How to Prevent Rapid Moisture Evaporation from GRC Exterior Walls in High-Temperature Regions?

In high-temperature regions, GRC components face the severe challenge of excessively rapid moisture evaporation during production and construction, which can easily lead to plastic shrinkage cracking, affecting strength development and long-term durability. For hot, dry environments such as the Middle East, Africa, and Northwest China, Qinglong Group has summarized a systematic prevention and control strategy of "water control in production, water retention in construction, and water adjustment in processing." In a hotel project in the hot, dry region of Algeria, we successfully ensured the excellent quality of GRC components by comprehensively applying these measures, with no shrinkage cracking after ten years of use.

Core Controls in the Production Stage: Reducing Evaporation Driving Forces and Timely Sealing

1) Optimize the mix proportion: While ensuring workability, reduce the water-cement ratio as much as possible to reduce the total amount of evaporable free water at the source. Using high-range water reducers is key to achieving a low water-cement ratio. 2) Use internal curing materials: Add lightweight porous internal curing materials (such as saturated lightweight ceramsite) to continuously supply moisture from within to the capillary pores during cement hydration, compensating for external moisture loss. 3) Timely covering and curing: After the components are formed, they must be immediately and tightly covered with plastic film before surface moisture evaporates (usually within no more than 15 minutes) to block air movement. They should then be moved as soon as possible into a high-humidity standard curing room or subjected to water spray curing.

Moisture Retention Measures in the Construction and Installation Stage

1) Wet application: Before installation, moderately spray water to moisten the back of the GRC components (but no standing water on the surface) to reduce the components' "water grabbing" from the bonding mortar. 2) Select materials with good water retention: Use polymer-modified special bonding mortar or grouting material; such materials have strong inherent water retention and can slow the rate at which moisture is drawn away by the hot substrate and air. 3) Avoid high-temperature periods: Arrange construction schedules reasonably and avoid tiling, grouting, and other operations during the hottest hours of strongest daily sunlight.

Using Process Techniques and Admixtures to Regulate the Hydration Process

1) Add retarders: At high temperatures, the cement hydration reaction accelerates sharply and heat generation becomes concentrated, intensifying moisture evaporation and thermal stress. Adding an appropriate amount of retarder can flatten the hydration heat release peak and reduce the risk of thermal cracking. 2) Use mist spray curing: In the early curing stage, use an automatic mist spray system to keep the component surface continuously moist, which is more uniform and long-lasting than simple water sprinkling. 3) Avoid direct sunlight and strong wind: For newly installed GRC walls, shading measures should be taken until the bonding material reaches sufficient strength, to prevent direct sunlight and strong wind exposure. Through comprehensive, multi-dimensional moisture management throughout the entire process, the adverse effects of high-temperature environments on GRC quality can be effectively overcome.