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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.

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The share of bio-based materials in modern construction needs to grow more rapidly due to increasingly stringent environmental requirements as a direct result of the climate emergency. This research aims to expand the use of hemp concrete in construction by replacing traditional lime binder with magnesium oxychloride cement, which provides a faster setting and higher strength, opening the door for industrial production. However, the negative feature of this binder is its low water resistance. In this work, the water resistance of magnesium cement was studied, and the possibilities of improving it by adding fly ash, various acids and nano-silica were considered. Nano-silica and citric acid showed the most significant impact, increasing the binder water resistance up to four times, reaching softening coefficient of 0.80 while reducing the compressive strength of the magnesium cement in a dry state by only 2–10%. On the downside, citric and phosphoric acid significantly extended the setting of the binder, delaying it 2–4 times. Regarding board production, prototype samples of hemp magnesium biocomposite demonstrated compressive strength of more than 3.8 MPa in the dry state but only 1.1–1.6 MPa in the wet state. These results did not correlate with binder tests, as the additives did not increase the strength in the wet state.

Abstract. The key focus of the presented research is on sustainable thermal insulation biocomposites which can be made from locally available hemp and lime. The main gains of the use of such material are given, with emphasis on CO 2 reduction. In the first stage samples of an artificial hydraulic lime using three different limes and three hydraulic additives are created and tested, the one with the highest compressive strength (DL60 lime with 40% metakaolin addition) are chosen for further research. In the second stage three different density mixes with the chosen binder are created, optimal hemp/binder ratio is determined, as well as compressive strength and thermal conductivity. Results indicate that created mixtures have good potential as self-bearing thermal insulation material used in low-rise buildings.

The aim of this paper was to study the microbiological stability of bio-based composite building materials, which are made using organic-rich lake sediments (further -sapropel) with lime and magnesium cement as binders and hemp shives as filler. The microbial stability properties of the obtained composite materials were investigated and compared to similar composites. Because of their high organic content, these materials are prone to biodegradation; therefore, they were coated with ALINA LIFE TM organoclay coating, which helps to extend the product life, reducing the rate of biodegradation compared to the biocides used in industry. The effect of the coating on the resistance to decay by the Aspergillus versicolor, Penicillium chrysogenum, Alternaria alternata, Cladosporium herbarum, Chaetomium sp. and Trichoderma asperellum fungi was investigated under different conditions: relative humidity modes of 75% and 99% at 20°C for 45 days and four months. The results indicated that the composites made of sapropel and lime have similar microbial stability properties as lime and magnesium cement binder composite materials. ALINA LIFE TM organoclay coating showed advanced resistance to biodegradation; sapropel-lime composites have shown several good properties that make them suitable to be considered for use in the construction material industry.