Comparative Study on Rheological Properties of Coir Fiber and Coir Powder Modified Bitumen

Rheology is a fundamental interdisciplinary science which deals with the study of the internal response of materials by the application of stresses. Bitumen rheology can be defined as the fundamental measurements associated with the flow and deformation characteristics of bitumen. The modified bitumen or asphalt reduces the amount and severity of pavement distresses and at the same time increases the service life of the pavement. The significance of this study is that the modifier used for binder modification is coir powder of size less than 75 μ and coir fiber of length 5 mm. Coir powder is used as a modifier because coir fiber takes advantage of a waste by-product, at the same time reducing environmental pollution. In this study, an attempt has been made to compare the rheological properties of coir fiber and coir powder modified VG30 bitumen. Here the coir powder and fiber in varying percentages of 0.4, 0.6, 0.8, 1 and 1.2% were mixed uniformly with VG30 bitumen. The bitumen–coir powder blend is prepared by mixing the two materials in a bitumen blending oven at 200 rpm, for a period of 30 min, and at a temperature of 145 °C. The mixing temperature is determined as per one of the methods suggested by Asphalt Pavement Environmental Council EC 101(2000), an industry guidance document. Based on EC 101(2000), the mixing temperature obtained is 145 °C. For determining the rutting susceptibility, the range of temperature variation corresponding to IS 15462:2004 was selected keeping angular frequency 10 rad/s and shear strain 10% constant. As per SHRP, when the value of G*/sinδ < 1, the pavement become susceptible to rutting failure. The results showed that the coir powder modified bitumen can withstand a higher temperature than fiber modified bitumen. The coir powder modified bitumen showed better rheological properties through an increase in complex modulus value and decrease in phase angle value.