Driveway thickness for RV

[Grandpa5x]

Originally Posted by Granite17

Our builder is just about ready to start constructing a driveway to support our DS4018. I have told him it needs to handle 50,000 lbs.

Any engineers out there or concrete contractors that can
share specs. to handle this kind of
weight. We live in the Texas Hill Country, very rocky soil conditions.
Interested in thoughts on base,
rerod size, placement and concrete depth?

Appreciate if anyone has experience with this.
Thanks!

6” reinforced concrete should sufficient, 8” is what is used in highways that supports constant traffic of 80K lbs. do yourself a favor before the pore and but some 6 mil plastic sheeting and completely cover where the concrete will be including on the form boards. I did that before I poured my shop floor in my pole barn that was built on slope, and when I sold my place 18 years later there wasn’t one crack in that floor 24’X36’. Every time it rained water ran down to the apron and I imagine there was plenty of ground moisture but never cracked the concrete. Good luck!

[Oregonpharme]

Talk to your concrete person as they will be the best source of advice for your soil type.

I use 6" fiber reinforced 3,800 lb mix on expansive soils for my 31,000 lb farm tractors and my two post hydraulic hoist. No cracks, no failures of any kind. But, the underlying support aggregate is at least a foot thick of well compacted 3/4 minus over pit run, and completely level before pouring the concrete.

[Freedom Road]

Originally Posted by Oregonpharme

Talk to your concrete person as they will be the best source of advice for your soil type.

I use 6" fiber reinforced 3,800 lb mix on expansive soils for my 31,000 lb farm tractors and my two post hydraulic hoist. No cracks, no failures of any kind. But, the underlying support aggregate is at least a foot thick of well compacted 3/4 minus over pit run, and completely level before pouring the concrete.

I have been in the commercial construction business for 24 years and on the design side 10 before that. Of all the specs and designs noted the above is probably the best value for the performance level desired. However, I would add rebar (on chairs) and offset that cost a bit by lowering the base thickness to 8”. As far as sub grade, your contractor suggested 12” undercut to facilitate placement of base. That is not a substitute for a well compacted sub base under it. Make sure he compacts the sub base (assuming virgin soil) and it has the proper moisture content and no unsuitable soils, (ie. sand, clays, or roots).

You didn’t mention where this slab was being built, important to the concrete thickness and rebar spacing. Also look to hire a local testing company to perform a few compaction tests (includes moisture content). Well worth the money and piece of mind because slabs fail when the support fails. Good luck

[Ray,IN]

If this were me, I would never tell the contractor how to pour concrete. If You do, you assume all responsibility for failures.

Originally Posted by JMH

Oh by the way our concrete is inset with rebar on 12” centers. You should look at doing this to keep cracks down.

Nothing will prevent concrete from eventually cracking! The purpose of rebar and metal mesh is to prevent cracks from pulling apart/widening, or shifting vertically.

[lstutts]

Originally Posted by Granite17

I received the engineering spec’s on this yesterday and here’s the plan:
Excavate to12”, compact, 6” of 3/4” limestone, compact, #4 rerod
centered on chairs, wire mesh on top, 7” of 4,000 psi concrete.
This looks pretty substantial to me and should do the trick!
Thanks for all the suggestions!

As a retired Ironworker, I have never seen mesh and rebar both used on a slab. Waste of money. All rebar and each do is keep cracks from opening up when they happen. They do not have any compressive strength.

[lstutts]

Originally Posted by Busskipper

Just about any concrete poured correctly will work - BUT - it needs to be on a Solid Base or unless you build a Bridge deck it will Fail.

Just My Humble Opinion,

Old Highway Contractor

Exactly! If you have a solid base that doesn't allow the concrete to flex it is hard for it to crack.

[fision]

Originally Posted by Granite17

I received the engineering spec’s on this yesterday and here’s the plan:
Excavate to12”, compact, 6” of 3/4” limestone, compact, #4 rerod
centered on chairs, wire mesh on top, 7” of 4,000 psi concrete.
This looks pretty substantial to me and should do the trick!
Thanks for all the suggestions!

I’ve worked doing industrial/commercial concrete flat work since ‘94, and have been a residential/commercial contractor since ‘04.
As a number have mentioned these engineered specs will be more than sufficient.
The only new comment I will add to this thread is to properly cure the concrete. It’s important to not put too much water in while pouring, and just as important to then keep the moisture in after it’s finished. “Cooling” the concrete is NOT curing; “curing” is maintaining the moisture in the concrete to delay shrinkage and so the hydration reaction can continue. Most cracks in concrete (discounting movement, whether caused by frost heaving, sub-grade failure or otherwise) are caused by concrete shrinkage, which is primarily caused by moisture loss, and occasionally by rapid cooling.
Curing can be done with a spray on compound (most $, least work), covering with plastic sheeting (try the 12’x400’ roll of painters plastic from HD or Lowes, $30) or flooding/misting the slab (generally least $, most work). Curing should commence Immediately after the finishing operation is done (being careful not to mar the finish), and should continue 7 days minimum. Longer is better, thus the simplicity of the spray on compound—it’s on and done.

