[TowerTalk] Mixing concrete for a base

Fri Mar 12 23:28:18 PST 2010

There's under water and under salt water... in his case (Chincoteague
Island) he's dealing with salt water.  I recall that you need a special mix
for that situation.  
>From site
http://www.epcserver.com/Structural/analysis/concrete/info_concrete_saltwate
r.asp

"Concrete in sea water should be impervious to protect the reinforcing
steel.  
Mixing water shall not exceed 5 1/2 gal per sack of Portland cement. 
The mix should contain at least 7 sacks of cement per cubic yard of
concrete. 
Entrained air should be between 3 and 6 percent. 
Aggregates should be verified not to be affected by sea water. 
Aggregate size should be limited to less than 1/6 the smallest dimension of
the member and never larger than 1 1/2 inches. 
Exceptions to the 1 1/2 inch aggregate size may be made for mass placements.

3 inches of cover should be provided for reinforcing and 4 inches should be
provided at corners. 
Metal reinforcement chairs should not extend to the surface and if possible
should not be used. 
Form ties should provide deep recesses with extra care provided when
patching. 
All attempts should be made to place concrete in a continuous operation. 
When construction joints are required, the placement shall be allowed to set
prior to a new placement. The bonding surface shall be blasted with a jet of
water and sand. Broom cement grout onto the cleaned surface and make the new
placement immediately. 
High frequency vibrators should be used. 
Curing is important to establish a watertight paste. The concrete should be
kept wet for 10 days at a temperature above 50o F."

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Pat Thurman
Sent: Saturday, March 13, 2010 12:56 AM
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] Mixing concrete for a base

Google "Tremie method"...  It is common to pour concrete underwater via a 
tremie chute for a variety of projects in water.  The key is to keep the 
concrete undisturbed while pouring so the water-cement ratio of the mix 
remains as designed.  Water curing is good.

73, Pat K7KR

----- Original Message ----- 
From: "Don Snider" <dsnider at rhrs.com>
To: "'Tower and HF antenna construction topics.'" <towertalk at contesting.com>
Sent: Friday, March 12, 2010 20:06
Subject: Re: [TowerTalk] Mixing concrete for a base

