news

With the rapid development of green buildings, urban renewal, and exterior wall prefabricated coating technology in China, traditional stone dry hanging, real stone paint, and ordinary water in water coatings are gradually unable to meet the comprehensive needs of building facade decoration texture, structural safety, durability, and environmental protection and energy conservation. As a new generation of composite stone like coating material, water in sand colorful coating combines the high-definition simulated texture of water in water colorful coating with the three-dimensional sandy texture of real stone paint. It has comprehensive advantages such as light weight, high stone like degree, excellent weather resistance, convenient construction, green low VOC, and outstanding cost-effectiveness. It has been widely used in various exterior wall projects such as new residential buildings, public buildings, renovation of old residential facades, and decoration of irregular components. This article systematically elaborates on the material composition, film-forming mechanism, and technical advantages of water in sand colorful coatings. It provides a detailed overview of the standardized exterior wall construction process, key process parameters, and quality control points. It deeply analyzes common quality problems and their causes during the construction process, such as blooming, exposed substrate, broken particles, color difference, cracking, and whitening, and proposes targeted prevention and optimization construction plans. Based on the comparison of engineering applications, summarize the comprehensive advantages of water in sand coating compared to traditional exterior wall decorative materials, analyze the shortcomings of current construction technology, and look forward to its intelligent, standardized, and functional development trends, providing theoretical support and engineering practice reference for the standardized and high-quality promotion and application of water in sand colorful coatings in exterior wall engineering.

Keywords: water in sand colorful coating; Building exterior walls; Construction technology; Quality Control; Imitation stone decoration; Durability performance

1 Introduction

The exterior wall finish of a building not only undertakes the function of building appearance decoration and beautification, but also has the core role of wall protection, anti-aging, waterproof and anti-seepage, heat insulation and weather resistance, and resistance to external wind and rain erosion, which directly determines the service life and overall quality of the building facade. At present, China’s building exterior wall decoration materials mainly include natural stone dry hanging, ceramic tiles, real stone paint, water in water colorful coatings, ordinary latex paint and other categories. Natural granite and marble have the best simulation effect and high-end texture, but there are significant shortcomings such as high self weight, high wall load, prominent risk of high-altitude detachment, high cost, environmentally unfriendly mining, and long construction period; Ceramic tiles are prone to hollowing and falling off, water seepage and alkali return, and difficult to maintain in the later stage; Traditional real stone paint has a heavy sand texture but a single texture, low degree of simulation, easy to accumulate dust and dirt, and is prone to powdering and whitening when outdoors for a long time; Ordinary water in water coatings have fine texture but no sand texture, weak impact and scratch resistance, making it difficult to meet the high-end durability decoration needs of exterior walls.

Water in sand colorful coating is a composite stone like coating developed based on water-based colorful coating granulation technology, belonging to the new generation of green water-based exterior wall coating system. The modified silicon acrylic/pure acrylic lotion is used as the film forming matrix, and the composite structure of “water with sand, grain sand combination” is achieved by coating the colored particles with protective glue and matching the fine fossil sand aggregate, which perfectly combines the high-definition stone texture of water in water with the three-dimensional sand texture of stone like paint, and the simulation degree can highly restore the effect of litchi surface and burning surface granite. At the same time, water in sand coating has multiple advantages such as water-based environmental protection, low VOC, extremely light weight, strong adhesion, excellent crack resistance, weather resistance, and pollution resistance. It is suitable for construction in multiple scenarios such as high-rise residential buildings, villas and villas, schools and hospitals, commercial complexes, industrial park buildings, and renovation of old exterior walls.

Compared with traditional decorative materials, water in sand coatings are not limited by building shapes and can be adapted to the overall painting of irregular components such as flat surfaces, curved surfaces, eaves, and Roman columns. They have high construction efficiency, low comprehensive cost, and convenient maintenance in the later stage. They are currently the mainstream material to replace natural stone and achieve lightweight, high-end, and green transformation of building facades. However, water in sand coating belongs to a highly sensitive composite system, and the forming quality is highly dependent on the base conditions, construction environment, spraying process, and supporting system. Improper control of the construction process can easily lead to quality defects such as particle turbidity, local color difference, exposed bottom and flower, irregular grid division, later rain whitening, coating cracking and peeling. Therefore, systematic research on standardized construction technology of water in sand, clarification of key process control points, and establishment of a complete quality control system have important engineering value and practical significance for improving the quality of exterior wall coating engineering, extending the service life of building facades, and promoting green imitation stone coating technology.

