Exploring the Dual Nature of Olive Husk: Fiber/Aggregate in Lightweight Bio-Concrete for Enhanced Hygrothermal, Mechanical, and Microstructural Properties

Belhadad, H ORCID: 0009-0006-9794-1342, Bellel, N ORCID: 0000-0002-2825-7559 and Brás, A ORCID: 0000-0002-6292-2073 (2025) Exploring the Dual Nature of Olive Husk: Fiber/Aggregate in Lightweight Bio-Concrete for Enhanced Hygrothermal, Mechanical, and Microstructural Properties. Buildings, 15 (11). ISSN 2075-5309

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Abstract

This study investigates the potential of thermally treated olive husk (OH)—a heterogeneous agro-industrial by-product comprising olive stones, pulp, and fibrous residues—as a multifunctional component in lightweight bio-concrete. Uniquely, this work harnesses the intrinsic dual nature of OH as both a fibrous reinforcement and a porous aggregate, without further fractionation, to evaluate its influence on the hygrothermal and mechanical behavior of cementitious composites. While prior studies have often focused selectively on thermal conductivity, this work provides a comprehensive assessment of all major thermal parameters; including diffusivity, effusivity, and specific heat capacity; offering deeper insights into the full thermal behavior of bio-based concretes. OH was incorporated at 0%, 10%, and 20% by weight, and the resulting concretes were subjected to a comprehensive characterization of their thermal, hygric, mechanical, and microstructural properties. Thermal performance metrics included conductivity, specific heat capacity, diffusivity, effusivity, time lag, and predicted energy savings. Hygric behavior was assessed through the moisture buffering value (MBV), while density, porosity, and mechanical strengths were also evaluated. At 20% OH content, thermal conductivity decreased to 0.405 W/m·K (a 72% reduction), thermal diffusivity dropped by 87%, and thermal effusivity reached 554 W·s0.5/m2·K, collectively enhancing thermal inertia and increasing the time lag by 77% (to 2.32 h). MBVs improved to 2.18 g/m2·%RH, rated as “Excellent” for indoor moisture regulation. Despite the higher porosity, the bio-concrete maintained adequate mechanical integrity, with compressive and flexural strengths of 11.68 MPa and 3.58 MPa, respectively, attributed to the crack-bridging action of the fibrous inclusions. Microstructural analysis (SEM/XRD) revealed improved paste continuity and denser C–S–H formation, attributed to enhanced matrix compatibility following oil removal via thermal pre-treatment. These findings demonstrate the viability of OH as a new bio-based, multifunctional additive for fabricating thermally efficient, hygroscopically active, and structurally sound concretes suitable for sustainable construction.

Item Type:	Article
Uncontrolled Keywords:	olive husk; bioconcrete; valorization; hygro; thermal performance; 4005 Civil Engineering; 40 Engineering; 33 Built Environment and Design; 3302 Building; 7 Affordable and Clean Energy; 1201 Architecture; 1202 Building; 1203 Design Practice and Management; 3301 Architecture; 3302 Building; 4005 Civil engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Divisions:	Civil Engineering and Built Environment
Publisher:	MDPI
Date of acceptance:	29 May 2025
Date of first compliant Open Access:	22 May 2026
Date Deposited:	22 May 2026 13:58
Last Modified:	22 May 2026 13:58
DOI or ID number:	10.3390/buildings15111950
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28622

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