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Chronological Thread  
  • From: David Neeley <dbneeley@gmail.com>
  • To: permaculture@lists.ibiblio.org
  • Cc:
  • Subject: [permaculture] Cement/concrete
  • Date: Mon, 22 Nov 2004 14:12:10 -0600

Production of Portland cement is environmentally somewhat of a
disaster, in that massive amounts of air pollution result. In
addition, it is a consumer of huge amounts of power--again with the
resulting environmental problems.

Because it is heavy, transportation costs are likewise high--and
contribute to the total embodied energy of the product.

Cement is used both in concrete and as an admixture in various other
materials such as stucco or clay renders used on buildings.

Here is a brief description of the issue from the MIT Press:

"Hydraulic (chiefly portland) cement is the binding agent in concrete
and mortar and thus a key component of a country's construction
sector. Concrete is arguably the most abundant of all manufactured
solid materials. Portland cement is made primarily from finely ground
clinker, which itself is composed dominantly of hydraulically active
calcium silicate minerals formed through high-temperature burning of
limestone and other materials in a kiln. This process requires
approximately 1.7 tons of raw materials per ton of clinker produced
and yields about 1 ton of carbon dioxide (CO2) emissions, of which
calcination of limestone and the combustion of fuels each contribute
about half. The overall level of CO2 output makes the cement industry
one of the top two manufacturing industry sources of greenhouse gases;
however, in many countries, the cement industry's contribution is a
small fraction of that from fossil fuel combustion by power plants and
motor vehicles."

David

>
> I keep encountering situations where some cement would fix things right up.
> But I seem
> to recall that cement is bad for the environment. Anybody know what
> problems cement causes?
>

> you know what I need clarification here. Cement is the bonding agent that
> holds together the aggregates.
>
> Concrete is the combination of aggregates and cement.
>
> ???don




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