Heave in stabilised/ modified material

[freelander]

Anyone got any ideas on a quick method of determining the heave potential of stabilised or modified material. The method used at present is BS1924 method i.e. air curing CBR for 3 days followed by 25 days soaking at 20 degrees centigrade. Can anyone reccommend a better test.

 

[iandig]

That is the quick test!!
What you are hoping is that within this short space of time (25 days is a very short space of time), an indication will be given as to the potential of the soil to be suceptable to swelling caused by the formation of sulphate alluminate hydrate (ettringite).
If you are looking for an alternative to this, I have used cylindrical specimens of the treated soil which are placed in a constant temperature water bath. The specimens are typically the specimen formed from the MCV test, which upon completion is extruded and used to determine the volume stability. As the entire surface of the sample is exposed to water, you tend to get a 'quicker' reaction than with a soaked CBR, especially as with the CBR, you are relying on the water being able to get through the pourous plates. From my own experience, I have found that with the soaking of stabilised soils, the lime from the soil can very easily 'cement' up the holes in the base of the CBR moulds, preventing water entering the sample freely. This means that even leaving the samples in the water for 25 days, you may not get water penetrating through the bottom of the sample.
With using the MCV test portions, you have the option of determining the UCS as well, and this can be used to monitor the strength gain and performance of the mixes.
Finally, obviously this is all once you have assessed that the Sulphates are not so high as to be restrictive