F & E- how to best solve it

[Coondog]

Hello,
I have a question, might should be in the mining and aggregates forum, but does not only apply to mining and I wanted to get the best chance for everybody to see it.

I have been studying some material and test running some different areas of a pit. The material is rock, specifically rhyolite, which is best defined as the volcanic equivalent of granite. We have crushed and sold some of this material for smaller projects and some to highway department. Since studying and what not I have made some observations. Very hard material, 25k to 49k psi breaking strength, 70% silica content, very abrasive, and absorption level is a little high. But also breaks pretty flat and englongated. This would be the area I am questioning.

I know that cone Crushers are typically bad for producing f and e. This rock seems to tend to be f and e. Maybe the two together is making the f and e problem worse. If you speed a cone crusher up, i am told that will cut down the f and e, but test cone is a jci k400, which is a high speed cone. I talked to the factory and spinning it faster Would def reduce wear life and bearing life, and not to mention the higher probability of a come a part, which ain't easy to fix. Been there already.

I hear that horizontal impact would break things more square, but wear life sucks, and we are already hardcore abrasive. Professional opinions from some of my suppliers says that we would kill an hsi. I have never been around one myself, but I trust my suppliers opinions to some merit or their profession.

Does anybody here have any further opinions or advise? The product coming out now is stellar, and also accepted by customers, those needing a spec even made a new spec because it passes easy on 5:1, but we would like to achieve 3:1.

 

[CM1995]

Coondog, enlighten us folks that don't know what the term F&E is. I don't know much at all about crushing stone, only know the end product and how it works in construction projects.

 

[mitch504]

I had to go back and read it over, but it's in his post.
Flat and elongated, now, that's all I know on this subject.

 

[Coondog]

Cm1995, Mitch has it right. F and e stands for flat and elongated, meaning the rock is being crushed in more of a rectangular fashion rather than cubical or more square. The ratio has to do with the length versus the width. There is a tool we use to measure this. Basically a 5:1 ration means that a rocks length cannot exceed 5 times it's width. This we can pass easily. Same with a 3:1, any specific rocks length cannot exceed 3 times it's width, making it harder to pass. By this logic a 1:1 would be perfectly square. F and e rocks are rectangular in shape, making them easier to be broken in half when placed down and driven on or compacted or whatever, supposedly making it unstable. However, if a rock passing 5:1 is broken in half, it makes it a 2.5:1 theoretically. In my mind that makes it better material than a 3:1, but I don't make the spec, ASTM does that. Anyways, that is the best description as I know it, hope it helps.


More interesting facts, most specs call for crushed stone to be broken on more than 3 sides I believe. We don't have problem here either, just a blasted f and e problem.

 

[CM1995]

Gotcha, understand it now. I can see, theoretically, where a flat elongated stone could be further broken down during placement and compaction thus changing it's structural capabilities. Although I don't think enough of the stone could be broken down further with a roller in a 6-8" lift to substantially affect it's structural integrity but like you said Coondog we don't make the specs.

 

[Oxbow]

A bit off-topic but:

The rhyolite that we have turns to mush when worked in very wet conditions, but it tends to have sub-water coming up through it this time of year (high water). We did a lodge foundation excavation where Rhyolite was encountered, and after removing the softer rock on top it became un-rippable. After hammering it out, we thought we could use it for driveway base but it desinegrated on us. It was very rainy at the time though.

 

[Coondog]

Cm1995, did you get your pickup truck running again? If I recall you got t-boned or ass-holed by a little car.

Oxbow, I can almost assure you that what you are calling rhyolite, and what I am calling rhyolite, are two different formations with differing characteristics. The rock I am dealing with hardly breaks down, mush less turns to mush. We have been crushing in a different area, same basic formation for 7 years now and we can crush it, but just barely. We wash it really really well and some of it may be stockpiled for months at a time and wetted down further. Months later we will load it out and there is no evidence of breakdown in the pile at all. We have dealt with other material that will have silt lines in it in impact spots. You will see a level of fines in certain places. We have never experienced that at all with this rock.

