Experimental investigations on carbon black in bituminous concrete mixes for road works

Abstract

This critique reports the laboratory investigations performed to evaluate the possibility of using carbon black as a modifier on VG 30 grade bitumen and bituminous concrete mixes to obtain improved mix characteristics. The influence of carbon black on physical, rheological, rutting and fatigue parameters, Marshall and workability properties at various dosages was investigated. To investigate the physical characteristics of modified bitumen, tests such as penetration, softening point, viscosity, separation, and elastic recovery were carried out. Rheological test was conducted to characterize the carbon black modified bitumen, using Dynamic Shear Rheometer (DSR) as per ASTMD7175-08 (2004) in terms of phase angle and complex modulus, hence rutting and fatigue parameters were determined.The mid-point gradation at 30% combined index was used to make the grade-I bituminous concrete mixes in accordance to MoRTH guidelines. The specimens underwent the Marshall Stability test in accordance to ASTM D 1559. The prepared specimens were subjected to conventional Marshall Stability test. Workability of bituminous mix was assessed in terms of torque value, which was in turn related to viscosity of bitumen and aggregate shape factors.Test results showed that carbon black is a potential material that can be used as a modifier in improving the bitumen properties. The test results of DSR showed that carbon black enhanced rutting and fatigue resistance of the bituminous mixes at wide range of temperatures compared to plain bitumen. The Marshall Stability test has resulted in better properties for bituminous mixes at optimum bitumen content using carbon black. Thus, the study offers encouraging findings that support the exploit of carbon black as modifier in bitumen. The study can prove to be a step closer towards global bitumen sustainability as well as achieve improved mix properties resulting in enhanced performance.