# Concrete Patio...what type of mix: 4 sack, 5 sack



## TarheelTerp

27 FEET by 21 FEET by even 2" thick (=3.5 yards) is a LOT of concrete to be doing by hand.
At the far more proper 4" depth and allowance... you're far closer to 8 yards.
Any job using this much 'crete should be getting it delivered.


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## hammerlane

TarheelTerp said:


> 27 FEET by 21 FEET by even 2" thick (=3.5 yards) is a LOT of concrete to be doing by hand.
> At the far more proper 4" depth and allowance... you're far closer to 8 yards.
> Any job using this much 'crete should be getting it delivered.



Tarheel: Where did you get the impression I was doing this by hand? Are you nuts I'm not mixing 7 yards by hand? Never mentioned that. The second sentence in my first post says: *Am taking estimates from local contractors. *

Purpose of my post was to get info on whether requesting the higher sack mix would be beneficial and not detrimental to what I want which is a patio slab.


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## concretemasonry

A general rule of thumb is that higher strength mixes have more durability for the same slump and with the same aggregate. Also absorption is lower.

If you have a freezing climate, the best thing you can do is to use air-entrained concrete (5%) to increase the freeze-thaw durability. It is minimal extra cost and any good concrete supplier has the equipment dosing equipment (a few ounces per yard) and had the approved mix designs.

Dick


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## hammerlane

Thanks concretemasonry.

Will the supplier know this for my area and have these additives in the mix?

Guess what Im trying to get at is I do not want the contractor to try save a few bucks on the concrete mix by not having the proper additives or sack mix if this is going to compromise final product. 

Im sure our winters are similar to St Paul's

Thanks


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## jomama45

For your climate, I'd suggest a 4000 psi (6 bag/sack equivalent) with air-entrainment as Dick mentioned above. The only difference is that I'd suggest it be a little closer to 6% than 5% (5.8% is the goal here typically).

Here's a good read from your state's ready-mix concrete assoc. Note that they're calling for a minimum 6.5 bag mix, but just remember that they're job is to sell cement/concrete...............

http://www.ohioconcrete.org/LITERATURE/Industry Recommendation for Exterior Flatwork-Final.pdf


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## Daniel Holzman

The "sack" method of specifying concrete is not very precise. Usually concrete is specified in terms of 28 day compressive strength, which is typically at least 3000 psi. How many sacks of cement are required per cubic yard of concrete is usually left to the concrete supplier to figure out, as long as they make the required compressive strength, the number of sacks of cement per yard is not critical, since some suppliers will use admixtures or fly ash to their mix. For a patio, 3000 psi concrete should be adequate.

The comment about air entrained is spot on, although I suspect that by default you are going to get air entrained concrete. Just as important as the 28 day strength, and harder to evaluate, is the quality of the workmanship installing the patio. The concrete has to be properly placed, compacted, cured and finished. The base has to be properly prepared. Poor workmanship will destroy the best concrete.


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## concretemasonry

Daniel & jomama45 -

As far a concrete strength, the better concrete suppliers here will not even supply or dump concrete (at any price) for patios, driveways and sidewalks unless it is 4000 psi and 5-7% air entrainment. Some contractors (not DIYers) can get something less if they sign a waiver provided by the driver. The suppliers are tired of getting dragged into court based on quality claims by people that do not place or finish concrete properly, since it is not worth it.

They prefer to turn their back on the low end (price and quality) concrete business.

Concrete has been referred to as the most expensive way to sell good aggregate.

Dick


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## jomama45

Daniel Holzman said:


> The "sack" method of specifying concrete is not very precise. Usually concrete is specified in terms of 28 day compressive strength, which is typically at least 3000 psi. How many sacks of cement are required per cubic yard of concrete is usually left to the concrete supplier to figure out, as long as they make the required compressive strength, the number of sacks of cement per yard is not critical, since some suppliers will use admixtures or fly ash to their mix.
> 
> It's certainly not uncommon for a contractor to choose between either "Bag/Sack" mixes or compressive mixes. We're often offered a number of options in each, and typically a "bag" mix is a straight cement mix with no admixes. It may not matter as much to a homeowner, but getting the correct concrete is critical for the contractor to succeed. So, simply put a "Bag/sack" mix generally refers to a straight cement mix, as in a "6 bag" mix literally has 564#'s of Portland cement per yard. A 4000 psi mix may have as little as 375#'s of Portland cement, with the remainder of the cementicious material made up from flyash, slag, etc... At the end of the day, they both may have similar break strengths, but have very different finishing qualities.
> 
> For a patio, 3000 psi concrete should be adequate.
> 
> From a compressive strength stand-point, sure, but from a water-cement ratio, it will likely not be even close to adequate.
> 
> The comment about air entrained is spot on, although I suspect that by default you are going to get air entrained concrete. Just as important as the 28 day strength, and harder to evaluate, is the quality of the workmanship installing the patio. The concrete has to be properly placed, compacted, cured and finished. The base has to be properly prepared. Poor workmanship will destroy the best concrete.


