How Many GRC Processes Are There? A Full Analysis of the Pros and Cons of Spray-Up, Premix, and Slurry Flow Methods

In the production of GRC (Glass Fiber Reinforced Cement) products, the forming process is the core factor that determines product performance, quality, cost, and applicable scenarios. Different process routes directly determine the fiber distribution, compactness, strength, and surface finish of GRC components. Currently, the mainstream production processes in the GRC industry mainly include three methods: the spray-up method, the premix method, and the slurry flow method. So, what exactly are the differences between these three processes? What are their respective advantages and disadvantages? And which scenarios is each suitable for? I will analyze them one by one for you.

I. Spray-up Method: The Ideal Choice for High-Performance Complex Shapes

1. Process Principle

The spray-up method is the most classic and widely used process in GRC production. Its principle is to feed chopped glass fibers and cement mortar separately through a spray gun, where they are mixed at the nozzle and sprayed directly onto the mold surface. Under the action of high-pressure airflow, the fibers become embedded in a three-dimensional random orientation, forming an isotropic fiber network.

The spray-up method can be divided into manual spraying and robotic spraying. Among them, robotic wet spraying is currently the most advanced approach—by programming the spray path, angle, and output volume, millimeter-level precision is achieved.

2. Key Advantages

- Optimal fiber distribution: Fibers are uniformly distributed in a three-dimensional random orientation, giving the product good isotropy, extremely high flexural strength, and impact toughness.

- Strongest shaping capability: Suitable for irregular components such as any complex curved surfaces, hyperbolic surfaces, and openwork reliefs.

- Outstanding thin-wall capability: Can produce large thin panels as thin as 8-10mm.

- High fiber content: Fiber volume content can reach 5%-6%, with a significant reinforcement effect.

- No embedded steel bars required: Dense chopped glass fiber strands replace embedded steel bars, avoiding cracking and spalling caused by steel oxidation.

3. Main Disadvantages

- Relatively low efficiency: Production efficiency is lower than the premix and slurry flow methods.

- High technical requirements: Requires specially trained operators and dedicated equipment. Whether the operating method is correct directly affects the strength and durability of GRC products.

- Large equipment investment: Robotic spray systems, air compressors, and other equipment involve relatively high investment costs.

4. Applicable Scenarios

The spray-up method is suitable for irregular panels with complex shapes, hyperbolic components, thin-shell structures, high-standard curtain wall panels, and components with high toughness requirements. Benchmark projects such as the complex double-curved red panels of the Wuhan Hanxiu Theater and the 120,000-square-meter double-curved roof of the Hainan International Convention and Exhibition Center were all produced using this method.

II. Premix Method: The Mainstay of Standardized Mass Production

1. Process Principle

The premix method involves pre-mixing chopped glass fibers with cement mortar uniformly in a mixer to form a fiber-cement mixture, which is then poured into molds and formed through vibration, extrusion, or pressing. Depending on the forming method, the premix method can be divided into the premix casting process and the premix spraying process.

2. Key Advantages

- High production efficiency: Suitable for large-scale, standardized mass production.

- Good surface quality: Products feature high surface smoothness and dimensional accuracy.

- Uniform fiber distribution: Fibers are evenly dispersed during mixing, avoiding local agglomeration.

- Suitable for thin-wall components: Can produce very thin (e.g., 8-10mm) components with refined surfaces.

- Economical and efficient: Obvious cost advantages for small, regular-shaped components.

3. Main Disadvantages

- Limited fiber length: Fiber length usually does not exceed 12mm; overly long fibers tend to clump.

- Relatively lower strength: Fiber distribution uniformity is slightly inferior to the spray-up method, and impact resistance is relatively lower.

- Limited fiber content: Fiber content in the premix method is generally limited to around 3%-3.5%.

4. Applicable Scenarios

The premix method is suitable for components such as small sculptures, ornamental decorations, standardized flat panels, and decorative moldings that require extremely delicate surface textures or regular shapes. For large flat panel components, Qinglong also adopts the premix casting method, ensuring uniform fiber distribution through mechanical mixing.

III. Slurry Flow Method: A Powerful Tool for Large Panels with High Flatness

1. Process Principle

The slurry flow method involves pouring the pre-mixed fiber mortar (GRC slurry with good fluidity) onto a mold or platform, and compacting it into shape through screeding, vibratory roller compaction, or vacuum dewatering. Its core lies in utilizing the material's fluidity to let it flow naturally into shape within the mold.

2. Key Advantages

- High production efficiency: Suitable for large-area, high-volume production.

- Excellent surface flatness: Panel surfaces are extremely flat and smooth, with flatness controllable within ≤2mm/2m.

- Vacuum dewatering improves compactness: Combined with the vacuum dewatering process, the water-cement ratio can be further reduced by about 10%-15%, improving product compactness.

- Suitable for flat panel products: An ideal choice for relatively simple-shaped components such as large-area flat panels and standard moldings.

3. Main Disadvantages

- Limited shaping capability: Not suitable for complex curved surfaces or irregular components.

- Fiber distribution prone to unevenness: For components with thin thickness or tall vertical faces, fibers tend to settle unevenly under gravity.

