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Concrete depth


Angie
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100mm is the nominal standard for a domestic drive although it's not quite that simple.

Clearly what you're laying it on has a major influence as does the mix and the anticipated maximum weight of traffic which will be using it.

On a rock base and for light passenger cars only you might only need a couple of inches reinforced with fibres whereas on soft earth you might need three times that reinforced with steel mesh.

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Thank you for your advice. I think we will go for the latter to be on the safe side. We have clay soil has a lot of rock in it but the site is quite sloping and we do get the occasional heavy vehicle at the house. Definitely using the wire mess and as its a large area want to get it right first time.
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[quote user="Angie"]We have clay soil has a lot of rock in it ...[/quote]

Hmmm.  I trust this doesn't mean you're intending to pour the slab directly on to the ground, i.e. with no sub-base? [:-))].  The ground and the concrete slab have to be able to move differentially, or you risk the concrete cracking.  That's one of the jobs of the sub-base.

[quote user="Angie"] ...Definitely using the wire mess (sic) ..[/quote]

I trust you are aware that the primary purpose of the mesh is to resist shrinkage as the concrete cures ?  It adds nothing to the compressive strength of the finished product.

[quote user="Angie"] ... as it's a large area want to get it right first time.[/quote]

Plan carefully.  Don't try to do it all at once.  Partition the area up into small bays with expansion joints between them.  Once that concrete hits the ground, there is no going back ...

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[quote user="Lehaut"]Concrete is not too pretty, top layer of nice gravel brought to the top with either acid or jet spray gives a more appealing look.[/quote]

This is a sloping driveway?  Well, if you live somewhere where it freezes in winter, you should rather think about tamping some diagonal grooves into the concrete to provide grip for vehicle tyres.  It might not look so nice; but a run-away on ice can have nasty consequences ...

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Our builder friend always made us dig deep and put in a very good base,

under the concrete, he assured us that even a path would crack without a

good base.......

There is only one thing I would say about bad

weather, yes, groves of some sort, but nothing that would stop a snow

shovel clearing the snow easily.
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  • 3 weeks later...
[quote user="Lehaut"]Concrete is not too pretty, top layer of nice gravel brought to the top with either acid or jet spray gives a more appealing look.[/quote]

I see this quite a lot in pedestrianised shopping areas and fancy doing it for my own drive. What exactly are the techniques involved?
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[quote user="jerrycan"]What exactly are the techniques involved?[/quote]

It's called an 'Exposed Aggregate Finish', and one method (for example) involves spraying a chemical known as a concrete retarder onto the surface of the fresh concrete and then returning 12-24 hours afterwards to spray and/or brush off the un-cured surface of cement, thereby exposing the aggregate.

This isn't the only way, but is the most usual.  Have a look on Tinternet under 'exposed aggregate'.  Can be fun, but best to practice on a sample area to hone your technique before launching into the real thing ... [:D]

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Only one comment which is, however, not too important for the OP's drive but might be useful for someone using exposed concrete aggregate for a terrasse. 

You can't jet clean the surface too vigorously because you'll loosen the stones.

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[quote user="ventodue"][quote user="jerrycan"]

Off topic are you the ventodue I've seen on other forums with a bevel drive Ducati?[/quote]

Strangely ... yes!  You'll have to reveal your alto ego, now ... [:D]

[/quote]

I'm on the bevel heads list, more of a lurker really, only post when I feel the 'Mericans need their "facts" correcting.

I have a Hailwood Replica which I'm trying to get registered here in France.
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  • 3 weeks later...
Thank you all for your advice and suggestions. We have decided, following comments on the forum, to concrete just the area around the house and re-gravel the long part of the drive as this is quite steep. The gravel/calcaire we had put down 8 years ago has lasted til now and it was pretty painless to install and relatively cheap. I have noted the comment about attempting to do all the concreting at once, partitioning off is sound advice. However, I do have one final question (hopefully) - how do you calculate the square metres of ready mixed concrete you will need on an area with unequal side lengths? We have done numerous calculations and come up with widely differing measurements every time!! If there is some mathematics whizz out there who could work it out for us (or tell us how to do it) this would be great! Measurements around the edge of the drive are 5, 13, 20, 5, 5 and 15 metres - depth of cement will be 15cm. As always, thank you everyone who has taken the time to reply
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Those figures make no sense at all.

As you have measured, if I were you, I would do a little diagram of the drive with those measurements next to each bit and take it into your local ready mix place and ask them how much you need. I'm pretty sure that that is what we used to do.

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 Around the drive or the house? how many sides of them? Is it an L shape or a 6 sided polygon?

For the former just calculate the area as two quadrilaterals, for the latter use co-ordinate geomoetry, i.e. break it down into triangles.

Multiply the calculated areas by the thickness.

1m3 of redimix will fill a volume of 1m3, you need about 1.5m3 of dry materials, sand, stones and cement to produce 1m3 of concrete if you mix yourself.

Dont expect the redimix supplier to be able or wiling to do co-ordinate geometry and trigonometry for you [:-))]

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Hi Chancer, yes you're right, the local supplier would not work it out for us. Its a six sided polygon as you have correctly surmised. Thank you for the mathematical advice, I will try that. Definitely not going to mix it ourselves!! Many thanks again
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