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

Yaser Abdellatef,Mehdi Iftekharul Alam,Mohammad Amil Khan,Miroslava Kavgic,Asif Khan

doi:10.3390/ma13215000

Yaser Abdellatef, Mehdi Iftekharul Alam + Show 3 more

Open Access

https://doi.org/10.3390/ma13215000

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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.

Highlights

Hempcrete, made of the hemp plant’s inner woody core mixed with a lime-based binder, is a promising lightweight biocomposite material that holds the potential to considerably improve energy and indoor environmental performance and sustainability of buildings [1,2]
As shown for the high moisture initial condition, the moisture buffer value (MBV) for the release phase starts with a higher value (2.4−2.6 gm/m2 relative humidity (RH)%) than that of the uptake phase (1.3−1.7 gm/m2 RH%)
For the low moisture initial condition case, the MBV for the uptake phase starts with a higher value (3−4 gm/m2 RH%) than that of the release phase (2−2.8 gm/m2 RH%)

Summary

Introduction

Made of the hemp plant’s inner woody core mixed with a lime-based binder, is a promising lightweight biocomposite material that holds the potential to considerably improve energy and indoor environmental performance and sustainability of buildings [1,2]. The utilization of hempcrete in the construction industry remains low, mainly due to the high variability of hemp-lime composites and lack of formulas that use widely available and locally sourced ingredients. The use of innovative binders and a better understanding of the material’s performance are indispensable steps for addressing hempcrete underutilization. An increase in the proportion of porous hemp hurd in hempcrete mixture reduced the dry density and the thermal conductivity [6,8]. There was a positive correlation between density and thermal conductivity of the hempcrete [9,10]

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