Recycled Rock?

[ponderosae]

I don't mean when they switched the oldies radio station to the '70s era (but that was lame, well not quite as lame as b-side disco music at the home depot).

Anyway, is recycled rock and asphalt like getting a set of used tires that are priced two dollars less than the new ones? I was reading a topic on here where some comments said the regrind was "quite expensive". Although, when I was reading about it elsewhere they were saying it was "very low cost"... they also said the asphalt percolated water to prevent pooling, but I was reading here that it would crack without a good base that was crowned. They say recycled concrete also works great for something-or-other and costs much less (but I don't know if it's used for 'gravel base' and 'cobble', just that those are some recycled rock products made of "aggregate"... sounds like concrete I guess).

[ESFted]

My local materials supplier has recycled concrete crush-n-run (or crusher run) much cheaper than the regular stuff.  I used it for a patio base and it compacted the same and appeared to have the same kind of mix of fines and larger pieces.  I wouldn't hesitate to use it again for anything the regular stone material would be used for...and save some $$$.

[ponderosae]

That sounds good, thanks.

Another question that came to mind was where did the concrete come from? So I was reading about Concrete degradation, and a lot of that occurs in the concrete used in sewers, or exposed to fire, and maybe even radiation.

One obvious sign that any of it may be used in the recycled rock are the different colored ones (that I saw in a picture of the product), which means it had thermal damage from very high temperatures (unless perhaps color was added when it was mixed—usually not pink or yellow like the burnt stuff though, and the brown could go either way).

As far as the asphalt goes, I don't know (maybe there's some road kill in that).  Well, there can be hazardous waste spills on the road too.

Not to discourage anyone from going green there (unless maybe it's glowing a neon green). Or, at least I'd hesitate to use it for landscaping a garden.

[barbender]

Crushed concrete makes an excellent road base, due to the angularity of the material. It locks together instead of rothe seperate pieces would, pea rock being an example of not having angularity. The crushing process also opens up some uncured cement, which will reharden. The main drawback of crushed concrete is that it is hard to regrade once it sets up. It's really hard to cut again.

[lxskllr]

Chunky concrete is popular for construction entrances. Makes a great road that hold together, but is rough to drive on for awhile. Also kind of fun looking at the different pieces, and speculating where they came from. Millings make a great driveway surface. It's not a "forever drive", but easy to fix, especially if you have a farm with farm equipment to regrade it yourself.

[Al_Smith]

If I'm not mistaken the resurfacing of asphalt in the state of Ohio contains a certain amount of "regrinds " .Before that I've seen many driveways that used chunked up pieces which after a few years of driving over crumbled apart and made a good base plus it was either free or cheap .
In a former life with a former wife I used reclaimed railroad ballast to install about 4-500 feet of driveway at $1.50 a ton .It made a real good base .

[ponderosae]

That's interesting, I didn't know the rocks on railroad tracks had to be replaced. So I was looking up why that is, and they say that fouling agents, especially coal dust, can drastically reduce the strength of the gravel (or its capacity to drain): Laboratory Characterization of Fouled Railroad Ballast Behavior  

[Al_Smith]

It was from about 50 miles of abandonment  of the Erie Lakawanna rail road which was about 200 yards  from where I lived at the time .The right of way,the rails ,the ties and the ballast were sold off .Fact in one day I hauled over 300 tons, 8 tons at a time with a 1957 Ford F-600 dump truck .
Worked out perfect .I had my brother in law running my D4 Cat .As I came with the next load he was making the last pass on the previous load and when I got on the right of way the loader operator had the next scoop ,no lost time .You can't "tail gate " heavy rock like that, just dump and blade it .

[barbender]

Yes Al, new asphalt almost always contains a percentage of "recycle".The amount is specified in most highway contracts, typically a paving contractor/plant operator wants to use as much as they can. As an aside, the more recycle a mix contains, the more miserable it is to work with, as far as any handwork goes. It gets really "gooey", even when it's good and hot it seems like cold mix. After wrestling with high recycle content hot mix, getting to use virgin material asphalt was a treat👍 At any rate, recycled asphalt is hard to get ahold of now, or fairly expensive, because it is no longer looked at as a waste product.

