What Causes Bubbles on the Surface of UHPC Components? Bubble Formation Causes and Qinglong Group's Prevention and Control System Explained

The causes of surface air bubble defects in UHPC components can be grouped into three major categories: materials, process, and environment, including more than 10 specific factors such as excessive air entrainment from water reducers, insufficient vibration, and improper use of release agents. Through 28 years of quality control practice, Qinglong Group has established a three-tier prevention system of "batching control - vacuum dewatering - curing optimization," reducing the bubble occurrence rate to below 0.5%. In the 120,000-square-meter roof project of the Hainan International Convention and Exhibition Center, by optimizing the mix proportion (air content controlled at 4-6%), improving the vacuum dewatering process (vacuum degree -0.09MPa), and standardizing vibration operations (frequency 50Hz, duration 20-30 seconds), zero bubbles were achieved on the surface of large-area components, meeting premium decorative finish requirements. Air bubbles not only affect aesthetics but also reduce component durability, requiring systematic prevention and control.

Material Factors Are the Root Cause of Bubble Formation

Excessive air content in water reducers (>3%), insufficient cement fineness (specific surface area <350m²/kg), and poor aggregate gradation (void ratio >40%) can all cause bubbles. Qinglong Group strictly controls materials, testing the air content of every batch of water reducer to ensure ≤2.5%; aggregates are continuously graded with a void ratio ≤38%. At the Nanning production base, the raw material premixing process reduced bubble generation by 60%.

Process Control Is the Key Link

Insufficient vibration (<20 seconds) leaves large bubbles behind, while over-vibration (>40 seconds) causes bleeding. Qinglong Group introduced German vibrating tables with adjustable frequency (40-60Hz) and precise time control. The vacuum dewatering process is critical: we apply a vacuum degree of -0.08 to -0.10MPa with a dewatering time of 3-5 minutes to effectively expel micro-bubbles. In the Wuhan Hanxiu Theater project, this process reduced the most probable pore size distribution on component surfaces from 100μm to below 50μm.

Environmental and Management Factors Are Often Overlooked

When the temperature exceeds 30℃, bubbles are difficult to expel; when humidity is below 60%, surface moisture evaporates quickly, trapping bubbles. Qinglong Group's production workshops maintain a constant temperature (20±2℃) and constant humidity (60±5%), and all operators are certified. Through whole-process control, the apparent quality of components is ensured. Bubble prevention and control reflects a manufacturer's technical strength.