Influence of bio-aggregates on the physical and hygrothermal properties of bio-concretes

Abstract

The escalating demand for sustainable and energy-efficient buildings has driven research into innovative construction materials such as bio-concrete. This study assesses the influence of bio-aggregates such as bamboo particles, wood shavings, and rice husk in volume ranging from 40 % to 50 % on bio-concrete's physical and hygrothermal properties. Three bio-concrete types were fabricated: Bamboo Bio-Concrete (BBC), Wood Bio-Concrete (WBC) and Rice Husk Bio-Concrete (RHBC), while maintaining a constant cementitious matrix and varying the bio-aggregate volume. In order to characterize the bio-concretes various analyses and tests were carried out such as scanning electron microscopic (SEM) analyses and Moisture Buffer Value (MBV) tests for bio-aggregates in addition to tests for apparent density, thermal conductivity, capillary water absorption, drying index test, MBV and water vapor permeability (WVP) for the studied bio-concretes. Results reveal that despite diverse microstructural characteristics, all bio-aggregates exhibited MBV values above 3.0 [g/ (m2% RH)], highlighting their role in determining hygrothermal properties. An increase in bio-aggregate volume led to improved hygrothermal properties for bio-concretes (thermal conductivity between 0.19 and 0.25 W/m.K and MBV and WVP in the range of 2.31–3.79 [g/ (m2.% RH)] and 1.11–1.97 × 10−11 [kg/(m.s. Pa)] respectively). Bamboo bio-concrete consistently exhibited higher density values, while rice husk bio-concrete demonstrated superior moisture dynamics and water vapor permeability. Wood bio-concretes exhibit intermediate behavior between bamboo and rice husk bio-concrete. A statistical analysis confirmed these trends. The study underscores bio-concrete's potential for passive hygrothermal regulation in internal building applications, contributing to enhanced energy efficiency and sustainable construction practices.