Cob: Origins of Cement vs Cob

[H. Wayne]

    Wow, I knew a lot of folks were talking out of their hat, but I was hoping some actually read a few books, or had some actual experiences to share.  Did I read the Egyptians used cement?  All the books I have read say it was the Romans.  Most of the great civiliations we know of did NOT use or make concrete structures, but the Romans did.  They did not make cement like we do, they just took natural materials they could find, heated some of these up (later in their history) and mixed them together.
    Really folks, all the opinions in the world do not help thoses of us looking for answers.  If you are going to offer advise, please have some REAL knowledge on the subject, or experience we all can profit from.  Even the subject of cob has gotten more into the realm of opinion than fact or experience.  I realize there are only a few really good cob books available for most of us, but to make statements that suggest cob is both strong and insulating is a bit of a stretch.  What are you comparing cob to?  The truth is cob is a very weak mixture of natural materials.
    I realize the faithful of cob will hate me for this, but for those who really want TRUE information about cob let me suggest a simple experiment.  Mix up a small batch of the best cob you can muster.  Form test blocks of 2 inch square cubes, say around a dozen.  Now, do the same with cement, making concrete blocks of the same size.  If you know anything about concrete, the blocks should be moisture cured for 28 days to get recordable results.  Now do the same with a adobe mix.  Now plaster mix.  By now you should have a dozen test cubes of each material that can be tested for endurance, strength, resistance to moisture breakdown, and a multitude of other tests.
    Take care to make each batch according to a BOOK on the subject, not by guessing.  What you want is a true test of the material, so that requires you learn how to make the test blocks properly.  Hint: all of the above materials are normally stronger if you only use just enough water, and cure the test blocks in the best possible environment for the material.  Hint: give most at least a month to gain strength.
    Ok, a month has past and you are ready to start testing each materials.  The simpliest test for endurance is to place a few test blocks of each material in standing water.  In a few weeks you will notice some are beginning to brake down.  This is a good way to simulate that material exposed to many years in a wet environment.  Other materials will not seem effected.  Another way to test moisture exposure is to make test sheets 1" thick and 3"x6".  Place the test sheets in a sea environment, where the tides rise and fall.  It is common to have a hole big enough for two nails, top and bottom of the test sheet for careful nailing to a dock pier just below high tide mark.  This will give you around 10 years worth of exposure to salt air in about a month.
    To test for strength, it is common to crush the test blocks by weight or pressure.  There are a number of way to do this, but the simplest is to mount a sharp object in a 2"x4" that is around 4 foot long.  Glue a dowel rod on the top side of the 2"x4" just above the sharp 10 penny nail.  Now start placing barbell weights, bricks, stones or what ever you have on that dowel (about 28" long, pointing straight up into the air).  The other end of the 2"x4" is anchored by a hing so it will stay put.  Attach the other end of the hing to a 4'x4' peice of 1" plywood or some other peice of wood (log?) to anchor it.
    Now to test the blocks.  Raise the whole mess about 12 inches, measured, and let it drop squarely on the test block of each material.  Which one servived?  The sharp nail, if properly glued into the 2"x4" arm with drive itself into most of the materials, crushing, shattering, and marking each according to the strength of the bond of the materials.  Now ask yourself, which one of these would make a good building material?  Does it stand up to moisture attack?  Will it decay, brake down, break apart during an earth quake or storm?  Is it worth my time, labor, and money to build with this material.
    By now you are starting to realize these simple tests do not offer as much information on each material as you might want.  Strength and endurance of a material is a realative measurement.  Each material has good points and weaknesses.  Of course the strongest and most long lasting is concrete or cement mixes.  The Romans built many structures over 2,000 years ago and they are stronger today then they were new.  One of the interesting characteristics of concrete is it gets stronger over the years.  That is assuming the person who made the concrete did it right.  There are a multitude of folks who work with concrete every day, but have never read one book to learn how to do it right.
    I read a lot of that here.  Lots of folks giving their opinions, never reading a book, or making any tests of their thoughts.  I know testing has it's limitations, and is something you have to learn, but is not the cob list a place to learn?  Are we here just to give our untested, unproven opinions or are we here to share facts, experiences, and knowledge?  Sometimes I wonder why folks say what they say.  Then I remember all those concrete workers that don't have a clue what they are doing and folks wonder why the most used materials in the world cracks, and breaks apart when it is suppose to be so strong and long lasting.
