Asphalt binder is a complex compound comprising a diverse and intricate range of hydrocarbons which makes it difficult to accurately ascertain its chemical structure. This study aimed to analyze the chemical composition of asphalt binder and establish an accurate molecular structure model of unaged asphalt binder fractions. An unaged asphalt binder was separated into four fractions based on their polarities, referred to as saturates, aromatics, resins and asphaltenes (SARA fractionation). A combination of results from analytical techniques including Fourier transform infrared spectrometer, 1H-Nuclear magnetic resonance, Gel permeation chromatography and Elemental analysis was used to analyze the chemical composition of the different fractions of asphalt binder. The parameters relating to the average molecular structure were calculated to construct an average molecular structure using an improved Brown-Ladner method. The results show that the improved Brown-Ladner method can be used to obtain the effective average molecular structure of the SARA fractions. This study also provides, perhaps for the first time, model molecular structures for each polar fraction using real asphalt binder samples that can be used in future studies on molecular modeling and simulation. The average molecular structure of saturates was seen to be relatively simple. However, there were many unsaturated aromatic compounds and polar functional groups in resins and asphaltenes. The presence of carbonyl groups in resins indicated that it could be more easily aged than other fractions. The average molecular weight increased from several hundred to nearly two thousand with an increase in polarity of the fraction (saturates, aromatics, resins, and asphaltenes). Similarly, the aromatic carbon ratio increased from 0.28 to 0.52, and the cycloalkane carbon decreased from 0.29 to 0.08 with an increase in polarity.

沥青结合料是一种复杂的化合物，包含多种复杂的碳氢化合物，因此很难准确确定其化学结构。本研究旨在分析沥青结合料的化学成分，并建立准确的未老化沥青结合料组分的分子结构模型。未老化的沥青粘合剂根据其极性分为四个部分，称为饱和物、芳烃、树脂和沥青质（SARA 分馏）。结合傅里叶变换红外光谱仪、1H-核磁共振、凝胶渗透色谱和元素分析等分析技术的结果，分析了沥青结合料不同组分的化学成分。使用改进的布朗-拉德纳方法计算与平均分子结构相关的参数以构建平均分子结构。结果表明，改进的Brown-Ladner方法可用于获得SARA馏分的有效平均分子结构。这项研究还可能首次提供了使用真实沥青粘合剂样品的每个极性部分的分子结构模型，这些样品可用于未来的分子建模和模拟研究。饱和物的平均分子结构被认为是相对简单的。然而，树脂和沥青质中含有许多不饱和芳香族化合物和极性官能团。树脂中羰基的存在表明它比其他馏分更容易老化。随着馏分（饱和物、芳烃、树脂和沥青质）极性的增加，平均分子量从几百增加到近两千。同样，芳碳比从 0.28 增加到 0.52，环烷烃碳比随着极性的增加从 0.29 减少到 0.08。