:thumbsup:


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## jomama45

concretemasonry said:


> Daniel & jomama45 -
> 
> As far a concrete strength, the better concrete suppliers here will not even supply or dump concrete (at any price) for patios, driveways and sidewalks unless it is 4000 psi and 5-7% air entrainment. Some contractors (not DIYers) can get something less if they sign a waiver provided by the driver. The suppliers are tired of getting dragged into court based on quality claims by people that do not place or finish concrete properly, since it is not worth it.
> 
> They prefer to turn their back on the low end (price and quality) concrete business.
> 
> Concrete has been referred to as the most expensive way to sell good aggregate.
> 
> Dick



I know, you've told me that same thing a number of times here already...... :thumbsup: :laughing:


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## Daniel Holzman

Jomama, are you indicating that as a contractor you actually specify a water/cement ratio for the concrete you use, and actually check if the supplier met your ratio? In 35 years of practice, I have never seen a contractor check water/cement ratio. All they ever check, so far as my experience, is the slump of the concrete, and of course they take concrete samples for lab testing to make sure the mix meets strength requirements. If the mix meets the strength requirement, and passes the slump test, so far as my experience goes, the concrete is fine.

So I have a hard time visualizing 3000 psi concrete failing whatever water/cement test you run.


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## Ravenworks

You guys will think that I'm nuts but I used 7 sack mix with 5% air.
I am going to agree with everyone else and say, at a minimum I would use the 6 sack mix however make sure it's a limestone mix.
If it is someone that you don't know faithfully I would go as far as paying the concrete bill, this way you know what you're getting.
You'll have a nice worry free patio for many years to come.


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## jomama45

Daniel Holzman said:


> Jomama, are you indicating that as a contractor you actually specify a water/cement ratio for the concrete you use, and actually check if the supplier met your ratio? In 35 years of practice, I have never seen a contractor check water/cement ratio. All they ever check, so far as my experience, is the slump of the concrete, and of course they take concrete samples for lab testing to make sure the mix meets strength requirements. If the mix meets the strength requirement, and passes the slump test, so far as my experience goes, the concrete is fine.
> 
> So I have a hard time visualizing 3000 psi concrete failing whatever water/cement test you run.


Where did I say there was a test for w/c ratio??? It's nothing more than a relatively simple equation to figure it out.

Here goes:

- It's known that a gallon of water weighs 8.33#'s.

- It's used as a given value that one cubic yard of concrete needs about 25 gallons of water total (includes moisture available in the fines & aggregate) just to merely hydrate the batch, or in other words get the concrete to a "zero slump."

- It's known that it takes approx. one additional gallon of water for every one inch increase in slump.

- It's known that the compressive strength (28 day) designation given by all ready-mix concrete suppliers is based on a 4" slump.

- It's known that a "bag/sack" of portland cement weighs 94#'s.

- It's known that a 6 "bag/sack" mix will achieve approx. 4000 psi compressive strength at 28 days if cured correctly.

- It's known that a 5 "bag/sack" mix will achieve approx. 3000 psi compressive strength at 28 days if cured properly.

- It's known that a lower water : cement ratio is advantageous. A W/C ratio of .45 or lower is the most often used ratio for the developed world. Although our state isn't under it's jurisdiction, I believe the IRC states that the max. allowable W/C ratio for concrete flatwork to comply is .50 W/C ratio.

- It's known that the W/C ratio is derived by taking the total weight of water divided by the weight of the cementicious material in one yard of concrete.

Examples:

3000 psi mix with straight cement only, no replacement cementicious material:

25 gals. of water to hydrate plus 4 gals. of water to get to a somewhat work-able 4" slump = 29 gals. of water @ 8.33 pounds = ~242 #'s of water

5 bags of cement at 94#'s = 470 #'s

242/470= .515 W/C ratio Well outside of the range for quality concreting, especially for areas prone to excessive freeze/thaw cycles.



4000 psi mix with straight cement only, no replacement cementicious material:

242 #'s of water.

6 bags of cement @ 94#'s = 564 #'s.

