concrete pour question

[Bob Myers]

I dug a hole. 7 ft x5ft x 5ft deep, filled it with concrete(2500psi). Roughly how long will this take to cure well enough to erect my antenna? My answers so far are leave it alone and don't touch it to even remove forms for a month. Sounds mighty long time to wait don't it?

There will be a 60' self support tower going on this block

[Peder_y2k]

I'd take the forms off in 5 days and backfill the hole using a vibrating shoe every 2ft depth of fill. Then two weeks before beginning assembly of the tower, guying religeously with tornados in mind.

[Bob Myers]

It is a folding tower, hinges over at 16 from the ground. Self supporting means no guy wires.

No back fill needed, I poured all the way to level with the ground, with a 40" square raised section in the center to be above ground level. Your recommendation of 2 weeks gives me ample time to finish the booms and mast that go on top of it

Here is a picture of it when it was being taken down for me to purchase.

[playboy]

If you poured to ground level and need no back fill then what forms are there ? 2 weeks should be plenty of time for curing before erection. If you have some edge forms around the top you can remove them the next day no problem and depending on the slump you poured and the temperature you could probably remove them sooner.

 

 

 

 

Next time don't leave your re bar in contact with the ground outside of the pour. the reason for this is the re bar with start rusting where it is in contact with the ground and over time the rust will migrate into the whole re bar system. But hey it will still out last us both.

[pmelah]

28 days for complete cure you can start erecting the tower after 7 days for as much concrete you have the tower wont make a dent in the weight that concrete will support

[Bob Myers]

Only ground contact is the 4 vertical post, they are copper clad 8 foot long ground rods, welded to the rest of the structure and driven over 5 foot each into the undisturbed clay base.

Yes, only form used is the 4 inch raised section in the center that will be visible after I throw sod down around the rest

[bongobobny]

What band are you going to be on??

[Bob Myers]

Presently I am all over the place, check into net on 80m around 7pm when I remember it, another net on 6m when the guy running it remembers to do it, rag chew 2m and 1.25m for a couple hours each night. Kenwood TS 2000 rig

On this tower(this is my second one) I'll have a 2m/440 vertical on top, and on a horizontal boom about 6 foot below there will be a 2m beam on one side, and a 1.25m beam on the other. 220 is starting to revive in this area and most of the people talking are just far enough away that a vertical is barely adequate.

My original tower still has a 6m vertical and a 6m beam on it. Some fool needs to climb it and work on the rotor. It also has my 80m skyloop which is 157 foot long. With the new tilting tower I'll only have to use the permanently mounted winch to let it down it something up there needs attention

Edited May 24, 2013 by Bob Myers

[Guest tx2sturgis]

You should wait 99 years.

 

Hoover Dam is STILL curing.

 

[CaptainJoe]

Dang!

 

You ought to be able to talk to Major Tom with that!

[djh3]

Last antenna I saw bent over like that one was the other way over the house and didnt fair so well. LOL Bob you got more irons in the fire, I dont know how you keep them all straight.

[Bob Myers]

Last antenna I saw bent over like that one was the other way over the house and didnt fair so well. LOL Bob you got more irons in the fire, I dont know how you keep them all straight.

Well, the key is, apparently, that you never finish anything. That way you always have something to do to occupy the few spare minutes you thought you may have.

[dacheedah]

I would say after 24 hrs spray sealer, 14 days of rest. 1 copper grounding rod for each leg, as close as you can get it to the leg, and bonded with heavy minimum 6awg cable to each.

[Bob Myers]

I would say after 24 hrs spray sealer, 14 days of rest. 1 copper grounding rod for each leg, as close as you can get it to the leg, and bonded with heavy minimum 6awg cable to each.

 

when I built the rebar cage I used 8 foot copper clad for the 4 corners, drove them 5 foot into the ground and welded them to the horizontal bars, which were in turn welded to the angle frame that holds the 7/8 all thread galvanized bars. These all thread bars will thread into an aluminum block I machined to set the legs in. So, in short the aluminum legs of the tower will be bolted to the frame work that is welded to the copper clad ground rods, should be a more secure connection than clamping a wire to each leg, what do you think? more ground wire still needed?

I never even thought about the sealer, I actually have a 5 gallon bucket of it I can dump on it. Bet it won't take a quart to cover it

Edited May 25, 2013 by Bob Myers

[Condor]

You should wait 99 years.

 

Hoover Dam is STILL curing.

 

 

So are the footings of the Golden Gate. As long as they stay wet they'll continue to cure...

[Bob Myers]

So are the footings of the Golden Gate. As long as they stay wet they'll continue to cure...

