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Engineering properties of petroleum coke ash (cross post)

Engineering properties of petroleum coke ash (cross post)

Engineering properties of petroleum coke ash (cross post)

I am searching for resources regarding petroleum coke fly ash and bottom ash.  Our goal is to prepare a testing program for our client to determine the properties of the ash and their applicability for various construction uses (ie. subgrade stabilization).  I am particularly looking for sources that discuss material testing, material properties, and how these propeties effect field performance.  

I would appreciate any information with regards to this topic.

RE: Engineering properties of petroleum coke ash (cross post)

Contact Coker Automation in Lynden, Washington
"CokerAutomation.com" <mail@baysideeng.com>

RE: Engineering properties of petroleum coke ash (cross post)

I did a little work in this area in the mid 1980's as a consultant to a company in Houston called Ash Management, Inc.  They were looking to use fly ash from a coal-fired power plant as landfill liner material.  The company's management was focused on the "mechanical" properties: workability under compaction, strength, etc.  I was more concerned about permeability and leachate.

We were only authorized to run one permeability test.  I ran a flexible wall permeability test, but it took almost two weeks to complete.  I backpressured the sample to 40 psi for three days, and only got a B-value of less than 0.7.  I increased the back pressure to 80 psi for two days and flowed three sample (not pore) volumes through the sample; the B-value went up to 0.75.  I cranked the back pressure up to 90 psi - the B-value only got to 0.8.  I was thoroughly baffled, and couldn't find anything in the literature to explain what was happening.

My epiphany came in the shower the next morning: the use of the B-value assumes the soil grains are incompressible.  Ash from a power plant isn't a soil; it's burned organic matter.  The individual particles are compressible.

Save yourself some time: if you use a flexible wall permeameter, develop a B-value acceptance criteria early in your testing program.

RE: Engineering properties of petroleum coke ash (cross post)

I have also run some perm samples on fly ash. We ended up using an inflow=outflow over a period of time to determine saturation. Even with flow through the sample it does take some time for the fly ash to saturate.

RE: Engineering properties of petroleum coke ash (cross post)

Just to provide a little experience we had and a word of caution. Make sure your source ash isn't susceptible to shrink-swell. Certain ashes, depending on the processes which they are produced should be used with great caution. To the best of my recollection, fluidized bed ash is one of the "bad ashes" to work with in the vicinity of anything semi-rigid (foundations, pavements, sidewalks, slabs, etc.). In the Richmond, VA area, millions of dollars were lost on buildings that used flyash as structural fill, only to find out after the ash started to react with water, that significant swell was observed. Enough be heave floor slabs, crack walls, and heave column foundations (some of the cases are still in litigation). There are resources out there now to help you identify the bad stuff from the good depending on the source. Unfortunately, I am only aware of microscopic analysis and x-ray defraction (i.e., not cheap)to help identify if a particular ash is susceptible to swell if the source is unknown or a mixuture of the products is used. If you are unsure about the shrink-swell behavior of a particular source or blend, I would advise DON'T USE IT!

I'm glad that more than one person has reached the flyash backpressure saturation conclusion. We hypothesized on this on (why didn't you save us the time and publish your thought) when we started perm testing in significant quantities around 1996. Anyway, in addition to Focht's comment that a burn material is compressible (it is - and I agree with the impact a stiff soil skeleton can have on measured B-parameters), we identified that many of the particles (as seen under a microscope) can also be hollow (filled with air) and that also contributed to the compressibility. Too bad such great information only comes from the eng-tips forum.


RE: Engineering properties of petroleum coke ash (cross post)

Sorry I didn't publish my results and save you (and others, too) the aggravation.  Ash Management was mad at me at the time since my lab test results were unfavorable to them.

On the round, hollow particle shape of the burned ash particles: I had suspected that in my work.  The as-delivered material had a relatively low unit weight, but the weight went up significantly during the process of developing moisture-density curves.  I had assumed the  manipulation of the material was the root cause, with hollow particles the mechanical property that allowed this to occur.  Some of my peers thought I was nuts at the time.  Glad to know that your work confirmed my hunch.

RE: Engineering properties of petroleum coke ash (cross post)

Also, on water contents (or other drying) you'll want to dry at 60 degrees C for a longer time and vaccuum specific gravities rather than boiling.

RE: Engineering properties of petroleum coke ash (cross post)

I believe if you are using bottom ash, your drying can be done at the normal 110C.  Reasoning being that bottom ash has already been subjected to heat orders of magnitude higher than that.

I work for a materials testing firm in Washington.  On the testing side of this, I have not been able to use nukes, due to the hydrogen/other chemicals in the material.  I used the sand-cone method, which proved to be extremely consistant with reasonable results.  Due to the vitric surface and sand-like grading, high moisture content turned out to work well for installation.  Actually, beileve it or not, we had best success putting a guy on a fire-hose that spayed the roller drum as he was compacting.  It sounds outrageous, but the material firmed up in only a few passes.  

There's my two pennies!  Best of luck.  Bottom ash was great material for our client at the time; cheap and lightweight.  I know the supplier had clients far and wide.  I was curious about its engineering properties, but did not give the approval for use.  Rumors had been circulating at the time of environmental mal-effects, but your supplier should have an analysis.  Our analysis appeared thorough and benign.  

Great discussion!  I wish I had this back when I was working with it.

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