dried until the moisture content is below 12%. The compressive strength is ≥ 8 MPa.

4. The process according to claim 1, characterized in that, In step 4, a diamond drill bit is used for drilling. The hole diameter is 0.5mm larger than the width of the bamboo nail, the hole depth is 60mm, and it penetrates into the substrate by no less than 30mm. The verticality deviation of the drilling is ≤2°. The tung oil putty is prepared by mixing tung oil, gypsum, and fine sand in a mass ratio of 4:3:

3. The fine sand particle size is 0.1-0.2mm.

5. The process according to claim 1, characterized in that, In step 4, the marble-textured coating is prepared by mixing base material, aggregate, and additives in a mass ratio of 40:55:

5. The base material is water-based acrylic resin, the aggregate is 0.1-0.3mm marble powder and 1-2mm marble particles in a mass ratio of 3:2, and the additives contain 0.3-0.5% benzotriazole UV absorber and 0.2-0.3% fluorinated anti-fouling agent. After layer color difference calibration, the overall color difference value of the coating is ΔE≤3.

6. The process according to claim 1, characterized in that, In step 5, the reversible elastic putty is prepared by mixing acrylic emulsion, talc powder, and biodegradable cellulose ether in a mass ratio of 50:45:

5. The repair thickness is 0.5-1mm, the flatness deviation after base layer pretreatment is ≤2mm, and the vapor permeability is ≥0.05g / (m·h·Pa).

7. The process according to claim 1, characterized in that, In step 5, the monitoring range of the miniature temperature and humidity sensor is 15-25℃ temperature and 50-60% relative humidity, and the vapor permeability of the breathable protective membrane is ≥0.08g / (m·h·Pa). The periodic testing indicators include: color difference value ΔE≤3, bonding strength ≥0.3MPa, and vapor permeability ≥0.03g / (m·h·Pa).

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