An approach to mitigate effects of colour variation, specularity and pores on microtexture analysis of aggregates

ABSTRACT

Previous research indicated that color variation, specularity, and porosity, which are not related to surface roughness or texture of aggregate, affect the value of Texture Index (TI) determined using standard procedures associated with Aggregate Image Measurement System (AIMS). In response, a new technique called Photometric Stereo-Independent Component Analysis (PS-ICA) was developed and found to effectively mitigate color variation effect. Reduced light intensity was found to partially, but not completely, mitigate specularity effect. However, effect of pores could not be mitigated with measurements obtained from existing AIMS procedures. An extensive evaluation was conducted on a broad range of aggregates to determine whether TI values obtained before and after polishing using PS-ICA and reduced light intensity resulted in appropriate assessment of polishing resistance. For aggregates exhibiting strong specularity, it was found that specularity effect increased after initial polishing, which increased TI, thereby confounding and sometimes overwhelming the reduction in TI associated with reduced roughness. The specularity effect appeared to remain constant after initial polishing, such that further polishing resulted in a more consistent reduction in TI. For aggregates not exhibiting specularity, reduction in PS-ICA TI after initial polishing was found to be an excellent parameter to assess polishing resistance.

KEYWORDS:

• Texture index
• microtexture analysis
• aggregate
• image
• friction performance

Acknowledgements

The authors would like to acknowledge and thank the FDOT's State Materials Office Geotechnical Materials Section for providing technical and financial support and materials for this study.

Disclosure statement

No potential conflict of interest was reported by the authors.