The CBR test (Californian Bearing Ratio), recognized as a diffusion kind of test, is followed for measuring how strong the roads are laid in the first place. Measurements attained through such types of tests are further considered to understand the component layer and the thickness of the adjacent pavement. CBR test process involves rightly calculating the type of pressure needed to penetrate within the about to be tested soil sample. Keep reading to learn the functionality of this type of test.
CBR test process – explained:
The CBR test is mostly applied upon an undisturbed or re-adjusted sample. The entire test process involves incorporating a cylindrical plunge that is about fifty mm diameter to go through the road components from a range of 1.25mm per minute. The sample should be sieved using a 20mm sieve. Then, take about five kilograms of the given soil, and add an optimum water amount required to moisten them. After mixing water, place the spacer disc above the base plate, the filter paper above the spacer disc. Divide soil into five equal portions. Clean up on the mould, apply oil over them accordingly. Fill up the mould part with pre-prepared soil. The diffusion plunger should be made to contact the soil to note down the load penetration levels.
Measuring pressure levels:
The pressure levels measured as per the CBR test are then sub-divided based on the type of pressure needed to attain the diffusion levels upon the crushed rock materials. If the provided surface is said to be more challenging at all, then the CBR value shall remain higher too. The test is usually carried over soil areas that tend to hold on the maximum particle size of about twenty mm.
Different CBR values for different materials:
If the provided material is clay soil at all, then it will have the lowest CBR value, which might be less than eight. Sands, in default, are granular and tend to drain faster with CBR values lying anywhere between fifteen and thirty-five. Grave holds onto the best set of CBR values, like starting from twenty-five and go up.
Papworths Construction Testing Equipment (PCTE) 