Investigation of Correlation between Component and Molecular Structure of Bitumen and Properties of High-Dosage Styrene-Butadiene-Styrene–Modified Bitumen for Waterproof Membrane

Abstract

Abstract In this article, the correlation between components and molecular structures of base bitumen and properties of high-dosage styrene-butadiene-styrene–modified bitumen (HSMB) for waterproof membrane was investigated. Saturates, aromatics, resins, and asphaltenes (SARA components) of eight base bitumens from different crude oils used to prepare HSMB were analyzed by column chromatography, and the molecular structures of these base bitumens were obtained by proton nuclear magnetic resonance, gel permeation chromatography, elemental analysis, and an improved Brown-Ladner calculation method. Softening point and low-temperature flexibility tests were used to estimate the high- and low-temperature performance of HSMBs. The results showed that the highest softening point of the HSMBs was 119.2°C, whereas the lowest was 102.5°C. The best flexibility of HSMB was −24°C, and the worst was −10°C. The softening point of HSMB raised with the increase of the content of saturates and aromatics, aromatic carbon ratio (fA), and condensation index (CI) while decreasing with the increase of H/C. The flexibility of HSMBs was most significantly influenced by the content of saturates, and when the saturate content was 17 %, the flexibility was optimal. However, the flexibility of HSMB was poor when the number average molecular weight (Mn) of bitumen was large. To prepare HSMB with excellent performance, it is recommended that the content of saturates should be between 12 and 17 %, aromatics content should be between 45 and 55 %, resins and asphaltenes content should not be excessive, and fA > 0.25, CI > 0.17, H/C ≤ 1.55.