Cob: soil tests

[Matthew HALL(SED)]

Hi Darel
I have a few offerings here that may be of interest
Without getting into laboratory type testing there are many field tests you can use here - a VERY
rough guide!

1) Sedimentation (ie jam jar test) will give you an idea of the particle size distribution.

2) Shaking the dry soil through a nest of different sized seives will tell you more about the
different types of granular material (ie sand & gravel)

3) Linear shrinkage - this is a good one to tell you about shrinkage and cracking. Take a small
trough or similar and place the wet mix inside scarping it flat with the surface of the trough.
Measure its length then allow the mix to dry. Push the dry mix upto one side of the trough and
measure amount of overall shrinkage

4) cohesive soils - if you are not sure whether it is silty or clayey, squash the soil into a ball
and cut it with a knife - clayey soil will shine, silty soil will appear dull. 

5) Rain durability - place the test sample on the ground beneath a bucket of water. Hang a thin
wick over the edge of the bucket such that it syphons out the water and drips small drops onto
your sample. Examine how much it pits, erodes etc. Experiment with having the sample flat and
proped up at a slight angle

There are literally dozens of these crude field tests, but they can give you a good yes/no idea on
soil suitability. If anyone wants to know more please e-mail me with specifics.
Regards
Matthew

____________________________________________________________________
Matthew Hall BSc (Hons) GradBEng
Centre for the Built Environment
Unit 9 Science Park
Sheffield Hallam University
Pond Street
Sheffield S1 1WB
England

Tel: +44 (0) 114 225 3200
Fax: +44 (0) 114 225 3206
E-mail: M.Hall at shu.ac.uk
Webpage: http://www.shu.ac.uk/schools/sed/earth