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Slojo
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Posts:7
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| 05/24/2008 10:43 PM |
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Seems like as good a place as any to ask this question: Which product is preferable for pouring a column that will be used for a deck support, Sakrete or Rapid set? I was originally going to go with the Sakrete, but the gent at the home improvement center pointed me to the Rapid Set. It should be noted that the location does not allow for access for a truck deliverery and I only need about a yard anyway so I was going to rent a mixer and do it myself.
Thanks
Joe-NY |
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James Eggert
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Posts:1006
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| 05/25/2008 11:36 AM |
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the regular sacrete for a pier or column consolidated properly should work fine, if large enough you may want to add a shovel or two of portland to each bag. The rapid set is ok, however you're usually just paying for an accelerator or hotter mix used where the traffic needs to get on it asap. Using the rapidset means paying close attention to water and timing, and some may not even be suggested for thick use such as a column versus say a floor patch.
As for Rapidset, I assume you do not mean High Early setting mix, which would fall in between the mixes you note. High Early woiuld be my choice if the column is over 4' out of the ground.
as for the HI suggestion, I suggest you read the bags yourself! |
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Take Care
Jim
Design/Build/Consulting
"Not So Big" Design Proponent |
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Slojo
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| 05/26/2008 3:44 PM |
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No, I am not talking about the High Early set although they also have a 'K' product, which is for specialized applications which I don't think suits my job requirements. I plan on calling Rapid Set as they have a Tech Support number, but want to make sure that a 10"x10" 20' tall column (+ rebar) will allow for enough 'flow' without vibrating. Time for curing is not an issue for me as I have plenty, and Rapid does also sell an additive that enhances flow, but the product literature was kind of vague about the amounts to be added, etc.
I am sure Sakrete has a number as well, just have to find it. Intesting thing about all the different Skrete products and they don't tell you the yield on all of them, so am not sure how much I will need to buy.....
Also, what about the PSI of these self mixed products. Rapid Set claims something like between 8k and 10k PSI in 28 days. Sakrete has a 7k PSI product. What is the typical PSI of truck delivery mix?
Thanks
Joe-NY |
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Alton
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Posts:337
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| 05/26/2008 10:17 PM |
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| The PSI of a mix of concrete from a delivery truck should be what is specified. In other words, there is no typical mix. Depends upon the job. Might be 3000 PSI for flatwork or 4000 PSI for wall forms. Only a cylinder test will confirm curing strength after so many days. Normally, we specify a certain PSI strength after the concrete has been properly cured for 28 days. |
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Alton C. Keown
Residential Designer and Construction Technology Consultant
Auburn, Alabama
334 329-0957 AT&T Cellular |
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James Eggert
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Posts:1006
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| 05/27/2008 6:55 AM |
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I'm not sure where you're proposing this, but a 10 x 10 column 20'? Someone needs to check into what was once called the "slenderness ratio? Is this done commercially? probably, but under very specific conditions. residential?
Personally, I'd use steel and then cover it! |
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Take Care
Jim
Design/Build/Consulting
"Not So Big" Design Proponent |
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Slojo
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Posts:7
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| 06/01/2008 12:13 AM |
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Yes, it is for a residencial application. I would go with a 12" x 12" if I could. Still looking into that. It's complicated to explain in a post, but they are actually round forms with square foam on the inside, then you peel away the cardboard and what you are left with is a seamless square column.
The columns will serve two purposes. The first will be to support a small ground level deck, say 10'x12'. The second will be to serve as an anchor point for temporary retaining system for excavation. It's complicated, but the space does not allow for any heavy equipment.
'Slenderness ratio'? Hence my concerns about PSI. 7k should be plenty, not to mention the rebar + pier footers.
Thanks
Joe-NY |
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Bruce Frey
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Posts:87
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| 06/01/2008 4:40 AM |
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Google on slenderness ratio and you will see. It should be checked. By inspection, it looks a bit dodgy.
Also:
How much horizontal load do you anticipate from the temporary soil retention system and where is it applied (to the column)? Does it act as a cantilever in the temporary condition? In many instances, constuction loads dictate the design, not service loads.
In the final condition, is the 20' braced at any point other than top and bottom?
