Thermal and mechanical characterization of adobes bio-sourced with Pennisetum setaceum fibers and an application for modern buildings

Abstract

The purpose of this paper is twofold: to propose a sustainable eco-construction practice using highly biosourced earth blocks in contemporary buildings, taking into account their poor mechanical properties; and to assess the effect of incorporating Pennisetum Setaceum (PS) fibers on the thermomechanical performance of adobes, where earth was biosourced with PS fibers at weight percentages of 0, 2, 4, 6, and 8%. Firstly, raw materials’ geotechnical, mineralogical, chemical and microstructural characteristics were identified. Afterward, the thermal and mechanical properties of produced PS-adobes were studied by hot disk method, uniaxial compressive and tensile splitting strength tests. The impact of fiber content on the durability of adobes was also discussed using capillary water absorption test. Experiments reveal that the strength performance of adobes decreases with increasing fiber content while the cohesiveness of mixtures improves. The cohesion improvement was confirmed via the water absorption test. Adding 8%wt of PS fibers can improve the thermal insulation and the heat capacity of adobe by 56.7% and 17.9%, respectively. Laboratory testing was followed by CFD analysis to underline the efficacy of a hybrid bio-based wall in which a PS-adobe layer is incorporated into a double hollow brick wall. The numerical results show that a 10-h time lag was achieved with biosourced earth layer thickness of 90 mm. As a result, high bio-content adobes may be employed as a green thermal mass element in modern buildings with a contribution to thermal insulation.