Wetting and drying of aerogel-based coating mortars in Swedish climates
Doctoral thesis, 2023
Therefore, an investigation was conducted to increase knowledge of the moisture performance of coating systems with ACMs. This investigation combined field and laboratory-based measurements with numerical hygrothermal simulations to study their moisture absorption under diverse wetting scenarios and evaluate their drying performance. Furthermore, the impact of surface water-repellent properties and surface cracks was assessed. The laboratory studies employed a newly developed small-scale test setup designed to simulate runoff wetting caused by typical wind-driven rain intensities in Sweden. Moreover, two supplementary capillary suction experiments under zero (free suction) and elevated hydrostatic pressure (created by Karsten tube) were conducted to explore additional wetting scenarios. A 15-month field test in Gothenburg, Sweden, combined with hygrothermal simulations were utilized to evaluate the early-stage drying and long-term hygrothermal performance of the coating system with ACM for four Swedish cities.
The laboratory measurements demonstrated minimal moisture absorption in the undamaged coating system with ACM, even during prolonged 24-h runoff wetting. As expected, applying water-repellent paint (sd = 0.01 m) to the exterior of the coating system effectively reduced the water absorption while maintaining the drying capacity. Conversely, coating systems with a 1 ± 0.5 mm wide surface crack had 3–5 times amplified water intrusion due to hydrostatic pressure from the created water film on the surface. This could increase the risk of local moisture accumulation. Capillary suction tests of the ACM revealed a substantial increase in water absorption after repeated wetting exposure. Meanwhile, the same tests on the complete coating system showed a consistently stable water absorption. Field measurements indicated that the built-in moisture in the ACM dried out within six months. Hygrothermal simulations for four Swedish cities revealed an early-stage drying period ranging from 134 to 336 days based on the climate and time of application. Over time, the ACM exhibited no hygroscopic moisture accumulation; however, walls highly exposed to wind-driven rain could experience elevated relative humidity within the ACM, thereby resulting in an average increase in thermal conductivity of up to 9%. The findings show that the examined coating system with ACM presents a moisture-safe solution for retrofitting external homogenous concrete and masonry structures, preventing moisture accumulation from rainwater wetting. However, considering the information regarding the anticipated early-stage drying time and the moderate elevation in thermal conductivity is crucial when evaluating the in-field hygrothermal performance of the coating system.
runoff
Aerogel
retrofitting
coating mortar
wetting
drying
wind-driven rain
render
Author
Ali Naman Karim
Chalmers, Architecture and Civil Engineering, Building Technology
Knowledge gaps regarding the hygrothermal and long-term performance of aerogel-based coating mortars
Construction and Building Materials,;Vol. 314(2022)
Review article
Increasing Water Absorptivity of an Aerogel-Based Coating Mortar in Subsequent Wetting and Drying
Gels,;Vol. 8(2022)
Journal article
Moisture absorption of an aerogel-based coating system under different wetting scenarios
Building and Environment,;Vol. 245(2023)
Journal article
Drying of an aerogel-based coating system in Swedish climates: Field tests and simulations
Journal of Building Engineering,;Vol. 84(2024)
Journal article
Despite their potential, ACMs remain relatively unexplored in Scandinavian countries like Sweden. To ensure their successful adoption, we must understand how they perform in the local conditions, especially in terms of moisture resilience. However, currently there is a knowledge gap regarding the fundamental properties of ACMs, such as watertightness under rainwater wetting and drying performance at early stages. Closing this gap is essential for developing moisture-safe designs and accurately predicting ACMs' thermal performance in real-world applications.
This thesis aims to contribute towards bridging this knowledge gap and provides insights into the practical applications of ACMs in the Swedish context. The thesis comprises experimental and numerical results obtained from a field test in Sweden, along with a tailor-made small-scale test setup. The latter is developed to evaluate the moisture performance of wall assemblies when subjected to realistic rainwater runoff based on typical wind-driven rain intensities in Swedish climates.
Super insulation render for renovation and new constructions
Swedish Energy Agency (2018-006152), 2019-01-01 -- 2021-12-31.
Super insulation plaster for sustainable renovation
Swedish Energy Agency (P2022-00872), 2022-11-01 -- 2023-12-31.
Subject Categories
Civil Engineering
Other Civil Engineering
Building Technologies
ISBN
978-91-7905-925-5
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5391
Publisher
Chalmers