I did some consultation for a company that was going to go to Vietnam to crush some so called rhyolite. Through a network of dealers and suppliers, they found out about us. They flew in on a corporate jet and came for a walk around, with a jci rep. They had only been to Vietnam one time to see the project and area, but had no chance to excavate at all. They had heard how wicked the rock was and wanted to do some homework. We showed them some of our liners and screens, which are typically much thicker or sturdier than the normal aggregate producer requires. They had some samples they brought back with them. We ran some qc test on them and quickly figured out that what they thought they had did not hold a candle to what we are dealing with here. Silver lining, I got to keep a couple of chunks of rock from Vietnam. I have busted it up and handed it out to suppliers and visitors, jokingly acting like it's really something. I believe the contractors were gng to crush the rock for cement to be used in a new sea port or something like that in Vietnam.

 

[CM1995]

Cm1995, did you get your pickup truck running again? If I recall you got t-boned or ass-holed by a little car.

It was a VW bug that hit my F350, broke the front frame horns and it was totaled. Bought a '13 F350 and have been happy with it so far.

Here's the thread - https://www.heavyequipmentforums.com/showthread.php?33827-VW-Bug-1-F350-0

 

[Oxbow]

Coondog, I'm sure we are talking about two different types of rock, or Rhyolite. The soil sample guys are the ones that called it Rhyolite, and it is sure different than our other rock formations here. As I understand how Rhyolite was formed, which may be incorrect, is that it is a product of up thrust from volcanic activities, and the properties may vary due to how quickly it cooled, etc.

Regarding your desire to get to 3:1 on your product, is the final product a 3/4" minus? One would think that the percentage passing that is still too elongated would be small enough not to be detrimental to the performance of the product, and that it would lock together even better than a 1:1 due to its angularity (no round naturals).

I am not an expert on crushing, and certainly not as well versed as you, but I should think that if the product performs that well then perhaps their spec does need to be modified. At some point it will not be cost effective to fund the extra effort to get it into the current spec if the performance of that spec is no better than what you are getting, and if the fines created by the attempt to get to a 3:1 require rejection of a portion of them. If the ratio of fines is high enough to create a condition in which there are no large voids during compaction, then the idea of breaking the elongated portion during compaction, especially if it is that hard to begin with, seems to be remote in my mind. If you are making concrete aggregate then perhaps there are other concerns.

Using a jaw crusher ahead of the cone seems as if it would be the best shot at what you are striving for, depending on what size rock you are starting with. Without the use of a cone would require the material to be cycled so many times to get it down to size that the cost of production would go very high.

I know I haven't said anything here to help you, I'm just putting my thoughts down here. I hope it all works out well for you.

 

[Coondog]

Oxbow, any discussion may lead to a theory regardless of knowledge. I have noticed that sometimes poeple who do not know anything about what is being discussed can ask the simplest of questions and solve a problem. I think those of us that think we know what we are talking about can be so encapsulated that we fail to see the obvious. Thanks for your replies. in the spec we are trying to meet top size is actually 2-1/4 and bottom being 3/4. It screen out very nicely leaving only .006 % of #200's before being washed, and it actually does not change much after being washed. It is not concrete rock, rather railway ballast. We are running a jaw before our cones as our feed size gets pretty big, the happiest medium so far is to bring it down to a 4-1/2 or 5 primary with the jaw and go down further with the cone as far as matching the two Crushers from a flow perspective.

I know that in concrete rock f and e is not acceptable for a couple reasons. One being workability, the more f and e there is, the more fines needed to sustain strength. The more fines you have the more water you need, but contrarily reduces strength. Also an f and e rock rock that breakes during the drying stage will leave two uncoated faces of rock under the surface which can cause pocketing under the surface it is claimed. There is not much concrete action taking place around me anyhow though.

On a side not, we hav something that forms in the voids in this rock called a dendrite. It is more of a water mark than a fossil, and looks like a fern or sea weed or something. But actually has nothing to do with plant. I have considered marketing it somehow but I have had little time and have not gotten it out there too good. I know I have a photo I will just need to figure how to get it on here.

