Construction Process Analysis and Key Technical Points for Retrofitting Existing Building Exterior Walls with UHPC Panels

Amid the wave of existing building stock renewal, facade renovation of existing buildings faces the dual challenge of "aesthetic enhancement" and "performance upgrading." As an industry pioneer with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, Qinglong Group leverages its technical expertise as a national high-tech enterprise to apply ultra-high performance concrete (UHPC) panels to the field of facade renovation, pioneering a brand-new solution for existing building retrofit. This article systematically analyzes the construction process and key technical points of UHPC panels in facade renovation, providing professional reference for designers and owners.

**Systematic Process Construction for UHPC Panel Renovation**

Applying UHPC panels to facade renovation of existing buildings requires a scientific and rigorous construction system. In the preliminary survey stage, three-dimensional laser scanning is used to obtain precise data on the building facade, combined with structural inspection reports to develop customized solutions—this is precisely the core strength of Qinglong's in-depth design team. The production stage relies on the 600,000-square-meter annual capacity of the Nanning, Guangxi production base, using automated production lines to achieve precision prefabrication of UHPC panels with compressive strength exceeding 150MPa, far surpassing traditional building material standards.

The installation stage innovatively adopts the "Dry Fixing" method, using aluminum alloy connectors for flexible connection with the original wall, which both resolves substrate unevenness issues and avoids construction delays caused by wet work. Qinglong's construction team's original "double insurance" anchoring system, combined with BIM technology for full-process visual management, ensures that installation errors for each UHPC panel are controlled within ±2mm. Before completion, waterproof sealing uses silicone weather-resistant sealant together with a special chamfered edge design on UHPC panels, forming a complete rainwater protection system.

**Breakthroughs and Applications of Four Key Technical Points**

Substrate treatment technology is the fundamental guarantee of renovation projects. Qinglong's technical team has developed specialized interface treatment agents for different wall substrate materials (concrete, masonry, existing curtain walls), using pull-out tests to ensure a bond strength between UHPC panels and the substrate of ≥0.8MPa. For structural cracks commonly found in older buildings, a pretreatment solution combining epoxy resin injection with carbon fiber cloth reinforcement is adopted to eliminate safety hazards at the source.

The lightweight and personalized customization technologies of UHPC panels demonstrate unique advantages. Compared with the 30-50kg/㎡ weight of traditional stone curtain walls, UHPC panels produced by Qinglong weigh only 15-20kg/㎡, substantially reducing building loads. Using parametric design software, precise processing of arbitrary curved surfaces and openwork textures can be achieved; in the Dongguan Women and Children's Activity Center project, specially shaped UHPC sunshades with a maximum span of 8 meters were successfully created, showcasing the material's artistic expressiveness.

Temperature stress control technology solves the challenges of existing building retrofit. By setting up an insulation rock wool layer and an air layer on the back of UHPC panels to form a composite insulation system, the heat transfer coefficient can be as low as 0.5W/(㎡·K). Specially designed sliding connection joints allow panels to expand and contract freely under temperature differences of ±50℃, effectively avoiding cracking caused by thermal expansion and contraction—a technology that withstood extreme climate conditions in the Century Plaza renovation project on Nanjing East Road.

Full life-cycle management technology reflects Qinglong's service characteristics. Each UHPC panel has a built-in RFID chip for quality traceability, and combined with Qinglong's self-developed maintenance management system, panel status can be monitored in real time. Relying on a nationwide network of offices, "one-stop" service from design consultation to after-sales maintenance is provided—this is precisely Qinglong's responsibility as a national "Specialized, Refined, Distinctive, and Innovative" enterprise.

From the 20,000㎡ UHPC curtain wall renewal in a Taikoo Hui renovation project in Guangzhou to the townscape preservation project in Xi'an's historic district, Qinglong has validated the unique value of UHPC panels in facade renovation with 28 years of industry experience. This new material, combining high strength, high durability, and high design freedom in one, is redefining the retrofit standards for existing buildings. As a Vice Chairman Unit of the China GRC Association, Qinglong will continue to promote the improvement of standards such as the "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)," contributing professional strength to industry development and enabling more buildings to be revitalized through UHPC technology.