A Study on Changes in Rheological Behaviour of Paving Grade Bitumen using Admixtures

Bitumen ageing is one of the principal factors causing the deterioration of bitumen pavements. It is responsible for deterioration of physical and chemical properties of the bitumen binder. The influence of vehicle traffic on road pavements causes natural aging processes and gradual loss of viscoelastic properties of bitumen binders. In the present study natural organic materials like sugarcane molasses were used in various percentages (0 to 3%) as modifiers in 60/70 grade bitumen. The effect on physical properties in terms of penetration, softening point, weight loss and rheological properties of the bituminous binders in terms of their complex modulus (G*) and G*/Sin δ before and after ageing were measured. Testing was performed at temperatures ranging from 45 °C to 70 °C in increments of 6 °C at a frequency of 10 rad/sec using dynamic shear rheometer (DSR). The results show that after ageing softening point increases and penetration decreases with increasing percentage of modifier. The G*/Sin δ is found to decreases with increase in percentage of modifier after ageing indicating little lesser rutting resistance than neat bitumen but the effect of ageing (hardening) on modified bitumen is less as compared to unmodified bitumen. Hence it improves the service life of pavement. From the point of economical viability, molasses is much cheaper than bitumen.