Performance assessment of organic-based synthetic calcium and boric acid modified bitumens

Abstract

This study investigates the modification of bitumen separately with two novel additive materials: Organic-based Calcium Compound (OBCC) and Organic-based Boric Acid Compound (OBBAC). These compounds were synthesized chemically at laboratory conditions. 50/70 penetration grade bitumen was modified with OBCC and OBBAC at the concentrations of 1% (w/w), 2% (w/w), 3% (w/w), 5% (w/w) and 10% (w/w). Conventional (Softening Point, Ductility, Marshall, Nicholson Stripping, Indirect Tension) and Superpave test methods (Rotational Viscosity, Bending Beam Rheometer (BBR), Dynamic Shear Rheometer (DSR)) were performed to determine the effects of the additives on the bitumen and bituminous mixture properties. The proper content of each additive was determined as 3% (w/w) based on the rotational viscosity test results. The viscosity and softening point were decreased and ductility was increased by OBCC and OBBAC. High temperature performances of the modified bitumens provide the same level with original bitumen according to DSR test results. BBR tests have showed that better low temperature cracking resistance was obtained through OBCC and OBBAC modifications. Marshall Stability, stripping resistance and stiffness modulus of the bituminous mixtures were determined to be improved by both of the additives.