> How about the quick-dry concrete used for fence posts? Can this be used 
> for
> towers? My hamshack is on Chincoteague island with a water table about 18
> inches down. Most people use the quick dry concrete for general projects
> because it will dry in the water but is it strong enough for an antenna
> base? The only other option may be to put well taps in and pump the water
> our while the concrete drys.
>
> Thoughts?
>
> Don
> N3MK
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Mike
> Sent: Thursday, March 11, 2010 11:18 PM
> To: 'Tower and HF antenna construction topics.'
> Subject: Re: [TowerTalk] Mixing concrete for a base
>
> Most cement/concrete guys are in terrible shape at the moment, they will 
> be
> happy to deliver minimum 3 yards.  They will make delivery charge, so try
> and pick a company close to you. Concrete pump people do not charge
> transport here anyway.
>
> Telephone a few different companies and tell each one that you have phoned
> around for quotes and you may be surprised what they will do.
>
> Even in California here I had 3 yards delivered and I had a concrete pump
> guy to pump the concrete into the hole.  The cost was around $900.00 total
> for pump, Concrete and delivery.  I can tell you the pump guy earned his 
> 260
> bucks with 30 minutes preparation and 30 minutes clean up time plus 15
> minutes to pump the concrete 50 yards. If you do use a concrete pump you
> have to let the concrete people know so that they can use smaller round
> stones.
>
> Usually if you have the concrete delivered they will wait about an hour or
> less (ask them for their waiting time) while you wheelbarrow it to the 
> hole
> and charge waiting time which is expensive after that time.  For some 
> reason
> if you use a concrete pump they will stick around for as long as it takes
> with no extra charge, maybe it is because the concrete delivery guy does 
> not
> have to do much work when you pump concrete.  With wheelbarrows he has to
> keep opening and shutting the valve for an hour.
>
> If you have concrete left over use it to make something like concrete
> weights. Put it in plastic buckets that pool tablets come in and make a "U
> shape" out of left over re-bar to make a hook and put into the center of 
> the
> concrete filled bucket.  When it is "set", a couple of them make a great
> cheap counter weight for a tilt over tower like a LM-470.
>
> Mike, K6BR
>
>
>
> -----Original Message-----
>
> There is such a thing as a false economy - but I think
> it would be difficult to finish 2.5 yards by hand, in a
> timely manner.  Such a pour should be done in one shot,
> that is going to be tough.
>
> If you have any value on your time, adding the cost of
> materials, etc, you quickly cost more than the price of
> redi-mix.
>
> Although some places have a 5 yard minimum, most of
> those will deliver 2.5 yards, with a extra delivery charge.  Most
> of the places I have bought concrete in the past 6 months,
> NY, PA, OH, MO, and OK, have been right around 75 bucks
> a yard, plus a delivery charge for under 4-6 yards.
>
> Cheaper to call them for me!
>
>
> Don't take your organs to heaven,
> heaven knows we need them down here!
> Be an organ donor, sign your donor card today.
>
> ----- Original Message ----- 
> From: "Ed Swiderski, KU4BP" <ku4bp at triad.rr.com>
> To: "'Tower and HF antenna construction topics.'" 
> <towertalk at contesting.com>
> Sent: Thursday, March 11, 2010 6:38 PM
> Subject: Re: [TowerTalk] Mixing concrete for a base
>
>
>>
>> No, don't like pain. Just trying to it right with the least amount of
>> money.
>>
>> Ed
>>
>> -----Original Message-----
>> From: towertalk-bounces at contesting.com
>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Blake Bowers
>> Sent: Thursday, March 11, 2010 7:17 PM
>> To: Tower and HF antenna construction topics.
>> Subject: Re: [TowerTalk] Mixing concrete for a base
>>
>> 6 bags of cement, 8 cubic feet of sand, and 20 cubic feet of gravel makes
>> on
>> square yard of concrete - using the 1, 2, 3 measuring.
>>
>> It also makes for a terrible day.
>>
>> Do you just like pain?  I cannot imagine mixing 2.5 yards, I would use 
>> the
>> local redi mix plant.
>>
>>
>> Don't take your organs to heaven,
>> heaven knows we need them down here!
>> Be an organ donor, sign your donor card today.
>>
>> ----- Original Message -----
>> From: "Ed Swiderski, KU4BP" <ku4bp at triad.rr.com>
>> To: "Tower Talk" <towertalk at contesting.com>
>> Sent: Thursday, March 11, 2010 5:57 PM
>> Subject: [TowerTalk] Mixing concrete for a base
>>
>>
>>>
>>> All,
>>>
>>> I'm considering mixing my own concrete for my installation. Been trying
>>> to
>>> get a grasp on how much cement, gravel and sand to get. My proposed base
>>> is
>>> for 70ft of 25G. Total, with the anchors, is 2.2 cu yds. Call it 2.5
>>> since
>>
>>> I
>>> plan to "bell" the base.
>>>
>>> I was pricing the ingredients today but got a little confused on the
>>> amount
>>> of each needed. I looked at 94 lb bags of cement and 50 lb bags for both
>>> the
>>> sand and gravel. The problem I had was determining how much in cu yds a
>>> bag
>>> would cover. I have seen that a 50 lb bag of sand covers .5 cu yd.
>>>
>>> So what I'm looking for is a formula of some sort so I can figure out 
>>> how
>>> much I will need of each. I've heard of the "1-2-3 rule" but not 100%
>>> sure
>>> I'm using it correctly.
>>>
>>>
>>> Ed KU4BP
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>> _______________________________________________
>>
>>
>>
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