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argile tile
01-06-2017, 12:02 AM
Hi. I'm making an overhang (or gazebo), to keep the snow off "something anyway", employing Columns.

Before I actually pour tomorrow sometime, I'm hoping anyone can comment :)

A question of "potential for cracking" or even general stability of 2" wall thickness tubes. My question is: looking at the specs, does anyone see any "big problem" here ...

I'm making 3 (greek) columns 7' high each, and a roof (magically) straddling them.

Each column will be 4 easier segments of 20" tall actually.

To reduce weight, they will be hollow (no concrete in the center). My specs are: 11.5" outer, and a 2" wall thickness (7.5 inner). (NOTE: specs are 1/2 inch off from being small sewer pipe specs, to put it into perspective). they will have mesh in the middle of the pour (hard to bend mesh round and stay at least 1/2" away from any outer wall - but have some done already that fit).

I'm using quickcrete high strenght (the cheapest) and will whitewash later before setting outside.

my concern: i think they are wide enough to be stable (esp with a roof tying the together) - but i'm worried about 2" wall thickness. they will lay flat on each other (they are not specially mated like sewer pipes - this is a DiY job with cardboard form - and no i can't afford to have a truck drop off sewer pipes or i'd have done it (though the price isn't bad: i imagine shipping would be))

any thoughts or idea (especially warning me before i go pour 4 sections and see the result) would be appreciated greatly

(i assume i should tile them for decoration - but maybe in the summer. i certainly can't use pine trim to make fluting in the mold: it would be like $300 for all the trim needed !)

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argile tile
01-06-2017, 05:33 PM
i'm having to re-shop the mortar or concrete i use for making Greek Columns
(outer 11.5, in 7.5, wall thickness 2 1/16 - maybe more if cardboard mold moves, 20" tall segments - 4 of these stacked to make 7' columns)

I need to make mortar/concrete by hand (see below*)

I've mixed mortar and or adjusted concrete with cement several times. However I'm not experienced enough to know what would be best for a 7' column as such.

I just bought fresh cement and sakrete multi-purpose sand from a different store*. The sand seems great - it's not playsand type as for brick mortar, it has small aggregate in it.

1:5 'fresh cement':'very rough sand'. Ok ratio for this app?

Can anyone give me a tip on why i should add lime, or more or less cement for such a column? Thanks much! It would help me decide what mixes to test and what not to bother testing!

I'm no mixing expert, I usually add cement to make something stronger, for rebonding, or facing, less occasionally i've done strong mortar with sand for concrete blocks.

---------------------------
* i bought high strength concrete because it's cheap not remembering to check aggregate size - it says 'for laying more than 2"', 2" is what i have - and i'm using tile mesh. the store i got it from stores it outside. i mixed it rather like deck mud. it would not clump - after wadding into baseball working it hard - it took very little for the ball to just fall apart. 4 hrs later i see it's still as loose as when i left. I'm not pouring that into a form - i just makes me think i'll have crumbling issues due to size of aggregate and even quality of cement.

http://www.johnbridge.com/how-to/deck-mud/

argile tile
01-06-2017, 05:42 PM
i dont need to consider adding (type s) lime for a column do i ?

argile tile
01-06-2017, 06:22 PM
i did forget to say: concrete (even premixed) is supposed to be tested before used - not just assumed, maybe even thinset should be too, and due to issues this will certainly be a job that gets it's batch tested before used ....

(when i study how to test it within the means i have - which is none at the moment)

cx
01-06-2017, 09:08 PM
While you may be able to turn out something that will support some vertical load, I sincerely hope you are not planning to use these columns where you will have any lateral loading at all.

I would recommend you pour a pre-bagged concrete mix such as you can find at your home center. Ones made by Quikrete or Sackrete would be good as each is made with both fine and medium aggregates. Your plan to use a sand/cement mix is not a good one to my thinking.

You say you will have "mesh in the middle of the pour." I'm curious to know just what type of mesh.

