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[GreenYes] Re: portland cement chemical analysis


If you're asking about using crushed concrete as cement, I believe
the formation of calcium-silicate crystal structures in portland
cement is a one-way trip. Portland cement cannot be crushed and used
as cement.

The use of crushed concrete as a concrete aggregate is another
question. One issue I believe is the balance of excess calcium
oxides present after cement cures, which may effect the curing of any
additional concrete added later. in other words, the process goes
out of control.

I believe a contractor is being prosecuted for using recycled
concrete in new concrete in the San Francisco Bay area. You might
search the web site in the local newspaper there.

I have heard of recycled concrete being used in Controlled Density
Fill, a much less stringent spec.

I think there are a number of studies that could be googled.

Bob Kirby


On Aug 30, 2006, at 1:45 PM, Wayne Turner wrote:

Greenyessers,

Slightly off-topic but still recycling related:

Does anyone know how the chemical composition/analysis of portland
cement changes once it undergoes the setting process? I'm interested
in this for the purposes of investigating the chemical properties of
crushed/pulverized concrete from the C & D waste stream. As always,
thanks in advance for any assistance.




Wayne Turner
Assistant Solid Waste Administrator
Winston-Salem/Forsyth County Utilities
phone: (336) 727 8418
fax: (336) 727-8432
email: waynet@no.address


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