[ponderosae]

As a rule of thumb, I gather that recycled asphalt pavement is 30% cheaper than new asphalt (according to a technical report by the Virginia DOT), yet it is also a 30% weaker material (as recycled materials would most often be degraded or they wouldn't have been recycled). For instance, the design guidelines in Texas reflect that it should be used as only 20% of the mix with concrete versus 50% for new asphalt. Another study says it only works well up to 50% with something else added to "rejuvenate" it...

"Limits on Percentage. When RAP is allowed, do not exceed 20 percent RAP by weight unless otherwise shown on the plans."

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https://static.tti.tamu.edu/tti.tamu.edu/documents/0-6037-2.pdf

"Fine aggregate matrix (FAM) is a crucial part in the fatigue resistance of asphalt mixtures with high RAP [reclaimed asphalt pavement] content... The fatigue life of FAM would be greatly shortened when the RAP binder replacement rate reached 50%. Adding RA [rejuvenating agent] could considerably improve the dynamic properties of FAM mixes with high RAP content, resulting in a decrease in modulus, increase in phase angle and elongating fatigue life, but could not recover to the level of virgin binder."

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https://www.mdpi.com/1996-1944/12/9/1508

Back to the colored concrete, it could be more reduced in strength than asphalt (which is why it may be relatively cheaper), since it is said that even the pink stuff should be removed from existing structures (and it can get a lot hotter than pink, yet the light gray might be more elusive to distinguish). From what I've seen, however, a noticeable percentage of the recycled concrete appears to have been over heated...

"Concrete exposed to up to 100 C (212 F) is normally considered as healthy. The parts of a concrete structure that is exposed to temperatures above approximately 300 C (572 F) (dependent of water/cement ratio) will most likely get a pink color. Over approximately 600 C (1,112 F) the concrete will turn light grey, and over approximately 1000 C (1,832 F) it turns yellow-brown.

One rule of thumb is to consider all pink colored concrete as damaged that should be removed."

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http://www.rumford.com/thermaldegradationconcrete.html

Not that it necessarily matters, if you're paving with either of those for relatively light use, just something else to be aware of for heavy use (or longevity) I'd imagine. Well, I was getting a general idea about the strength there, not planning anything structural in particular (but I'd probably not attempt building more than a sidewalk with 100% recycled stone). Of course, your mileage may vary (and on a rainy day, I was just noticing all of the full lane puddles over the streets around here, so maybe they should use more of that stuff for drainage, or maybe not).

[Al_Smith]

Before I retired in a massive installation of an entire automotive engine assembly line they completely recycled a concrete floor. Broke it up with a giant vibratory device originally made for breaking up air port runways .Removed whatever amount of reinforcing rod etc and ran the concrete through a crusher and used it for the new base .
Part of the idea was due to  the fact the old concrete which could be contaminated with oils etc and since it never left the site no special procedure  was necessary for disposal . My word imagine the huge piles of crushed concrete from 12" to 16" thick and 400 by 1800 feet long .Then remember the mountains of reclaimed reinforcing rod .It was certainly a sight to behold .

[ponderosae]

Wow, maybe they added more reinforcing rods and fibers to make up the difference.

[ponderosae]

Vaguely in comparison, I've used recycled wood to make shelving. It was from a pallet/crate type thing that I took apart, along with other scraps I had laying around, then I glued the built-up posts together to reinforce the cracked nail holes that I didn't want to reuse. After all, if the shelves are big enough, it will take up half of their space to store the left-over scrap wood, if I start with all new materials. But they're strong enough to fill up with recycled stone too.

[Al_Smith]

That crushed recycled concrete wasn't remixed to make new .Rather it was compacted to make new base over which about 8" of "foundation floor  concrete" was poured .Over that another 8" of steel fibered concrete was poured .Needless to say it's a very sturdy floor .
When they started out with the pours it was often around  10,000 cubic yards in a day .One after another concrete trucks every single one had "slump "tests before it was accepted .Probably 4 or 5 different concrete companies were involved as well as a small army of laborers and concrete finishers .