Is there more than one column?
How much reinforcing do you anticipate in the column? Seismic issues?
Related quetion now that you have horizontal loads: Would you span 20' with 10" beam? It is also bit "on the edge" by inspection.
Even IF it is OK from a design standpoint, trying to place and consolidate concrete in a 10" reinforced column that high will be a challenge.
If I understand your form correctly, the round tube that contains the square form will be about 14" in diameter. Why not use a round 12" or 14" column? Aesthetics?
Bruce
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ReadyToRetire
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Posts:209
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| 06/01/2008 6:32 AM |
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Slojo,
You've likely played with "slenderness ratio" but never used the term. Pick up a long slender stick and put a compressive load on it -- put one end on the ground and press straight down on the other; it bends. Now break off a piece and try again. Each time the stick gets shorter, it takes more load to make it bend even though it's cross section has not changed. With structural members, the load is a lot higher, but the issue is the same. You want to make sure that the posts' cross-section is large enough so that -- at the length you will use -- they don't bend under load. With the stick, you stopped pushing once it started bending; with the post, your deck or other load doesn't go away: it collapses.
Very respectfully,
Larry
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Slojo
Registered Users
New Member
Posts:7
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| 06/01/2008 11:31 PM |
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Yes, square for the look. Yes 14" diameter. The plan is hold as the Mrs. keeps changing her mind about location and what not (typical). Yes, ok I undertand the 'Slenderness Ratio'. The vertical load on the columns will not be all that substancial as the deck will be rather small as decks go, approximatetly 10'x12'. The plan was to have 4 columns, but that can easily be adjusted upwards if needed. It should me noted that although the overall column length of the form would be 20', only 11'-12' would be free standing, ie, the remaing length would be permanantly below grade.
There are no seismic issues.
I am not sure I understand the question about canterlevering. The simplest way I can explain my overall concept is that it is similar to how a telephone pole is placed, except that telephone poles have most of it's length above ground, whereas my columns will be more like 50/50.
Yes, I am also concerned about being able to either mix the concrete with the correct flow to allow proper consolidation or wheelbarrowling in an extrordinary amount from a mixer in the street (slightly uphill of course).
Yes, the concrete will be reinforced with rebar, 4 vertical + horizonal overlapping wraparounds ever 18". Speaking of which, have any of you gents (or ladies) uese Con-Tie for connecting rebar. What is your feedback?
Thanks for all the info.
Joe-NY |
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Bruce Frey
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Posts:87
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| 06/02/2008 3:43 AM |
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Posted By Slojo on 06/01/2008 11:31 PM
Yes, square for the look. Yes 14" diameter...............The vertical load on the columns will not be all that substancial as the deck will be rather small as decks go, approximatetly 10'x12'. The plan was to have 4 columns, but that can easily be adjusted upwards if needed.
It should me noted that although the overall column length of the form would be 20', only 11'-12' would be free standing, ie, the remaing length would be permanantly below grade.
I am not sure I understand the question about canterlevering. The simplest way I can explain my overall concept is that it is similar to how a telephone pole is placed, except that telephone poles have most of it's length above ground, whereas my columns will be more like 50/50.
Thanks for all the info.
Joe-NY
That helps. Slenderness should not be a problem in the permanent condition. Any chance of a sketch showing a vertical section? A description of the anticipated construction sequence or a method statement would be helpful, especially about what horizontal loads may be imposed relating to the soil retention or temporary conditions.
Are there footings under these columns or are you making "concrete telephone poles"?
Are the four columns arranged along the 12' side of the deck, i.e., 4' on center, with the other long side attached to the house? Or one column at each corner?
Bruce |
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Slojo
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Posts:7
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| 06/03/2008 11:43 PM |
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I will have to work on a sketch. Things are kind of crazy at work right now so it might take me a few days. In the mean time:
The columns will not have a footer per se, but instead somthing akeen to a mushroom or bell bottom, like a flare. Make sense?
The maximum space between columns will be no more than 8', so in the case of a 12' span there would be three columns evenly spaced on that side.
I have some numbers around here somewhere about the horizontal loads, just have to see if I can lay my hands on them...
Thanks
Joe |
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