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Claude Green
CAD technician
Asked a question last year

What is the CBR value for sub grade in rigid pavement road construction?

What is the CBR value for sub grade in rigid pavement road construction?

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Fasi Ur Rahman
Author at The Constructor

CBR value for subgrade in road construction in India

California bearing ratio(CBR) value is used to decide the thickness of road pavement

CBR value for subgrade in road construction in India as per IRC: 37-2012 is 3 – 15%

CBR value for

  • Clay soil: less than 8
  • Sand: 15 -35
  • Gravel: 25 and more than that

Rigid pavements because of their nature, allow for a larger variation in subgrade material (in terms of strength), unlike flexible pavements. That is why rigid pavements can be built over almost any kind of soils with appropriate ground improvement.

The general range for CBR is 2% to 14% or 15%. If it is found below 6%, then the code specifies some necessary subgrade improvement before laying the concrete slab directly over it.

Also, the CBR could be increased up to say 40% or 50% by ground improvement, and still, the subgrade may be fit for rigid pavements.