Modification of Bitumen Properties Using Pine Cone Ash, Micronized Alumina and Silica Coated with Oleic Acid and Stearic Acid

At first, inorganic powders including pine cone ash, micronized silica and alumina were coated with oleic and stearic acid in technical grade solvents including ethanol (96%) and toluene under heat treatment. Then, the different amounts of each coated powders and their mixture were used to modify the bitumen. Different properties of the modified bitumens including penetration rate, softening point, and the results of dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep recovery (MSCR) tests were compared with the pure bitumen sample. The results showed that the penetration rate is increased with increasing of the percentage of the coated additives. In addition, the softening point of the pure bitumen sample has no significant change with addition of the coated powders. This phenomenon is an advantage in the modification of bitumen. The results of DSR test showed that the maximum total shear stress modulus (G*) at three different temperatures is related to the silica sample coated with oleic acid. The results of BBR test showed that the maximum creep hardness at -6 and -12°C is related to 4% silica coated with oleic acid and 2% pine cone ash coated with stearic acid, respectively. The MSCR test indicated that the maximum recovery percentage in a stress of 100 and 3200 Pa was observed for 2% silica coated with stearic acid and 4% pine cone ash coated with stearic acid, respectively