[ponderosae]

Ah, I was thinking of the other context, but it looks to be used as a base that way too:

"According to a 2004 FHWA study, 38 states recycle concrete as an aggregate base; 11 recycle it into new portland cement concrete..."

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https://www.cement.org/learn/concrete%2Dtechnology/concrete%2Ddesign%2Dproduction/recycled%2Daggregates

Something about it also involves more shrinkage potential, but maybe not with a crushed base:

"Concrete experiences two unique phenomena known as creep and shrinkage. Both phenomena represent increased deformations over time, one regardless of load (shrinkage) and the other proportional to the amount of load applied to the member (creep). Going back to the wooden floor joist example, if the joists were instead made of concrete and you were to stand in that exact same spot for 5 years straight, the joist would deflect slowly over that time period as a result of creep and shrinkage. RCA [recycled concrete aggregate] concrete will generally experience increased creep and shrinkage (i.e., increased time dependent deflections) as compared with NA [natural aggregate] concrete. Based on testing of full scale beams, if NA is fully replaced by RCA it is possible to see total deflection (i.e., immediate and long-term) as much as 70% greater as compared to an equivalent NA concrete beam."

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https://schaefer%2Dinc.com/use%2Drecycled%2Dproducts%2Ddaily%2Dnot%2Drecycled%2Dconcrete/

That's an interesting figure anyway. So the recycled asphalt was said to be 30% weaker, while the recycled concrete may be 70% weaker than its initial structural use, although the same article says that using it as a crushed fill for roads is non-structural. I don't know about them mixing it into new concrete though, which could be a structural use (I'd guess it would depend on the percentage as with asphalt).

[charles mann]

A little late on the topic, but i have used crushed crete with great success. As a reply mentioned, extremely hard to fine grade once its packed down. I hauled on my gn flatbed, 10 loads weighing in between 20,000-27,000 lbs per load and built up my driveway. After blading it out and a few months of driving on it, my box blade root rippers with 1000# of sac-crete and a 70hp tractor found difficulties digging in. I had another 6 bobtail tck loads brought in to set my conex shop on and its holding up fine. Only issues iv found is rebar, nails, crete wire in the material. Before buying new tires and selling my tractor for a bigger 1, i had probably 8-10 plugs in ea tire and that was after running a magnet over the material after blading and picking up metal for weeks after putting it out. I ended up offering my son $0.10 per piece of metal and after 1 day, he picked out $40 in metal. 

[ponderosae]

Was he listening to heavy metal music?

I don't mean when they switched the oldies radio station to the '70s era (but that was lame, well not quite as lame as b-side disco music at the home depot).

Well, one thing that isn't lame about it also has to do with recycling rock lately:

The Rolling Stones go green

If you see the Stones in concert this summer and go get a drink, there may be no single-use plastic cup for you. The band and its promoter are working with Michael Martin — he's produced a bunch of big Earth Day concerts. The Stones approached Martin and asked for help in eliminating plastic waste. He came up with a simple solution.

"When you come up to get your first beverage, you put down a $3 deposit, you get a really high-quality Rolling Stones-branded cup," says Martin. "You use it throughout the night, and at the end of the event you can turn your cup in and get your $3 back or you can keep your cup." If you return the heavier plastic cup at the end of the show, it gets washed and used again. Or recycled...

Hmm... not to follow something positive with something lame, but 'washed and used again, or recycled'?  I would have to ponder that one, but someone already did:

Reusable or Disposable: Which coffee cup has a smaller footprint?

It would take between 20 and more than 1,000 uses, depending on the cup/mug type and the environmental indicator, to make up for the impacts of a single-use cup. If a reusable cup is used fewer times than that, the single-use cup is better for the environment... What should we do then? Can we help the environment? The answer is yes: by reusing your cup for several years and by limiting the quantity of soap and hot water for washing it, the reusable cup should be the way to go.

Rock on!