Physical and microstructural properties of insulating hempcrete mixes and their impact as infill system on the foundations due to increase in dead load
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Date
2020-03
Authors
Khan, Mohammad Amil
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Abstract
Hempcrete is a particularly promising lightweight, porous, and breathable biocomposite material that has the potential to significantly reduce the embodied energy related to the construction of buildings while improving their indoor air quality. However, hempcrete’s properties and performance depend on various parameters such as ingredient amounts, binder type, hurd characteristics (e.g., particle size and porosity), and the amount of water. Therefore, there is a great need for research that will focus on the development and production of hempcrete mixes and materials using local, Canadian resources. This research study characterizes the physical, microstructural, and mechanical properties of nine hempcrete mixes developed using lime and eco-friendly pozzolans such as metakaolin, crushed brick, and natural hydraulic lime in varying relative proportions. Furthermore, it compares three different types of hempcrete walls against the conventionally insulated walls of a single-story house located in Winnipeg, using S-Timber 2019 software. The microstructure analysis of hurd particles showed their porous nature. The dry densities of all design mix range from 294.59 kg/m3 to 399.68 kg/m3, with the majority (⁓73%) falling between 320 kg/m3 and 370 kg/m3. The average compression strength of the developed samples ranged between 0.11 MPa and 0.51 MPa, whereas the average splitting tensile strength ranged between 0.010 MPa and 0.0348 MPa. The results show a positive correlation between the hempcrete’s mechanical properties and density, mainly, in the case of compressive strength. The microstructure analysis of all the design mixes exhibit adequate adhesion at the interface, and present high carbonation with some hydrates. The main findings suggest that locally sourced metakaolin and crushed brick are excellent alternatives to the expensive, imported hydraulic lime. The modeling analysis indicates an increase in the dead loads and foundation sizes due to hempcrete infill compared to the base case. The results also indicate that the best option for a house considering the increase in dead loads and foundation sizes, is a wall case that meets the energy code through the thinner wall composed of 100 mm of mineral wool and 140 mm of hempcrete.
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Keywords
Hempcrete, Mechanical properties, Microstructure, Dead loads, Foundation sizes, Physical properties