UTILIZATION OF COIR FIBERS TO IMPROVE THE BEARING CAPACITY AND TENSILE STRENGTH OF EXPANSIVE CLAY

Reinforcement is a method to improve soils with low bearing capacity and tensile strength. Coconut coir waste is an alternative reinforcement material because coir fibers have high tensile strength, high shear strength, and high resistance to compressive stress. This study performed the soaked and unsoaked California Bearing Ratio (CBR), the swelling, and the indirect tensile strength tests focusing on expansive clay reinforced with coir fibers. The content of coir fibers was between 0.00% to 1.25% by weight of the mixture. The fibers were cut into 30 mm to 50 mm long pieces, then mixed randomly into the soil in various content. The mixture was compacted based on the maximum dry density and the optimum moisture content of the clay. The test results revealed that the soaked and unsoaked CBR reached the maximum values at 1% fiber content. Originally of poor quality, the soil condition became quite good after being reinforced with an optimum fiber content of 1%. All specimens swelled when soaked. The swelling values tended to increase with the addition of coir fibers. Hence, the expansive clay must be chemically stabilized to reduce swelling. The tensile strength reached the maximum value at 0.6% fiber content.