Even at only 20-inch sections you may have trouble properly consolidating a mix of reasonable (5" to 6" max - I'd prefer 4") slump. What is your plan there?

Stacking the finished sections using thinset mortar to bond them (I've got that right?) will, again, work fine for the vertical loading and may suffice for some lateral loading, but I actually see the lateral loading failures in the sections themselves rather than the joints. Gonna depend upon your concrete mix, your reinforcing material, and just how well you manage to get it consolidated and cured.

For the curing I'd recommend you submerge the sections in a large container of water for at least the first ten days or so after the first 24 hours.

I should put my usual disclaimer in bold type for this one, but........

My opinion; worth price charged.

argile tile
01-06-2017, 09:15 PM
1:5 ? 1:2? (cement to coarse sand not playsand)

I'm still short on aggregate knowhow for two inches or less ... and worse it appears materials i need are not in stores i know of or nearby - not sand not agg

so i'm trying roughly 1:5 (deck mud) and 1:2 to see what the tradeoffs are, and they are still wet. google says concrete is 1:3:3 (cement,sand,rock)

the 1:5 is more cohesive than "sakrete high strength" (wadded into a small snowball), however it still doesn't take much handling for it to fall apart. it stays a ball when set down.

1:2 on the other hand is more fatty / spongey and is cohesive, which would be less "is it packed well?" worries for a pipe mold. to test open time i took half of it to make it loose - but it took a chopping to loosen it was so well together.

but i have no idea what the performance tradeoffs are as to cracking and crumbling for a column


i'm just learning, noting lime is nowhere to be found in my area: neither is, ie 1/4 gravel. i have to go outside my area or mail order? (i only know the quarry refuses to sell stonedust for safety, anymore - but can be found elsewhere).

i'm now further confused - i can't find articles on "when to use what size aggregate"

knowing 'high strength' gravel is too large for 2" lays is just enough info to confuse me.

perhaps sakrete "high strength" (with more cement?) is best. but is says "no" right on the package - not for 2" or less (i'm guessing 2 1/8 after pouring if i'm lucky)

argile tile
01-06-2017, 09:32 PM
> While you may be able to turn out something that will support some vertical load, I sincerely hope you are not planning to use these columns where you will have any lateral loading at all.

just a light 12'8' roof to stay the rain and snow a little

> I would recommend you pour a pre-bagged concrete mix such as you can find at your home center. Ones made by Quikrete or Sackrete would be good as each is made with both fine and medium aggregates. Your plan to use a sand/cement mix is not a good one to my thinking.

I still might. I might replan. I did material returns and pour testing, but no pouring. I'm only set on not wasting my cut pouring tubes if i don't have to :)

> You say you will have "mesh in the middle of the pour." I'm curious to know just what type of mesh.

27 in. x 8 ft. Steel Lath, .5 lb, "for stucco" - what i think i see in tile pictures. i don't think rebar will be useful for 2". perhaps i could increase to 3" and re-design. ouch - i already cut all the lath and have some tied in rolls that fit. it is a cylinder shape, sits about in middle of wall thickness not closer than 1/2" from either wall, and is 1/2" shorter on each end to avoid being too close to ends (i hear exposed reinforcement can cause surface differential and cracking, so 1/2" was goal).

> Even at only 20-inch sections you may have trouble properly consolidating a mix of reasonable (5" to 6" max - I'd prefer 4") slump. What is your plan there?

thank you for the term "slump (flow) test". i've just started reading some articles having that. i'd have to make a 10-30 cone. i have nowheres to send samples to, which i took 2 min before doing the slump and visual test that wouldn't reject me on the grounds it's DiY i'd guess. i'm probably wrong.

> Stacking the finished sections using thinset mortar to bond them (I've got that right?)

that's how $160 molds are being sold - flat on all ends. they use 10 3/4 wide and 3" thick for molds. i'm unsure if bonding is necessary, but think your right

> For the curing I'd recommend you submerge the sections in a large container of water for at least the first ten days or so after the first 24 hours.

i had no idea so much water might be useful during curing period, i'd only heard of spraying lightly/frequently

> I should put my usual disclaimer in bold type for this one, but........