I guess I need some schooling on this. Why does being wet make it take years instead of days to cure? I have been led to believe you can pour concrete under water and it'll setup and cure out, not as fast obviously as if it were above water.

[Dano]

when I built the rebar cage I used 8 foot copper clad for the 4 corners, drove them 5 foot into the ground and welded them to the horizontal bars, which were in turn welded to the angle frame that holds the 7/8 all thread galvanized bars. These all thread bars will thread into an aluminum block I machined to set the legs in. So, in short the aluminum legs of the tower will be bolted to the frame work that is welded to the copper clad ground rods, should be a more secure connection than clamping a wire to each leg, what do you think? more ground wire still needed?

I never even thought about the sealer, I actually have a 5 gallon bucket of it I can dump on it. Bet it won't take a quart to cover it

 

Being a master electrician, I think you pretty much have good grounding conduction there....

[rbig1]

galvanized and aluminum are not compatible. they will react together and fail it may take 4 to 5 years. set some street lights and found this out. lucky no one was hurt.

[tazmocycle]

when you hear of green concrete, that's what is meant, the color is dark green looking, when it get to a lite gray or white, it's cured. if you pour in water or cold weather, you can add calcium to it to make it kick off(it gets hot to touch) and cure out faster. you can also do the same thing to fiberglass, add more catalyst to the resin, but it will get hot enough to catch on fire, so you have to be careful !!

http://www.concretenetwork.com/curing-concrete/when-to-cure.html

you can read on curing, this may help out.

on putting alum and copper together you can use a stainless washer between the two, to still get the connection. you can also use some dielectric paste or grease to keep it from corroding. if you can get a split bolt the right size, you can get one that's made for al/cu connection.

http://www.elecdirect.com/catalog/a6e77b09-b40a-4072-b284-58d0e60cfa85.aspx?utm_source=bingads&utm_medium=cpc&utm_campaign=split+bolts

it has a bar that goes between the 2 different metals to stop corroding. I've seen huge copper split bolt blown apart because of the different harmonics and eddy currents, my brother put a piece of hard wood between the 2 wires to get them up and running till we could go and get the right connectors.

Edited May 25, 2013 by tazmocycle

[alwrmcusn]

Well, the key is, apparently, that you never finish anything. That way you always have something to do to occupy the few spare minutes you thought you may have.

 

Oh that's terrific! I'm going to have to use that myself!!

[Brake Pad]

The best Builders code to follow, is the Miami Dade/ Broward County, Builders Code.

I wish I was there to help you.

[Bob Myers]

the actual cradle of all thread that supports the antenna was tied into the concrete at three different levels. First one was a simple angle iron cross app 8 inches from floor, second one was full triangle, 18" above that, and final one was another 18" above the second one, leaving app 10" of concrete on top of the last one before getting to the 4 inch riser in the middle.

But thanks for the Dade mumbo. I guess building on sand or sand stone would be quite different than what I have here.

[Bob Myers]

galvanized and aluminum are not compatible. they will react together and fail it may take 4 to 5 years. set some street lights and found this out. lucky no one was hurt.

 

Didn't know that, interesting. I can still make my threaded connection from a stainless, and then bolt the aluminum to the stainless, but that is getting pretty busy for the connection. I'll have to do more research since you brought this up.

 

On Edit;

According to what I can find to read the galvonic process is most likely not going to be a problem in this area. Humidity and coastal air play a huge part in expediting that.

Edited May 26, 2013 by Bob Myers

[dacheedah]

when I built the rebar cage I used 8 foot copper clad for the 4 corners, drove them 5 foot into the ground and welded them to the horizontal bars, which were in turn welded to the angle frame that holds the 7/8 all thread galvanized bars. These all thread bars will thread into an aluminum block I machined to set the legs in. So, in short the aluminum legs of the tower will be bolted to the frame work that is welded to the copper clad ground rods, should be a more secure connection than clamping a wire to each leg, what do you think? more ground wire still needed?

I never even thought about the sealer, I actually have a 5 gallon bucket of it I can dump on it. Bet it won't take a quart to cover it

 

I would still bond it on the surface, cheap protection (for your house and people) If it took a direct strike it may actually smoke the bonding wire, if you can see it you can fix it for the next event. I personally would not rely on something I could not visually inspect and repair.

[utadventure]

Bob-

 

Concrete is designed to acheive full strength at 28 days. I cures on a curve, with most mixes having 70% of their total strength at 7 days and then continuing to cure over the remaining 21 days, each day the strengthening deminishes.

 

Dave