Concrete driveway...how thick?

[trunk monkey]

we're building a road from the street to our carpark (carpark just started). the road from the carpark from the street is likely about 80 meters, and will start if it ever quits raining here.
i'm working in india right now, my wife says the builder (who built our house and whose opinion i trust) says 10 cm. depth is enough, with no steel included in the pour. the biggest load that i can think of would be the septic truck which has a very small tank on it.

if it were you, a person of experience hopefully, would you increase the depth, or include rebar/mesh into the pour. if i was a rich man i know what i would do, but is steel entirely necessary with a 10 cm. pour? would it be better to go 15 cm. without steel or 10 cm. with steel.

i'm not asking for price quotes as we all know the price of steel and concrete changes quickly. i'm just trying to get feedback from people who have done something similar.

thanks in advance for any help.

tm

[jandajoy]

From what I've read 10cm is ok but the steel is essential. Also pour in 10m sections to allow for expansion.

There are, however far more qualified people on here.

Have you browsed the construction threads. They're very good.

[flash]

not an expert but i would imagine your driveway wouldn't last very long without steel.
another option you could use is PVA fibres, they are small threads of plastic that are mixed with the concrete, gives excellent reinforcement. I have read too that you can reduce the thickness of the concrete when using this method.

[Thetyim]

If you don't reinforce then a loaded septic tank will crack the concrete after a few years.

[oldgit]

We made floors 15cm thick with reinforcing mesh when doing factory floors where forklift trucks ran, best to be on the safe side than dig it up and do again when it cracks.(more expense and labour)

[S Landreth]

6 inches! With steel reinforced mesh (or rebar)! Make Damn sure your contractor gets the base right (at least 12 inches of well compacted material under the concrete slab). Make sure there are expansion joints (your slab will crack without them),…it’s Thailand and it gets hot real quick in the morning here.
What ever the cost,…….do it right,….the first time. You don’t want to walk out of your home every morning and see cracks (that will only get worse during the rainy season).

[pai nai ma]

There is another thread on this topic as well.

Quite thorough, it was.

Worth a search. (op was obsidian)

Titled "how do you quantify cement?" bumped if for you.

[Happyman]

6 inches! With steel reinforced mesh (or rebar)! Make Damn sure your contractor gets the base right (at least 12 inches of well compacted material under the concrete slab). Make sure there are expansion joints (your slab will crack without them),…it’s Thailand and it gets hot real quick in the morning here.
What ever the cost,…….do it right,….the first time. You don’t want to walk out of your home every morning and see cracks (that will only get worse during the rainy season).

Agree 100%
Make sure that they don't just drop the mesh straight on the dirt though -get them to make up a load of spacers so the mesh is in the middle of the pour .

[Norton]

(op was obsidian)

Too bad he's not around for a helpful link.

[Texpat]

Don't know how thick my driveway is but they used reinforcing steel and spaced-out separate 6m slabs. It's holding together far better than the 1m concrete walkway around the house, that has settled ...

[oldgit]

Oops! forgot to mention the hard core.

[Deck Ape]

80 meters! That's gonna cost a few baht.

Would you want gravel?

[meepho]

1 - Well compacted earth
2 - 50 - 75mm well compacted crushed stone or similar
3 - 100mm concrete with steel mesh 25 - 35 mm below finished surface
to go over the top for added strenght you could put 2 laters of mesh in the concrete one 20mm below the top and th other one 20mm above the bottom of the concrete.

[friscofrankie]

4" (100mm) is adequate. If it were me I would opt for 6" (150mm) thick. The fool telling you that reinforcing steel is not necessary is looking for a future job maybe? Reinforce with 4" fabric. fabric should be spaced up so it is in the middle of the slab. They might try to sell you 6" fabric but I'd got for the denser.

[jandajoy]

The fool telling you that reinforcing steel is not necessary is looking for a future job maybe?

I must say, when I first responded to this I wanted to suggest that you might be looking at a new builder. No way you'd not lay reo.

