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RE: Low alkali cement

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Some essential reading on the topic. 
http://pubs.usgs.gov/bul/b2209-k/
 
You also need to reference ACI 221.1.  It is a bit dated, but an essential read. 
 
This is a newsletter from FHWA http://www.fhwa.dot.gov/pavement/concrete/reactive/issue01.cfm
 
Do a Google search with: "alkali aggregate reaction".  This will generate a lot of good data. 
 
You should also take a look at Section 2.4.3 of the USACE Spec 03 30 00.
http://www.wbdg.org/ccb/DOD/UFGS/UFGS%2003%2030%2000.pdf
 
Alkali Aggregate Reaction AAR or Alkali Silica Reaction ASR was first noted as a problem in the 1940's, but we really took note in the 1970's when we started having problems.  The traditional method of cement manufacture was a wet grind process.  When we invoked EPA standards, we forced the cement production to a dry grind process which resulted in higher alkalinity.  In the 1980's and into the 1990's the dry grind technology allowed cement to be produced that was low alkali more easily.  Today, most cements produced are low alkali.  Therefore there is generally no extra cost.  I only specify low alkali cement if I need it. 
 
AAR has been more well studied in paving for airports and highways.  But it is a real problem in building structures as well. 
 
See the documents above for answers to some of your other questions.  It is a very wide spread problem with highly regional solutions.  In Florida, they mostly import aggregate.  In most other areas, they add F ash.  Lithium is used for smaller projects in Alaska.  If it is a big project, they will truck in F ash. 
 
The testing is generally done only if requested.  I have learned my lesson by the mistakes of others.  Make sure the aggregate is tested, and if it is reactive, mitigate it.  That said, the tests can be tripped up inadvertently.  You can show reactive aggregate and it will not be a problem in the field.  You can show aggregate non-reactive and it will develop the paste and cause problems. 
 
I have seen paste form in as little as 18 months in concrete not exposed to weather.   
 
Regards, Harold Sprague


 

Subject: Low alkali cement
Date: Thu, 19 Feb 2009 16:30:17 -0500
From: David.Dickey(--nospam--at)masonandhanger.com
To: seaint(--nospam--at)seaint.org

When specifying the type of portland cement to be used in a concrete mix, do you specify low alkali cement? 

 

Do you specify it on all of your projects?  Or none or your projects? 

 

Is there data available that shows areas of the country with siliceous aggregates that could contribute to alkali-silica reaction? 

 

How much more does low alkali cement cost?

 

Is the testing that can be specified to determine the alkali-aggregate reactivity, ASTM C1260, something that is routinely done by the concrete supplier that can be requested, or would the testing be a significant additional cost to the project?

 

Thanks,

 

David Dickey, PE

Lexington, KY



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