[Stoves] Calculation help in brick making

[frank at compostlab.com]

Dear Crispin,

I have a proctor hammer and the right equipment for doing the three lifts, 27
drops per lift, determine the density etc. All the books say to plot a smooth
curve based on the three or four moisture points vs weight and estimate the
optimum moisture. But it seems there is enough info for a formula ... but not
from me. I had never heard of the method you described so thanks for adding it
to my collection. 

The project I am now working is for a crew planning to repair an adobe
building using 'forms' and sun drying. You use a rammed earth method and there
are, I am sure, others. I would rather see them use your suggested equipment. 

What I think, and missed by others, is the moisture / density plots should be
done on bricks made with the exact equipment used for making bricks for the
building.  Run a batch of bricks through with three different % moisture
readings, determine the dry weight per brick and plot to find the best
moisture content to produce the heaviest brick (highest density). At seems
this would be a better way than the ASTM procedure that is required by the
regs. And one already has most of the equipment!  It may be that making bricks
in forms need to be wetter to fill in all the corners and with no cavities
than a mix with the optimum moisture for a ram or hammer that packs in the
soil. But the only brick I have ever made is in toilet paper rolls.

My plan is to determine the optimum moisture from the hammer, mix up a batch
and fill my toilet paper rolls with the soil mix, dry at 40 deg. C for a week
and measure compaction using my $10 garage sale spring tester. And hope to get
above 300 lb/in sq. I can do a lot of tests for a little money. Once I find
what I think is the best soil-water ratio they will make some and send it in
for the 'real' test. 




Thanks

Frank



  












On Fri, 29 Jun 2007 12:25:29 +0800, Crispin Pemberton-Pigott wrote
> Dear Frank
> 
> You are definitely on the right track assuming you don't have the right
> equipment.  It will work as you describe.  This test is done many 
> times a day at soil labs on construction sites using a special tool 
> (cheap!) this looks like a plumb bob.
> 
> It is a conical piece of steel with a sharp point, an included angle 
> of about 30 degrees and a circle etched into it about 1/3 of the way 
> up from the tip at the bottom.
> 
> It is placed so that is can penetrate the soil which is packed into 
> a flat cylinder, like a cookie.  It is about 1/2 to 1 inch thick.
> 
> You have of course recorded the mass of dry soil in the shallow cylindrical
> mould.
> 
> Put the whole thing on a scale.  Patiently add water one drop at a 
> time.  At some point the plump bob will start to sink into the soil. 
>  When it reaches the inscribed ring, it is the optimum moisture 
> content.  The mass of water added is divided by (the original soil 
> mass+water added) and you get the optimum H2O% = OMC.
> 
> The trick of course is to get hold of the plump bob.  There might be
> something on it at the CSIR (Council for Scientific and Industrial 
> Research) website in South Africa.  They were selling a soil testing 
> kit that included this device. I am not sure if they invented it but 
> it works really well.
> 
> Anyone who wants to build a rammed earth, clay, solid structure of 
> brick can make use of this little device.
> 
> Regards
> Crispin


--
Frank Shields
Soil Control Lab
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