Driveway in Colorado Strong Enough to Support Garbage Truck

Replacing driveway...

Please advise the existing construction and condition, and the purpose for this replacement.

Frost line depth? Dimensions? Undefined restrictions (e.g., budget, DIY, covenants)

The previous recycled asphalt was removed including dirt 4-6". 4-5" of 1.5" granite rock was installed and rolled (packed). Driveway connecting street to shop (where garbage dumpster is stored) is 325' long x 12' wide and will have to support the garbage truck. Remainder of parking area will need to support tandem axle camper weighing 12,000lbs pulled by diesel pickup. Total weight across 4 axles is 20,000lbs.

No covenant restrictions. Not DIY--I will be hiring a local Denver concrete company to install.

Not sure about frost line depth but Colorado has relatively mild winters by most standards with typical winter nighttime temps in the 20-30F with brief periods down to 0F. Summers can go 100F but typically in the 90F range.

I was able to locate the frost line depth for my area = 44".

I live on the SE corner of Denver just east of Parker, CO.

https://international.fhwa.dot.gov/pubs/pl07027/llcp_07_03.cfm

Looks like 6 - 8" thickness of concrete...

https://alphapavingtexas.com/concrete-slab-thickness/

Around 73 yds at 6"....about $6500

https://www.concretenetwork.com/concrete/howmuch/calculator.htm

Thank you. What about mesh, rebar, or steel fiber to reduce thickness?

As well, what about crack control, watershed, perhaps in-slab heat (ice control)?

Concrete seems to be, in the circumstance, contraindicated. Is concrete simply what you want, or does this really need to be a fresh, smooth, concrete drive surface?

The steel fiber seems to be a solution to the cracking problem. Load bearing is what's driving me to concrete. The asphalt guys won't guarantee anything with a garbage truck on it. Does not have to be smooth but the 1.5" granite rock is worse than rough. I got taken to the cleaners on that recommendation.

I can imagine the 1.5" stone to be too rough for your purpose. If all the drive will ever see is big tires it might have been okay.

Is a trash collection truck truly the heaviest per square inch the drive will ever carry? Delivery vehicles, water truck, fire apparatus, farm or construction machinery... these can be pretty heavy.

Seems with the size described and the use intended that welded mesh or rebar is in order. The 6" thickness seems about right, with perhaps 10" at edges.

General rule of thumb: Any monolithic concrete slab 14'0" or more will crack - regardless of reinforcement used. Crack joints (sawed) alternated with cold keyed joints at 14' max are likely called for.

Many thanks, and yes, the garbage truck is by far the heaviest. No farm equipment and the propane truck is lighter than the garbage truck. My local concrete guy also recommended 10-12' flex cuts as well. Much appreciate the quick responses!

For weight, what about the fire department tanker? Multi-thousand gallons of water will be heavy.

Your 12' width would suggest that this is not necessary but I would consider a cut down the center for the full length of the driveway. The full 325' of length is a long way to assume that you never have a left side vs. right side base problem. You would still need cross cuts as recommended.

Isolating the left and right sides would trend toward having the truck exert downward compression under the dual wheels and tend to reduce the strain on the concrete spanning the wheel base.

The truck turn-around area might deserve extra thought.

WARNING: I'm an electrical engineer so I don't actually know what I am talking about.

"Isolating the left and right sides"

Could be an idea to save on materials too: with a two four six split yo'd save a 1/3

A vehicle with a six foot axle and 1 foot wheels could drive either spanning the gap or on the six foot wide section; any wider vehicle would just span the gap and any narrower would use the six foot.

That was just a first attempt: I wonder what the minimum requirement would be, assuming no nervous drivers (or reliant robins).

starting with a good base that is smooth is imperative. The base needs to be 8-12" thick or better, depending on what your ground is. if the base can support the weight, then we know the concrete will. A smooth, flat base surface is a must. the slab will expand and contract thought the seasons and even night to day. if the sub-surface is not smooth, the concrete will grab and will crack. I spoke with my son-in-law who runs a concrete crew, he said the minimum thickness for an apron is 6" (in Ohio), he said if there is a concern, he would go with 8". he said to ask for "4500#mix with air" and to use wire mesh. He said the concrete company will know what that means...

His company has the Menard's contracts (and others) in the area as well as residential drives and basement walls.

Sounds like I need to add a few inches of smaller gravel on top of the 1.5" granite rock and then rolled again. Easily done and much appreciate the comments.

I would add, don't forget to seal the concrete with at least 2 coats of good quality concrete sealer....

https://www.tristar-concrete.com/learn-about-concrete/what-base-concrete-slab

to reply to your reply on base thickness of adding a few inches....

well, maybe not. if your base is pretty firm and there for quite a while, you are probably good. i was talking about a new drive.

Very good comments--I'm very glad I posed the question. My garbage truck only comes every other week and backs up the driveway and departs straightaway so no turning around or leaving the pavement. NO parking of the garbage truck long term.

