Durability of water-based silane/siloxane treated coal char brick subjected to weatherometer exposure

Abstract

Coal char-based bricks have recently gained attention for their innovative use of coal-derived materials, along with their high compressive strength and lightweight properties. Ensuring their durability in outdoor applications requires evaluating their resistance to environmental factors such as sunlight, moisture, and temperature fluctuations over time. The weatherometer test, an accelerated aging method, is commonly used for this purpose. However, currently, there is a lack of research on the effect of weatherometer exposure on the properties of char bricks. This study evaluates char bricks at various intervals of weatherometer exposure, analyzing changes in their physical, mechanical, mineralogical, and microstructural properties. To improve the water repellency of char brick, a silane/siloxane concrete sealer is applied. The effect of different treatment methods (i.e., untreated, spray-treated, and vacuum-treated) on char bricks subjected to weatherometer exposure is also investigated. It is found that after 3750 h of weatherometer exposure, all char bricks with relatively sharp edges and smooth surfaces exhibit high compressive strength (39.4–46.9 MPa), significantly exceeding the ASTM standard C62 Grade SW brick (20.7 MPa). All treated char bricks retain hydrophobicity up to 3000 h of weatherometer exposure but become hydrophilic at 3750 h. Although surface cracks and efflorescence appear in vacuum-treated bricks, they show higher water contact angles at the same exposure time interval, compared to spray-treated bricks. This study would provide practical insights for engineering applications of char bricks, especially in regions with extreme or fluctuating weather conditions, where the durability of building material is crucial.