Cob: Re: cob walkways- use lime

[Don Stephens]

On Tue, 2 Nov 1999, Michael Saunby responded:

> On 02 November 1999, Don Stephens wrote:
> >
> > What is meant by "earth" and "soil"?  <<G>> These are very unspecific
> > terms - I'm used to dealing with catagories like "clay", "silt", "sand",
> > "humus", etc., or mixes of these.

> I guess for most people it means the earth on their doorstep, no point 
> moving it from one place to another if you don't have to.  I expect most 
> traditional building techniques are fairly insensitive to the actual makeup 
> of the soil.....
 
working with cob, rammed earth and soil cement, I've hardly found this to
be the case!  Certainly the "manuals" I've seen on these techniqes also
place great emphisis on soil constituants and ratios...

> > ( ...I have a multi page report on what they did...

Thanks for the source info, Charmaine.  I hope it provides more on what
types of soils they found to be within the range of suitability...

> ......A slightly arched (to give 
> drainage to the sides) pathway of well compressed clay with fine gravel 
> packed down hard.  Doesn't last forever, but is easily maintained, if you 
> can spare a little labour to fill any holes/depressions that might happen 
> from time to time and control weed that might grow if it's not used 
> regularly...

Even if it gets a bit mushy when saturated?  Snow doesn't run of a crowned
pathway in our part of the planet and when it melts it turns clay to
slime, allowing the gravel to be pushed down.  Filter fabric under helps
with this, but it still can sit on top, the consistancy of half-melted
chocolate-chip ice cream....

> > On the other hand, what eco-drawbacks are there to lime?  What escapes
> > into the air during its mining, processing and hydrating? (and would one
> > get even better results with hot lime?) Is it as energy-intensive as
> > cement?  Where is it produced for use in various regions of the US, with
> > how much transport energy consumption, typically?  And what harm, if any,
> > is caused when it's used in on-earth applications like paths?  Does bad
> > stuff leach down to harm plant roots and water tables?  Perhaps this has
> > already been discussed on the lists, while I was off-line and up to my
> > ears in design projects and overlooked it. If so, sorry, but perhaps a
> > reitteration would be beneficial anyway, or reply off-list, if you wish.
> > Thanx....Don

Any other info on this, fellow dreamer/builders?....

> No idea where lime is produced in the US.  In the UK limestone is fairly 
> common in many areas. It gives off carbon dioxide when "burnt" doesn't it? 
> Hardly a big problem I'd have thought.

I concider the release of ancient CO2, trapped away from the atmosphere
for eons, back into our already CO2 overloaded sky a big problem.  That's
one of the big fall-downs of concrete, thtat makes me want to get away
from it.  IMHO, if lime production does the same thing, it's apparently
little better, at least in this regard, unless it releases less per ton or
less is required in building mixes for similar performance.... 

> Produce only what you need and use it only when you need it - 
> sustainability is more about common sense than choice of materials. 
> Michael Saunby

It seems to me that "choice of materials" is a big part of sustainable
"common sense"!  Those generating power at Chernoble would, no doubt, have
said they were only using those nuclear materials when they needed them.
<<G>>  For me, recognizing BENIGN, local, plentiful/unvalued/reusable/
recyclable/renewable MATERIALS and using them for as much of constuction
as possible, is one of the primary underpinnings of sustainable building.
.....Don