It would be beneficial to establish connections between the agricultural sector and the building industry in order to design housing that is both sustainable and cheap in the future. Building can only be sustainable if it employs the utilization of renewable resources or materials reclaimed from construction debris¹. In the current article, we looked at hemp's (Cannabis sativa) potential as a construction material when combined with hydraulic lime. Hemp is a rapid-growing evergreen perennial plant that may reach a height of 1.5 m to 4 m when cultivated². About 40% of all energy consumed and 36% emissions of co₂ are caused by the built environment³. Consequently, it is crucial to create carbon-negative, environmentally friendly building materials with minimal embodied energy to substitute cement-based technologies. Concrete made from hemp and lime is referred to as hemp–limecrete. The binder in this concrete is lime In the 1980s and early 1990s in France, it replaced daub and wattle to lighten Portland cement (PC) concrete used to restore historic buildings. Since then, hundreds of buildings throughout Europe have been built using or retrofitted with this ecologically friendly material.

The carbon negative nature of the lime concrete is one of its most remarkable eco-benefits. When lime is manufactured, carbon dioxide (CO₂) is released into the atmosphere; however, this is balanced out by the hemp crop's which has the ability to store carbon. Hemp takes in carbon dioxide (CO₂) as it grows, and this carbon is then incorporated into the plant's structure. As a result, the carbon does not escape from the walls made of hemp and lime. According to the findings of Boutin et al. (2006), the production of 1 m² of hemp–lime wall with a thickness of 260 mm takes between 370 and 394 megajoules of energy and absorbs between 14 and 35 kg of carbon dioxide over the course of its lifetime⁴. In addition to having a strong reputation for being environmentally friendly nature, hemp limecrete also have a good performance on thermal conductivity. In addition to its eco-friendliness, hemp limecretes also have great insulating properties due to their high thermal capacity, medium density, and low thermal conductivity. The purpose of this study assesses the impact of the binder on the durability and mechanical strength (biodeterioration, salt exposure, and freeze–thaw resistance) of hemp limecrete. Hemp limecrete is made using hydraulic lime to accelerate the setting and hardening processes.

Since the hemp aggregate is capable of absorbing a significant amount of water i.e., in 24 h it can absorb 325% water of its own weight⁵, which has the potential to inhibit hydration, several of the concretes that were studied included a water retainer⁶. Hemp fibre is a excellent reinforcing material due to its high tensile strength and tolerance to alkaline environments, according to Li et al.⁷. This makes hemp fibre an ideal material for usage in reinforcing materials. When combined with a cementitious binder, hemp creates a building material that is distinct from conventional concrete in terms of its mechanical, thermal, and acoustic properties. This is because hemp fiber have a low density and a high porosity, meaning that there are a lot of spaces between the fiber. Because it has a superior capabilities on acoustic insulation, lower thermal conductivity and lower density, so it is be beneficial to employ in building^7–9. Lime–hemp concrete (LHC) is a construction material that consists of hemp fiber, hydraulic lime, hydrated lime, water, and admixtures and may be used in conjunction with a load-bearing timber framework to create walls, etc. Its composition determines whether or not it may be utilized in floors or roofs¹⁰. These days, you can get a wide range of hemp and lime goods from a number of European firms that may be used to make an LHC. In addition to being able to support weight, a good wall should be able to meet the requirements for these other functions as well: insulation, soundproofing, airtightness, fireproofing, and protection against moisture. Traditional brick or wooden walls consist of many levels, each of which serves one or more of the aforementioned purposes. With the exception of a load-bearing hardwood structure and lime rendering, LHC walls don't need any other supplementary construction materials to operate properly¹¹.

Hemp concrete is often used in conjunction with a load-bearing structure since it is not a load-bearing material individually. In spite of this, its mechanical strength is significant since it is the most often determined characteristic which permits comparison between the various binders. Due to its inherent weakness while wet, hemp concrete requires rapid development of its compressive strength (which could be greater than twice as substantial as its dry state). Compressive strengths for blends with a 2:1 ratio of (hemp by weight to binder) may vary anywhere from 0.12 to 0.2 MPa^9,11–15, with the majority of the variance coming from factors such as density, binder type, and age. Previous studies^16–18 have established that flexural strength is between 0.06 and 1.2 MPa, despite the fact that flexural strength is low overall. According to Elfordy et al.¹⁹ the disorderly organization and the hemp particles ductility nature are responsible for the poor strength of the hemp concrete. According to Nguyen, the concrete has a lesser compressive strength in comparison to other lightweight concretes¹⁷ because of the large porosity of the shiv.