The ground here is very (VERY) hard with bentonite making it greasy at times...but never mushy.

I'm curious about using plastic fiber in lieu of the steel fibers recommended by the manufacturers I've spoken with. They seem to claim I can forego the rebar altogether and use steel fibers instead.

Anything steel will rust...and the rust swells...not good....you don't really need any reinforcement, just proper mixed concrete, and proper cured...The sealer keeps the moisture out and keeps the concrete strong....the last thing you want is for moisture to get into the concrete and freeze...and you don't want to apply the sealer until the concrete is completely dry....several weeks at least...

http://www.bnproducts.com/blog/what-are-the-different-types-of-rebar-and-why-do-types-matter/

From #14: "put their initials next to their hand prints. And maybe a date"

I really don't think it will do much good to put the granddaughter's date in the concrete. After a week or two goes by another boy will take his place and you will be right back where you started.

This info comes from my cousin,who I consider an expert on concrete,having poured airport landing strips in the Marshall Islands and shopping centers all over the States.

Having supervised the pouring of many miles of concrete,he recommends fiberglass(not plastic) reinforced concrete (FRC) with 4% Sodium Acetate added to the mix.This is in addition to the wire mesh or rebar,and very important to get the rebar properly placed in the form,or strength will suffer.If rebar is cut,make sure there is a "eye" bent into the end to anchor it into the concrete

The Sodium Acetate enhances the strength of the concrete,and act as a one-way valve for the concrete,allowing water vapor to escape but not allowing liquid water to penetrate.However,it is still important to install a plastic vapor barrier on top of the base to prevent moisture from penetrating from below.It is still important to keep the concrete wet during the cure,which is a minimum of 7 days,and longer if possible.Concrete is funny stuff..it needs all the water it can get while curing,but not while being mixed,and after curing, you do not want any water getting into the concrete.Concrete is a chemical reaction,that needs water to properly react with all of the ingredients,but it has to be in the proper amounts,at the proper time.You can drive light loads on the concrete while still covered in plastic,but keep it wet for at least 7 days,that is the standard curing time for testing the concrete strength.

It will strengthen over time. Get sample containers,and get a sample from every load of concrete. Tell the concrete company that you want a slump test performed on site for each load,and tell them you will want on-site samples from each load.Ask for a slump of 2" to 3" for maximum strength.This will keep them honest just by knowing you are doing this.Make sure the truck rotates at least 80 times before each pour to ensure a thorough mix.In addition,the air entrained mix is a good choice,it resists frost and increases work ability.A top sealer coat of Sodium Acetate is highly recommended.

Follow these and other great recommendations on the site and you should have many years of satisfaction with your driveway.

Here is a link for proper sump test procedure:

https://www.aboutcivil.org/concrete-slump-test.html

And a link for the Sodium Acetate:

https://www.equipmentworld.com/study-adding-sodium-acetate-to-concrete-increases-strength-reduces-water-absorption/

Good luck.

I think you are mistaken to add a vapor barrier to an outside slab where it will freeze in the winter. moisture barrier (visqueen) is surely recommended for an interior slab to stop moisture from coming up from the ground, but you are asking for trouble outside i can assure you water will collect and raise and lower your slab. your slab is porous, you will not make it hermetic, when the concrete cures, the area that had water will now have voids. i agree with everything else you say, although i have never heard of addition of fiberglass but we do not use steel fiber either. as SE mentioned the steel will corrode, i cannot imagine that the concrete company will be using a nickel based alloy? concrete is very alkaline and will cause the steel to corrode especially noticeable on small fibers with a lot of surface area. I question the validity of adding these fibers be plastic steel or otherwise. I don't know the mechanism to deflect a crack since there is plenty of air voids in concrete. if it had zero pore, then i would say yes to it, but i think the surface finish is more important as these fibers make it harder to cream and drop gravel. I mentioned aeriated concrete, this is used to combat entrapped water during freezing periods. it creates voids for the water to expand when freezes. something you may want to consider.

I am quoting info from a very experienced concrete man.His recommendation is always a vapor barrier under the concrete.Experience has shown him that it pays off in the long run.I cannot argue either way,I am simply passing on from a man with years of experience an many square miles of concrete.I am sure there are local conditions that are an exception to the rule,as in all rules.The Sodium Acetate makes the concrete hydrophobic once cured.

Your best advice is to consult a local reputable concrete contractor,ask for references and look at some of his large jobs that have a few years of age on them,such as shopping centers,malls,etc.

Never heard of FRC?It has been around for many years,maybe it is seldom asked for,but it is certainly well known at the concrete plants.

One other thing my cousin mentioned: A steel towel or float will bring gravel to the top,an aluminum one will not..he did not know why,but I suspect that the specific gravity of aluminum is lighter than the concrete mix,and the steel is heavier.

