Abstract
This experimental study was focused on the application of a surface-modified hemp- hurds aggregate into composites using an alternative binder of MgO-cement. This paper presents the results of the comparative study of the parameters (chemical and physico-chemical modification, and hardening time) affecting the physical (density, thermal conductivity coefficient and water-absorption behavior) and mechanical properties (compressive strength) of the bio-aggregate-based composite. A test of the parameters of the bio-composite samples showed some differences, which were determined by the chemical and surface properties of the modified filler, and which affected the mechanisms of hardening. The bulk density values of the hemp hurd composites hardened for 28 days place this material in the lightweight category of composites. The values of water absorption and the thermal conductivity coefficient of bio-composites decreased, and the strength parameter increased with an increase in the hardening time. The lower values of compressive strength, water absorption, and thermal conductivity coefficient (except for the ethylenediaminetetraacetic-acid-treated filler) were observed in composites based on fillers chemically treated with NaOH and Ca(OH)2) compared to referential composites (based on original hemp hurds). This is related to changes in the chemical composition of hemp hurds after chemical modification. The composites with ultrasound-treated hemp hurds had the greatest strengths at each hardening time. This is related to pulping the bundles of fibers and forming a larger surface area for bonding in the matrix.
Highlights
Innovative building solutions for conserving non-renewable resources are connected to the development of sustainable building materials based on the use of renewable natural raw material resources
Hemp hurds as a bio-aggregate waste material are a very attractive organic filler for bio-composites with inorganic matrices used in the building industry
The values of compressive strength, thermal conductivity coefficient and water absorption of the hemp composites depend on the chemical composition of the polymer material, modified by the treatment process and hardening time
Summary
Innovative building solutions for conserving non-renewable resources are connected to the development of sustainable building materials based on the use of renewable natural raw material resources. There is a growing interest in the utilization of natural lignocellulosic materials/fibers (usually derived from plants) as organic fillers and/or their reinforcement into lightweight composites called “green” composites/concretes for sustainable constructions. These provide healthy living solutions, thanks to the natural fibers’ ability to regulate humidity inside buildings by absorbing and/or releasing water molecules, depending on the air conditions [1]. Due to their many advantageous properties—e.g., their eco-friendly and economical characteristics [2]—natural fibers or lignocellulosic materials can adequately replace synthetic fibers or wood particles in composites [3,4]. The Buildings 2018, 8, 25; doi:10.3390/buildings8020025 www.mdpi.com/journal/buildings
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