Abstract
To decrease the environmental impact of the construction industry, energy-efficient insulation materials with low embodied production energy are needed. Lime-hemp concrete is traditionally recognized as such a material; however, the drawbacks of this type of material are associated with low strength gain, high initial moisture content, and limited application. Therefore, this review article discusses alternatives to lime-hemp concrete that would achieve similar thermal properties with an equivalent or lower environmental impact. Binders such as gypsum, geopolymers, and starch are proposed as alternatives, due to their performance and low environmental impact, and available research is summarized and discussed in this paper. The summarized results show that low-density thermal insulation bio-composites with a density of 200–400 kg/m3 and thermal conductivity (λ) of 0.06–0.09 W/(m × K) can be obtained with gypsum and geopolymer binders. However, by using a starch binder it is possible to produce ecological building materials with a density of approximately 100 kg/m3 and thermal conductivity (λ) as low as 0.04 W/(m × K). In addition, a preliminary life cycle assessment was carried out to evaluate the environmental impact of reviewed bio-composites. The results indicate that such bio-composites have a low environmental impact, similar to lime-hemp concrete.
Highlights
Energy consumption in the building maintenance and construction sector constitutes 40% of the total energy consumption in the European Union (EU)
It is calculated that by creating sustainable building operation and construction processes in EU countries, the total energy consumption could be decreased by 40%, total CO2 greenhouse gas emissions could be decreased by 35%, and construction material consumption could be decreased by 50% [3]
As lower amounts of binder can be used to achieve the same compressive strength compared with lime hemp concrete, bio-composites with magnesium binders show a low environmental impact [12]
Summary
Energy consumption in the building maintenance and construction sector constitutes 40% of the total energy consumption in the European Union (EU). One material that can be used to replace lime-based binders in lime hemp concrete and increase its mechanical properties is the magnesium-based binder, known as magnesium oxychloride cement This binder is commonly used in combination with various fillers of biological origin [18], such as wood chips, rapeseed straws, and other agricultural by-products. As lower amounts of binder can be used to achieve the same compressive strength compared with lime hemp concrete, bio-composites with magnesium binders show a low environmental impact [12]. This study considers three alternative binders that can be used in conjunction with a bio-based filler to form bio-composites for thermal insulation and envelope structures These binders are gypsum, geopolymers, and starch. A preliminary LCA will be carried out to compare these alternative binders with the existing bio-based material binders, as information available on this subject is somewhat limited
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