Assessment of Deflection and In-Situ California Bearing Ratio (CBR) of Clayey Subgrade of Flexible Pavement Reinforced with Waste Tyre Scrap Material

Abstract

This study evaluated the deflection and field or in-situ California Bearing Ratio (CBR) of subgrades in flexible pavements, comparing normal soil subgrades with tyre scrap-modified subgrades. It involved laboratory tests (modified proctor compaction and CBR) for assessing load-bearing capacity and strength and field studies using the Dynamic Cone Penetration Test (DCPT), and Falling Weight Deflectometer (FWD) for in-situ CBR and structural capacity evaluation. DCPT provided in-situ CBR values correlated with those for cohesive soils, while FWD focused on measuring subgrade deflection using the Lower Layer Index (LLI). Results indicated a 37.5% reduction in deflection with the tyre scrap-modified subgrade, demonstrating its potential in road construction for improved durability, cost savings, and waste utilization. This finding suggests the viability of tyre scrap in enhancing road infrastructure sustainably and efficiently.