Effect of Palm Oil Fiber (POF) to Strength Properties and Fracture Energy of Green Concrete

The lack of research on concrete which utilizes Palm Oil Fuel Ash (POFA), Rice Husk Ash (RHA), Recycled Concrete Aggregate (RCA) and Palm Oil Fiber (POF) simultaneously in concrete was globally observed. To meet this gap, a study on green concrete consisting of POFA, RHA and RCA with added untreated POF as binders was conducted. The study focusses on the effect of varying percentages of untreated POF, ranging from 0%, 0.25%, 0.50% and 0.75%, to the strength properties and fracture energy of green concrete. The strength properties of green concrete were investigated by conducting the compression strength test and tensile strength test on forty-eight (48) cubes and cylinders at the curing age of 7 and 28 days. The tests show that the strength of green concrete decreases, as the percentage of POF increases. This was preceded by the establishment of an optimum percentage of POF at 0.25%. The fracture energy of the green concrete was determined by testing twelve numbers of notched beams with dimensions of 100mm x 100mm x 500mm under the three-point bending test. From the three-point bending test, the load-deflection profile for each specimen with different percentages of untreated POF was obtained. Three existing theoretical models, namely Hillerborg, Bazant and CEB models were used to measure the fracture energy of the green concrete with varying percentage of fiber. Results range from 37.94 N/m to 153.81 N/m was observed. The study also successfully established the reliability of Hillerborg’s model to fracture energy when models by Bazant and CEB surprisingly shows a decrease in fracture energy measurements with increase in fiber content.