CBR Moisture

[RonII]

Hello,

The ASTM method for CBR requires a moisture be taken after the test is complete from the middle and the top one inch. What is the purpose and how frequently is it used.

Thank you

Ron

 

[Ron]

Are you referring to taking a moisture sample before compaction and after compaction for a soaked sample?

The moisture content can change within the sample from the compaction process. If the moisture content is slightly above optimum, the excess moisture will tend to accumulate near the bottom of the sample.

If I remember correctly (it has been a while since I've done the test), the sample is taken only before and after the compaction process, not after the penetration testing.

 

[AussieGeoEng]

RonII - a moisture content in the top one inch may significantly increase after soaking while the remainder of the sample increases only slightly (e.g in clays). The comparison between the moistures can be used to infer reasons for low values.

From what I understand the two moistures should be completed for each test. How frequently used - well that would depend on the user.

 

[RonII]

Thanks. The moisture I am referring to is after it has soaked for 4 days and after the penetration. ASTM procedure calls for the moisture to be taken from the top 1 inch and the middle. Just not sure why it is required.

Ron