Can someone give me a very simple tutorial on what I should be looking for in having a new concrete driveway poured
driveway will have a F250 parked on it every day—-occasionally/often with 8-10 square of shingles in the back of the truck
one price in so far– mentions 4 inch of 6-1/2 sack,4500 PSI, broom finish,fiber or wire—and verbally something mumbled about 3 or 4 inches of crushed concrete fill.
I am assuming an adequate amount of a specific fill/base is critical–but what—-and what is 6-1/2 sack—-and is 4500 PSI sufficient?
Stephen
BTW- new driveway will be 864 square feet.
thanks
Replies
User information as to your location helps with frost line
Quality of soil affects longevity of concrete, do you have any idea of soil quality in your area. Shoveling a few test holes can give some information
Fibers questionable but are used to minimize cracking
Welded Wire Mesh essential to minimize concrete cracking or placement failing, must be suspended in center of profile to perform correctly.
How big is driveway, is it flat or sloping.
Parking area could be thicken to increase bearing for truck with shingles onboard
Site preparation is cheap compared to placed concrete expense
Plan for control joints
How much is price per square foot in quoted price
No expert here but I know a bit.
# of sacks is a reference to the yield strength of the concrete.
1 sack= 94lbs. of cement.
( a bit like referring to shingles by the # of years of warranty instead of by weight)
6 1/2 = the 4500lb.PSI (added benefit is that higher cement ratio resists water penetration better)
Job I am on right now calls for 6" slab, 517 lbs of cement per cu/yd, 2-4" slump, air entrainment ( reduces freeze thaw cycle cracking)and a water reducing agent (which allows for less water and higher slump or ability of concrete to flow, excess water reduces strength of concrete).
Yield strength is 3500 psi. Use is a commercial winery work area and floor, way more weight and traffic than your driveway will ever see.
But regional differences in weather rule for additives.
Sounds as if compressive strength is being substituted for thickness in your drive. Make sure they do a 6" deep approach/apron , 4" just never hold up under the years of abuse.
Wire IMO is useless except to hold concrete together after cracking or cutting, the wire adds no compressive strength nor real structural strength. Want strength add rebar.
Well compacted fill, well drained fill is as much or more important than the concrete PSI.
Crushed concrete fill is recycled concrete, crushed to 3" and smaller particles around here, includes "fines" which are sand, rock dust etc. to fill voids. Works just fine for fill, very good compaction when mechanically compacted with a roller and placed in 6-8 lifts. Just placed over 100 yds of the stuff here.
Saw cut or provide expansion joints in as close to a square grid as possible, helps prevent cracking. Fill the cuts afterward with a urethane sealant. Sika makes good ones just for this purpose.
to all----- this is just the first price-- which appears to work out to about $2.80/sq. ft for a driveway and walkway. driveway is VERY short- frankly the truck will probably stay on the steet.I al ready have a new apron--courtesy of the Gas company who dug up the old one last year--- and I am not about to pay for another one--as the city plows just zip around the curve in the street and tear it up anyhow, LOL. driveway has a 1/12 slope to 2/12 slope-- nothing tramatic. soil here is heavy clay-- i assume compacted fill is important--- but how much?--- this guys paper work mentions nothing about fill---- he just verbally mutteres something about 3-4 inches crushed re-cycled concrete-- I am hoping for someone who spells things out a little clearer.
stephen
4" minimum. really depends on local soils. Preaching to the choir but get it in writing, depth of fill, composition of fill and compaction type. You could almost "proof roll" the fill on your own with your truck. Load the truck to max weight, roll slowly over the fill and have someone watch to see if "waves" develop in the fill . If so the undersoil is too wet and not compacting, it is just displacing moisture under the compactor.
They can't get your Goat if you don't tell them where it is hidden.
Personally, I'd frame it with 2x6's. And use a 6 sack mix. All sorts of steel. Fence posts, the fence, strips of angle iron, whatever you got laying around. Of course, that's assuming you are on sand and have driven your dump truck over it for the last 6 months.
But be sure of your finishing that you get the slope and height right.
DUDE! Seriously, how long have you posted here... and you don't have your profile filled out. Thats like using a sidewinder on the west coast - major foo paw!
