This standard specifies the laboratory method for determining the California Bearing Ratio (CBR) of undisturbed and remoulded soils. It details the preparation of soil specimens, soaking procedures to simulate worst-case moisture conditions, and penetration testing to evaluate subgrade strength for flexible pavement design.
Specifies the laboratory procedure for determining the California Bearing Ratio (CBR) of prepared soil samples.
Quick Reference Values
Rammer weight4.9 kg
Rammer drop height450 mm
Number of compaction layers5
Blows per layer (1000 cc mould)25
Blows per layer (2250 cc mould)56
Small mould volume1000 cc
Large mould volume2250 cc
Key Formulas
Dry Density (yd) = y / (1 + w/100) — where y is bulk density and w is moisture content in percent
Practical Notes
Ensure the soil is mixed thoroughly with water and allowed to mature/cure before testing to ensure uniform moisture distribution.
Use the larger 2250 cc mould if the soil contains a significant proportion of coarse material (more than 20% retained on the 4.75 mm sieve).
Take representative soil samples for moisture content determination immediately after extracting the compacted specimen to avoid moisture loss.