Synergistic effect of fibres on the physical, mechanical, and microstructural properties of aerogel-based thermal insulating renders

There is an increasing demand for highly efficient thermal insulating materials in buildings. This study presents a novel solution incorporating nanomaterials, such as silica aerogel, which can achieve low thermal conductivity values (below 0.030 W m-1 K-1) in renders. A key challenge of using aerogels is their low mechanical strength and high capillary water absorption. Here we describe a novel approach employing fibres which mitigates against some key properties which are decreased as a consequence of using aerogel. The incorporation of aramid (0.50%), sisal (0.10%), and biomass (0.10%) fibres (by total volume) was evaluated experimentally in terms of physical, mechanical, and microstructural properties. A synergistic effect between the fibres and aerogel increased mechanical resistance and a reduction in the capillary water absorption, when compared to the reference render (without fibres), whilst maintaining the low thermal conductivity. However, these properties depended significantly on whether the fibres were synthetic or organic. This study is important as it demonstrates that aerogel-based fibre-enhanced thermal renders can contribute to higher energy efficiency in both new construction and retrofitting. The use of these materials will have a direct positive impact on addressing the climate crisis

Synergistic effect of fibres on the physical, mechanical, and microstructural properties of aerogel-based thermal insulating renders

There is an increasing demand for highly efficient thermal insulating materials in buildings. This study presents a novel solution incorporating nanomaterials, such as silica aerogel, which can achieve low thermal conductivity values (below 0.030 W m-1 K-1) in renders. A key challenge of using aerogels is their low mechanical strength and high capillary water absorption. Here we describe a novel approach employing fibres which mitigates against some key properties which are decreased as a consequence of using aerogel. The incorporation of aramid (0.50%), sisal (0.10%), and biomass (0.10%) fibres (by total volume) was evaluated experimentally in terms of physical, mechanical, and microstructural properties. A synergistic effect between the fibres and aerogel increased mechanical resistance and a reduction in the capillary water absorption, when compared to the reference render (without fibres), whilst maintaining the low thermal conductivity. However, these properties depended significantly on whether the fibres were synthetic or organic. This study is important as it demonstrates that aerogel-based fibre-enhanced thermal renders can contribute to higher energy efficiency in both new construction and retrofitting. The use of these materials will have a direct positive impact on addressing the climate crisis

Evaluation of the Ecotoxicological Potential of Fly Ash and Recycled Concrete Aggregates Use in Concrete

This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from concrete mixes produced with a replacement ratio of Portland cement with 60% of FA and 100% of natural aggregates and produced with 60% of FA and 100% of RA were classified as clearly ecotoxic mainly towards Daphnia magna mobility. Therefore, raw materials with weak evidences of ecotoxicity could lead to the production of concrete products with high ecotoxicological potential. Overall, the results obtained highlight the importance of integrating data from the chemical and ecotoxicological characterization of materials’ eluate samples aiming to assess the possible environmental risk of the construction materials, namely of incorporating non-conventional raw materials in concrete, and contributing to achieve construction sustainability