Technical Essentials for Renovating GRC Components on Existing Buildings: A Systematic Project of Assessment, Repair and Performance Enhancement

Renovating and retrofitting GRC elements on existing buildings is a systematic project more complex than new construction, with its core lying in “precise assessment, scientific repair, performance enhancement, and architectural harmony.” Qinglong Group has participated in numerous GRC renovation projects for historical buildings and existing public buildings, and has summarized a four-in-one technical implementation approach of “inspection and appraisal first, categorized repair measures, protective system reconstruction, and structural safety reinforcement.”

Step 1: Comprehensive inspection and damage mechanism diagnosis. This is the foundation of all work. Multiple methods must be employed, including sounding, infrared thermography, rebar scanning, core sampling, chloride ion content testing, and carbonation depth testing, to scientifically diagnose the damage types of GRC elements (cracking, spalling, corrosion, water seepage), as well as their extent, severity, and causes. For example, surface crazing and cracks along rebar have vastly different causes and hazards. Only by identifying the root cause can the right remedy be applied.

Step 2: Develop categorized repair techniques. Based on the degree of damage, treatment is typically divided into three levels: 1) For surface contamination and chalking, clean with specialized cleaning agents and then reapply protective coatings; 2) For non-structural cracks (width <0.3mm), repair using low-pressure epoxy resin injection; 3) For structural cracks, rebar corrosion, or localized damage, local chiseling, rust removal, and repair with polymer-modified mortar are required, with carbon fiber sheets or steel plates added for reinforcement when necessary. All repair materials must be compatible with the original GRC substrate and have low shrinkage.

Step 3: Rebuild a long-lasting protective system. The core goal of renovation is not only “restoring the old as old,” but “restoring the old better than old.” After repairs are completed, a new generation of protective coatings must be applied, such as high-weather-resistance fluorocarbon paint and silane impregnation agents, to enhance resistance to UV rays, acid rain, and freeze-thaw cycles, with a protection cycle far longer than the original design.

Step 4: Systematic safety reinforcement. Where overall load-bearing capacity is insufficient due to inadequate original design standards or structural aging, the GRC support and connection system must be assessed and reinforced. For example, replacing with stainless steel anchors of a higher safety factor and adding seismic release devices. The entire renovation process requires a detailed specialized plan, with attention to protecting and continuing the building's historical character. Qinglong Group's renovation technology gives old buildings new life and a longer service life.