Mostly OT: replacing driveway

[todd]

Not completely off-topic since this driveway connects the gar-shop to the street. ;-)

As the final part of a new addition to our house, we will need to install a new driveway. The existing driveway is about 100 feet long and 10 feet wide. It appears that once upon a time, it existed as a concrete driveway. I'd say it has been resurfaced twice with asphalt. (House is 50+ years old). The new driveway will be about the same length, but gets moved over 5 feet or so. The approach to what will be the new gar-shop will be somewhat different as well.

a) How difficult would it be to demo the existing driveway? My dad has a combination (and a bulldozer) that we could use, and I suppose we could rent anything else that might be desirable. My guess is removing the asphalt will be simple...perhaps as easy as putting the bucket of the combo down and scooping it up. My big worry is the concrete. I don't know how they were building concrete driveways 50 years ago. If we're talking concrete reinforced with rebar, I think we could have a job on our hands. If, OTOH, it was not reinforced, it might not be as bad. Obviously, no one knows what conditions exist, so take your best WAG.

b). Once the old stuff is gone, would I be nuts to try to pour this myself? Honestly, I've never poured anything this large. However, the old man has and he's got other friends who have also. Of course, after the old driveway was demo'd, the new driveway base would have to be prepared before we could form up for the new driveway.

I'm looking for opinions from people who have poured large slabs. If you think I'd be stupid to attempt it, that's a fair opinion. I'm wondering about it myself.

todd

[Sonny]

Yep, you have a nice tough job ahead of you, but I think you can do it if you have some help handy. The existing concrete may not be 4" thick. It may be 2&1/2" to 3" and not have reinforcement wire or bars. A 4" existing slab would be about 12.5 yds of debris to dig out, plus the asphalt. Is the old slab deep enough for you to pour the new drive on top of it. The old slab is a good foundation, already compacted. What is your conditions, such that, cutting half the slab (the length) for removal, and leaving the other half for foundation? .... Use the concrete debris, of the half you demo, to prep the bed of the other new half, hence you wouldn't have to haul it off. Is this feasible for you? Any dirt dug out for the new area can be used to refill the dug-out part of the old area. As for as using old concrete debris as prep foundation, if it's small enough chunks, the dozer can be used to compact it well enough, I would think.

A normal drive is 4" thick, or about 12.5 yds of concrete. Pouring a

6" slab is about 18.5 yds or about $600 more for a 6" slab (concrete is about $100 per yd here, these days). Can your circumstances accommodate a 6" slab? That thick of slab would be less likely to crack under pressure, as compared to a thinner slab, of course. Get at least a 3000 psi mix, not the normal 2500 psi mix for driveways. Pour a 12" X 12" footing at the road and also at your garage, to prevent cracking at those junctures. Place expansion joints at least every 15 feet, better at every 10 feet, but your conditions may be different than here, along the Gulf coast, for such considerations. I suppose you know to use an edger, to round over the edges of your slab, so as not to have sharp edges.

When sweeping the surface, for a somewhat rough finish if desired, don't sweep any area, that has been in the shade, at the same time you sweep an area that has been in the sunlight. The areas in the sunlight will have dried faster than in the shaded area, and the swept finished surface will be different if you sweep them at the same time. Allow the shaded areas to dry a bit longer before sweeping. Test the two different areas for the sweeping to be the same.... Use your common sense to judge the difference in these two conditions .... I'm sure you will do a reasonably good job in this department..... This is not rocket surgery. If your Dad and others know about this, then great. Allow them to use their knowledge regarding these two drying conditions, with regard to sweeping these surfaces.

When it comes to the pouring and floating, if you have good help, it should go well and fairly easy. Most of your hard work will be the removal of the old and the prep work for the new. If you have any concern about whether you will have enough help to float the pured concrete before it dries too much/too fast, then ask the cement company to add a bit of deterrent to the mix, delaying the drying time of the mix. But with a little help on hand, you should not need this additive for delayed drying.

Have a BBQ and invite some friends over...you always want someone else around to share the blame for things that don't go well. Plan well and you should do fine. Hope this helps. Sonny

[RicodJour]

Demo and pouring won't present much in the way of problems. Finishing it is a little more tricky. You should definitely have someone with a fair bit of finishing experience on hand. The trick in finishing is the timing, with weather/temperature, mix and speed of the finisher all playing part.

It's unlikely that they put rebar in a driveway slab. Usually it's either no reinforcing at all or welded wire mesh. A gas cutoff saw is my preferred demolition tool. You could also cut the WWM with a sawzall, angle grinder with a diamond blade or bolt cutters.

BTW, a better prepared base and a suitably thick slab will be less likely to crack than a slab with reinforcing that isn't prepared correctly.

R

[Leon]

Looks like a big job filled with too many "If's", IMHO. Considering how much it would cost you to do it your self, how much more would it cost to have someone that does this all the time do the work? It might be worth the extra cost to end up with something better than "Iffy" results.

[Virgle]

Todd, Asphalt over concrete is not really a good application. Every crack in the concrete will work it's way through the asphalt. The concrete will move enough with heat changes to make a crack in the asphalt. I worked with a large road building firm for 30 years until retireing. We had to use a special fabric over the concrete then usually 3 layers of different mixes. On some jobs we had a machine to break the concrete into small pieces.

Virgle

[Teamcasa]

Todd, If the concrete has been resurfaced then it was probably too thin and lacked rebar or wire. With the bulldozer, removal will be easy. Lift one corner and the old concrete will break easily.

Think through and form the new driveway carefully, paying particular attention to levels, water flow/drainage, tree roots and crack-line placement. Proper compaction and a good 6"-8" base (sand/gravel mix), a 16" grid of #3 or #4 rebar and a 4 1/2" - 5" thick (3/4 rock) - 3000lb concrete will insure the new driveway a very long life.

Finishing a 100' of driveway is not that difficult to finish - unless you are by yourself and lack a laser screed (

)

Do yourself a favor and hire a finishing team. 4-5 guys should be able to do this easily. It will be the best money your spend.

Dave

[fredfighter]

You may be able to use a metal detector to determine if there is reinforcement in the concrete. I don't know how easy it woudl be to distinguish between mesh and rebar. I have seen people break up concrete and dig in bedrock (Sharon conglomerate-- natural concrete) by pounding the bucket down on it. You could probably break mesh that way, rebar would need to be cut with a power saw or a jackhammer.

[Lew Hodgett]

Way back when, I faced a similar situation, when I wanted to build about a 10x20 patio behind the house.

Hauled in the sand fill, one wheel barrow at a time, built the forms, then started to get prices for concrete.

At the last minute, called a guy in the neighborhood who was a cement contractor and asked if he would give me a price.

The long & the short of it is that the contractor did the job.

IT WAS THE BEST DECISION I EVER MADE.

Laying concrete is an art form as well as hard work.

You are going to need a crew of at least 4-6 people who know what they are doing.

If you can get the permits, have the means to remove and dispose of the existing driveway, then by all means do it, but setting forms and laying a new driveway is not a job for rookies, IMHO.

Your back will thank you and you will thank yourself in years to come by walking away from this one.

Lew

[robo hippy]