;)
I had asked about concrete drives years ago and did some research. The better the base, the better the surface will be. With that small a drive, you could go to a deeper base than anyone would normally think of (like 12") and build up your fill from there.
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
and verbally something mumbled about 3 or 4 inches of crushed concrete fill.
Would get that guy dropped from my sub list immediately.
Fill is the most important part of a concrete job, from sidewalks to structural slabs.
Really with 9-12 inches of well-placed fill, properly compacted, you could use 2800-3000psi concrete with not much more than #6-8 wire mesh (flat, not rolled).
If this is getting a load of salvaged concrete vaguely dumptruck rolled out, then, yea, 4500 crete will be needed. I'd want 6-8" with #4 @ 15" OCEW, with fly ash, in proper formwork. Yes, that's near to bridge specs, but given the crummy fill, that's what you'll need anyway.
If you've got clay soil beneath it with poor drainage, the slab is going to rise with the frost. So you'ld better have a strong one that is sectioned off with deep crack control lines cut into the slab. Preferably, no more than 10' x 10' or so.
In my opinion, the mix is plenty rich, but the slab is too thin. One of the problems with 4" slabs is that if the fill under it is not perfectly graded, you will end up with areas that could be thinner than the location of the crack control line, and you could get random cracking.
We usually pour 5" or 6" slabs with 6 bag mix and never have trouble. Basically, a slab is only as good as the base material. If you don't do that right, you will have trouble, but a thicker slab can take more abuse.
If you've got soil that will freeze and move, I would use re-rod in the slab.
A LOT has to do with the underlying soil. We get wet clay and often have to dig out 18" deep and refill with mineral fill and compact it.
Next thing is that you do not want to let them put too much water in the mix. No more than a 4" slump in any way. most slab guys put too much water in to make their work easier but that weakens the mix and causes shrinkage cracks and sometimes scaling surface.
His description sounds to me like a guy who substitutes extra portland for good prep. That makes for a harder surface true, but it also can make it more brittle for cracking if the soil base is not up to par.
Good base and you can do with a 4" slab, but for his base prep desription, I want 6" and the extra potland and steel rebar at 16" OC grid.
4500# is un-necessary if you are not putting steel post point loads on it. 3500#is fine with good base. 4500# is worthless at 4" if not a good base.
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your drive way will crack, I quartee that
6 1/2 sack is a 4000-4500 mix.
it will crack because they will pour wet, its a driveway, they always pour wet. you going have to fight with them to get a good product, really fight
now what do you need. some place use rock base, its fine, we dont use rock here. Compact the soil. over and over and when you think its tight. compact again. rebar, if you want, not neccasay but I did on mine. 6 inch slab if you can afford it. 4 will crack
ok school has begun.
when you apply a load to a slab, the weight will cause the slab to bend. this bending is what cause the cracking. If the soil is compacted it will fight the bending. If the concrete is thicker, it will take more load to cause the bending. If concrete is stronger it will resist the bending. water weaken concrete strength.
rebar will bend on side but it will take a tension resistance on ends. so with rebar in slab. when the slab start to curl, bend, it will pull on the rebar, which will counteract the force to bend. BUT. you got to have concrete coverage to keep the rebar in place or it will pop out of the slab. this is also spalling type effect if rebar too close to surface.
entrained air, a chemical added to concrete to create small air bubble so when concrete freezes, it have somewhere to go. without this you have spalling.
fly ash. a coal product that has the same properties as cement but will not get hard as fast. with fly ash the concrete will be cooler so less cracking will happen due to shrinkage. also fly ash particles are round and smooth so they flow against each other easiler so it be a smoother paste without the extra water.you can place at a lower water content, create a higher strength concrete. since the strength comes in at the later of the curing cycle it will be a cooler product reducing cracking.
so you need a six sack mix, with entrained air and flyash. six inch slab #5 1 foot each way, place at no more than a 4 inch slump. make sure to use a mechanical vibrator.
a 4500, 4000 will resist cracking better, but if done right, a 3000 is just as good, with a 3000 done right and being cheaper you could go thicker at the same price as a 4500.3000 will hold the load with no problem
Edited 3/13/2009 7:42 pm by brownbagg
I would like to thank everybody for their advice here- particularly Brownbagg and his expertise. i have a contractor for this now that I am very comfortable with----------
tremendous referall from my neighbor who is a landscape contractor------ they have worked together on 10-12 projects-we are also all part of an extended "old school" network who supports each other and referrs back and forth,hires back and forth etc.Price is about $1000 more than I was hoping for, about $4500 less than I was afraid of and considerably more than the first guys estimate.( I looked at the first guys broom finish and it looked like he did it with a garden rake or a horse drawn harrow,LOL) at any rate- thanks again guys,
stephen
Where are you? The climate makes a big difference.
