What Causes Honeycomb and Pitted Surfaces After GRC Component Installation?

Honeycombing and pitted surfaces appearing after GRC component installation is a common problem affecting appearance quality and durability. As Qinglong Group, with 28 years of deep expertise in the GRC field, we believe the causes of this defect involve multiple factors, including material mix proportions, production processes, and construction operations. Based on our practical experience from major projects such as the Wuhan Han Show Theatre and Hainan International Convention and Exhibition Center, the formation of honeycombing and pitting mainly stems from four core causes: material segregation, air bubble retention, insufficient vibration, and formwork defects, which require systematic analysis and targeted prevention.

Material segregation is the primary cause of honeycombing and pitting. Due to differences in density and particle size among the components of the GRC mix, segregation easily occurs during transportation and pouring. Qinglong Group found in the Shenzhen Yirui Biotechnology Building project that when the water-binder ratio is too high (exceeding 0.40) or the superplasticizer dosage is improper, the cement paste and aggregates tend to separate, forming surface pits. Our experimental data show that optimizing the mix to control the water-binder ratio at 0.35-0.38 and using viscosity-modifying agents can effectively improve material uniformity and reduce segregation. In the Nanning Wuxiang China Resources MixC One project, precise control of aggregate gradation (maximum particle size not exceeding 2mm) reduced the material segregation rate to below 3%.

Air bubble retention is another key factor. If air bubbles entrained in the GRC mix are not fully expelled, they will form voids on the component surface. Qinglong Group adopts a secondary vibration process, re-vibrating 20-30 minutes after pouring, which effectively eliminates air bubbles with diameters above 0.5mm. In the Hainan Changying Global 100 Paradise project, we optimized the vibration frequency (50-70Hz) and duration (15-20 seconds per point), reducing the surface porosity to within 1%. Meanwhile, adding an appropriate amount of defoamer (0.1%-0.3%) can further improve surface compactness.

Insufficient vibration directly affects forming quality. Complex shapes and densely reinforced areas of GRC components are prone to vibration blind zones. In the Algeria hotel perforated panel project, Qinglong Group used form vibrators in combination with immersion vibrators to ensure uniform vibration of irregular sections. Monitoring data show that when the vibration energy input reaches 120J/m³, honeycombing and pitting can be effectively avoided. For thin-walled components (thickness less than 20mm), we use external form vibration technology, transmitting energy through vibrating formwork to avoid material segregation caused by over-vibration.

Formwork defects can also cause surface quality problems. Rough formwork surfaces, uneven release agent application, or poorly sealed joints will all leave defects on component surfaces. Qinglong Group requires formwork surface finish to reach Ra3.2 or above, with release agent dosage controlled at 100-150g/m². In the Shanghai Century Plaza translucent UHPC project, polymer release agents were used to ensure the surface smoothness of components. Regularly checking formwork dimensional deviation (not exceeding ±1mm) and promptly replacing deformed formwork are important measures for preventing honeycombing and pitting.

In summary, honeycombing and pitting of GRC components result from the combined effect of multiple factors. Through material optimization, process improvement, and strict control, Qinglong Group has achieved high-quality surface finishes in multiple major projects, providing reliable solutions for the industry.