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GSBN: Digest for 6/28/07



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-> RE: GSBN:Cemento
     by "Rikki  Nitzkin" rikkinitzkin@...
-> Fwd: Pakistan strawbale photos
     by Mark Piepkorn mark@...
-> RE: GSBN:Cemento
     by Mark Piepkorn mark@...


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Date: 28 Jun 2007 12:35:05 -0500
From: "Rikki  Nitzkin" rikkinitzkin@...
Subject: RE: GSBN:Cemento

I mean about not using cement at all.  I know all the arguments, but I don't
have any firm statistics from reliable sources to back up my arguments.  The
other day I was talking to a sculptor who works with cement (without added
chrome) and I had trouble convincing him...a lot of people want to know
WHERE I get my information.

Rikki Nitzkin
Aulas, Lleida, Espana
rikkinitzkin@...
(0034)657 33 51 62 
www.casasdepaja.com (Red de Construccion con Balas de Paja)
 
> -----Mensaje original-----
> De: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] En nombre de Martin Hammer
> Enviado el: miercoles, 20 de junio de 2007 3:30
> Para: GSBN
> Asunto: Re: GSBN:Cemento
> 
> Hello Rikki,
> 
> Do you mean why we shouldn't use (Portland) cement at all (in foundations,
> slabs, paving, plasters, etc) because of its high embodied energy and its
> emission of green house gases during its production?  Or do you mean why
> we
> shouldn't use cement in plasters over straw bales because of cement
> plaster's low vapor permeabliity?
> 
> Martin Hammer
> California
> 
> (Thanks Tom Woolley for the article critiquing how the highest awards for
> contemporary architecture go to buildings that either ignore
> sustainability
> or exemplify unsustainability)
> 
> 
> 
> > I am looking for some document with Numbers explaining why we shouldn1t
> use
> > cement.
> 
> > If anyone can send me one or direct me to a web-page I would be
> grateful.
> 
> 
> 




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Date: 28 Jun 2007 13:01:16 -0500
From: Mark Piepkorn mark@...
Subject: Fwd: Pakistan strawbale photos

Forwarded message from Sarah Machtey:

>From: mudhome@...
>
>>Ok folks,
>>
>>I've got some of my Pakistan pictures on the web for you. There are even a
>>few pictures taken after I left and kindly sent to me by my Pakistani
>>friends. I still need to write many more captions and add more pictures.
>>
>><a  target="_blank" href="http://www.sageearth.com/naturalbuilding/photos/v/pakistan/";>http://www.sageearth.com/naturalbuilding/photos/v/pakistan/</a>
>>
>>Sarah Machtey


         Feel free to forward to anybody who might be interested.

         She'll also be putting up some of the photos she took while
helping the Steens with the sculptures in D.C. at some point. She's
still on the road, so it might take a couple weeks.


Mark Piepkorn
www.potkettleblack.com

   "A slow sort of country!" said the Queen. "Now,
here, you see, it takes all the running you can do,
to keep in the same place. If you want to get
somewhere else, you must run at least twice as fast
as that."
   - Lewis Carroll



----------------------------------------------------------------------

Date: 28 Jun 2007 17:41:55 -0500
From: Mark Piepkorn mark@...
Subject: RE: GSBN:Cemento

At 08:33 AM 6/24/2007, Rikki  Nitzkin wrote:
>I know all the arguments, but I don't have any 
>firm statistics from reliable sources to back up my arguments.

The text of a 1993 article from Environmental 
Building News, without its charts and diagrams, follows below.

On the whole, the cement industry hasn't changed 
a lot since the article. One thing to note is 
that in the U.S., we import a lot of cement - 
it's not always a local or even regional product. 
We even bring it over from China.

We had a couple higher-ups from the Portland 
Cement Association's sustainability task group - 
yes, they actually have one - in our offices last 
year. They didn't have horns and tails, and were 
surprisingly forthright in acknowledging their 
industry's shortcomings. Doesn't mean that we 
don't use way too much concrete in the built 
environment, though. For their spin, see www.concrete.org

I'd like to recommend Bruce King's book, Making 
Better Concrete: Guidelines to Using Fly Ash for 
Higher Quality, Eco-friendly Structures.