I don't think vapor barrier would work in my situation with 4-5 inches of 1.5" granite rock base. This large rock base "breathes" from all sides.

I am a retired general contractor from the Chicago area and have poured a few driveways , most residential , We used fiberglass mesh in most all drives that We poured including My own which is 20 years old. I have had no complaints of cracking and i can vouch for My own drive that it has no cracks except through the saw cuts made after the pour (8 feet apart). In lieu of steel reinforcing fiberglass works just fine. If you want more to ease Your worry add the wire mesh.

oilcan13

I find the comment given here very useful and comprehensive. My specifications for concrete work are for factory settings that carry heavy equipment at times. For the type of work I do a few of the things I ask for: I specify a 95% minimum compaction of the subgrade, subbase and base aggregate and the composition material of each. I will also ask for slump tests ranging from 2"-4" and compression test 4000psi after 25-28 days to be done. ( I tend toward a 5 bag mix which of course is harder to work) The thickness of the concrete slab in your case, nothing less than 6'', I would like to see 7" especially since you probably will not be testing the base compaction or have the slab compression tested. After reading ccoop609's comments you should be well prepared to ask questions and have a good understanding when talking to a contractor about your project.

I have prepped and placed my fair share of cement, but I am not an engineer. But I have this to add (for what it is worth).
Best bang for your buck is thicker or more rebar vs thicker cement.
Don't use steel mesh if you can, terrible to work with and hard to get it placed properly.
As for rebar chairs, I disagree with placing it in the middle, that is the worst place to place. It should be placed(for your use) on the bottom 1/3rd of the cement, so 2 inchs off the bottom. This will place the top of the cement in compression(where cement excels) and the bottom of the slab will be in tension and the rebar will hold it together. Even if your sub base is good, you are still going to get some settlement and cracking.

Stronger cement 4500PSI vs 3500 PSI is a small cost to increase(all my personal cement is 4500 psi) I think for 35 m3, it was $600 more on my last pour and it is a common mix.
If it were me, I would use 6" of 4500 psi cement, 2 inch chairs, and 15mm rebar. I would space them 18" x 18" apart, and in high use or stress areas, I would go down to 12" x 12" centres.
Further, I would do the rebar myself to save some $$$, it is super easy and the cost savings will more then pay for the extra rebar.
I live in Canada, temperatures go from lower then -40F, to 110F. Frost is dependent, but on my driveway it is easily greater then 60 inchs. My pad holds my 14 ton excavator, my army truck when completed (15,000 pds) and many other things like my gantry crane, lathe, etc. My garage and parking pad is 6" of 4500 psi cement and the rebar grid is 12" x 12", 15mm bar.
Good luck,
Ty
PS 15mm rebar is a type, not a metric measurement just to clarify. Good luck, and let us know what direction you go. :-)

I appreciate everyone's comments. Lots to think about. Regarding fire trucks I confirmed they cannot exceed 20,000lb per axle--same as the garbage trucks.

Helix steel fibers (coated) is the product I was considering in lieu of rebar. I spoke with the company and they recommend 20lbs/CY of their 5-25 (25mm) twisted coated steel fiber to replace #5 (5/8" - 15mm) rebar at 18" spacing using 6" of 3500" psi mix. They specifically prefer 3500 psi vs 4500 psi as it will crack less during the cure period.

My next question I suspect may be the proverbial "Ford vs Chevy" for this group but I'll pose it anyway. What are the pros/cons of 3500 psi vs 4500 psi concrete using my estimates above? I'm specifically interested in longevity--not cost.

Thank you!

I forgot the link to Helix steel fibers information and videos:

https://www.helixsteel.com/news/tag/helix-steel/

https://www.youtube.com/watch?v=ORrawHcaA0M

https://www.youtube.com/watch?v=cxeVh20UzLA

The more Portland Cement in the concrete,the faster the surface will dry,while the main mass is still not cured and this creates internal stresses that will eventually lead to cracking.It is very important to keep the surface wet for as long as possible.Concrete hardens and increases in compressive strength over time,and the longer it is wet,the harder it gets.

Even a 50/50 mix of Portland Cement and sand will not crack if kept wet during the entire curing period.This mix is waterproof and crack free as stucco if done right,so the main thing here is to keep it wet.

I have seen old smokestack footings that were so hard from being buried underground that hydraulic jackhammers,on trackhoes would not crack it,explosives were the only way to break it up.

It was very difficult to drill the holes for the explosives in this stuff.

It had been underground in a damp area for about 100 years.

The contractor lost his butt on this job,he thought it would be a snap to bust it up.

If you want the ultimate in compressive strength,use pre-stressed concrete,as they do on highway overpasses or bridges.

Consult with a highway engineer,or a well informed concrete company.

"If you want the ultimate in compressive strength,use pre-stressed concrete,as they do on highway overpasses or bridges."

a good way to apply compressive force is to imbed cables under load and then release after concrete cures. i don't how much or what force, i am sure you can get this info online.