Evaluation of the physical and thermomechanical properties of compressed earth bricks reinforced with raw and treated Alfa fibers for sustainable rural construction

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The use of local and eco-friendly materials in the construction sector offers a practical pathway to enhance environmental sustainability and energy efficiency. In this context, this study aims to utilize local resources, particularly soil and alfa fibers, to develop a high-performance building material capable of improving the durability of earthen structures in rural and mountainous areas, particularly in the Jbel Saghro–Tinghir region, located in the Drâa-Tafilalet region of Morocco. The main objective is to analyze the physical-mechanical and thermal properties of compressed earth bricks (CEB) reinforced with raw (RAF) and treated alfa fibers. The fibers underwent two types of treatment: an alkaline treatment and a hydrothermal treatment, resulting respectively in alkaline-treated alfa fibers (ATAF) and hydrothermally treated alfa fibers (HTAF). First, a physicochemical characterization of the soil and the fibers, in their raw and treated states, was performed; in addition, geotechnical tests were also conducted on the soil. Then, CEBs reinforced with treated and untreated alfa fibers were produced with fiber percentages ranging from 0 to 2% by weight. The results show that the soil studied meets the minimum requirements for the manufacture of CEBs. Furthermore, the treatments applied to the fibers reduced the proportion of amorphous phases. Tests conducted on the CEBs indicate that the incorporation of alfa fibers, whether raw or treated, significantly improves thermal performance. The addition of 2% RAF, HTAF, and ATAF fibers results in a decrease in thermal conductivity of 37.87%, 36.33%, and 33.80%, respectively, while causing a slight reduction in density. However, the incorporation of fibers is accompanied by a decrease in compressive strength, reaching approximately 31.76% for raw fibers. Nevertheless, the applied treatments effectively mitigate this mechanical loss, with reductions of 24.14% for HTAF and 15.71% for ATAF representing improvements of 10% and 19%, respectively compared to CEB reinforced with 2% RAF. These results show that the use of alfa fibers improves the thermal performance of CEBs. Furthermore, treating the fibers helps limit the loss of mechanical properties.