[fision]

For those with budget considerations:
knowledgeable persons were correct in saying that with excellent sub grade a 4” slab is sufficient; thickened edges are cost effective additions to the weakest point (the edges). Steel reinforcement is recommended and a must if frost heaving is a possibility. Concrete plants want to sell fiber-reinforcement because it’s high markup/profit, contractors like it because it requires no effort. Unless high doses of the larger fibers (so-called macro, vs micro) are used it does VERY little. Spend your $ on more steel if you must...
What is “excellent subgrade”? Undisturbed (or 95%+ compacted) gravel; no organics, clay, etc. Easy way to test?— How much of a tire print does a heavy vehicle leave on the gravel? What about after the ground gets REALLY wet? Excellent soils will have no visible deflection. As the quality of subgrade descends the design quality of concrete must compensate.

[Yonder]

Rebar won't stop cracks. Concrete will shrink as it dries so some cracking is to be expected for most jobs of the cost level you're discussing. The grooves you see in concrete are placed there to "capture" the crack and keep it straight and fairly concealed.

Concrete is very strong in compression but brittle so weight and poor substrates are problematic. Rebar is excellent at helping with that and keeping the slab from shifting when it does crack.

I'm a contractor. My DP is 34K lbs and change. I just poured our driveway this summer ... 6" thick over well compacted crushed gravel with fines and #4 rebar at 16" O.C. One thing I've not seen mentioned here: CureTime. I drove my pickup on the new drive a week after the pour but I let it sit for 4 weeks before I put the rig on it.

[Journey39n]

All these suggestions are great for the individuals wanting to overbuild. Standard 3000 psi concrete with fibers is more than adequate for any RV pad or driveway. The key is compaction of the proper subgrade material, and drainage.

With the right subgrade material, and compaction, 3" slabs work well. Remember, your tire patches are all that transmit the weight. Figure 1 tire patch, at about 6" x 8" = 48 sq inches. 48 x 3000 psi = 144,000 pounds. And you have 6 - 8 tires. How much does your RV weigh? Really! Perhaps 7000 pounds per tire.

The thickness helps distribute the weight over imperfections in the subgrade, rebar and mesh in tension, also help hold the bottom part of the slab together (if placed properly) and control cracks to the pre-planned joints.

Great to pour thicker if you have the money, but when doing highways and airports we always designed to what was needed, extra inches meant millions more dollars.

[Warlock]

Originally Posted by Granite17

Our builder is just about ready to start constructing a driveway to support our DS4018. I have told him it needs to handle 50,000 lbs.

Any engineers out there or concrete contractors that can
share specs. to handle this kind of
weight. We live in the Texas Hill Country, very rocky soil conditions.
Interested in thoughts on base,
rerod size, placement and concrete depth?

Appreciate if anyone has experience with this.
Thanks!

Concrete 8 inches thick with rebar!

[Scottybdivin]

Originally Posted by Johnnycb

6 inch thick @ 3000psi with #3 rebar @ 12"OC (on center) should be enough. I am not an engineer but an inspector and have inspected many a slab for vehicular traffic and most are this size with an occasional 8" depth for 18 wheelers.

I live in Austin, where do you live in the Hill Country?

Who do you inspect for? I've been in construction in Austin for 34 years.

[George Weiss]

The pavement is MUCH less important than the base! In N CA I have had driveway for 20 years of very well compacted road base with no concrete or asphalt. 10" of gravel compacted by double vibrating " steam roller". Since no traffic bouncing along at 65 mph, no real need for wearing surface. Underneath is clay. 35" rain this year with no problem. A little slope allows drainage. Cheap doormat and step covers keeps carpet clean. ( Just saying, I have Master of Civil Engineering in Concrete from Cornell University. Supervised many miles of Interstate Highway construction)

[LJowdy]

When I purchased my current home it had a 56' long x 20' wide motor home garage. I have a 100' driveway to get the motor home into the garage and only 4" concrete for the whole length. (Including the concrete in the motor home garage. I've had 3 motor homes in the past 13 years I've lived here. Two were 40' diesel pushers and now a 43' pusher. No cracks in the driveway so far and I have no idea what kind of concrete was used but it's holding up just fine.