2. Material System and Technical Advantages of Water in Sand Colorful Coatings

2.1 Material Composition and Film Formation Mechanism

The sand in water multicolor coating is a multi-phase composite water-based system. Its core consists of five parts: color base paint, inorganic quartz sand aggregate, polymer protective adhesive, continuous phase lotion and functional additives. The colored base paint provides a stone like texture color, which is coated with protective glue to form stable and independent colored particles, avoiding construction shear breakage and color mixing; Quartz sand aggregate creates a three-dimensional sandy texture in the coating, enhancing the hardness, impact resistance, and wear resistance of the paint film; Silicone acrylic/pure acrylic lotion is used as the film forming matrix to ensure the coating compactness, adhesion and outdoor weather resistance; Wetting, defoaming, thickening, anti-corrosion and other functional additives are used to regulate the storage stability, construction leveling and film uniformity of the system.

Its film forming mechanism is different from that of single stone like paint and ordinary latex paint: after spraying, the water in the system gradually evaporates, the coated color particles and sand aggregates are closely stacked under the bonding effect of lotion, the polymer lotion is crosslinked and solidified to form a continuous and dense elastic paint film, the color particles are evenly embedded in the sand coating, and the surface is sealed and protected by the finishing varnish, finally forming a composite stone like coating with a sense of texture hierarchy, a sense of sand three-dimensional and a dense protective layer, realizing the integration of decoration and protection.

2.2 Core application advantages

(1) High degree of simulation and high-end decorative effect. Water in sand can accurately restore various natural granite textures, color differences, and lychee surface textures. The textures are natural and transparent, with rich layers, without the dull and grainy feeling of real stone paint. The decorative effect is close to natural stone, which can meet the design needs of high-end building facades.

(2) Lightweight and lightweight, with a high safety factor. Compared to dry hanging stone, water in sand coating has a thin thickness and extremely light weight, which will not increase the structural load of the wall and completely eliminate the safety hazards of high-altitude stone falling off. It is suitable for exterior wall coating of super high-rise buildings.

(3) Excellent durability performance. The high-quality silicone propyl water in sand coating has outstanding resistance to UV aging, rainwater erosion, freeze-thaw cycles, and contamination. It is not easy to powder, lose light, change color, or accumulate dust after long-term outdoor service, and the service life of the exterior wall can reach more than 10 years.

(4) Green and environmentally friendly, construction friendly. The entire process is water-based, solvent-free, low VOC, and free of harmful substances such as formaldehyde, which meets the environmental protection standards for green buildings; Spray molding at room temperature, no dust pollution, safe construction, and no risk of open flames.

(5) Wide adaptability and excellent cost-effectiveness. It can adapt to new wall painting, old wall renovation, and shaped components, with a construction efficiency much higher than that of stone dry hanging. The comprehensive cost is only 1/4~1/3 of that of stone dry hanging, and it is easy to maintain and renovate in the later stage.

3. Standardized construction process of water in sand for building exterior walls

The water in sand exterior wall coating follows the complete process of “base pre-treatment – sealing and reinforcement – leveling and polishing – grid shaping – main material spraying – surface protection”. The standardized construction process is: base inspection and treatment → crack defect repair → anti crack mortar leveling → exterior wall putty scraping → polishing and dust removal → alkali resistant sealing primer spraying → same color intermediate coating construction → grid joint pasting → water in sand main material spraying → removal of decorative paper → topcoat spraying → finished product maintenance. Each process is interrelated and directly determines the final forming quality and durability performance.

3.1 Grassroots treatment and defect repair

The quality of the base layer is the foundation for the long-term stability of the water in sand coating. Before construction, a comprehensive inspection of the wall base layer is required to ensure that the wall is solid, dry, flat, clean, and free of defects such as floating ash, oil stains, loose peeling, hollowing, cracking, alkali peeling, and whitening. For minor cracks in the wall, elastic joint filling mortar is used to fill and repair them; Wide cracks require the addition of alkali resistant mesh fabric to enhance crack resistance; Loose powdery base must be thoroughly removed and re plastered and leveled; The alkali prone areas on the wall are neutralized with oxalic acid solution and allowed to dry before proceeding to the next process, to eliminate the hidden dangers of coating whitening, peeling and detachment in the later stage. The moisture content of the base layer should be strictly controlled below 10% to avoid later moisture leakage causing coating bubbles and color differences.

