Causes and Prevention of Air Bubbles on UHPC Component Surfaces — Qinglong UHPC Air Bubble Control Technology System

The formation of surface bubbles on UHPC components mainly stems from four factors: air content in raw materials, mixing process, pouring method, and curing conditions. Specific manifestations include: air content in fresh UHPC exceeding 4%, improper mixing speed (>60rpm) entraining excessive air, pouring drop height exceeding 1.5m generating impact bubbles, and sudden curing temperature rise (>15℃/h) causing expansion bubbles. Through systematic control, the surface bubble rate can be kept within ≤3%, with bubble diameter ≤1mm, meeting premium quality standards.

In a landmark project in Shenzhen, Qinglong UHPC achieved outstanding results through the following measures: using defoamer (dosage 0.1%-0.3%) to control air content within 2%-3%; optimizing the mixing process (40-50rpm for 3-5min); employing chute pouring (drop height ≤0.8m); and step-wise heating curing (≤10℃/h). Ultimately, bubbles covered ≤1.5% of the component surface area, fully meeting mirror-finish requirements.

Raw Material Control Standards

Cement air content must be tested (≤2.5%); aggregate clay content ≤0.5%; compatibility testing between water reducer and defoamer; fiber dispersion ≥90%. Controlling bubble formation at the source.

Mixing Process Optimization

Use twin-shaft mixers with speed controlled at 40-50rpm; feeding sequence: dry materials first, then liquids; mixing time of 3-5min to ensure uniformity; vacuum mixing technology (-0.08MPa) to remove bubbles.

Pouring Process Control

Pouring drop height ≤1m with tremie pipe feeding; layered pouring thickness ≤300mm; vibration frequency 100-120Hz for 15-20s per point; apply defoaming release agent on formwork surfaces.

Scientific Curing Regime

Rest period of 1-2h (temperature 20±2℃); heating rate ≤10℃/h; constant temperature of 80±5℃ for 24-48h; cooling rate ≤15℃/h. Strict control prevents temperature-induced bubbles.

Bubble control requires a systematic solution. Qinglong UHPC's complete technical system ensures the surface quality of components.