POUR NEW CONCRETE OVER OLD?

[paulharvey]

I recommend ripping out old, so that you wont get reflective crackinging, mirroring the old squares. No gravel, just tamped clean fill. House slabs are 4" thick, 3000 psi concrete, so 5000 is way over kill. I do recommend using WWF but aslong as you saw cut or tool control joints you probably can get away with skipping it (theres no fiber, wire, or rebar in sidwalks).

 

[Gary Fowler]

If you have frost heave, then follow my PM on installing the 1" HD foam on top of existing concrete and pour a 3" thick 3000 PSI strength concreted slab. NO other prep will be required other than forming it up. The 1" foam will allow the ground to heave a bit without moving the slab. I doubt you will get much movement under the existing slab.

 

[paulharvey]

I recommend ripping out old, so that you wont get reflective crackinging, mirroring the old squares. No gravel, just tamped clean fill. House slabs are 4" thick, 3000 psi concrete, so 5000 is way over kill. I do recommend using WWF but aslong as you saw cut or tool control joints you probably can get away with skipping it (theres no fiber, wire, or rebar in sidwalks).

 

[Egon]

If you have frost heave, then follow my PM on installing the 1" HD foam on top of existing concrete and pour a 3" thick 3000 PSI strength concreted slab. NO other prep will be required other than forming it up. The 1" foam will allow the ground to heave a bit without moving the slab. I doubt you will get much movement under the existing slab.

There are better ways to eliminate frost heave.

 

[don45640]

As a former concrete contractor I'd say as small as it is,just take up the old concrete as has been suggested. Remove any sod or soft fill and replace with gravel and run a compactor on it. 5"thickness is a LOT stronger than 4" ,and on a slab that small,just use a grooving tool and cut your fresh joints where the major stress will be,usually at the outside edge away from the building.
If you don't want it to settle near your building,drill some holes and use 1/2"rebar to dowel the new slab into the foundation. Tape the ends of the dowels which stick into the fresh concrete with a couple layers of furnace tape. This will let it slip enough to keep it from cracking the new edge.
Freeze/thaw can be combatted by pouring a skirt around the edge 4-6"thick and down 12" to keep water from running in under the edge of new work.
Just a few thoughts you can choose to use or ignore.LOL!
And I never poured a 5 bag,3000 psi mix if the finish is important down thru the years. Order 4000 psi and you MIGHT get 517 lbs. cement per cubic yd., but I doubt it.There is no business I know of where it is so easy to cheat the customer as to what he orders than in the concrete mixing business.
They can add flyash,they can blow it up with excess air entrainment, they can short you on volume, they can send you an OLD load,they can use inferior grade aggregates, and unless you have a concrete testing company there,you'll never be able to prove anything. But by ordering the load to arrive early in the AM,you generally avoid getting an OLD load.
The only way I was ever able to keep a concrete company on the straight and narrow was their knowledge that I WOULD core drill and have the crete tested if they misbehaved.
Oh,I forgot......6X6X10 gauge wire mesh would be fine for your light duty app here,but IF you wanna lil'extra strength,line the perimeter with 1/2"rebar.
Finish the concrete however desired,but cure and seal it(roller works well) with Diamond Clear for a good result don-ohio ^)

 

[Carl Bert]

I feel bad for you since you are getting so many different bits of advice. My family has been in the concrete business longer then I can remember. Trust me when I tell you, in an area where frost is an issue, as you and I live in, you need to have a 6" base of cut stone. And it's very important that you tamp down the stone in order to fill any voids. This will give you the proper drainage necessary to prevent frost from cracking your slab.

No matter what thickness or strength concrete pad you pour, without the proper base you can almost guarantee it will crack.

 

[bigtiller]

Good advice Carl.

I hope the O.P. isn't totally confused or irritated with us. This thread reminds me of another one asking how far apart to plant trees along his driveway. A lot of answers ranging from 2' to 100' apart. We didn't help that guy at all.

