In this era of industrialization, material selection is primarily based on pricing and the type of facility utilized for manufacturing or processing. Due to the lack of reliable technical information on locally avialable materials, consumers primarily depend on industrialized materials, for which information is readily available [3]. As a result, industrialized materials such as steel continue to dominate the construction industry. To mitigate this issue, the industry has focused on green and sustainable alternatives. Palmyra, a structural timber found abundantly in the northern region of Sri Lanka, has been identified as a potential candidate for reinforcing concrete elements. In this study, the feasibility of utilizing palmyra strips as a reinforcement material was examined by replacing steel reinforcement with palmyra strips fully and partially. The mechanical properties of palmyra wood were initially evaluated through flexural, tensile, and compressive tests[2]. Subsequently, beams reinforced with steel reinforcement and palmyra strips were cast and subjected to a four-point bending test according to ASTM C78[1].

In the case of the control specimen, a top and bottom of 8mm diameter steel were utilized. For the replacements, square wooden strips of 25mm x 25mm cross-sectional size were used based on the characteristic tensile capacity of palmyra wood obtained through the initial experimental investigation. The selection of the appropriate area for the Palmyra wood strip was based on maintaining an area-to-strength ratio of one. As such, for a full replacement, both the top and bottom reinforcements were made of 25mm palmyra strips, while for a partial replacement, the top reinforcement was made of 25mm palmyra wood, and the bottom reinforcement was made of 8mm diameter steel. Three specimens were cast for each type of beam and water cured for 7 days before being left to cure in the air for an additional 21 days. Then the beams were subjected to a four-point bending test, with continuous loading applied to each specimen at a constant rate of 0.04 MPa/s until failure occurred. Midpoint deflection was measured using a dial gauge over time and relevant loads were recorded, and consequently, stress-strain curves were developed. Crack patterns were also recorded for each specimen. The test results indicated that the control specimen reinforced with steel exhibited the average maximum strength of 12.83 MPa, while full and partial replacements of steel with palmyra strips exhibited strengths of 11.76 MPa and 12.46 MPa, respectively. The full replacement type exhibited the maximum strain of 0.019%, the steel reinforcement showed the minimum value of 0.014%, while partial replacement showed an average strain of 0.020%. Strain energy values at the maximum stress point were obtained as 0.067, 0.102, and 0.087 kJ/m³ for the control,  partially replaced, and fully replaced beams respectively. Cracking always initiated from the bottom and showed shear failures. The results of the study suggest that partial replacement of the top reinforcement, and full replacement can be adopted in lightly loaded concrete beams with marginal changes.