Looking for help in choosing a concrete contractor for a 3,100 sq ft driveway expansion.

Quote 1: ~$26,000
4" concrete; 3/8" rebar on 12" centers; keway expansion joints every 12-15 ft; 3500psi

Quote 2: $27,000
4" concrete; 3/8" rebar on 12" centers; redwood expansion where needed; 3500 psi

Quote 3: $19,000
4" concrete; 3/8" rebar on 12" centers; wood expansion joints every 10-12ft

None include haul off as they'll just pile the existing dirt/gravel and i'll spread elsewhere. None are planning on compaction, one said it's not needed because everything "will be cut" but said I can add a vibratory roller if I want. Another also said he didn't plan to compact because it's good sandy soil we'd be pouring on.

Quotes 1 and 2 are generally larger, more well known companies. Quote 3 is a guy that was recommended to me who did concrete for 28 years with a bigger local company before going out on his own.

Obviously the price is attractive with #3, just trying to look out for any pitfalls in the decision. Is there anything else I can ask or is there anything particularly concerning with the quotes I have so far?

Regular pine expansion joints are going to rot quicker. I would specify that he use redwood. What are they doing for backfill?

I wouldn't think twice about going with the cheaper option. You will probably get better service from someone who is just starting out. Where are you located?

How much to have #3 use redwood instead? Surely cheaper than #2.
Ultimately many concrete guys get the concrete from the same place. It's all in the prep/finishing. I'd go with 3. You can buy a lot of redwood for $8k.

Not an engineer, so gleaned from them, my advice is tainted by very poor expanding clay soils in Aggieland that "support" concrete and make concrete repair companies in demand. Well, if no solid report nor engineer, then pay-me-later, correct?


1. Cost should not be weighed more important than done-wrong = costs more in long run, so dismissed unless 20% out of order

2. At least get compaction and pour before the weather ruins its "90% Proctor" rating. If any doubts, then elect lime stabilization ... many options.

3. We switched to #4 rebar Grade 60 (if you can get this higher strength) @ 15"ocew as better/equal + big feet more easily fit through the squares, less likely to mash the steel mat all way to grade, even with "slab savers" trying to hold mat 1/3 from top WHERE IT SHOULD BE when covered up

4. Expansion joints are best served by asphalt board & sealer topping so it CAN expand/contract as per name/definition. Redwood work poorly for awhile and less immediate rotting ala "wood". Keyways metal have served but variations in temperatures make concrete grow/shrink into each other = cracks, etc. Even bridge engineers supply large distance expansion joints, so much do exposed concrete expand with weather.

5. Locally anything hard, e.g. flatwork, stucco ,etc. get EJs @ at least 15ft o.c. and suspect to crack corners get one as well. Through the EJs come rebar "dowels" that tie level one slab to the other.

6. Locally, flatwork (drives/walks) is best served as 5" tk due to our poor soils, even if covered with docile earth fill. I might suggest 4.5" but call a local engineer doing flatwork in your locale.

7. Curing as defense against cracks post-pour = a) sprinkler every place you don't want a crack 24-48 (weather depending then plastic cover it all ... or better b) chemical spray curing, a no brainer.

8. NOTE: it's easier to pull concrete into spots desired if watered down at the truck = more cracks later, so if offered Pozzolith additives (weather dependent), spend the money so water is no longer desired

TMI ... again

While lot of truth in this post!

I spent over a decade in the concrete industry on the supplies side.

When we built our home and sit the flatworm around, I insisted on asphalt fiber expansion joint with cap strip that leaves a perfect 1/2"x1/2" joint to be sealed with elf leveling joint sealant.

Also, the expense for going from a #3 to a #4 will be fairly insignificant for the benefits allowed. Also, would not used no grade bar. Must be grade 60 at a minimum for me. We used domestic bar in our home, but that was a personal thing for me and the cost of using US made steel vs Foreign bar was worth it to me.

No way would I allow for my driveway to be place on ground that wasn't compacted. The could lead to uneven joints and issues down the road. It's cheaper to do it right in the long run!

Thanks for all of the input guys.

So my takeaways at the moment are:

• Upgrade to #4 rebar (done on 15" centers instead of 12")
• Use asphalt fiber expansion joints (curious if there are alternatives to self leveling sealant? I've seen it look good but I've seen it look terrible)
• Insist on subgrade compaction (was reading on lime stabilization which sounds like it may not be helpful in our sandy soil)
• Optional - increase to 5"

On the curing, is this something the contractor should do as far as watering etc... or should I go out and get some plastic covers etc...

