concrete and rebar

[Uno]

Hello newsgroups,

Only recently have I used usenet to help me with my handymanning projects, and I have found it tremendously helpful. Is this something you can see?

Anyways, it's a gate with a concrete pad. I have 2 questions.

q1) On the lip of the pad that is the exposed vertical surface, one sees the cottage cheese from lack of vibrating on the concrete. How do I simulate the action of the bigass vibrators we used to use when pouring into forms?

Still q1) To make it nicer, would I just buy a quikrete mortar mix, and trowel it on?

q2) This is a theoretical question. I have 2, square 4' pads poured under the same conditions with only one difference, in one, the rebar that is in the middle and 3 inches from the edge is tied on one, and on the other the pieces aren't tied at all.

In other words, how does it affect the strength of the buiding system when the rebar is left untied. Under what circumstance would the untied pad fail while the tied one did not?

Alright, thanks for your comment. It's raining here in Albuquerque.

Beautiful rain, like God's own mercy--you'd understand if you worked through the heat I had to to create this gate.

[PeterD]

Link requires logon... Try using a public image hosting service instead, or perhaps you can adjust your permissions/privacy settings.

[Uno]

>

Thanks so much for pointing this out, and I apologize to those who are cussing me right now.

Let me put in a plug for the nice folks who do my image hosting for free:

I keep it bookmarked.

[willshak]

Uno wrote the following:

I have concerns about that concrete 'pad' (or is it a 'sill'). People unfamiliar with it could trip over it.

[HerHusband]

Hi Uno,

I assume you are talking about voids in the concrete, where the aggregate (stones) are showing?

Are you talking about plate compactors for compacting the base before the pour? If so, you can rent those from any tool rental store. Or just screw a block of wood to the end of a pole and tamp it by hand.

If you're talking about vibrating the concrete during the pour, you can simply use a stick. Just poke it up and down in the concrete to work out the air pockets, especially around the forms where it will show.

Your local home center should carry "patching" mix. You mix it with water like concrete, but it doesn't have the aggregate. Then just trowel it on, pushing into the voids.

You might want to pick up some bonding agent and apply that before patching, just to make sure it all stays together.

On the other hand, if the voids are in the sides of the slab, just bring the dirt or pavers up flush with the slab and hide the imperfections.

Most "pads" (sidewalks and the like) are poured without any rebar. I usually stick a couple of bars in for extra strength, but I doubt you'll have any issues tied or untied in a non structural situation like that.

Good luck!

Anthony

[Jim Elbrecht]

-snip-

Buy a $100 vibrator from Harbor Freight. At least 100 times better than a stick/shovel/hoe/rebar/stomping-on-it-in-your-bare-feet.

-snip-

None I've poured-- but then I just read a lot and never worked for a 'real' construction crew. I've been tempted to go with fibers and forgo the rebar or mesh-- but it just doesn't see right to me.

Jim

[jloomis]

[HerHusband]

For most small jobs, a stick works fine. We poured the foundations for our house and garages using the stick method to work the concrete around pipes, under vents, along the forms, etc. It's how it was done before vibrators were available, and still does the job today.

If you MUST have a vibrator, I would probably rent one. It's not the kind of thing you'll use often, and it's just one more thing taking space in your garage.

We used fibermesh in our garage slab (no wire mesh or rebar). Nine years later, and it's still in perfect shape. The guys trying to put the steel finish weren't crazy about it, saying it was hard to get a good finish. But I'm thrilled with the way it turned out.

Anthony

[rustyjames]

I agree, you can get good results with rodding the concrete and tapping on the forms. However, as with using a vibrator, don't go too crazy.

[Uno]

There's a lot of grade here in abq, so making a proper step out of inclines is not untypical. The part that needs to be raised is what I call Micah's Path of Stumbling Drunkenness, which runs between the driveway and this gate. It's 3 inches lower than everything else, and despite good intentions, collects crap to trip on.

Has anyone tried cementing flagstone in a path?

[Uno]

If you were going to pour sidewalk one square at a time, where would you put the rebar and what would you do with expansion joints, given that the field condition are that of abq?

[RicodJour]

You don't. Sidewalks don't require rebar. In fact they're more likely to cause problems than prevent them. Code requires plain steel rebar to be covered with 3" minimum of concrete. The reason for this is that concrete is not waterproof and steel has this nasty habit of rusting. When steel rusts, it expands, and the concrete will crack. The way to keep a slab from cracking is to prepare the sub-grade adequately.

As far as your other questions, you could use either mortar or thinset to fill the voids in the edge of an existing slab. Thinset (yes, the tile setting stuff) works great and adheres tenaciously. The latex- modified stuff is just the ticket.

If you want to vibrate a small form, take the blade out of a reciprocating saw and place the foot on the form and pull the trigger. It's also a good idea to coat the inside of the form with a form release agent. That's a fancy name for oil, or an oil and kerosene mixture.

If you want the best advice anyone will give you on Usenet, search alt.building.construction for posts by Bob Morrison including the search terms "slab grade mesh rebar grade". That will give you a short list of the excellent answers provided by one of the true gents of Usenet. He is no longer with us, but his excellent advice lives on.

R