[tsicar]

it all depends how good your substrate is, plus what you are going to drive on your driveway.
if you have a good substrate, such as hard,stable soil, and you compact properly, you will not need any steel reinforcement.
i recently laid a driveway for my sawmill, where the 8 ton rigging trucks we use, travel up and down all day: absolutely no steel necessary.
a 3.5 ton forklift, sometimes carrying a log of 3.5 ton, with five workers hanging off the back, to keep it from tilting, also travels up and down all day.
no problem.
it makes sense:
if your car can travel up and down without distorting the earthen driveway, then you could, in theory, get away with an inch thick layer of concrete.
make sure you dig out all the topsoil, compact well, and WHATEVER YOU DO: do not let the village idiots mix your concrete. get the readymix truck in, with a 30mpa mix, lay it about 100mm thick:do not let the village idiots add any more water to the mix, and work it well, vibrating it as you go, within a simple formwork. allow joints for expansion every few metres, allow it to set slowly, keeping the surface slightly wet for a few days, and you should have no problems.
if you do not have stable soil, eg:clay, then obviously you will need to reinforce

tip: if you saw the expansion joints to about two thirds the depth of the concrete,, instead of casting them in, the rest of the thickness of concrete will crack through, allowing a kind of "finger-joint" which will hold the sections together and prevent one section from lifting higher than the other.

[tsicar]

The fool telling you that reinforcing steel is not necessary is looking for a future job maybe?

as concrtete increases in strength the older it gets (reaches full strength after about 20years), then the fool will be caught out very soon after the concrete is laid: ie, while it is still newly laid and at its weakest.
steel is the safest bet, but only necessary under certain conditions.

[blackgang]

In Thailand you had better be there and make damn sure that they compact the roadbed, as everyone knows they do not even compact for govt. hyways here and the fuckers crack and sink before the road is open to traffic and they are out digging it up and repouring the road surface, Brain dead bastards can't seem to figure it out even after all these years of trying to build a decent road.

Left to their own devices they will pour it directly on the surface of the existing soil, no compaction and the first rain will wash the dirt out from under the concrete and it will crack with no traffic on it at all.

[friscofrankie]

I've poured a few million yards of concrete; not one pour was without reinforcement. Only a fool would pour without reinforcement. A four or six inch slab that is going to get traffic should have steel. I have poured mat pours for high-rise building footings that were four feet deep. Believe me, the soil was prepared better than anything you are going to get here and was oinly going to bear a static load or more concrete; there was plenty of steel in every damn one. Concrete has next to nothing in tensile or shear strength, post or pre stressed beams can bear side load but that is moot here. this is why steel is needed. driving over a slab you are applying a compressive load but also unless the substrate is perfectly compacted and absolutely uncompressible you are also creating side load stresses.

A properly prepared substrate can help to prevent the poured concrete from having to bear an unsupported side load and ensure that majority of the load is compressive. Vibrating the poured concrete as it is laid is a very good insurance that there will be no voids or aggregate impaction, I have never seen a job here with a vibrator onsite, let alone used. And yes, we even used them on slabs. Use Steel.

reaches full strength after about 20years

Yeah but who's going to wait that long? Concrete is measured at 28 days and I have rarely seen pours that required a longer cure time than 7 - 10 days before it began bearing load. Not sure about the 20 year figure but it is a few years to be sure.

Some one above mentioned a proper base preparation; this is impoortant and poor substate will kill you with or without steel. I do not care how good the prep is, I will reiterate; Use Steel Reinforcement.

i recently laid a driveway for my sawmill, where the 8 ton rigging trucks we use, travel up and down all day: absolutely no steel necessary.

We'll see if it makes that 20 year full strength life
if you are bearing that kind of load and opted for no reinforcement you took a helluva chance with your investment. How thick?
No matter how well you prepare the substrate, soil is soil. it is subject to erosion (yes even under a slab o' concrete) and settling; not using steel was a mistake in my opinion.

[Happyman]

You want to do as I have done in the past to see the neccessity for re-bar.
Been on cleanup after many major earthquakes and the difference in damage to structures was in direct proportion to the amount of steel in them .
Taiwan 1998 was the worst I have ever seen for that !

[Joe66]

steel price is on a low level now,
but I would first check the level of the government road.
If they make a few new road covers on the gov. road, the next 10 years,
and your road level will be lower, then the road level of the government road,
you will create a little river in rainy season,
cause the water will go the wrong way.

So make your road at least 30 cm higher than the actual government road level.

[jubby]

Most of my drive is only about 4inch thick, if that. laid by the village idiots. I have one crack because they didn't use joints every few metres. Its reinforced if I can use the term loosely with bamboo matting instead of steel. most of its been down for 10 years, no problems. had a couple of very large trucks on the drive a couple of months ago with 1000 bricks on them each. pretty heavy. They crushed the concrete over the drain ditch at the entrance on the way in but didn't damage the driveway. I'd probably use bamboo again. definately need something.