Causes and Solutions for Bubbles on UHPC Component Surfaces

In the field of modern architectural decoration, UHPC (Ultra-High Performance Concrete) has become the preferred material for high-end projects such as grand theaters and commercial complexes, thanks to its outstanding mechanical properties and expressive formability. However, surface air bubble problems in UHPC components often trouble the industry, affecting both aesthetics and durability. Drawing on 28 years of full-chain UHPC/GRC/GRG/GRP experience, Qinglong Group will analyze in this article the causes of air bubbles—from material properties and production processes to construction management—and provide systematic solutions.

1. Analysis of the Core Causes of Air Bubble Formation in UHPC

The unique nature of UHPC material determines the complexity of its bubble control. In terms of mix proportion, the high-density blending of ultra-fine powders and steel fibers easily makes the slurry too viscous for air to escape, while excessive use of high-range water reducers may trigger air-entraining effects that cause tiny bubbles to cluster. In production, insufficient mixing speed leads to uneven material blending and trapped air bubbles; if immersion vibrators are used, localized over-vibration can actually introduce new air, and bubble accumulation is even more likely at the corners of irregularly shaped components. In addition, improper mold surface treatment (such as uneven application of release agent) and imbalanced temperature and humidity in the curing environment can also obstruct bubble escape, ultimately forming honeycomb-like defects on the component surface.

2. Whole-Process Air Bubble Control Technical Solutions

To address the bubble problem, Qinglong Group, drawing on the technical expertise of its national-level R&D center, has built a trinity solution of "materials–process–management." At the material optimization level, the gradation ratio of silica fume to cement is adjusted to reduce slurry viscosity, and a new composite water reducer is adopted to precisely keep air content within 3%. In production technology, German-imported planetary mixers are introduced to achieve 360-degree, no-dead-angle mixing; for complex-shaped components, a combined process of vacuum vibration plus a high-frequency vibrating table ensures efficient bubble discharge. In mold treatment, the industry's first nano-scale release agent coating technology is applied, together with mirror-finish stainless steel molds, to reduce bubble adhesion. During curing, an intelligent temperature control system maintains humidity above 90% in the heating phase, allowing bubbles to escape fully before hardening.

3. Air Bubble Treatment Cases in Engineering Practice

The UHPC double-curved cladding panels of a landmark project once suffered from surface air bubbles. Qinglong's technical team used 3D scanning to locate areas with dense bubbles and found that the root cause was inadequate sealing of the mold joints. Elastic sealing strips were promptly adopted to optimize the mold joints, and a three-step "pre-vibration–rest–re-vibration" procedure was added to the vibration program, ultimately raising the component bubble pass rate to 98%. This solution has been successfully applied to multiple UHPC projects, including the Nanjing East Road Century Plaza renovation project, where the bubble control precision of translucent concrete components reached below 0.2mm, winning the AALBORG WHITE Cup UHPC Innovation Award.

4. Industry Perspective: Air Bubble Control and UHPC Quality Upgrade

As a participating unit in drafting the industry standard "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)," Qinglong Group believes that bubble control is not merely a surface quality issue but a direct reflection of material densification and durability. By introducing BIM technology for pre-construction simulation and combining RFID chips to achieve full-process production traceability, bubble risks can be reduced at the source. In the future, as UHPC expands into fields such as bridges and utility tunnels, bubble control technology will become a key indicator of a company's core competitiveness, driving the industry from "qualified products" toward "premium projects."

The air bubble problem in UHPC components is, in essence, a combined challenge of materials science and engineering management. Built on 28 years of industry experience, Qinglong Group transforms bubble control into a quality advantage through technological innovation and refined management, providing designers and owners with UHPC solutions that combine aesthetic value with structural safety. Guided by the mission of "Creating Aesthetic Architecture," Qinglong is continuously driving UHPC technology upgrades, helping Chinese construction move toward higher quality.