Kenaf fibres from Burkina Faso valorization in the improvement of durability, thermal properties and fracture behavior of adobes amended with cement

This study aimed to improve the thermal properties and fracture behavior of adobes. A mixture of clay, cement (2 wt%) and kenaf fibres (1.5 and 3 cm long) was used to manufacture the adobes. The physico-chemical and microstructural properties of the kenaf fibres were analysed, revealing they are mainly composed of cellulose (71 wt%), hemicelluloses (20 wt%), lignin (4 wt%) and ash (2 wt%) according to Van Soest’s method. The elaborated adobes were then evaluated. Their mineralogical, microstructural, physical (water absorption by capillary, erodibility by the spray test, thermal conductivity) and mechanical (compressive and flexural strength) properties were measured. The addition of kenaf fibres enhanced the performance of the adobes compared to those stabilized with cement alone. This is attributed to the strong adhesion between the fibres and the clay matrix due to rough surface of fibres which prevents cracks propagation in adobes. It is also attributed to the formation of hydrogen bonds between clay particles, fibres molecules and formed CSH. The presence of fibres confers a ductile behavior to the adobes, with multiple fracture peaks. The first is due to the destruction of the clay-cement matrix, while the others are from the fibres taking up loads after cracking. The presence of cellulose (with insulating character) in fibres and increased macroporosity of adobes significantly reduced thermal conductivity, especially with the 3 cm fibres. An optimal fibres content of 0.2 wt% was identified, with short fibres offering better water properties and long fibres improving mechanical properties. These enhanced adobes are thus suitable for the construction of durable and thermally comfortable buildings in a dried climate. •Additions of kenaf fibres to clayey -cement matrix do not modify its mineralogy.•Adobes amended by cement and reinforced by kenaf fibres have good water resistance.•Additions of kenaf fibres to raw adobes improve their mechanical resistance.•Thermal conductivity of elaborated adobes decreases with kenaf fibres content.•Adobes reinforced with kenaf fibres have elasto-plastic behavior.