In Vegas a commercial driveway is 5-inches of 3500-psi concrete, with #4 bars @ 12-inch on center both ways, on 5 or 6-inch of gravel base.
thanks all, interesting------Recession?---what recession? have called 3 concrete contractors so far---2 of which are highly recommended--- THOSE 2 have yet to even return the phone call. the third guy has already been out--given me a price---and given me adresses of former jobs and the address of the job he expects to begin on 3-16-09.
stephen
Dude - I know where you're coming from!No offense to the fine concrete gents that occasionally post advice here, but back in '01-'02 when we were looking for concrete guys for a pretty good residential project...We had 13 calls out (i.e. talked to them, set up a time), only five actually showed up. One wouldn't give us a bid, one gave us a ridiculously low bid (10k off on an ~15k job), one had to have his dad show up with him to calculate the square footage. It was easy to rule him out after finding out his license was expired. I got a call from him the next morning around 5:00am (the missus was VERY happy about that...) explaining that it was the county's fault... Two weeks later, I had two very professional outfits show up, and gave bids within a 1% of one another. We went with the outfit that had the hot babe doing the field work. I never saw her again, but I've always been a sucker for a gal that knows what to do with a tape measure...
LOL! The company with the "babe" knows how to put the frosting on the "concrete bid"
Virginbuild
sounds good to me.
I'd wanna know if the "crushed concrete fill" is gonna be actually crushed ... or hunks of the old that are "jack hammer size". Most likely ... he's planning on throwing the old driveway into the new hole. Which isn't a bad thing on it's own.
I'd want some gravel thrown in there to level the whole deal out and fill the voids that'll be there if the chunks are typical jack hammered out chunks.
and I'd also point out I have a tape ... and can read to 4" ... so I expect the full 4 inches. Also let him know you'll be parking the occasional load on it, make sure the crack control joints are cut spaced tight enough to work.
If you usually park said loaded truck down by the bottom ... or up near the top ... nothing wrong with digging an extra inch or two right around there to be safe.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
I am not inclined to write the first guy off immediately----- because when I first moved in here I got a price for a similar project from a guy with rave reviews from my friend and neighbor--apparently THAT guy is INSANE about how far down he digs, how much fill etc.
THAT guy came- talked to me an hour and gave me a price scribbled on a business card that's why I want to meet a few more----- maybe this is how they ALL behave----- maybe this is just an estimate form--maybe the actual contract is more detailed------ I don't have enough experience with concrete guys to know.
stephen
BTW-- i am sure the crushed concrete is actually crushed concrete---- he actually did talk to me about where he gets it from etc. and he made a point of telling me that he takes one day to dig out the old, fill,form etc.---and pours the next day and that I would be able to inspect everything in between--- but frankly I wouldn't even begin to pretend I even knew what I was inspecting
Edited 3/15/2009 7:24 am ET by Hazlett
Stephen, you don't have to be modest.
"but frankly I wouldn't even begin to pretend I even knew what I was inspecting"
I have found that you inspect by using common sense and a tape measure. Find out if what he promised is what you have. Measure the fill in several places and the depth of the forms. You neighborhood, contractors will help you,(old men like me, with nothing better to do), will be happy to put in their 2 cents!
"gave me a price scribbled on a business card"Don't write him off for that.The best and most professional SR guy in my area does the same way. He will come out, measure, look around and scratch his chin for a while ( don't interrupt his train of thought while he is doing this job in his head) and then scribble the number.And that is always exactly what the bill comes to inc complete cleanup
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After removing the old slab, keep driving and parking on the dirt or fill (if its not raining). This will assure the base for the driveway is fully compacted.
Also determine how many and what type of joints are going into the slab.