Micro-morphologies of SBS modifier at mortar transition zone in asphalt mixture with thin sections and fluorescence analysis

Yue Xiao,Xiwen Chang,Xiaoshan Zhang,Mujaheed Yunusa,Boxiang Yan

doi:10.1186/s43065-021-00037-y

Yue Xiao, Xiwen Chang + Show 3 more

Open Access

https://doi.org/10.1186/s43065-021-00037-y

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Abstract

The microstructure control of modified asphalt, especially the micro-dispersion of the SBS modifier in the mortar transition zone, is a critical technology for the performance design of modified asphalt. To characterize the micro-dispersive morphology of SBS modifiers, thin-section preparation techniques that can be used to analyze the original microstructure of the asphalt mixture were proposed and introduced in this study. Flexible resin is filled into the mixture at vacuum conditions to ensure accepted sample conditions for preparing thin sections of asphalt mixture. The morphology parameters, including SBS area ratio, box dimension, SBS average particle area and its coefficient of variation, area-weighted average axis ratio, and coefficient of variation, were plotted from fluorescence images to characterize the micro-morphological distribution of the SBS modifier in detail. Results have shown that the area ratio increased with the increase in SBS content, while the box dimension was reduced and the distribution uniformity of the particles decreased. The superfluous SBS modifier in the binder at a too high adding ratio will decrease the value of the box dimension. Lower modification temperature worsened the SBS modifier in the mixture, resulting in a wide range of particle size, higher axis ratio, and higher area ratio. The micro-morphologies of SBS in the asphalt mixture phase varied a lot from the asphalt binder phase. The additional materials of mineral filler and fine aggregate, together with the other heating processes, will significantly influence the swelling state and particle size of the SBS modifier.

Highlights

Asphalt pavement is laid and compacted from an asphalt mixture, considered a composite material with coarse aggregates, fine aggregates, mineral filler, asphalt binder, and other additives
SBS micro‐morphologies in mix The influence of modification conditions on SBS micromorphologies in asphalt mixtures was studied with the help of the thin section preparation method and fluorescence image analysis
SBS adding ratio dependency Figure 5 shows the fluorescence microscopy images of the SBS modifier in the asphalt mixtures under blue excitation light. It illustrates that the cross-section of an asphalt mixture with a flat surface can be successfully used in fluorescence microscopy analysis

Summary

Introduction

Asphalt pavement is laid and compacted from an asphalt mixture, considered a composite material with coarse aggregates, fine aggregates, mineral filler, asphalt binder, and other additives. Many innovative modifiers, including fibers [1, 23], polymers [26, 31], and Nano-clay [20], were developed to enhance the performance of asphalt binder. Among these modifications, SBS (Styrene–butadiene–styrene) modified asphalt binder is. The microstructure of modified asphalt binder and the inner structures of a mixture are believed to influence the binder’s performance and its corresponding mixture significantly. Wang et al [24] used digital image processing techniques to quantify aggregate skeleton structure, including orientation, distribution, and contact properties of the aggregate. Navaro et al [18] proposed a microscopic observation technique for observing the

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