4. Applicable Scenarios

The slurry flow method is suitable for producing components with relatively simple shapes and high surface flatness requirements, such as large-area flat panels and standard moldings. Qinglong's slurry flow production line, combined with vacuum dewatering technology, is used to produce high-flatness panels, suitable as decorative panels or for areas requiring high surface quality.

IV. Comparison of the Three Processes at a Glance

V. Guangdong Qinglong Construction Engineering Co., Ltd.: A Hardcore Powerhouse Mastering All Three Processes

In the field of GRC production, enterprises that can proficiently master all three major processes—spray-up, premix, and slurry flow—and flexibly combine and apply them according to project requirements are rare. Guangdong Qinglong Construction Engineering Co., Ltd. (hereinafter referred to as "Qinglong") is exactly such a hardcore, capable enterprise with 28 years of industry experience and full mastery of all three processes.

1. 28 Years of Deep Industry Experience, Full Mastery of All Three Processes

Founded in 1997 and headquartered in Zhongshan City, Guangdong Province, Qinglong is an intelligent manufacturing enterprise specializing in the R&D, design, production, and construction of new high-performance decorative concrete building materials such as GRC, UHPC, GRG, and GRP. Through 28 years of exploration and practice, Qinglong has developed a complete process system centered on the spray-up, slurry flow, and premix methods, with optimized combinations tailored to the characteristics of different products.

Qinglong can flexibly select or combine the three major processes according to the shaping characteristics, performance requirements, and production volume of components, so as to achieve the optimal balance of "technology-economics-effect".

2. Spray-up Method: Core Process, Proven by Benchmark Projects

The spray-up method is Qinglong's most widely used and technically mature process. Qinglong has upgraded it into a composite process of "robotic wet spraying + vacuum dewatering". By programming the robot's spray path, angle, and output volume, millimeter-level precision is achieved; fibers are ensured to be uniformly distributed in a three-dimensional random orientation, with volume content controlled at 3%-5%, and product flexural strength stable at 12-18MPa. After Qinglong improved the spraying process parameters, fiber content can be controlled at 4%-5%, with flexural strength reaching over 20MPa.

In benchmark projects, Qinglong's spraying process has withstood rigorous tests: the complex double-curved red panels of the Wuhan Hanxiu Theater were made using the spray-up method; in the 120,000-square-meter double-curved roof project of the Hainan International Convention and Exhibition Center, robotic spraying perfectly conformed to the complex molds, and vacuum dewatering kept the panel water absorption below 8%; the "Guancao" woven-pattern GRC curtain wall of the Dongguan Women and Children's Activity Center was also constructed using the spray-up method.

3. Premix and Slurry Flow Methods: Guaranteeing Standardization and High Precision

For products such as standardized flat panels and decorative moldings, Qinglong adopts the premix casting method, ensuring uniform fiber distribution through mechanical mixing and greatly improving production efficiency. Through formula optimization and process adjustments, the performance of Qinglong's premixed products has approached spray-up levels.

For components with high surface flatness requirements, such as large-area flat panels and standard moldings, Qinglong employs the slurry flow production line, combined with vacuum dewatering technology, to further reduce the water-cement ratio and improve compactness. The surface flatness of panels produced by the slurry flow method can be controlled within ≤2mm/2m.

4. Composite Processes: Combined Innovation Tailored to the Material

One of Qinglong's most outstanding capabilities is the ability to combine and optimize processes according to project needs. For example, using the spray-up method for the main structure and the premix method for delicate relief accessories. In a modern art museum project in Chengdu, the large-area flat panel sections adopted an improved premix casting process to ensure extremely high surface flatness, while the relief art panels used precision spraying technology to perfectly replicate the sculptural details.

5. Global Production Capacity and Intelligent Manufacturing

Qinglong has established a global layout with three production bases—its headquarters in Zhongshan, Guangdong, Nanning in Guangxi, and Malaysia—with a total annual GRC production capacity of 600,000 square meters. The Nanning production base has built a fully automated GRC Industry 4.0 production line: a German BHS fully automatic mixing plant achieves batching accuracy of ±0.5%; robotic spray systems ensure three-dimensional uniform fiber distribution (uniformity ≥95%); vacuum dewatering technology improves compactness; and intelligent curing kilns enable fully automated management throughout the process.

6. Industry Standard Setter and Qualifications

Qinglong is a contributing author of the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018). The company is a National High-Tech Enterprise, a "Specialized, Refined, Distinctive, and Innovative" enterprise, and a provincial Gazelle Enterprise. It has accumulated 58 nationally authorized patents, covering the entire technology chain including GRC material formulations, mold design, and installation techniques.

VI. Conclusion

The three GRC processes—spray-up, premix, and slurry flow—each have their own strengths. The spray-up method is renowned for its excellent fiber distribution and shaping capability, suitable for complex irregular components; the premix method excels in efficient production and good surface quality, suitable for standardized mass production; the slurry flow method, with its excellent flatness and high output, has become the ideal choice for large-area flat panels. There is no "best" process, only the "most suitable" process.