There is a difference of view concerning the impact that the hydraulicity of the binder has in determining the strength of the concrete. It was discovered by Hirst et al. (2010) that the strength may not rise for the strength of the binder¹⁴. Nguyen (2010) claims that stronger binders increase strength if the hemp's capacity to absorb water does not limit its hydraulicity¹⁷. Murphy et al. 2010 found that concretes prepared using a hydraulic industrial binder had greater final flexural and compressive strengths than those made using lime, and that strength development relied on the binder's hydraulicity¹³. Additionally, De Bruijn et al. (2009) demonstrated that cement-rich binders may achieve greater compressive strengths²¹. There hasn't been a lot of investigation on how long hemp concrete will last. Lime, on the other hand, has been employed in construction projects since ancient times, and it is often combined with organic materials like wood (beams and lath), hair or straw. These kinds of buildings have shown to be very long-lasting. Homes constructed from hemp–lime has been in France for more than 20 years without any major weathering or durability issues being documented²². As a result of the lime's high alkalinity, the material has a reputation for being resilient to insects and mould, which could be supported by empirical evidence²³.

Carbonation, alkali-aggregate interaction, chloride penetration, sulphate attack and freeze–thaw cycle are the primary issues in concrete durability. Biodeterioration, salt crystallization and freeze–thaw action were believed to be among the most potential instigators for the hemp concrete because of the absence of steel reinforcement, silica-based aggregate or tri-calcium aluminate. A mortar's freeze and thaw resistance mainly hinge on its pore structure's ability to endure strain from water freezing. According to a study of resistance to the freeze–thaw of lime and cement mortars conducted by Botas et al. the authors found that resistance to freeze–thaw reduced when lime hydraulicity is improved²⁴, most likely as a result of the mortar's micropores. In addition, it was found that the air entraining agents had no effect on the mortar's resistance to freeze:thaw, while increasing its overall permeability. The influence of the hemp limecrete mortars' stronger mechanical strength overcomes the pore structural features, which indicates how they showed a greater resistance. A "wall combination" hemp limecrete was able to withstand severe freeze–thaw of 20 cycles, but it was discovered that limes that were either too hydraulic or inappropriate changed after just two cycles²⁵. Additional study has shown that the compressive strength of concrete does not reduce even after being subjected to 25 freeze–thaw cycles²⁶. Ilija Bošković²⁷ study employs life cycle assessment to analyze greenhouse gas emissions from hemp–lime concrete. It reveals that variables such as hemp shiv sequestration, binder carbonation, and transport distances significantly impact emissions. Optimistic scenarios showed a negative global warming potential, while pessimistic ones were positive. The study also emphasizes the influence of hemp shiv degradability on emissions, highlighting the material's environmental sensitivity. Moletti et al.²⁸ study examines the hygrothermal properties of hemp–lime, a sustainable building material made from lime-based binders and hemp shives. By conducting experiments over three years and using numerical simulations, the research demonstrates that the material's performance improves with maturation, primarily attributed to binder carbonation and reduced initial moisture content, as confirmed by XRD and TG-DTG analyses. Rotem et al.²⁹ study evaluates the environmental impact of lime hemp concrete (LHC) with unfired binders as a lime replacement compared to standard LHC and conventional building materials. In an arid region, it reveals that LHC with unfired binders can reduce energy consumption and CO₂ emissions by up to 90%, making it a highly sustainable construction option.

Several studies have been published on how hemp shive affects material qualities, was previously stated. Although this information is useful, it is incomplete since the studies cited above focus on a subset of the features of composites and a subset of the proportions of fiber based on cement. The impact of shive size on the composite's other characteristics, like porosity, density, microstructural analysis and thermal heat conductivity, has to be investigated further for lime hemp limecrete. In the present investigation, we examined these consequences for hemp limecrete. Basic features of the hemp limecrete were also examined, including compressive strength, flexural, thermal conductivity and water absorption to see how much impact fiber had on these characteristics of the hemp specimens.

This study introduces groundbreaking innovations in construction materials and sustainable building. It introduces hemp limecrete as an eco-friendly construction material, offering a sustainable alternative to traditional concrete. The study precisely identifies the optimal combination of fiber content (4%) and length (1 cm) for hemp limecrete, providing essential guidelines for effective usage. The manuscript employs a holistic approach by analyzing mechanical properties, thermal conductivity, and microstructure through SEM and EDS. Emphasizing sustainability, it highlights hemp limecrete as a promising eco-friendly material, aligning with global trends in sustainable construction. These innovations collectively position hemp limecrete as a revolutionary, environmentally conscious choice for the construction industry.