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    Volume 44, Issue 3 (May 2016)

    Evaluation of Coarse Aggregate in Cold Recycling Mixes Using X-Ray CT Scanner and Image Analysis

    (Received 16 May 2014; accepted 23 October 2014)

    Published Online: 2016

    CODEN: JTEVAB

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    Abstract

    The performance of cold recycling (CR) mixtures has been widely evaluated, but these studies rarely focused on the internal structure of CR mixtures. The objective of this research is to investigate the distribution, orientation, and shape properties of coarse aggregates in CR mixtures with emulsion by processing a series of sectional images from an X-ray CT scanner. The uniformity index (UI) was derived to describe the distribution of coarse aggregates. The aggregate orientation was obtained by calculating the average angle of inclination θ and the coherence of orientation Δ. The morphological indices, such as the flat and elongated ratio (FER), angularity index (AI), and surface texture index (STI) were used to address the shape properties of CR mixtures. According to the results, the distribution uniformity of CR aggregates becomes worse with coarser gradation. Compaction methods significantly influence the aggregate orientation in CR mixtures. The superpave gyratory compaction (SGC) method makes the best coherence of aggregate orientation, but the static load compacted specimen shows the opposite result. The CR mix tends to have worse uniformity of aggregate distribution, larger angle of aggregate inclination, and more random aggregate orientation compared with the HMA mix. It is estimated that more crushed faces of aggregates are produced in the process of pavement milling and the surface texture of RAP materials decreases with the long-term effects of traffic loading and environment. Adding new coarse aggregates to CR mixtures disturbs the aggregate distribution, but it can improve the average surface texture of aggregates in CR mixtures.


    Author Information:

    Gao, Lei
    Ph.D. Student, School of Transportation, Southeast Univ., Nanjing,

    Ni, Fujian
    Professor, Road Maintenance Technology Engineering Center of Jiangsu Province, Southeast Univ., Nanjing,

    Luo, Hailong
    Master Student, School of Transportation, Southeast Univ., Nanjing,

    Wang, Hainian
    Key Laboratory for Special Area Highway Engineering of Ministry of Education, Chang'an Univ. South Erhuan Middle Section,

    Chen, Yunqing
    Master Student, School of Transportation, Southeast Univ., Nanjing,


    Stock #: JTE20140231

    ISSN:0090-3973

    DOI: 10.1520/JTE20140231

    Author
    Title Evaluation of Coarse Aggregate in Cold Recycling Mixes Using X-Ray CT Scanner and Image Analysis
    Symposium ,
    Committee D04