 

[Deere Dude]

After reading all the different opinions, I agree with them all.

 

[Don87]

After reading all the different opinions, I agree with them all.

Too bad the OP doesn't have a slightly larger pad to pour. He could try them all

 

[smiley]

View attachment 299915View attachment 299916
Needing some opinions
.

the morer i readses, the cofuseder i gits!!!

 

[Don87]

the morer i readses, the cofuseder i gits!!!

:rotfl:

 

[mjaybee]

OK here's the last bit of advice you need. Like I said earlier, I've been in the concrete industry for 25 years but I'm 59 years old, so when my front and back patios were poured, I hired a concrete contractor to do the work and then I went to work, which was not pouring (and yes that is a correct term for it, as it pours out of a truck, it doesn't place out of a truck) it. My point is, hire a concrete contractor with experience.

 

[case245]

you can do it yourself all you need to get portland cement and sand mix it 50to1 its not that hard take your time

 

[mjaybee]

you can do it yourself all you need to get portland cement and sand mix it 50to1 its not that hard take your time

It may not look hard, but there's more to it then just getting cement and sand. I seen bad jobs from people who thought is wasn't that hard. Concrete is something you want to look good around your house. You don't want to do it twice.

 

[Rock knocker]

you can do it yourself all you need to get portland cement and sand mix it 50to1 its not that hard take your time

Check your math, aggregate has to be in there somewhere

 

[Carl Bert]

It may not look hard, but there's more to it then just getting cement and sand. I seen bad jobs from people who thought is wasn't that hard. Concrete is something you want to look good around your house. You don't want to do it twice.

Yeah I have to agree with mjaybee. Unless you can find at least one person, who has some experience with concrete, you shouldn't attempt it yourself. I'm not trying to say that you're not capable, come to think of it, I don't even know the size of this job, but it does take some experience to do the whole job from start to finish.

How big is this pad anyway?

 

[Don87]

Yeah I have to agree with mjaybee. Unless you can find at least one person, who has some experience with concrete, you shouldn't attempt it yourself. I'm not trying to say that you're not capable, come to think of it, I don't even know the size of this job, but it does take some experience to do the whole job from start to finish.

How big is this pad anyway?

9x12. post number 1.

 

[Carl Bert]

9x12. post number 1.

So you're pouring just under 1 1/2 or 1.3333 yds if your doing a 4" slab. Are you getting a truck or mixing by hand? If you're mixing by hand you definitely want some help. One guy mixing while the other is dumping and spreading. If you get a truck, then yes it can be done by one person, but he still needs to know something about pulling up and finishing concrete.

If you do get a truck, you are going to want to find one that mixes on site. The truck comes with all dry materials and they mix exactly what you need on site. The other option is pre-mix concrete, which is the typical concrete truck you see on the road. Problem with pre-mix is price. You're going to need, what is called a "short load" which can get very expensive, depending on how they charge in your area. In my area you pay a fortune for a short load.

Hope this helped.

 

[mjncad]

It may not look hard, but there's more to it then just getting cement and sand. I seen bad jobs from people who thought is wasn't that hard.

I've drawn up more concrete details in my life than I care to think about, and concrete IN THEORY is easy; but in reality there is a lot more to it than just pouring a wet mix of glop and making it strong and look good. Personally I hate working with concrete, whether new or old.

If you do get a truck, you are going to want to find one that mixes on site. The truck comes with all dry materials and they mix exactly what you need on site.

Hope this helped.

I used one of these on-site mix trucks on a project requiring about 1 to 1.5 cubic yards of concrete, and it worked great. It was easy to have the operator tweak the mix as we were pouring the concrete.

 

[crashz]

I'm a civil engineer and like Gary, spent a lot of time providing Quality Control or Quality Assurance, as well as design for concrete projects.

I'm not going to add to the the confusion here as much of the advice has some merit. But I personally would follow Gary's advice with and emphasis on the "well drained" subgrade.

BTW - "Placing" is the correct term. As well as "curing" rather than drying.