242/564= .429 W/C ratio Much better result form the additional cement, and safely within acceptable margins.



These are best-case scenario's for W/C ratio's as well, as replacing the portland cement with cementicious admix's/fillers will only bring the overall cementicious weight down, resulting in even higher W/C ratios..................



Too much info for a DIY forum???? :yawn:


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## Daniel Holzman

This puts things in a bit of perspective. See http://www.ce.memphis.edu/1112/notes/project_2/PCA_manual/Chap09.pdf

for a complete description of concrete mix design. At a maximum allowable water/cement ratio of 0.5, you are going to end up with 4000 psi concrete. Since IRC apparently specifies a maximum allowable W/C ratio of 0.5 for concrete exposed to freeze/thaw, the minimum practical strength that would be delivered is 4000 psi concrete. Of course, since only the plant actually knows the water/cement ratio used, the only relevant data about the actual water/cement ratio comes by back calculating the water/cement ratio based on the concrete strength test results. This assumes you actually take and measure a concrete test cylinder. Or you could mix the concrete yourself, then you would know the actual water/cement ratio.

Conclusion: for exposed concrete subject to freeze/that, order minimum 4000 psi concrete, take a cylinder, and get it tested to make sure you got what you ordered.


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## hammerlane

Got it done a few days ago...a few pics:


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## hammerlane

a few more:


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## Canarywood1

Daniel Holzman said:


> The "sack" method of specifying concrete is not very precise. Usually concrete is specified in terms of 28 day compressive strength, which is typically at least 3000 psi. How many sacks of cement are required per cubic yard of concrete is usually left to the concrete supplier to figure out, as long as they make the required compressive strength, the number of sacks of cement per yard is not critical, since some suppliers will use admixtures or fly ash to their mix. For a patio, 3000 psi concrete should be adequate.
> 
> The comment about air entrained is spot on, although I suspect that by default you are going to get air entrained concrete. Just as important as the 28 day strength, and harder to evaluate, is the quality of the workmanship installing the patio. The concrete has to be properly placed, compacted, cured and finished. The base has to be properly prepared. Poor workmanship will destroy the best concrete.


 
+1 to what Daniel said, compressive strength's are common practice,as opposed to the bag mix ,the reason being cement is the most expensive ingredient in concrete,and if you can reach the required strength using admixtures instead of cement,you keep your production cost's down which is a must if you intend to stay competetive.


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## jomama45

Canarywood1 said:


> +1 to what Daniel said, compressive strength's are common practice,as opposed to the bag mix ,the reason being cement is the most expensive ingredient in concrete,and if you can reach the required strength using admixtures instead of cement,you keep your production cost's down which is a must if you intend to stay competetive.


So I'm going to go out of business if I continue to pour straight cement mixes???? :huh:

FWIW, as a contractor, the actual cost difference between a yard of concrete with 3000 psi (both cement & fly-ash) and a straight 6 bag (4000 psi) mix is $8.00. 

If I pour a small complicated pour that's only 5 yards, and have 4 of us standing there waiting for the fly-ash loaded concrete to set for an extra 30 minutes, I've wasted far more than $40.00. Not to mention I've put down an inferior end-product...........

I find it comical that a few folks here can justify wasting money on fibers ($8.25 per yard here) but can't justify paying a few dollars per yard additional for decent concrete.............


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## Canarywood1

jomama45 said:


> So I'm going to go out of business if I continue to pour straight cement mixes???? :huh:
> 
> FWIW, as a contractor, the actual cost difference between a yard of concrete with 3000 psi (both cement & fly-ash) and a straight 6 bag (4000 psi) mix is $8.00.
> 
> If I pour a small complicated pour that's only 5 yards, and have 4 of us standing there waiting for the fly-ash loaded concrete to set for an extra 30 minutes, I've wasted far more than $40.00. Not to mention I've put down an inferior end-product...........
> 
> I find it comical that a few folks here can justify wasting money on fibers ($8.25 per yard here) but can't justify paying a few dollars per yard additional for decent concrete.............


 

Fly ash gives no strength to concrete,it will improve the density and the finishing properties,but thats all,and if you planned ahead you would have added an accelerator to speed up the set,and it's not an inferior product,it's just less compressive strength that more than likely was not needed in the first place.


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## Ravenworks

Salesmen :thumbsup:


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## Canarywood1

Ravenworks said:


> Salesmen :thumbsup:


 


Facts man,just the facts!!


