How to Prevent Rapid Moisture Evaporation in GRC Exterior Walls in High-Temperature Regions: Anti-Plastic Shrinkage Cracking and Qinglong Group's Process Control

When constructing GRC exterior walls in hot, dry regions, the core challenges are preventing plastic shrinkage cracks in freshly mixed GRC slurry caused by excessively rapid evaporation of surface moisture, and avoiding cracking of installed components due to severe drying shrinkage at high temperatures. For projects in high-temperature regions such as Xinjiang and the Middle East, Qinglong Group has developed a comprehensive prevention and control system integrating "materials, processes, and curing." In terms of materials, we use retarding admixtures to delay setting time, and incorporate internal curing materials (such as saturated lightweight aggregates) and high water-retention cellulose ether to lock in moisture from within. In mix design, the water-cement ratio is kept as low as possible while ensuring workability, reducing the total amount of evaporable water.

Control of production processes and construction procedures is even more critical. We specify that during hot seasons (daily maximum temperature >30℃), ice water or chilled water may be used for mixing to lower the discharge temperature of the mix. After spraying or casting into shape, immediate measures must be taken to prevent moisture evaporation: first, covering with moisture-retention film (such as plastic sheeting or wet geotextile), followed by mist curing. At a project site in the UAE, we erected movable sunshade canopies equipped with automatic misting systems, keeping the micro-environmental humidity at the component surface above 90% at all times until initial setting.

For GRC panels already installed on walls, the focus of protection under high temperatures is controlling drying shrinkage stress. We allow panels to shrink freely by properly setting expansion joints. Panel joints are sealed with low-modulus, high-movement-capability sealants to accommodate thermal expansion and contraction. During summer construction in Wuhan, we adjusted working hours to avoid the high-temperature afternoon period, and immediately after installation, temporarily shielded panel joints to prevent direct sunlight from causing a sharp rise in panel surface temperature. Through this series of refined measures, Qinglong Group has successfully achieved "zero" harmful cracking of GRC exterior walls in numerous high-temperature region projects, ensuring the ultimate appearance.