    By the way, cement, or concrete is suppose to last without cracking, flaking, chipping forever!  Yes, that is right, forever.  It gains strength, ever so slowly after the first 28 hours forever.  Of all the concrete structures we can find, and peices of concrete we have unearthed, it has been found they were still getting stronger, not weaker with age.  Kind of like a fine wine, it just gets better as the years go by.  That is why concrete is a wonderful investment for the future, and it is one of the cheapest building materials available all over the world.  Concrete products are the most cost effective, enduring, and useful materials man has learned to make.
    Now you understand why third world countries, China, USA, and others make so much cheap concrete.  We may not understand why it works, but since the earth can be a hostile environment, it is a blessing.  Science may never fully understand how concrete goes from a liquid mass to a rock hard solid, but we can test and learn how to make it stronger and more useful.  Concrete is very much like bamboo, the more you work with it, the more uses you find for it.  Cob can be the same way, but you have to appreciate the limitations cob has.
    The most wonderful thing about cob is it can be made with nearly no cost.  It will provide a wonderful building material, as long as you don't ask too much of it.  You must also realize you have to protect it from moisture.  Rain is your enemy.  Time is your enemy with cob.  All of us will have a useful purpose for cob since we all have a need for a temporary structure from time to time.  Some of us like to make scultpures that are not meant to last forever.  I think it should be a law that anyone who wants a house should first be required to build it of cob.  Live in it for at least three years, modify it to meet their needs.  Then if they are sure the house design meets their needs, when they want, they can replace some or all of the cob elements with materials that will last longer.
    The biggest problem with that idea is people don't stay put.  We also want things we can not afford.  Most folks bulk at the idea they could build a home of cob or anything else.  Of course, a cob high rise is not practical.  Cob would crush itself under it's own weight after four floors unless it was made super strong by adding, (dare I say it?) cement.  If you look at it from a concrete man's view, how dare you pollute perfectly good cement with a cob mix.  From the die hard cobist view, how dare you make cob with cement in it.  It is NOT true cob anymore.  Oh well, what can I say.  Some folks are just not open to suggestion, no matter how helpful the idea might be.  Enough of that.  Time to get off the soap box and read some more opinions for the .... (I dare not say!)
    Wayne
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<DIV><FONT color=#000000 size=2>    <FONT color=#000000>Wow, I 
knew a lot of folks were talking out of their hat, but I was hoping some 
actually read a few books, or had some actual experiences to share.  Did I 
read the Egyptians used cement?  All the books I have read say it was the 
Romans.  Most of the great civiliations we know of did NOT use or make 
concrete structures, but the Romans did.  They did not make cement like we 
do, they just took natural materials they could find, heated some of these up 
(later in their history) and mixed them together.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    Really 
folks, all the opinions in the world do not help thoses of us looking for 
answers.  If you are going to offer advise, please have some REAL knowledge 
on the subject, or experience we all can profit from.  Even the subject of 
cob has gotten more into the realm of opinion than fact or experience.  I 
realize there are only a few really good cob books available for most of us, but 
to make statements that suggest cob is both strong and insulating is a bit of a 
stretch.  What are you comparing cob to?  The truth is cob is a very 
weak mixture of natural materials.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    I realize 
the faithful of cob will hate me for this, but for those who really want TRUE 
information about cob let me suggest a simple experiment.  Mix up a small 
batch of the best cob you can muster.  Form test blocks of 2 inch square 
cubes, say around a dozen.  Now, do the same with cement, making concrete 
blocks of the same size.  If you know anything about concrete, the blocks 
should be moisture cured for 28 days to get recordable results.  Now do the 
same with a adobe mix.  Now plaster mix.  By now you should have a 
dozen test cubes of each material that can be tested for endurance, strength, 
resistance to moisture breakdown, and a multitude of other 
tests.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    Take care 
to make each batch according to a BOOK on the subject, not by guessing.  
What you want is a true test of the material, so that requires you learn how to 
make the test blocks properly.  Hint: all of the above materials are 
normally stronger if you only use just enough water, and cure the test blocks in 
the best possible environment for the material.  Hint: give most at least a 
month to gain strength.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    Ok, a 
month has past and you are ready to start testing each materials.  The 
simpliest test for endurance is to place a few test blocks of each material in 
standing water.  In a few weeks you will notice some are beginning to brake 
down.  This is a good way to simulate that material exposed to many years 
in a wet environment.  Other materials will not seem effected.  
Another way to test moisture exposure is to make test sheets 1" thick and 
3"x6".  Place the test sheets in a sea environment, where the 
tides rise and fall.  It is common to have a hole big enough for two nails, 
top and bottom of the test sheet for careful nailing to a dock pier just below 
high tide mark.  This will give you around 10 years worth of exposure to 
salt air in about a month.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    To test 
for strength, it is common to crush the test blocks by weight or pressure.  