- - - - - -

Cement and Concrete:
Environmental Considerations
Feature - Environmental Building News March/April 1993

Cement and concrete are key components of both 
commercial and residential construction in North 
America. The cement and concrete industries are 
huge. There are approximately 210 cement plants 
in the U.S. and 4,000 to 5,000 ready mix plants 
(where cement is mixed with aggregate and water 
to produce concrete). The Portland Cement 
Association estimates that U.S. cement 
consumption has averaged between 75 and 90 
million tons per year during the last decade, and 
projects that consumption will exceed 100 million 
tons per year by 1997. Worldwide, cement 
production totaled 1.25 billion tons in 1991, 
according to the U.S. Bureau of Mines.

What does this mean in terms of the environment? 
Are these products good or bad? As builders and 
designers, should we be looking for alternatives 
or embracing concrete over competing materials? 
As with most building issues, the answers are not 
clear-cut. Concrete and other cementitious 
materials have both environmental advantages and 
disadvantages. This article takes a look at how 
these materials are made, then reviews a number 
of environmental considerations relating to their 
production, use, and eventual disposal.


Cement and Concrete Production

Cement is the key ingredient in concrete 
products. Comprising roughly 12% of the average 
residential-grade ready mix concrete, cement is 
the binding agent that holds sand and other 
aggregates together in a hard, stone-like mass. 
Portland cement accounts for about 95% of the 
cement produced in North America. It was patented 
in England by Joseph Aspdin in 1824 and named 
after a quarried stone it resembled from the Isle of Portland.

Cement production requires a source of calcium 
(usually limestone) and a source of silicon (such 
as clay or sand). Small amounts of bauxite and 
iron ore are added to provide specific 
properties. These raw materials are finely ground 
and mixed, then fed into a rotary cement kiln, 
which is the largest piece of moving industrial 
equipment in the world. The kiln is a long, 
sloping cylinder with zones that get 
progressively hotter up to about 2700#161#F (1480#161#C). 
The kiln rotates slowly to mix the contents 
moving through it. In the kiln, the raw materials 
undergo complex chemical and physical changes 
required to make them able to react together 
through hydration. The most common type of cement 
kiln today (accounting for 70% of plants in the 
U.S.) is a dry process kiln, in which the 
ingredients are mixed dry. Many older kilns use the wet process.

The first important reaction to occur is the 
calcining of limestone (calcium carbonate) into 
lime (calcium oxide) and carbon dioxide, which 
occurs in the lower-temperature portions of the 
kiln - up to about 1650#161#F (900#161#C). The second 
reaction is the bonding of calcium oxide and 
silicates to form dicalcium and tricalcium 
silicates. Small amounts of tricalcium aluminate 
and tetracalcium aluminoferrite are also formed. 
The relative proportions of these four principal 
compounds determine the key properties of the 
resultant portland cement and the type 
classification (Type I, Type II, etc.). These 
reactions occur at very high temperatures with 
the ingredients in molten form. As the new 
compounds cool, they solidify into solid pellet 
form called clinker. The clinker is then ground 
to a fine powder, a small amount of gypsum is 
added, and the finished cement is bagged or 
shipped bulk to ready mix concrete plants.

Concrete is produced by mixing cement with fine 
aggregate (sand), coarse aggregate (gravel or 
crushed stone), water, and - often - small 
amounts of various chemicals called admixtures 
that control such properties as setting time and 
plasticity. The process of hardening or setting 
is actually a chemical reaction called hydration. 
When water is added to the cement, it forms a 
slurry or gel that coats the surfaces of the 
aggregate and fills the voids to form the solid 
concrete. The properties of concrete are 
determined by the type of cement used, the 
additives, and the overall proportions of cement, aggregate, and water.


Raw Material Use

The raw materials used in cement production are 
widely available in great quantities. Limestone, 
marl, and chalk are the most common sources of 
calcium in cement (converted into lime through 
calcination). Common sources of silicon include 
clay, sand, and shale. Certain waste products, 
such as fly ash, can also be used as a silicon 
source. The iron and aluminum can be provided as 
iron ore and bauxite, but recycled metals can 
also be used. Finally, about 5% of cement by 
weight is gypsum, a common calcium- and 
sulfur-based mineral. It takes 3,200 to 3,500 
pounds of raw materials to produce one ton (2,000 
lbs.) of finished cement, according to the 
Environmental Research Group at the University of British Colombia (UBC).

The water, sand, and gravel or crushed stone used 
in concrete production in addition to cement are 
also abundant. With all of these raw materials, 
the distance and quality of the sources have a 
big impact on transportation energy use, water 
use for washing, and dust generation. Some 
aggregates that have been used in concrete 
production have turned out to be sources of radon 
gas. The worst problems were when uranium mine 
tailings were used as concrete aggregate, but 
some natural stone also emits radon. If 
concerned, you might want to have the aggregate tested for radon.

