Are UHPC Exterior Walls in Humid Regions Prone to Mold Growth? Mold Risks and Prevention Solutions

In humid regions, high air humidity and frequent rainfall cause moisture to adhere easily to the surface of UHPC exterior walls, creating conditions for mold growth. However, with scientific prevention and control measures, the risk of mold growth can be effectively reduced. Drawing on project experience in humid regions, Qinglong analyzes the causes of mold growth and the corresponding prevention and control solutions.

I. Core Causes of Mold Growth on UHPC Exterior Walls in Humid Regions

Mold growth requires three conditions: moisture, nutrient sources, and suitable temperature. Environmental factors: annual relative humidity in humid regions is ≥75% and can exceed 85% during the rainy season, with frequent rainfall. A water film easily forms on UHPC surfaces, and this continuously damp environment provides the basis for mold survival. Surface contamination: dust, pollen, organic matter, and other airborne particles adhere to UHPC surfaces and become nutrient sources for mold growth, especially on exterior walls left uncleaned for long periods, where accumulated contamination easily triggers mold growth. Material properties: if the UHPC surface has fine pores or rough areas, it tends to absorb moisture and contaminants, increasing the probability of mold growth. In inspections of the Guiyang Huaguoyuan project, Qinglong found that UHPC panels with rougher surfaces had higher mold growth rates.

II. Hazards and Risk Assessment of Mold Growth

Mold growth not only affects appearance but may also damage material performance. Appearance impact: mold forms black and green patches on UHPC surfaces, severely affecting building aesthetics and reducing project quality. Material damage: long-term mold erosion may cause UHPC surface powdering; although the impact on structural strength is small, it damages surface protective coatings and accelerates material aging. Health risks: mold spores dispersed into the air may cause respiratory discomfort, with a particularly significant impact on buildings such as residences and hospitals. Risk levels: coastal humid regions and tropical rainforest regions have a high risk of mold growth (level ≥3), while inland humid regions face moderate risk (level 2-3), requiring targeted prevention and control.

III. Full-Process Prevention and Control Solutions for Mold Growth

Prevention and control measures should be implemented throughout the entire process of design, production, construction, and maintenance to block the conditions for mold growth. Production stage: optimize the UHPC mix to improve surface density and use high-pressure vibration molding to reduce surface porosity to below 3%, minimizing moisture absorption. Surface treatment: apply anti-mold coatings (such as fluorocarbon coatings containing nano-silver ions) to inhibit mold growth; in the Hainan Changying Global 100 project, Qinglong used anti-mold coatings to reduce the risk of mold growth. Construction stage: ensure the drainage slope of UHPC exterior walls is ≥2% and install drainage channels to accelerate rainwater runoff and prevent surface water accumulation. Routine maintenance: clean exterior wall surfaces every 3-6 months to remove contaminants and mold spores, keep surfaces dry, and increase cleaning frequency during the rainy season; Qinglong provides specialized cleaning services for effective mold prevention and control.

IV. Treatment and Repair Measures After Mold Growth

Treat mold growth promptly to prevent its spread. Mild growth (area <10%): clean with a neutral detergent combined with a high-pressure water gun to remove mold patches, then apply an anti-mold protective agent after drying. Moderate growth (area 10%-30%): use a specialized mold remover (such as chlorine-based disinfectant, diluted before use), let it sit for 10-15 minutes after application, then rinse thoroughly to avoid residual chemicals corroding the surface. Severe growth (area >30%): surface coating renovation is required; first thoroughly remove the mold and aged coatings, polish the surface, then reapply anti-mold primer and topcoat. In the Nanning Wuxiang China Resources MixC One project, Qinglong effectively resolved the mold problem through coating renovation, restoring the building's appearance.