# licensed concrete contractor balks at 4000 psi concrete for driveway



## pman6 (Jul 11, 2012)

Can anyone think of bad reasons to use 3500+ psi concrete for a driveway?

This contractor says it's harder to work with and wouldn't explain why. 

"harder to work with" is not an acceptable reason coming from a contractor who has been doing this for over 20 years.


----------



## user1007 (Sep 23, 2009)

Not sure and do not want to speak for him but higher strength and higher performance concrete usually has a different slump, and as part of that are poured out of the truck dryer I believe (I do not have 20 years experience finishing concrete, just that many ordering it at times). They also incorporate different ingredients than the basics and may have different aggregate size. I guess it could be more challenging to level and float to a nice surface and would likely have a different working time window. 

High strength concrete is above 5800psi. High strength concrete is also high performance. Not all high performance concrete is high strength. 1450psi to 5800psi is the typical rating of standard concrete. 

There are of course special mixes for things like driveways, surfaces to be stamped with a pattern, finishes to be stained, etc. What has you thinking you need 4,000psi for your drive? Is code calling for it for some reason? Is that the only criteria you have locked in on? What are you driving, flying or sailing that requires that kind of resistance in a driveway? Not saying you are wrong. Just seems like a weird spec to be worried about all by itself. Like you said, the contractor has 20 years experience ordering material and doing this everyday. You have checked references and looked at a few projects if at all uncomfortable? Why not trust him?


----------



## concretemasonry (Oct 10, 2006)

In some areas, you cannot even get concrete for a driveway unless it is over 4000 or 4500 psi (depending on the supplier) and has air entrainment. This is because of durability in cold climates and many good suppliers will not bother with lower quality mixes and usually will refer you to a smaller supplier. They will also not add any water on the site unless the customer signs and releases the liability.

It is all about the problems with small jobs and marginal contractors and eliminates the legal cost and time if there is a problem down the road. - A business decision.

Dick


----------



## jomama45 (Nov 13, 2008)

pman6 said:


> Can anyone think of bad reasons to use 3500+ psi concrete for a driveway?
> 
> This contractor says it's harder to work with and wouldn't explain why.
> 
> "harder to work with" is not an acceptable reason coming from a contractor who has been doing this for over 20 years.


I would guess that the contractor feels it's harder to work with because it' sout of his comfort zone, and likely set's faster than he's accustomed to, and may even set faster on the surface in your weather making it more complicated to finish.

I can tell you that here in the Midwest, 4000 psi is the minimum that should be used. I'm sure there's plenty of exterior flatwork around these parts that never made 3500 psi and lasted OK, but why chance it in "THIS" climate?

In LA, I'm not sure I'd be concerned with pouring 4000 psi, I would think with the moderate climate, you'd be just fine........




sdsester said:


> Not sure and do not want to speak for him but higher strength and higher performance concrete usually has a different slump, and as part of that are poured out of the truck dryer I believe (I do not have 20 years experience finishing concrete, just that many ordering it at times). They also incorporate different ingredients than the basics and may have different aggregate size. I guess it could be more challenging to level and float to a nice surface and would likely have a different working time window.
> 
> High strength concrete is above 5800psi. High strength concrete is also high performance. Not all high performance concrete is high strength. 1450psi to 5800psi is the typical rating of standard concrete.
> 
> There are of course special mixes for things like driveways, surfaces to be stamped with a pattern, finishes to be stained, etc. What has you thinking you need 4,000psi for your drive? Is code calling for it for some reason? Is that the only criteria you have locked in on? What are you driving, flying or sailing that requires that kind of resistance in a driveway? Not saying you are wrong. Just seems like a weird spec to be worried about all by itself. Like you said, the contractor has 20 years experience ordering material and doing this everyday. You have checked references and looked at a few projects if at all uncomfortable? Why not trust him?


Might I suggest you stick to giving painting/interior design advise????? :whistling2::whistling2:


----------



## joecaption (Nov 30, 2011)

So what does this contractor suggest using?


----------



## user1007 (Sep 23, 2009)

jomama45 said:


> Might I suggest you stick to giving painting/interior design advise????? :whistling2::whistling2:


Suggestion taken. I believe the only advice I really gave was to trust the contractor though. Issues with that are?


----------



## concretemasonry (Oct 10, 2006)

You cannot always trust a contractor because he may really be a DIYer in hiding that should not give advice unless he is experience, qualified, licensed and insured.

Dick


----------



## Tscarborough (Mar 31, 2006)

What does this have to do with doing it yourself?


----------



## user1007 (Sep 23, 2009)

Tscarborough said:


> What does this have to do with doing it yourself?


Well, I think one role of DIY site is to help people decide what is and is not a DIY project, what is not, or what may be some sort of hybrid approach assuming a contractor will let them do some of the work. I think pouring, floating and surfacing a drive beyond most DIYers but they could certainly do the majority of the excavation and demolition. 

I think the role can also extend to helping the DIYer hire sub-contractors directly---when appropriate---without someone in the middle by nailing down specs and sorting out contractor bid submissions that vary dramatically. 