There are a number of way to do this, but the simplest is to mount a sharp 
object in a 2"x4" that is around 4 foot long.  Glue a dowel rod 
on the top side of the 2"x4" just above the sharp 10 penny nail.  
Now start placing barbell weights, bricks, stones or what ever you have on that 
dowel (about 28" long, pointing straight up into the air).  The other 
end of the 2"x4" is anchored by a hing so it will stay put.  
Attach the other end of the hing to a 4'x4' peice of 1" plywood or some 
other peice of wood (log?) to anchor it.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    Now to 
test the blocks.  Raise the whole mess about 12 inches, measured, and let 
it drop squarely on the test block of each material.  Which one 
servived?  The sharp nail, if properly glued into the 2"x4" arm 
with drive itself into most of the materials, crushing, shattering, and marking 
each according to the strength of the bond of the materials.  Now ask 
yourself, which one of these would make a good building material?  Does it 
stand up to moisture attack?  Will it decay, brake down, break apart during 
an earth quake or storm?  Is it worth my time, labor, and money to build 
with this material.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    By now 
you are starting to realize these simple tests do not offer as much information 
on each material as you might want.  Strength and endurance of a material 
is a realative measurement.  Each material has good points and 
weaknesses.  Of course the strongest and most long lasting is concrete or 
cement mixes.  The Romans built many structures over 2,000 years ago and 
they are stronger today then they were new.  One of the interesting 
characteristics of concrete is it gets stronger over the years.  That is 
assuming the person who made the concrete did it right.  There are a 
multitude of folks who work with concrete every day, but have never read one 
book to learn how to do it right.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    I read a 
lot of that here.  Lots of folks giving their opinions, never reading a 
book, or making any tests of their thoughts.  I know testing has it's 
limitations, and is something you have to learn, but is not the cob list a place 
to learn?  Are we here just to give our untested, unproven opinions or are 
we here to share facts, experiences, and knowledge?  Sometimes I wonder why 
folks say what they say.  Then I remember all those concrete workers that 
don't have a clue what they are doing and folks wonder why the most used 
materials in the world cracks, and breaks apart when it is suppose to be so 
strong and long lasting.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    By the 
way, cement, or concrete is suppose to last without cracking, flaking, chipping 
forever!  Yes, that is right, forever.  It gains strength, ever so 
slowly after the first 28 hours forever.  Of all the concrete structures we 
can find, and peices of concrete we have unearthed, it has been found they were 
still getting stronger, not weaker with age.  Kind of like a fine wine, it 
just gets better as the years go by.  That is why concrete is a wonderful 
investment for the future, and it is one of the cheapest building materials 
available all over the world.  Concrete products are the most cost 
effective, enduring, and useful materials man has learned to 
make.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    Now you 
understand why third world countries, China, USA, and others make so much cheap 
concrete.  We may not understand why it works, but since the earth can be a 
hostile environment, it is a blessing.  Science may never fully understand 
how concrete goes from a liquid mass to a rock hard solid, but we can test and 
learn how to make it stronger and more useful.  Concrete is very much like 
bamboo, the more you work with it, the more uses you find for it.  Cob can 
be the same way, but you have to appreciate the limitations cob 
has.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    The most 
wonderful thing about cob is it can be made with nearly no cost.  It will 
provide a wonderful building material, as long as you don't ask too much of 
it.  You must also realize you have to protect it from moisture.  Rain 
is your enemy.  Time is your enemy with cob.  All of us will have a 
useful purpose for cob since we all have a need for a temporary structure from 
time to time.  Some of us like to make scultpures that are not meant to 
last forever.  I think it should be a law that anyone who wants a house 
should first be required to build it of cob.  Live in it for at least three 
years, modify it to meet their needs.  Then if they are sure the house 
design meets their needs, when they want, they can replace some or all of the 
cob elements with materials that will last longer.</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    The 
biggest problem with that idea is people don't stay put.  We also want 
things we can not afford.  Most folks bulk at the idea they could build a 
home of cob or anything else.  Of course, a cob high rise is not 
practical.  Cob would crush itself under it's own weight after four floors 
unless it was made super strong by adding, (dare I say it?) cement.  If you 
look at it from a concrete man's view, how dare you pollute perfectly good 
cement with a cob mix.  From the die hard cobist view, how dare you make 
cob with cement in it.  It is NOT true cob anymore.  Oh well, what can 
I say.  Some folks are just not open to suggestion, no matter how helpful 
the idea might be.  Enough of that.  Time to get off the soap box and 
read some more opinions for the .... (I dare not say!)</FONT></FONT></DIV>
<DIV><FONT color=#000000 size=2><FONT color=#000000>    
Wayne</FONT></FONT></DIV></BODY></HTML>