Soil compation for concrete driveway 4

[Whyzman]

My questions have to do with the correct preparation of the substrate for a concrete driveway.

I am replacing the asphalt driveway in our recently acquired home. The asphalt was literally coming undone and beginning to leave car tracks!

I live in the Minneapolis, MN area. Upon removal of the asphalt I found there was virtually no class 5 base, and the soil is comprised of a substantial amount of clay.

My research pointed me in the direction of at least 5" of base material. I'm using a crushed recycled concrete/asphalt blend that is being used in road construction here in MN. I'm planning a 5" concrete pour which will be fiber and rebar reinfored.

We have been hit this past week with rain nearly every day. Yesterday I attempted to do a bit more excavating after allowing a half day for things to dry. I wound up digging down more than my planned grade and am wondering if I should fill and compact with the removed material once dried, or fill and pack with the base material?

Also, how long should I allow things to dry up before adding the base material and packing? Should I attempt to pack the existing soil first since I have disturbed it in the excavating process?

I was hoping it was going to be pretty much a cut and dry situation...instead, it's been a hurry up and wait learning situation...It's raining again today! ARGH!

Your comments and help would be much appreciated!

Whyzman

 

[jheidt2543]

With the clay subsoil, I would recommend not using it for backfill. I would go with additional grandular fill to help get water to drain away from under the slab and reduce the amount of frost heave during the winter. It is a little more expense, but over the 30 year life of the driveway, it would be a small price to pay. I think the 5" slab would be fine. Be sure you have crack control joints about 15' on center each way and it is a good added idea to caulk them with a traffic grade caulking material, Tremco and Chemrex both make them.

 

[Whyzman]

Thanks jheidt2543 for your input! Control joint caulking is an excellent idea! I initially removed 10" of soil to be able to provide my 5" base and 5" pour. On the first 1/3 of the drive (from the garage floor outward) I've already placed the class 5. I'm wondering in light of the clay content if I'd be better off adding another inch of base material and going with a 4" pour?

Also, any input as to the length of time I would need the existing soil to dry before placing and compating the remainder of the class 5 base material?

 

[jheidt2543]

Most drive ways in my area are poured 4" thick. I also know of one city street poured using 5" thick reinforced concrete! So, your 4" thickness should be fine for car traffic.

If you can run a plate compactor over the subgrade without water pumping up through it, the sub soil should be dry enough to pour the concrete.

Regarding the crack control joints. You should saw cut the joint as soon as the slab can support the weight of the saw and the blade doesn't dislodge aggregate as you cut. Waiting 24 hrs. is a little too long in most situations.

Best of luck.

 

[Whyzman]

Most often I've seen the control joints being cut early the following morning of a pour.

My calculations put me close to 18 yards which is far to much to attempt at one shot for "my crew." I certainly would prefer to be able to do a continuous and dice it all up the next morning! Unfortunately, unless I come up with an alternative, I'll have to do it in three "manageable" pours....

Thanks for the input on the plate compactor!

 

[eschwarzrock]

depending on how much you overecavated, I would not replace the overexcavated soil. Use the extra base material. 5" of base sounds like enough.

A 5" concrete slab with both fiber and steel reinforcement sounds like it will just about handle the wheel loads of your 747. You are landing a plane here, right? Given your extreme northern locale and clay subgrade, I would shift some of the cost into a thicker base material (maybe 8&quot and forget about the steel reinforcement (maybe just keep some steel at the corners). The increased base thickness will certainly pay for itself. I would also install a geotextile between the base and the subgrade soil to prevent the clay from working up into the base over time and causing premature failure. Your'll get much longer life out of your runway !

 

[DRC1]

If you are excavating a clay material and replacing it with a draining material, be sure the water in the base can drain to dalight so you are creating a bath tub.

 

[Whyzman]

eschwarzrock,

I have no idea why my response to your input did not show up. So, I'll try it again!

The base material is placed sans a geotextile. I questioned a couple of the general contractors that I work for regarding the use of a geotextile and both only required it when placing a substrate for pavers. I'm in agreement with you, although too late at this point, that it would have been wise to use one.

I was planning on pouring the upper slab this morning, weather permitting, but I was dissuaded from doing so by the concrete salesman. Very impressive, as he passed on a sale with advice that if I could wait until the spring it would be a wise move.

He pointed out that with the possibility of extreme flucuations of weather and the concrete needing a good 30 days to cure properly, I could be jeopardizing all my hard work up to this point.

Well, I opted to wait! That'll also give things a chance to settle and I can repair if needs be before placing the concrete in the spring.

As far as the runway possibility, it's just that the brakes of the 747s landing would have to be replaced continually. The drive is only 52 feet long....It wouldn't be very cost effective....Oh, and they'd have to shorten the wings, or for sure the retaining wall would do that for them...only 26 feet wide....

Thanks for your input...and sense of humor!

 

[BigH]

Love these threads!

Did you ever think of using 6 to 8" well graded crushed stone (base) with a open concrete blocking (like geoweb)that you could infill and plant grass?

What a site driving on the grass up to your garage!!!

They use this in apartment complexes when they want the grass landscaping but need the traffickability for fire trucks, etc. These are open retangular paver blocks (like pipes) and can be laid down. Might be less costly and such blocks usually can take the ground's natural tendency to go up and down with frost.

You got good advice earlier.

Best regards