3.2 Leveling and polishing process

After passing the grassroots acceptance, apply two coats of special anti cracking putty for exterior walls. The first coat of rough putty is mainly used for overall leveling of the wall surface, filling the holes and concave convex defects on the wall surface; The second layer of fine putty is finely leveled to ensure the smoothness and delicacy of the wall surface. After each layer of putty is completely dry, it is sanded with sandpaper to remove burrs, joint marks, and protruding particles. Then, it is thoroughly cleaned with dust to ensure that the wall is clean and dust-free, laying the foundation for subsequent primer penetration and sealing.

3.3 Sealing primer and intermediate coating construction

Alkali resistant sealing primer is a key layer that blocks wall alkali precipitation and enhances interlayer adhesion. The uniform spraying method is used for construction to ensure that the primer is thin and uniform, without omissions or accumulation, fully penetrates the pores of the base layer, seals the capillary channels of the wall, effectively inhibits the outward precipitation of alkaline substances in cement mortar, and improves the interlayer bonding strength between the putty layer and the intermediate coating and main materials. After the primer is completely dry, spray a medium coat of the same color to unify the wall base color, eliminate the color difference of the base layer, avoid the problem of exposed base and flower after the main material is sprayed, and ensure that the overall finishing color is uniform and consistent.

3.4 Grid seam treatment

Dividing is the core process of restoring the effect of stone assembly and enhancing the layering of the exterior facade. According to the architectural design requirements, snap lines and divide them into grids, paste high-quality decorative paper to ensure that the dividing lines are horizontal and vertical, evenly spaced, and uniformly wide and narrow, accurately simulating the natural stone joint effect. The grid pasting should be firm and tight to avoid the infiltration of paint into the gaps during the spraying process, which may cause rough edges and contamination of the lines, ensuring clear and orderly grid division in the later stage.

3.5 Spray coating of sand in water main material

The spraying of the main material directly determines the texture and forming quality of the imitation stone. We strictly follow the construction principles of thin spraying multiple times, cross spraying, and uniform and stable spraying. We use specialized colorful paint spray guns and stable air compressors for construction. The spraying pressure is controlled at 0.4~0.6 MPa, and the spray gun is perpendicular to the wall, moving at a constant speed at a distance of 30~50 cm. Divided into two layers of molding: the first layer is a thin spray primer with a coverage rate of about 60%, ensuring uniform adhesion of color particles and laying the foundation texture; After drying at room temperature for 15-20 minutes, perform a second cross spray coating, fully covering and forming, with a total dry film thickness controlled at 0.5-0.8 mm. It is strictly prohibited to spray thick once to form, to avoid defects such as coating accumulation, sagging, dense accumulation of color particles, particle breakage and turbidity. Complete the same facade in one go to reduce joint marks and ensure uniform texture overall.

3.6 Removal of masking paper and surface protection

Before the main material spray surface dries, timely and slowly tear off the masking paper diagonally to prevent tearing off the tape and damaging the edge neatness after the paint film solidifies. After the main material is completely dried and cured for 24 hours, evenly spray a matte/glossy weather resistant topcoat. The topcoat can seal the surface pores of the coating, greatly improving the water resistance, stain resistance, UV resistance, and rain erosion resistance of the paint film. It effectively prevents long-term outdoor dust accumulation, fouling, and powdering, and is a key protective process for extending the service life of exterior walls.

3.7 Finished product maintenance

After the overall coating is completed, it is necessary to ensure a normal temperature curing period of more than 7 days. During the curing period, it is necessary to avoid rain wash, external force bumping, and dust pollution, so as to ensure that the lotion is fully crosslinked and solidified, forming a high-strength dense protective film, and giving full play to the durability and protection performance of the coating.

4 Common quality problems and their causes in construction, as well as prevention and control measures

4.1 Color particle breakage, coating turbidity and graying

Main causes: excessive spraying pressure, close distance between spray guns, excessive stirring force, damage to the protective adhesive coating structure, resulting in color particle breakage and color mixing; Insufficient static storage of coatings and poor system stability. Prevention and control measures: Strictly control the spraying pressure and spraying distance, prohibit violent mixing, and gently mix the coating before construction; Ensure the curing time of the coating and guarantee the stability of the color particle structure.