The use of fly ash from coal-fired power plants 
is beneficial in two ways: it can help with our 
solid waste problems, and it reduces overall 
energy use. While fly ash is sometimes used as a 
source of silica in cement production, a more 
common use is in concrete mixture as a substitute 
for some of the cement. Fly ash, or pozzolan, can 
readily be substituted for 15% to 35% of the 
cement in concrete mixes, according to the U.S. 
EPA. For some applications fly ash content can be 
up to 70%. Of the 51 million tons of fly ash 
produced in 1991, 7.7 million tons were used in 
cement and concrete products, according to 
figures from the American Coal Ash Association. 
Thus, fly ash today accounts for about 9% of the cement mix in concrete.

Fly ash reacts with any free lime left after the 
hydration to form calcium silicate hydrate, which 
is similar to the tricalcium and dicalcium 
silicates formed in cement curing. Through this 
process, fly ash increases concrete strength, 
improves sulfate resistance, decreases 
permeability, reduces the water ratio required, 
and improves the pumpability and workability of 
the concrete. Western coal-fired power plants 
produce better fly ash for concrete than eastern 
plants, because of lower sulfur and lower carbon 
content in the ash. (Ash from incinerators cannot be used.)

There are at least a dozen companies providing 
fly ash to concrete producers. Talk to your 
concrete supplier and find out if they are 
willing to add fly ash to the mix. Portland 
cement with fly ash added is sometimes identified 
with the letter P after the type number (Type 
IP). The EPA requires fly ash content in concrete 
used in buildings that receive federal funding 
(for information call the EPA Procurement 
Guidelines Hotline at 703-941-4452). Fly ash is 
widely used in Europe as a major ingredient in 
autoclaved cellular concrete (ACC); in the U.S., 
North American Cellular Concrete is developing this technology.

Other industrial waste products, including blast 
furnace slag, cinders, and mill scale are 
sometimes substituted for some of the aggregate 
in concrete mixes. Even recycled concrete can be 
crushed into aggregate that can be reused in the 
concrete mix - though the irregular surface of 
aggregate so produced is less effective than sand 
or crushed stone because it takes more cement 
slurry to fill all the nooks and crannies. In 
fact, using crushed concrete as an aggregate 
might be counterproductive by requiring extra 
cement - by far the most energy - intensive component of concrete.


Energy

Energy consumption is the biggest environmental 
concern with cement and concrete production. 
Cement production is one of the most energy 
intensive of all industrial manufacturing 
processes. Including direct fuel use for mining 
and transporting raw materials, cement production 
takes about six million Btus for every ton of 
cement. The industryis heavy reliance on coal 
leads to especially high emission levels of CO 2, 
nitrous oxide, and sulphur, among other 
pollutants. A sizeable portion of the electricity 
used is also generated from coal.

The vast majority of the energy consumed in 
cement production is used for operating the 
rotary cement kilns. Newer dry-process kilns are 
more energy efficient than older wet-process 
kilns, because energy is not required for driving 
off moisture. In a modern dry-process kiln, a 
pre-heater is often used to heat the ingredients 
using waste heat from the exhaust gases of the 
kiln burners. A dry-process kiln so adapted can 
use up to 50% less energy than a wet-process 
kiln, according to UBC researchers. Some other 
dry-process kilns use a separate combustion 
vessel in which the calcining process begins 
before the ingredients move into the rotary 
kiln-a technique that can have even higher 
overall efficiency than a kiln with pre-heater.

In the United States, producing the roughly 80 
million tons of cement used in 1992 required 
about .5 quadrillion Btus or quads. This is 
roughly .6% of total U.S. energy use, a 
remarkable amount given the fact that in dollar 
value, cement represents only about .06% of the 
gross national product. Thus, cement production 
is approximately ten times as energy intensive as 
our economy in general. In some Third World 
countries, cement production accounts for as much 
as two-thirds of total energy use, according to the Worldwatch Institute.

