California Bearing Ratio
Reference work entry
The California bearing ratio (CBR) is an index that compares penetration resistance of laboratory-compacted soil material to that of a durable, well-graded (poorly sorted), crushed rock material.
The test was developed by the California Department of Highways in the late 1920s with the intention to characterize cohesive soil in the subbase and subgrade of pavement sections. It is a standard test with procedures specified by American Association of State Highway and Transportation Officials (AASHTO 2013) and American Society for Testing and Materials (ASTM 2016) in North America. The test uses a standard compaction mold with a diameter of 152.4 mm and a height of 177.8 mm. The degree of compaction and range of moisture content are specified for the test depending on project requirements. In most cases, the sample is compacted into the mold and then submerged in water for 4 days prior to testing. The sample and mold are removed from the water, a ring-shaped surcharge...
- AASHTO (2013) Standard method of test for the California bearing ratio. American Association of State Highway and Transportation Officials Test T 193. https://bookstore.transportation.org/item_details.aspx?ID=2117. Accessed Apr 2015
- ASTM (2016) Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils. American Society for Testing and Materials Test D1883-16. http://www.astm.org/Standards/D1883.htm. Accessed Apr 2016
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