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## jomama45

Canarywood1 said:


> Fly ash gives no strength to concrete,
> 
> Better check again, as it sure does add compressive strength......
> it will improve the density and the finishing properties,but thats all,and if you planned ahead you would have added an accelerator to speed up the set,
> 
> Using a non-chloride accelerator cost pretty much the same as the additional cement......
> 
> 
> and it's not an inferior product,it's just less compressive strength that more than likely was not needed in the first place.


A 3000 psi mix is a far inferior mix to a 4000 psi mix, no matter where you live. In places like OH, where the OP is from, high freeze-thaw cycle action requires a lower water to cement ratio, which can't be attained easily from a garbage 3000 psi mix, or even a straight bag mix........


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## Canarywood1

jomama45 said:


> A 3000 psi mix is a far inferior mix to a 4000 psi mix, no matter where you live. In places like OH, where the OP is from, high freeze-thaw cycle action requires a lower water to cement ratio, which can't be attained easily from a garbage 3000 psi mix, or even a straight bag mix........


 
Better check again, as it sure does add compressive strength......
it will improve the density and the finishing properties,but thats all.

Thats only in class C fly ash and then it's very little,it cost's more to haul it into the plant than it's worth, class F has none and there's very little fly ash used anywhere,it's always been a disposal problem for power generating co.'s

" lower water to cement ratio, which can't be attained easily from a garbage 3000 psi mix, or even a straight bag mix"

That's excatly why you use a water reducing agent instead of cement,and if you think your getting 6 bag's of cement when you order 4000 PSI think again.


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## Mort

I don't remember the last time I hauled concrete without admixtures. Our cheapo mixes at least have mid-range water reducers (which is also a mild retarder).


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## Canarywood1

Mort said:


> I don't remember the last time I hauled concrete without admixtures. Our cheapo mixes at least have mid-range water reducers (which is also a mild retarder).


 

He seems to think he's getting a straight cement mix, when the industry quit using them at least 40 years ago or more.


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## concretemasonry

hammerlane -

It looks very good!!!

As Daniel mentioned that the "bag" or "sack" concept is not the best way to refer cement content and it is getting very outdated. In Canada, Lafarge Cement is now bagging in 44# bags (20 kg) instead of the old 94# or so bags due to injuries and insurance (dictated by their version of OSHA). I assume the cost per pound of bagged cement per pound will be slightly more because the cost of bagging, handling and cost of the bags (bags are not cheap) will go up, but bulk cement will not be changed because it is never bagged for ready-mix concrete.

Dick


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## jomama45

Canarywood1 said:


> He seems to think he's getting a straight cement mix, when the industry quit using them at least 40 years ago or more.


Your throwing an awefully big blanket out there right now. I can indeed still order, and to the best of my knowledge, receive a straight cement mix with no admix/fillers/slag/flyash/etc.... Of course, their QC guys could be lieing to me, and the mix design print outs could be BS as well but I guess I have to entrust my own instincts, as well as the info they provide.

We can easily order a straight 6 bag with 564 pounds of Portland cement.

Another common mix in that range contains 15% fly ash, but has a total of 564 pounds of cementicious material, 480 pounds of Portland, 84 pounds of fly ash.

A third, cheap 4000 psi mix would contain about 440 pounds, or less of Portland, and about 65 pounds of Fly ash.

All of these would fall into the "4000 psi heading", although with everything equal, the middle one would typically break around 4600 @ 28 days, the first at about 4300 @ 28 days, and the last at a minimum of 4000 @ 28 days.

When you say "the industry" moved away from straight cement 40 years ago, I think you're being ignorant to areas outside of what you;re familiar with. Here, the logistics of Portalnd cement delivery are extremely simple, many of the mines are less than 200 miles away by water. As such, 5-10 years ago when we faced a "Cement shortage", it really had little to no effect on us here, other than a temporarily inflated price due to "demand". In FLorida, it was obviously an entirely different situation, as it made more sense to ship overseas for the additional profit potential, thus the shortage issues down there.

Keep one other thing in mind: The company(s) you worked with in the past may have been dishonest with selling straight cement mixes in the past, because you can get away with it in warm climate, but you won't be in business long as a ready-mix supplier here in hard freeze-thaw climates by cheating on your materials. Don't think this isn't or hasn't been an issue here in the past, but you can believe it doesn't take Mother Nature long to expose "corner-cutting" on concrete in the rust belt...........