While cement manufacturing is extremely energy 
intensive, the very high temperatures used in a 
cement kiln have at least one advantage: the 
potential for burning hazardous waste as a fuel. 
Waste fuels that can be used in cement kilns 
include used motor oil, spent solvents, printing 
inks, paint residues, cleaning fluids, and scrap 
tires. These can be burned relatively safely 
because the extremely high temperatures result in 
very complete combustion with very low pollution 
emissions. (Municipal solid waste incinerators 
operate at considerably lower temperatures.) 
Indeed, for some chemicals thermal destruction in 
a cement kiln is the safest method of disposal. A 
single cement kiln can burn more than a million 
tires a year, according to the Portland Cement 
Association. Pound for pound, these tires have a 
higher fuel content than coal, and iron from the 
steel belts can be used as an ingredient in the 
cement manufacturing. Waste fuels comprise a 
significant (and growing) part of the energy mix 
for cement plants, and the Canadian Portland 
Cement Association estimates that waste fuel 
could eventually supply up to 50% of the energy.

Energy use for concrete production looks 
considerably better than it does for cement. 
Thatis because the other components of concrete - 
sand, crushed stone, and water - are much less 
energy intensive. Including energy for hauling, 
sand and crushed stone have embodied energy 
values of about 40,000 and 100,000 Btus per ton, 
respectively. The cement, representing about 12% 
of concrete, accounts for 92% of the embodied 
energy, with sand representing a little under 2% 
and crushed stone just under 6%.

Use of fly ash in concrete already saves about 44 
trillion Btus (.04 quads) of energy annually in 
the U.S. Increasing the rate of fly ash 
substitution from 9% to 25% would save an additional 75 trillion Btus.


CO2 Emissions

There are two very different sources of carbon 
dioxide emissions during cement production. 
Combustion of fossil fuels to operate the rotary 
kiln is the largest source: approximately 3/4 
tons of CO2 per ton of cement. But the chemical 
process of calcining limestone into lime in the cement kiln also produces CO2:

CaCO 3 i CaO + CO 2 limestone i lime + carbon dioxide

This chemical process is responsible for roughly 
1/2 ton of CO2 per ton of cement, according to 
researchers at Oak Ridge National Laboratory. 
Combining these two sources, for every ton of 
cement produced, 1.25 tons of CO2 is released 
into the atmosphere. In the United States, cement 
production accounts for approximately 100 million 
tons of CO 2 emissions, or just under 2% of our 
total human-generated CO 2. Worldwide, cement 
production now accounts for more than 1.6 billion 
tons of CO2 - over 8% of total CO2 emissions from all human activities.

The most significant way to reduce CO 2 emissions 
is improving the energy efficiency of the cement 
kiln operation. Indeed, dramatic reductions in 
energy use have been realized in recent decades, 
as discussed above. Switching to lower-CO 2 fuels 
such as natural gas and agricultural waste 
(peanut hulls, etc.) can also reduce emissions. 
Another strategy, which addresses the CO 2 
emissions from calcining limestone, is to use 
waste lime from other industries in the kiln. 
Substitution of fly ash for some of the cement in 
concrete can have a very large effect.


Other Air Emissions

Besides CO 2, both cement and concrete production 
generate considerable quantities of air-pollutant 
emissions. Dust is usually the most visible of 
these pollutants. The U.S. EPA (cited by UBC 
researchers) estimates total particulate (dust) 
emissions of 360 pounds per ton of cement 
produced, the majority of which is from the 
cement kiln. Other sources of dust from cement 
production are handling raw materials, grinding 
cement clinker, and packaging or loading finished 
cement, which is ground to a very fine powder - 
particles as small as 1/25,000 of an inch.

The best way to deal with the dust generated in 
cement manufacturing would be to collect it and 
put it back into the process. This is done to 
some extent, using mechanical collectors, 
electric precipitators, and fabric filters 
(baghouses). But recycling the dust is difficult, 
according to UBC researchers; it first has to be 
treated to reduce its alkalinity. Some cement 
kiln dust is used for agricultural soil 
treatments, and the rest (of that collected) is 
often landfilled on site. There was investigation 
into the possibility of using cement kiln dust 
for treatment of acidified lakes in eastern 
Canada, but rather than simply buffering the low 
pH of the water, the dust chemically created a potentially harmful salt.

In addition to dust produced in cement 
manufacturing, dust is also generated in concrete 
production and transport. Common sources are sand 
and aggregate mining, material transfer, storage 
(wind erosion from piles), mixer loading, and 
concrete delivery (dust from unpaved roads). Dust 
emissions can be controlled through water sprays, 
enclosures, hoods, curtains, and covered chutes.