Just my opinion.


----------



## Tscarborough (Mar 31, 2006)

The role of a DIY site is not to question contractors. You either trust them to do the work or you do not. You check references, you check past work. Asking a question like this is useless. The type and method of concrete placement is site specific and local.

As noted above, there is no way that 3500 PSI un-entrained concrete would be acceptable in some parts of the country while in others 3000 PSI un-reinforced, much less un-entrained is not only acceptable but desirable.

The OP did not ask what would be a good mix design, he only wanted info to question the contractor. My advice is: If you question his methods, don't hire him and either do it yourself or find someone willing to work to your specifications.


----------



## Canarywood1 (May 5, 2012)

pman6 said:


> Can anyone think of bad reasons to use 3500+ psi concrete for a driveway?
> 
> This contractor says it's harder to work with and wouldn't explain why.
> 
> "harder to work with" is not an acceptable reason coming from a contractor who has been doing this for over 20 years.


 
Only reason i can think of ,is the load that it's supposed carry,otherwise there's no logical reason i can think of.


----------



## pman6 (Jul 11, 2012)

joecaption said:


> So what does this contractor suggest using?



4" thick, 2500 psi.

In my primary home, I think I have 2500psi, poured 20 years ago, and it's cracked all over, even with 10x10' control joints.

In my 10x10 panels, the cracks are centered, giving me four 5x5 cracked sections.


So that's why I'm worried.

I asked here because it seems some contractors post on this forum.


----------



## Tscarborough (Mar 31, 2006)

Do you know what causes most concrete to crack?


----------



## RWolff (Jan 27, 2013)

Tscarborough said:


> Do you know what causes most concrete to crack?



Poor prep work on the ground, and a lousy mix that's too watered down would both be common.


> This contractor says it's harder to work with and wouldn't explain why.
> "harder to work with" is not an acceptable reason coming from a contractor who has been doing this for over 20 years.


"harder to work with" usually = higher price if you insist on specifying.
He might figure it won't be worth the extra cost or you wouldn't want to pay it.

For a slab you drive a car over, or for floors in a high rise building, the weight on the concrete would be what rebar etc would take care 
of not so much the PSI compression strength, with a slab you mostly have a weight force that would crack the bottom of the slab first- tensile force, which is why the rebar would be near the bottom where it's needed the most to keep the concrete from pulling apart.

You'd want that 4000 PSI instead of 2500 PSI figure for things like foundations, brick wall and column supports- compression strength is vital there.


----------



## concretemasonry (Oct 10, 2006)

A typical architectural answer for a technical problem.

The key is a higher compressive strength, lower moisture content coupled with good placement (density in the end) and finishing of a slab. I course, if you have freeze/thaw cycles (not just freezing like minor cold nights), air entrainment is obviously necessary.

Dick


----------



## cleveman (Dec 17, 2011)

You guys must really be living high on the hog to have a concrete driveway. People around these parts who have concrete driveways also have their yards sodded.

Just form up your driveway like you will pour it. Put in a good base of 3" minus rock, then some smaller stuff for the last lift. Finally, keep some 1/2" minus or even 1/4" clean for the final screed. Compact down about 8" of this stuff, screeding across all the time, and you will have a fine driveway which is also green and non-impervious. Can I just say pervious?


----------



## Tscarborough (Mar 31, 2006)

Compacted fill is impervious.


----------



## RWolff (Jan 27, 2013)

cleveman said:


> You guys must really be living high on the hog to have a concrete driveway. People around these parts who have concrete driveways also have their yards sodded.


Sounds like some kind of sub-division or something the driveway is to go.
Around these parts most people use gravel, and the most common local stuff they call "white rock" which is just limestone actually.
I think I had my whole 50 foot driveway rocked with a FULL dump truck of the rock for about $150-$200 maybe, a few years back, the guy did a beautiful job with the truck's spreader laying out a nice even layer of rock from one end to the other, avoiding a tree and power lines- he did it like a BOSS!
it compacts down nice and hard, and the white color is very nice, who needs more anyway!


----------



## user1007 (Sep 23, 2009)

cleveman said:


> Just form up your driveway like you will pour it. Put in a good base of 3" minus rock, then some smaller stuff for the last lift. Finally, keep some 1/2" minus or even 1/4" clean for the final screed. Compact down about 8" of this stuff, screeding across all the time, and you will have a fine driveway which is also green and non-impervious. Can I just say pervious?


Isn't going to happen within city limits of any S California city, where the OP lives. Too many Ferrari windshield's to be dinged by gravel.


----------



## Mort (Nov 26, 2008)

I've poured a few driveways in my day, almost all of them have been 3000psi with air. 

The reason he's probably balking at the higher strength mix is that it won't be a cement only mix, it'll have flyash or slag, along with water reducing chemicals. They tend not to finish as nicely as the old school 4-ingredient concrete does, because it doesn't give you the creamy stuff that makes a smooth surface. 

That, and it costs more. 

I don't know that I'd go with a 2500psi mix, though. For patios and pathways, maybe, but not something you park a car on.


----------