Just ask them to spray a curing compound. It's been about 10 years since I was in that world. Used to be ASTM 309 for curing compound. They will know what curing compound is.

I wouldn't worry so much about the material in your constructions joints, instead, put down some sika flex in the joints so it seals it up, so you don't have to worry about rot.

I caulked all my drivway joints (construction and contraction)

It's a clean look (grey sika flex) and it keeps water out from under my slab.

https://www.amazon.com/dp/B01N8YIZ7W/

Thickness is the major factor (even more than the strength of the concrete) in determining a driveway's structural capacity. Place concrete at a minimum thickness of 4 inches. Increasing the thickness from 4 inches to 5 inches will add approximately 20% to your concrete cost, but will also boost your driveway's load-carrying capacity nearly 50%

Also consider thickening the edges of the driveway by 1 or 2 inches to provide additional structural support in the area most likely to be subject to heavy loading. The thickened sections should extend in from the slab edge 4 to 8 inches. (I would include this at the expansion joints also - TA '87)




Concrete Driveway Construction - Thickness, Rebar & More - Concrete Network

Thanks for the input, the cheaper option guy did specifically mention he would reinforce with a deeper beam where the driveway meets our gravel road and also along the edges that we will pull our camper over.

Going to piggyback here since I haven't seen it discussed.

DFW. I have a handful of bids for a similar project, and some are recommending to dowel into the adjacent house slab, and some are not. What is the right answer, if it exists?

Generally only dowel at areas that movement relative to the existing slab is critical (i.e. doorways)

In my opinion, you don't want to dowl to the house in case the driveway heaves some. If doweled at the house, it could cause the driveway to slope towards the house causing drainage issues. Better to let it come up or down flat.

Others may have a differing opinion.


****Edit to add - It would be appropriate to dowel into the garage slab at the garage door since that is a path of travel that you do not want to become a lip or drop.****

Also interested in this as there's a small rectangle between our current driveway and the house slab that is going to be filled in. Only one contractor has mentioned tying into the existing slab.

If it were me, I would completely get rid of the expansion joints and large majority of rebar. You will never be able to properly seal the expansion joints as they move too much. Even redwood will rot, dowels corrode, subgrade erode and distresses happen. This is how all these Pavements fail. I've had to replace the wood expansion joints in my driveway and they aren't even needed!

I'd suggest using 4 lbs of macro fiber in the concrete, full force 750 is a good brand. Then sawcut the joints on a max spacing of 8' x 8' to a depth of 1". As mentioned, going up to 5" helps a lot in terms of structural capacity. The steel does not add load carry capacity, it only prevents slabs from moving after cracks form. In this case, you will only need expansion joints adjacent to things like a house slab that move differently than the pavement due to environmental stresses, but not in the middle of your driveway. If you want to know more about this, search "jointed plain concrete pavement". The American Concrete Pavement Association has good resources.

Alternatively to using macro fiber, you could put tie bars #4 across the longitudinal joints (space at 18" and 24" long). I don't think you need dowels across your transverse joints unless you have heavy vehicles routinely, or soils are bad. The dowels would need to be 3/4" Dia at most, spaced at 12", 18" long. But I doubt you need them.

Compaction of the soil is very important. Depending on how good the sandy soils are, you could mix up to 3% cement into the soil if you need to increase strength and reduce moisture susceptibility. Lime won't do anything for you as it wont chemically react.

Curing was also recommended in this thread and I highly recommend using a white pigment and ensure it covers the pavement like a "bed sheet" as soon as the finish and broom is complete.

The only problem with my recommendation is you do need a contractor who knows what they are doing.

Feel free to DM me and I can help further if you like.

Macro fiber, or 'micro fiber'?

I'm in construction and we've done micro fiber. No saw cuts. Also only 4" instead of 6".

About a 20% premium over typical 6" with 6x6, 2.9 mesh.

62strat said:

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Macro fiber, or 'micro fiber'?

I'm in construction and we've done micro fiber. No saw cuts. Also only 4" instead of 6".

About a 20% premium over typical 6" with 6x6, 2.9 mesh.

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Micro fiber is not structural and only protects against plas5ic shrinkage cracking. With good practices, that really shouldn't be needed on most jobs...but contractors like to use excess water and don't protect the surface well against excess water loss, hence micro fibers are used.

Macro fibers are more robust, longer, and are considered structural. They are measured based on how much post crack strength they have in a beam break test. They will add cost to the typical cubic yard, but it does allow removal of expansion joints, keeps joints tight, and reduces time / cost dealing with steel.

With a proper joint layout and accompanying knowing where to put tie bars/ dowel bars and contractor knowledge, the fibers wouldn't really be needed.