laboratory evaluation of subgrade and subbase coarse materials in road construction. CBR is a comparative measure of the shearing resistance of a soil .It can be defined as the load per unit area ( pressure) required to force a piston into the soil a certain depth , expressed as a percentage of the load per unit area ( pressure) required to force the piston the same depth into a standard sample of crushed stone . usually depth of 0.1 and 0.2 inches are used , but depths up to 0.5 inch can be used if desired . The CBR value appears with the percentage sign omitted
Standard : ASTM & AASHTO
Test- equipments
Code Description weight approx (kg)
· CBR mould
· Split CBR Mould
· Filter screen.
· Spacer disc with "T" handle.
· Spacer disc conforming to UNE standards 7.5
· Annular surcharge weight,
· Slotted surcharge weight,
· Sliding weight rammer.
· Cutting edge 0.5
· Straight edge.
· Solid CBR base 1
· Whatman filter paper.
· SWELL TEST APPARATUS
Perforated plate with adjustable stem (swell plate)
Dial gauge tripod
· Large soaking tank
· CBR LOADING FRAME AND PRESS