Mechanical, Thermal, and Moisture Buffering Properties of Novel Insulating Hemp-Lime Composite Building Materials

Abstract

Hempcrete is a sustainable biocomposite that can reduce buildings’ embodied energy while improving energy performance and indoor environmental quality. This research aims to develop novel insulating hemp-lime composites using innovative binder mixes made of recycled and low-embodied energy pozzolans. The characterization of composites’ mechanical and hygrothermal properties includes measuring compressive strength, splitting tensile strength, thermal conductivity, specific heat capacity, and moisture buffer capacities. This study also investigates the impact of sample densities and water content on compressive strength at different ages. The findings suggest that mixes with a 1:1 binder to hemp ratio and 300−400 kg/m3 density have hygrothermal and mechanical properties suitable for insulating infill wall applications. Hence, compressive strengths, thermal conductivity, and specific heat capacity values range from 0.09 to 0.57 MPa, 0.087 to 0.10 W/m K, and 1250 to 1557 J/kg K, respectively. The average moisture buffer value for all hempcrete samples of 2.78 (gm/m2 RH%) indicates excellent moisture buffering capacity. Recycled crushed brick pozzolan can enhance the hygrothermal performance of the hemp-lime composites. Thus, samples with 10% crushed brick have the lowest thermal conductivity considering their density and the highest moisture buffer capacity. The new formulas of hydrated lime and crushed brick have mechanical properties comparable to metakaolin and hydraulic lime formulas.

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Assessment of Mechanical and Thermal Properties of Hemp-Lime Mortar

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“…Johra et al [14] constructed an indoor hygrothermal environment model which is composed of an indoor hygrothermal balance equation and a coupled faç ade hygrothermal transfer model, they tested the change law of indoor hygrothermal environment under different weather conditions and applied actual cases to analyze the impact of different building envelop structures on the cooling load of air conditioners, the heating load of heaters, and the indoor hygrothermal environment; then they proposed a set of indoor hygrothermal environment regulation methods that suit the load characteristics of zero energy consumption buildings. The coupled hygrothermal transfer of external facade materials have a great impact on the energy consumption of air conditioners and the indoor hygrothermal environment [15][16][17][18]. Mukai et al [19] researched the theories of coupled hygrothermal transfer in buildings, they built an experimental platform to measure the temperature, relative humidity, and indoor and outdoor temperatures and compared the measured results with the simulation values; at the same time, they also compared the indoor temperature, relative humidity, heat flow, and humidity flow of the inner layer materials and insulation materials of buildings under natural conditions, and used the WUFI-Plus software to simulate energy consumption with humidity transfer time taken into consideration.…”