Strength characteristics of SBS modified asphalt mixes with various aggregates

In recent years, many authors have researched polymer-modified bituminous (PMB) mixes and tried to better understand the effect of these modifiers on the strength characteristics of hot mix asphalt mixes. The objective of this study is to determine the effect of bitumen modification with varying percentage of Styrene bitudiene styrene (SBS 3%, 5% and 7%) for preparing the hot mix asphalt (HMA) containing various aggregates (marble, granite and quartzite) and compare the results with mixes prepared with neat VG 30 HMA. The selection of aggregates has been made on the basis of their acidic and basic nature depending upon the amount of silica oxide and calcium carbonate present in them. Dynamic shear rheometer (DSR) was used to determine the mixing and compacting temperatures of modified bitumen and performance grade based on G*/Sin δ value. The physical and mechanical properties of SBS modified bitumen and neat bitumen aggregates mixes are evaluated. Retained Marshall Stability (RMS) test and tensile strength ratio (TSR) tests were carried out to determine the moisture susceptibility and wheel tracking test was performed to compare the results of permanent deformation in samples.The results indicate that there was significant improvement in the strength characteristics, rutting resistance and moisture susceptibility of SBS modified mixes. Aggregates basic in nature i.e. with higher calcium (Ca) content show better bonding with neat bitumen compared to acidic aggregates i.e. aggregates with higher silica (Si) content. But with modified bitumen the percentage improvement in strength and moisture susceptibility is more pronounced in case of siliceous aggregates compared to calcareous aggregates.

► Siliceous aggregates.
► Calcareous aggregates.
► Tensile strength ratio.
► Dynamic shear rheometer.
► Wheel tracking test.
► SBS modified bitumen.