4.2 Wall flower, local color difference, and exposed substrate

Cause: Uneven base color of intermediate coating, uneven thickness of spraying, leakage of spraying and bottom, and obvious intermittent joints during construction; Uneven moisture content and localized alkali leaching at the grassroots level. Prevention and control measures: Ensure full coverage of the intermediate coating without color difference; Unified spraying technique and number of passes, one-time molding of the facade; Strictly control the dryness of the base layer and the alkali removal process.

4.3 Irregular grid lines and burr contamination

Cause: Poor adhesion of masking paper, too late removal timing, and tearing after the paint film has solidified. Prevention and control measures: The seams should be tightly sealed and compacted. Before the surface of the main material dries, the paper should be torn diagonally in a timely manner to ensure that the lines are clean, straight, and regular.

4.4 In the later stage, it may rain and turn white, accumulate dust and dirt

Cause: Failure to spray topcoat or leakage of topcoat during thin spraying; Insufficient curing of the main material paint film and high porosity of the coating. Prevention and control measures: Fully cover with weather resistant topcoat, strictly follow the curing cycle, and ensure that the paint film is completely cross-linked and dense.

4.5 Coating peeling, cracking and detachment

Cause: Loose and powdery base layer, high moisture content, insufficient strength of putty layer; Primer sealing failure and poor interlayer adhesion; Excessive coating thickness and uneven drying inside and outside result in internal stress. Prevention and control measures: Strictly control the quality of grassroots, strengthen the sealing of primer, thin spray multiple times to form, and avoid stress cracking.

Analysis of the application advantages of 5 water in sand exterior wall coating projects

5.1 Comparative advantages with traditional exterior wall materials

Compared to natural stone dry hanging, water in sand has a light weight, no safety hazards of detachment, low cost, and short construction period, making it suitable for large-scale exterior walls of super high-rise buildings; Compared to real stone paint, its texture is delicate, highly realistic, less prone to dust accumulation, and has stronger weather resistance and durability, without the disadvantage of sand particle detachment; Compared to ordinary water in water coatings, its sand texture has a prominent three-dimensional effect, high hardness, excellent scratch resistance, impact resistance, and stronger protective ability; Compared to exterior latex paint, it has a higher decorative grade, significantly improved resistance to aging and rainwater erosion, and is fully suitable for long-term outdoor service scenarios.

5.2 Multi scenario engineering adaptability

In newly constructed commercial housing and villa buildings, water in sand can achieve high-end stone facade effects, enhancing the overall texture and grade of the building; In public buildings such as schools, hospitals, and government buildings, their environmentally friendly, low odor, weather resistant, durable, clean and easy to clean characteristics are suitable for the high standard requirements of public spaces; In the renovation project of the exterior walls of old residential areas, painting can be directly applied on the reinforced old base without the need for large-scale demolition, significantly reducing construction waste, shortening the construction period, and lowering renovation costs; In industrial parks and irregularly shaped buildings, it can perfectly adapt to curved surfaces, eaves, and component shapes, achieving a unified stone like decorative effect and compensating for the limitations of stone processing.

6 Problems and optimization directions of current construction technology

6.1 Shortcomings of Existing Technologies

At present, sand in water construction still heavily relies on manual experience, and the level of craftsmanship of construction personnel varies greatly, which can easily cause color differences and uneven texture in the project; The coating system is sensitive to temperature and humidity, and construction in low temperature, high humidity, and strong wind weather is prone to poor film formation, slow drying, and uneven particle distribution; Some low-end products have poor stability of the protective adhesive system, low construction fault tolerance, and insufficient quality controllability; The popularization rate of mechanized and standardized construction is low, and the stability of large-scale projects is difficult to unify.

6.2 Optimizing Development Trends

In the future, sand in water construction will develop towards standardization, mechanization, functionalization, and intelligence. By unifying construction process standards, curing spray parameters, and implementing a model first system, standardized control of engineering quality can be achieved; Promote mechanical spraying equipment to reduce quality fluctuations caused by manual differences; Develop a high weather resistance, high crack resistance, self-cleaning, thermal insulation and energy-saving functional water in sand system to further expand its application scenarios; Improve the construction technology that adapts to low temperature, high humidity, and complex climate conditions, and enhance the stability of coating projects throughout the year.

If you need relevant technical guidance, please contact our technical personnel by leaving a message on the website

You can also contact us through the following ways:

Whatsapp:+86 18068723597

Mail:  sandy2000@huidechemical.com