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## Canarywood1

jomama45 said:


> Your throwing an awefully big blanket out there right now. I can indeed still order, and to the best of my knowledge, receive a straight cement mix with no admix/fillers/slag/flyash/etc.... Of course, their QC guys could be lieing to me, and the mix design print outs could be BS as well but I guess I have to entrust my own instincts, as well as the info they provide.
> 
> We can easily order a straight 6 bag with 564 pounds of Portland cement.
> 
> Another common mix in that range contains 15% fly ash, but has a total of 564 pounds of cementicious material, 480 pounds of Portland, 84 pounds of fly ash.
> 
> A third, cheap 4000 psi mix would contain about 440 pounds, or less of Portland, and about 65 pounds of Fly ash.
> 
> All of these would fall into the "4000 psi heading", although with everything equal, the middle one would typically break around 4600 @ 28 days, the first at about 4300 @ 28 days, and the last at a minimum of 4000 @ 28 days.
> 
> When you say "the industry" moved away from straight cement 40 years ago, I think you're being ignorant to areas outside of what you;re familiar with. Here, the logistics of Portalnd cement delivery are extremely simple, many of the mines are less than 200 miles away by water. As such, 5-10 years ago when we faced a "Cement shortage", it really had little to no effect on us here, other than a temporarily inflated price due to "demand". In FLorida, it was obviously an entirely different situation, as it made more sense to ship overseas for the additional profit potential, thus the shortage issues down there.
> 
> Keep one other thing in mind: The company(s) you worked with in the past may have been dishonest with selling straight cement mixes in the past, because you can get away with it in warm climate, but you won't be in business long as a ready-mix supplier here in hard freeze-thaw climates by cheating on your materials. Don't think this isn't or hasn't been an issue here in the past, but you can believe it doesn't take Mother Nature long to expose "corner-cutting" on concrete in the rust belt...........


 

"Portalnd cement delivery are extremely simple, many of the mines are less than 200 miles away by water."


So your telling me that cement is mined now,i think i've heard enough of your nonsense.


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## jomama45

Canarywood1 said:


> "Portalnd cement delivery are extremely simple, many of the mines are less than 200 miles away by water."
> 
> 
> So your telling me that cement is mined now,i think i've heard enough of your nonsense.


I's originated from limestone, which is mined from the Earth. Do you think it's purchased at Walmart, or do you actually want to add some substanance to the conversation??? So far, I think you're in in relatively deep and you're about to drown.........


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## Mort

Perhaps he also thinks that farmers don't deserve any extra money, because we can all just buy bread at a store instead?


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## Ranger Har

Nice pictures BTW. 
Fly ash sucks and is the first break down of concrete. No highway job for you Fly ash...:no:
concretemasonry you have made some good post in this thread and other ones. I know _new guy buys the first round.:drink:
Drinks on me.
_


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## Ravenworks

jomama45 said:


> I's originated from limestone, which is mined from the Earth. Do you think it's purchased at Walmart, or do you actually want to add some substanance to the conversation??? So far, I think you're in in relatively deep and you're about to drown.........


We have a cement quarry right down the street from us,it used to be called "Diamond Portland" back in the 70's it is now owned by Essroc and it sure is mined.
The patio looks great BTW,I have one planned like it but I am going to come off of the house with semi circular steps.


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## Canarywood1

Ravenworks said:


> We have a cement quarry right down the street from us,it used to be called "Diamond Portland" back in the 70's it is now owned by Essroc and it sure is mined.
> The patio looks great BTW,I have one planned like it but I am going to come off of the house with semi circular steps.


 
And i'd be willing to bet it's a limestone quarry, and not a cement quarry,since that's the major ingredient of cement,which is a manufactured product,and Essroc is a cement producer.


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## concretemasonry

Ravenworks- 

Thr cement is NOT mined. They mine the limestone from a quarry any locate cement production plant right at the quarry to minimize the shipping of limestone, which represents raw vast portion of raw materials and the other materials (gypsum, iron, fly) are share shipped to the plant. In very rare cases the plant cannot be built at the plant site (usually because of zoning, ecology, etc. and some plants ship in limestone by water since it is often cheaper than rail.

The raw materials are ground along with the limestone and fired into a clinker in large rotary kilns that usually operate 24/7, except for scheduled downtime and maintenance.

If cement really existed in the ground, even grinding down (to get it fine) will not help and it would have no real strength.

Dick


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## Ravenworks

We always called it such "Cement Quarry" as kids and I shouldn't have worded it that way,however I do understand the process.
Essroc buys their Gypsum from the power plant on the Ohio river as it is a by-product from the new scrubber system we installed,iron is shipped on rail.
The rest is done on premises.
I set their drum kilns when they replaced them and they are about twice the size of any asphalt plants I've ever seen and weight almost 200 grand with out fligths


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