1. Introduction
Rapid urban construction generates substantial volumes of concrete demolition waste, and diverting this material into pavement sub-base layers offers a lower-value but high-volume beneficial reuse pathway that can materially reduce both landfill burden and virgin aggregate extraction.
2. Methodology
Recycled concrete aggregate sourced from a demolition processing facility was blended with natural crushed stone aggregate at replacement levels of 0, 30, 60 and 100 percent by weight, with each blend characterised for gradation, California Bearing Ratio under soaked conditions, and permeability, benchmarked against the design specification thresholds for granular sub-base material in flexible pavement construction.
3. Results
The 30 and 60 percent replacement blends met all specified CBR, gradation and permeability criteria for granular sub-base use, with the 60 percent blend achieving a soaked CBR of 24 percent against a 20 percent design threshold, while the 100 percent replacement blend achieved only 17.2 percent CBR, a 14 percent shortfall against the threshold, attributed to increased fines generation from residual mortar fracturing under compaction.
4. Conclusion
Recycled concrete aggregate can substitute for a majority share of natural aggregate in pavement sub-base layers without compromising design performance, though full replacement requires either aggregate pre-treatment or blending with virgin material to meet strength criteria. Future work will assess long-term field performance under trafficked conditions.
References
[1] Poon C. S. and Chan D., Feasible use of recycled concrete aggregates and crushed clay brick as unbound road sub-base, Construction and Building Materials, 2006. [2] Arulrajah A. et al., Geotechnical properties of recycled construction and demolition materials, Journal of Materials in Civil Engineering, 2013.