Other air pollution emissions from cement and 
concrete production result from fossil fuel 
burning for process and transportation uses. Air 
pollutants commonly emitted from cement 
manufacturing plants include sulfur dioxide (SO2) 
and nitrous oxides (NOX). SO2 emissions (and to a 
lesser extent SO3, sulfuric acid, and hydrogen 
sulfide) result from sulfur content of both the 
raw materials and the fuel (especially coal). 
Strategies to reduce sulfur emissions include use 
of low-sulfur raw materials, burning low-sulfur 
coal or other fuels, and collecting the sulfur 
emissions through state-of-the-art pollution 
control equipment. Interestingly, lime in the 
cement kiln acts as a scrubber and absorbs some sulfur.

Nitrous oxide emissions are influenced by fuel 
type and combustion conditions (including flame 
temperature, burner type, and material/exhaust 
gas retention in the burning zone of the kiln). 
Strategies to reduce nitrogen emissions include 
altering the burner design, modifying kiln and 
pre-calciner operation, using alternate fuels, 
and adding ammonia or urea to the process. The 
cement industry claims to have reduced overall 
pollution emissions by 90% in the last 20 years.


Water Pollution

Another environmental issue with cement and 
concrete production is water pollution. The 
concern is the greatest at the concrete 
production phase. iWash-out water with high pH is 
the number one environmental issue for the ready 
mix concrete industry,i according to Richard 
Morris of the National Ready Mix Concrete 
Association. Water use varies greatly at 
different plants, but Environment Canada 
estimates water use at batching plants at about 
500 gallons per truck per day, and the alkalinity 
levels of washwater can be as high as pH 12. 
Highly alkaline water is toxic to fish and other 
aquatic life. Environment Canada has found that 
rainbow trout exposed to portland cement 
concentrations of 300, 500, and 1,000 
milligrams/liter have 50% mortality times (the 
time required for 50% of the population in test 
samples to be killed) of 68, 45, and 29 minutes, respectively.

At the batch plant, washwater from equipment 
cleaning is often discharged into settling ponds 
where the solids can settle out. Most plants are 
required to have process water discharge permits 
from state, federal, or provincial environmental 
agencies to dispose of wastewater from these 
settling ponds. As long as the pH of this 
wastewater is lower than 12.5, it is not 
considered a hazardous material by U.S. law. Some 
returned concrete also gets put into settling 
ponds to wash off and recover the aggregate. On 
the positive side, many newer ready mix plants 
have greatly reduced water use in recent years 
because of both wastewater disposal issues and 
drought conditions in some parts of the country. 
iMore companies are going to completely 
closed-loop systems,i according to Terek Kahn of 
the National Ready Mix Concrete Association.

Despite the apparent significance of the 
wastewater concern, the National Ready Mix 
Concrete Association to date has not developed 
standards for member companies on wastewater 
treatment, including rinsing of trucks and chutes 
at the building site. John Mullarchy of the 
association says that procedures are developed on 
a company-by-company basis. In many areas, 
environmental regulations dictate procedures 
relative to wastewater treatment. In more urban 
areas, the on-site rinse water (for chutes) often 
has to be collected and treated or disposed of at the plant.


Solid Waste

While the cement and concrete industries can help 
reduce some of our solid waste problems (burning 
hazardous waste as cement kiln fuel and using fly 
ash in concrete mixtures, for example), one 
cannot overlook the fact that concrete is the 
largest and most visible component of 
construction and demolition (C&amp;D) waste. 
According to estimates presented in the AIA 
Environmental Resource Guide, concrete accounts 
for up to 67% by weight of C&amp;D waste (53% by 
volume), with only 5% currently recycled. Of the 
concrete that is recycled, most is used as a 
highway substrate or as clean fill around 
buildings. As more landfills close, including 
specialized C&amp;D facilities, concrete disposal 
costs will increase and more concrete demolition 
debris will be reprocessed into roadbed aggregate and other such uses.

Concrete waste is also created in new 
construction. Partial truckloads of concrete have 
long been a disposal problem. Ready mix plants 
have come up with many innovative solutions 
through the years to avoid creating waste - such 
as using return loads to produce concrete 
retaining wall blocks or highway dividers, or 
washing the unset concrete to recover the coarse 
aggregate for reuse. But recently, there have 
been some dramatic advances in concrete 
technology that are greatly reducing this waste. 
Concrete admixtures are available that retard the 
setting of concrete so effectively that a partial 
load can be brought back to the ready mix plant 
and held overnight or even over a weekend - then reactivated for use.

