Project Status: In Progress


Granular materials used in the design and construction of pavement base and subbase layers are often assessed for suitability based on the California Bearing Ratio (CBR) value. This measure provides an indication of the load penetration resistance of a compacted material. Both Australian (AS 1289.6.1.1) and local (WA 141.1) test methods require all material retained on the 19 mm opening size sieve to be excluded from testing. Anecdotally, the “oversize” coarse particles contribute significantly to the strength and stiffness of the material in-service. Consequently, suitable materials including locally available gravels are excluded from use due to their low, non-representative CBR values. WARRIP is seeking to develop a revised test method based on current best practice that will account for the effect that the oversize portion has on the bearing strength of granular pavement materials.