CCB as Earth Fill

[fattdad]

Dear Folks:

I've been googling for references on the use of coal-combusion byproducts as earth fill for building pads and subbase for slab-on-grade construction. I'm looking for any recent information related to LEED credits and qualities that are known to be favorable for specifying. Here's what I know: There's bottom ash, there's flyash, there's FGD (flue-gas desulfurization products); there's type F and Tpe C flyash, there's self-hardening flyash, and there's ash derived from fluidized bed combusters (more likely to have comingled sulfur compounds). I also have a copy of ASTM E-2277-03.3

Ten years ago, there was MUCH damage in Central Virginia from improperly mixed CCB materials. Entire buildings had to be reconstructed owing to a chemical reaction that took place within delivered CCB materials. Swelling from remineralization was the culprit. I'm trying to establish a chemical fingerprint to safeguard folks from reliving our unfavorable experience.

Comments?

f-d

¡papá gordo ain’t no madre flaca!

 

[DMcGrath]

The formation of the mineral ettringite is thought to be the usual suspect when it comes to swelling of CCBs. Keeping water out of the fill is the usually easiest to implement to safeguard against swelling. A white paper from the Ash Library of flyashinfo.org has a mechanical test for swelling. Not exactly what you asked for, but it is a start.

http://www.flyash.info/2005/135has.pdf

 

[fattdad]

DM,

Thank you very much. I am familiar with the mineral ettringite and am aware of it as a culprit.

f-d

¡papá gordo ain’t no madre flaca!

 

[SlideRuleEra]

Bottom ash makes a good fill material "as-is" (unless the heavy metals in it cause a problem with ground water contimination).

The real problem materials are fly ash and FGD waste; both have to be stabilized with an additive such as lime to make them work properly. Since the additive is relatively expensive (considering the large quantity of material that needs to be treated) electric utilities try to use the minimum amount needed to do the job. Sometimes they may fail to meet the minimum. I suggest that you analyze CCB material samples for the percentage of the additive present - these results will likely be the "smoking gun" needed to predict if there will be trouble ahead.

http://www.SlideRuleEra.net