 

[Oxbow]

Thanks for the reply Coondog, where it is railway ballast I can see the concern for breaking elongated pieces where there are essentially no fines in the material. As you mentioned earlier though, if it were to break it would then be closer to 1:1.You would think that whatever settling occured would be consistent and would not create a problem. They poweres that be have a reason to request a certain spec though.

Good luck with it!

 

[Oxbow]

One final thought Coondog, I don't know what size cloth your using in your screen plant, but if the top deck was 1 3/4" the diagonal distance of the opening would be 2.47". This would mean recycling more through the cone and more rejects under 3/4", but perhaps it would help to get your ratio more in line with what you want. If you have a market for the material passing through the 3/4" screen, which ought to be excellent for driveways, parking lots, or perhaps even highway road base, then the added production cost may be offset by that.

Maybe the second pass won't make the f&e problem any better, I don't know.:beatsme

 

[Delmer]

Coondog, I'm sure we are talking about two different types of rock, or Rhyolite. The soil sample guys are the ones that called it Rhyolite, and it is sure different than our other rock formations here. As I understand how Rhyolite was formed, which may be incorrect, is that it is a product of up thrust from volcanic activities, and the properties may vary due to how quickly it cooled, etc.

I don't know Rhyolite, but in Northcentral WI there is "decomposed granite" which is granite that is so weathered that a backhoe bucket can dig it easier than hard clay. It's the same type of rock, just a little older, or more weathered.

Sorry, I know even less about F and E.

 

[Coondog]

this is my first time to attach a photo. hope it works. this is naturally occurring, like I said above, a dendrite or dendritic crystal. has nothing to do with a plant at all, something about water that is high in iron seeping into cracks in a formation that is high in silica.

 

[CM1995]

That's a beautiful stone. Is the crystal engrained in the stone - does it rub or scrape off? That would make a very nice and expensive stone tile.

 

[Coondog]

The marking is engrained in the stone, but only maybe a quarter inch deep at most. I have taken hammer and chisel to it to see how much it takes to knock it off. It is quite resilient. It will not wash off. I have one that has been watered everyday for a period of time and marking is still there. I have some in the ground that have been walked on a lot and no significant wear of the marking is visible. It's pretty tough. These things come out of our current pit all the time. We moved about a 15 ton rock to the courthouse lawn for the county. I believe they are supposed to get some engraving done on it. My grandparents on my mothers side had both passed last year, and we had a headstone made for them out of one. It's pretty neat. I have a couple fairly good sized ones that I plan to saw and place on my porch before I build the roof over it making a big table inside that will never be moved. The operators just grab them out of the feed material when they see them. Most of the time they are from 4 to 10 inches thick and a cubic foot or two. But we find them small as your hand sometimes too. The one pictured is probably a 2000 lb rock.

 

[CM1995]

My grandparents on my mothers side had both passed last year, and we had a headstone made for them out of one. It's pretty neat. .

I bet that's one magnificent headstone.

 

[stumpjumper83]

I'm going to assume that your drilling and blasting... What happens when you change your hole pattern?

 

[Coondog]

Stump jumper, yeah we drill and blast, it as no real effect on the rock flowers. I'm just kidding, we have changed hole patterns many times With no real difference except in the larger sizes. Easiest we have hit it was 4" holes on a 9x9 using .75 powde factor to 6-1/2" holes on a 15x11 with a powder factor of 1.20. The latter pretty much produced road base. We still double deck, that's because the formation dampens energy pretty good. But drill and blast is where it all begins, what we do there can make the rest of the process pretty difficult if we don't do it right. So good point. Thank you.

 

[JDOFMEMI]

Coondog

Have you thought of trying a set of rolls for your secondary? I have seen a balast operation that was running that way and getting the desired product. It seemed to work better than the cone, and the rolls will make less of a reduction ratio, so you make less of your rock too small for the bottom size needed for the balast.

I know rolls are hard to find, and high maintenance. Put a welder to them every night to keep them tight, but other than that they work well for the application.