RHEOLOGY OF BITUMEN WITH DIFFERENT WARM MIX ADDITIVES

Abstract

Increased environmental awareness and strictness in emissions regulations have led to a development of warm mix asphalt (WMA). The potential of using WMA in reducing the energy consumption of hot mix asphalt (HMA) is becoming more and more attractive nowadays. The goals for the WMA are to lower mixing and compacting temperatures by reducing the viscosity of binder, and using the same HMA plants to produce mixes that still meet specifications. The benefits of WMA include reduced emissions, decreased energy (fuel) consumption, reduced asphalt oxidation and early traffic opening. Several technologies of WMA are available today such as Aspha-min, Sasobit, Evotherm and Akzonobil. Viscosity of the binder is used to determine its mixing, laying and compaction temperatures. In the present study Brookfield Viscometer is used for determination of the viscosity of bituminous binders with different combinations of additives at different temperatures ranging from 90°C to 160°C. Four binders VG 30, PMB 40, PMB 70 and CRMB 55 and three additives Sasobit, Evotherm and Akzonobil are used. The results shows that the viscosity of the bituminous binders varies exponentially with the temperature and linearly with respect to the dosage of Warm mix additives and the mixing temperature can be reduced by 20°C to 25°C while laying and compaction temperature can be reduced by 10°C to 15°C by using these additives. In India, the rheological characterization of bituminous binder is based on the properties of such as penetration, softening point, ductility and absolute viscosity, which are inadequate to characterize the bitumen. The dynamic shear rheometer (DSR) is used for determination of the rheological properties of bitumen over a wide range of temperature. The changes in rheological properties of VG 30, PMB 40, PMB 70 and CRMB 55grades bitumen modified with different percentage of Sasobit, Evotherm and Akzonobil were studied. The rheological properties of the bituminous binders in terms of their complex modulus (G*), stiffness and overall resistance todeformation , storage modulus (G'), binder viscosity, loss modulus (G"), viscous behavior and phase angle, visco elastic behavior were measured by using Rheometer. Testing was performed at temperatures ranging from 0.1°C to 100°C at a frequency of 10 rad/sec. The physical properties of bitumen improved with addition of the polymers. The complex modulus of the binders is higher as compared to neat bitumen. The phase angle values illustrate the improved elastic response of the modified binders as comparative to their respective base bitumen. However, phase angle decrease with increase in percentage of modifier and increases with increase in temperature. The complex modulus increases with increase in percentage of modifier and decreases with increase in temperature. The parameter shear modulus (G*/sin S) is an indicator of stiffness or resistance of binder to deformation under load at specified temperature. Key words :- Warm mix asphalt, Hot mix asphalt, Viscosity, Brookfield viscometer, Sasobit, Evotherm, Akzonobil, VG 30, PMB 40, PMB 70, CRMB 55,Rheometer, Complex modulus, Complex viscosity, Loss modulus, Storage modulus, Phase angle