Document Type


Publication Date



The study aims to understand the effect of different admixtures on improving the quality of flexible pavement subgrades. In this paper, recycled concrete aggregates (RCA) and Fly Ash were used as the admixtures in improving the maximum dry density (MDD), swelling potential, and California bearing ratio (CBR) of subgrade soil. The percentages of RCA and fly Ash used were 5%, 10%, and 15%. With the upscaling in fly ash dosage, the optimum moisture content and the California bearing ratio increased. However, the MDD of soil decreased for higher fly ash contents. On the contrary, the optimum moisture content (OMC) of the soil decreased and the MDD and California Bearing Ratio increased with an increase in RCA content. Both RCA and fly ash-treated soil demonstrated lower values of swelling. At 5% dosage, both RCA and fly ash admixtures were found to improve CBR. However, at higher percentages (10% and 15%) of fly ash, the CBR values decreased while in comparison, soil samples performed significantly better in the CBR test with the increasing dosage of RCA. The findings of this research can be used to examine the suitability and effects of recycled aggregate and fly ash on the performance of soil in terms of CBR, particularly when the soil is planned to be used as a subgrade in highways.


Under a Creative Commons license

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Publication Title

Hybrid Advances





To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.