When it is possible to use pre-cast concrete 
components instead of poured concrete, doing so 
may offer advantages in terms of waste 
generation. Material quantities can be estimated 
more precisely and excess material can be 
utilized. Plus, by carefully controlling 
conditions during manufacture of pre-cast 
concrete products, higher strengths can be 
achieved using less material. The Superior Wall 
foundation system, for example, uses only about a 
third as much concrete as the typical poured 
concrete wall it replaces. Waste water run-off 
can also be more carefully controlled at 
centralized pre-cast concrete facilities than on jobsites.

Another interesting trend that relates to waste 
minimization is the idea of producing reuseable 
concrete masonry units. The National Concrete 
Masonry Association has been working on 
interlocking blocks called Formwallo, designed 
specifically so that they can be reused. While 
these blocks are not yet on the market, this type 
of thinking is a big step forward.


Health Concerns

Working with wet concrete requires a number of 
precautions, primarily to protect your skin from 
the high alkalinity. Rubber gloves and boots are 
typically all that is required to provide 
protection. Cement dermatitis, though relatively 
uncommon, occasionally occurs among workers in 
the concrete industry who fail to wear the proper protective clothing.

Once it has hardened, concrete is generally very 
safe. Traditionally, it has been one of the most 
inert of our building materials and, thus, very 
appropriate for chemically sensitive individuals. 
As concrete production has become higher-tech, 
however, that is changing. A number of chemicals 
are now commonly added to concrete to control 
setting time, plasticity, pumpability, water 
content, freeze-thaw resistance, strength, and 
color. Most concrete retarders are relatively 
innocuous sucrose- (sugar-) based chemicals, 
added in proportions of .03% to .15%. Workability 
agents or superplasticizers can include such 
chemicals as sulfonated melamine-formaldehyde and 
sulphonated napthalene formaldehyde condensates. 
Air-entraining admixtures function by 
incorporating air into the concrete to provide 
resistance to damage from freeze-thaw cycles and 
to improve workability. These are usually added 
to the cement and identified with the letter A 
after the type (Type IA). These materials can 
include various types of inorganic salts (salts 
of wood resins and salts of sulphonated lignin, 
for example), along with more questionable 
chemicals such as alkyl benzene sulphonates and 
methyl-ester-derived cocamide diethanolamine. 
Fungicides, germicides, and insecticides are also added to some concrete.

Because of these chemical admixtures, todayis 
concrete could conceivably offgas small 
quantities of formaldehydes and other chemicals 
into the indoor air. Unfortunately, it is 
difficult to find out from the manufacturers the 
actual chemicals in these admixtures. For 
chemically sensitive clients, it may be advisable 
to specify concrete with a bare minimum of 
admixtures, or use a sealer on the finished 
concrete to minimize offgassing. 
Asphalt-impregnated expansion joint filler, 
curing agents that are sometimes applied to the 
surface of concrete slabs to reduce water 
evaporation, special oils used on concrete forms, 
and certain sealants used for treating finished 
concrete slabs and walls can also cause health 
problems with some chemically sensitive individuals.

Finally, concrete floors and walls can cause 
moisture problems and lead to mold and mildew 
growth, which cause significant health problems 
in certain individuals. There are two common 
sources of moisture: moisture wicking through 
concrete from the surrounding soil; and moisture 
from the house that may condense on the cold 
surface of concrete. To eliminate the former, 
provide good drainage around a foundation, 
dampproof or waterproof the outside of the 
foundation walls before backfilling, provide a 
layer of crushed stone beneath the slab, and 
install a polyethylene moisture barrier under the 
slab (protected from the concrete with a layer of 
sand if possible). To reduce the likelihood of 
condensation on concrete surfaces, they should be 
insulated. In northern climates, installing a 
layer of rigid foam on the outside of the 
foundation wall and under the slab will generally 
keep inner surface of the concrete warm enough 
that condensation will not occur. With interior 
foundation insulation, provide a vapor barrier to 
keep moisture from reaching the concrete surface. 
In southern climates, protecting against condensation may be more difficult.


Summing Up

Cement and concrete are vital components in 
building construction today. Concrete has many 
environmental advantages, including durability, 
longevity, heat storage capability, and (in 
general) chemical inertness. For passive solar 
applications, concreteis ability to function as a 
structural element while also providing thermal 
mass makes it a valuable material. In many 
situations concrete is superior to other 
materials such as wood and steel. But cement 
production is very energy intensive-cement is 
among the most energy-intensive materials used in 
the construction industry and a major contributor 
to CO 2 in the atmosphere. To minimize 
environmental impact, therefore, we should try to 
reduce the quantity of concrete used in 
buildings, use alternative types of concrete 
(with fly ash, for example), and use that concrete wisely.




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