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Abstract
With the increased awareness of building sustainable transportation systems, recycled materials and industrial byproducts increasingly are being used in highway construction, especially as base materials. When compared to traditional base materials, such as crushed aggregate, recycled materials and industrial byproducts often display unique properties. However, the physical properties of recycled materials and industrial byproducts have yet to be fully characterised for the purpose of pavement design. This study evaluated the mechanical properties of a full-depth reclaimed pavement material (RPM) and RPM stabilised with high carbon/high calcium fly ash, and compared these with properties of a conventional crushed aggregate. It was found that RPM exhibited higher modulus than the traditional base course material (crushed aggregates) did. However, RPM also showed higher plastic strain than crushed aggregate, indicating a higher potential for rutting in RPM base. Adding high carbon/high calcium fly ash significantly increased the California Bearing Ratio (CBR) and resilient modulus and lowered plastic strain of RPM. The strength and stiffness of field-mixed RPM stabilised with fly ash was significantly lower than that of laboratory-mixed mixtures, as indicated by different measures, i.e., CBR, resilient modulus and unconfined compressive strength (UCS). Data obtained in this study, along with other data obtained from similar studies, indicate that there are good correlations between resilient modulus and CBR (R 2 = 0.96), as well as between resilient modulus and UCS (R 2 = 0.94) for recycled base materials stabilised with fly ash. However, there is still a need for more testing to further verify the proposed relationships. Nonetheless, the proposed relationships constitute the first such relationship proposed and can be useful in pavement design. Additionally, it is shown that flexural strength is about 20% of UCS as it is recommended for materials stabilised with other cementitious materials.
Acknowledgements
This research was undertaken by a grant from the U.S. Department of Energy. The authors wish to thank Mr Robert Patton for his help on this project. They also thank Minnesota Department of Transportation for the collaboration on the field test section construction and Bloom Companies for compaction tests. Recycled Materials Resource Center provided the additional data used in the analyses. Mr Xiadong Wang and Justin Warner assisted with the project in the field and Victor Damasceno and Ron Breitmeyer provided technical support for the project in the laboratory.