## 1 Introduction  
The materials of biological origin, used as a replacement for the natural aggregate in cement-based and lime-based composites, can help reduce the construction industry's negative impact on the environment [1]. An example of the aggregate of biological origin is hemp shive, derived from the fragmentation of the igneous core of industrial hemp (_Cannabis sativa_ L). It is a by-product of hemp processing [2]. Because of the porous structure, the hemp shives are light, have good acoustic properties [3, 4], good thermal insulating properties [5, 6], and high ability for carbon dioxide sequestration [7, 8, 9]. The most developed building material based on hemp shives is lime-hemp concrete (LHC). LHC is a lime-hemp composite created by combining the hydraulic and non-hydraulic lime with the aggregate containing mainly hemp shives with a small number of hemp fibres or hemp shives alone. The length of the hemp shive particles is 5-40 mm [10]. LHC has good insulating properties; its thermal transmittance is 0.08 to 0.16 W m\({}^{-1}\) K\({}^{-1}\) for the apparent density at a dry state between 300 and 670 kg/m\({}^{3}\)[11, 12, 13]. However, its LHC strength is low compared to that of the other building materials. The compressive strength of LHC does not exceed 2 MPa [14, 15, 16]. For LHC to achieve the strength of 10 MPa, it requires a very high content of the binder (up to 700 kg/m\({}^{3}\)) or high compaction (compaction ratio up to 4.5) [17]. Hemp concrete (HC) production investigations can be categorised regarding the binder type and share of the hemp shives in the concrete mix. Various binders were used for hemp concrete manufacturing, like ordinary Portland cement (OPC) [18; 19; 20; 21], a combination of lime and cement [20; 21; 22], binders containing zeolite [20], magnesium cement [20], magnesium phosphate cement [23], and the alkali-activated cement binders [24; 25; 26; 27]. The research described in [27] has confirmed that increasing hemp shives content in the concrete mix worsens the compressive strength with the same binder content. Pressing LHC elements allows for the production of insulating boards and hollow bricks that fill walls with a wooden frame or serve as insulation for roofs and ceilings [1; 22]. Due to the low load capacity, the LHC is used only with specially designed load-bearing structures or pillars, most often made of softwood [22]. Using the aggregate of the biological origin in the building materials requires protection against bacteria and fungi. Such protection in LHC is ensured by the lime used as a binder [21]. The antibacterial activity of hemp has many applications. It is used in medicine (e.g., drugs and wound dressings, medical devices, implants, or prostheses made from hemp polymer composites), cosmetics, clothing and textiles, food packaging, and food storage [28; 29]. In recent years, building materials containing antimicrobial additives have aroused great interest among technologists and scientists [30]. With this approach, the reduction of mould and bacteria is achievable. It is worth noting that antimicrobial protection is easily accessible during manufacturing. Due to long-term protection against microorganisms and their metabolites (e.g., mycotoxins), these materials can be helpful in the creation of cleaner indoor environments. The research objective was to obtain hemp concrete with a compressive strength close to the lightweight concrete of LC8/9 class (according to the European Standard EN-206 [31]). To achieve this aim, two binders were used for concrete production: Portland cement and hydrated lime. Based on the literature data, the limit volume of the binder in the composite has been accepted as 50%. The hemp shives, obtained from the Polish variety of industrial hemp, were used as an aggregate with a grain size from 0.5 to 16 mm. Besides the composites' basic mechanical properties, the changes in the thermal and microbiological properties were analysed.