Experimental evaluation into improving the mechanical properties of adobe using palm fibers

The relatively low compressive strength and negligible tensile resistance aligned with inadequate ductility are considered as major drawbacks of earthen buildings leading to their vulnerability against the gravity and lateral loading including seismic-induced forces. In this study, the possibility of using palm fibers as a natural reinforcement in order to improve the mechanical properties of adobe bricks including compressive strength, tensile strength and ductility are evaluated. To this end, adobe bricks with dimensions of 200 × 200 × 50 mm3 are made by adding palm fibers of 0, 0.25, 0.5, 0.75, and 1% of soil weight. Compressive properties are determined using cubic samples with dimensions of 50 × 50 × 50 mm3 cut from the full-scale adobe bricks while the ductility factor is obtained using the compressive stress-strain curves. To evaluate the tensile strength of specimens, three point flexural tests are conducted on prismatic specimens of 50 × 50 × 200 mm3 cut from the full-scale adobe bricks. The obtained results indicated adding 0.25% palm fibers can add the compressive strength of adobe bricks by 50% and adding 1% palm fiber can twice the tensile strength. Further, based on the analysis of the results obtained from the compressive and three-point bending tests, analytical expressions are proposed to estimate the compressive and tensile strengths of adobe bricks reinforced by palm fiber (from 0 to 1%).