I may just have to make a wrong before a right.

My other choice was Craftsman columns (1' wide, 3' tall, brick, with 4' tall 4x4 taking the remainder. a cost saver and attractive. but i've heard wood and concrete mortar don't mix (espansion) - so attatching the post is an issue, maintenance of brick or brick cracking - thought concrete would be easier! i'm now unsure which is faster/easier.)

So i'll test the high strength again, this time being more believing i've not yet given it the time and attention it deserves to outperform a custom 1:2 batch.

argile tile
01-07-2017, 10:40 AM
my tests turn out:

1:2 (cement coarse sand) sets far more quickly than HSC premix. 1:5 also seems good but is a little more flakey after 12 hr. - however in early hours it hardly held together. for molding time: time spent in mold is a concern - 1 or 2 moulds and 12 todo.

i made "small balls" of 2" and 4" for hsc. the 1:2 was simply durable after 12 hr (that doesn't mean higher psi rating in a building as to hsc, of course, but hsc with extra cement in place of sand in hsc is higher load)

HSC after 12hr is "hard" but also crumbles easily given slight hand pressure

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Load requirements?

If i remember IBC says a roof must support 20 lb/sq-ft roughly in areas with snow (or 22?)(angle of roof aside here), which for 12'x8' or 2,222 lb. on one column of 62" sq, that's 17 PSI upon the 2" round shaped area of column (though if not level, would be higher on one side). (1/2 the total load on one column)

It seems to me my concern should be protection against: crumbling, edge chaffing (ie, while shifting columns to align them), and as always, cracking, as well as a few days v. a few weeks turn-around.

I'm going to try something like 1:3 for cost but also turn-around time of 12 pieces.

I have no idea if my strength measurements are realistic

(being blind isn't bliss in this instance)

cx
01-07-2017, 11:53 AM
You really, really don't wanna use expanded metal lath as your reinforcement. You'll want some sort of re-bar or welded wire mesh for that.

When you get done experimenting, use the Quikrete Concrete Mix (1101).

My opinion; worth price charged.

argile tile
01-07-2017, 11:55 AM
ok. and i was just thinking my hopes of no real lateral load were probably wishful thinking ... ie that the roof tying the 3 together is important as things stand. though i'm likely to change it now.

i think my best plan now is, for the cost of a few dollars and effort, to make just 1 20"er, the wrong way, as a model, so i can see for myself what the issues are. while i'm thinking about how to get 7.5" to 6.5" or 5" so i am not at the 2" min (no room for rebar, wire tricky at best) mark

((my third option (after Craftsman column, which is 2nd), was using welded re-bar. the lower part hammered into the soil some, and welded framing, maybe 9 total bars 7' high tied by arc welding. my assessment was: while strong cheap and fairly quic: it would be very difficult to "do the finishing work" in a way to make it presentable - and i very much feared the time it might take to "make it right". i know many buildings are an iron frame which (glass is hung on) - that concrete is not what holds them up (but is a part of, ie in central stairwell), though that building methods using rebar have much expanded lately)

thuffner3
01-08-2017, 12:20 AM
Two different sizes of sonotube, corrigated fiberglass roofing fine radius,
flex roofing around inside of larger sonotube, line with chicken wire, drop and support smaller sonotube inside this and fill with fine aggregate high strength cement. all cement exposed surfaces should be coated with wax or some type of release agent????. When firm remove molds and wrap with clothe to hydrate for several days.
Sinces it's hollow provide a solid support post to settle nerves.
Done
JMTCW
Neil

argile tile
01-08-2017, 04:53 PM
Thank you jim (and cx), with your advice i did look into it further

Your right jim, concrete tubes with steel reinforced inner/outer are popular, only reason i hand't used PVC (which i had costed) is it's 4" inner and say 7.5" outer then requires a base for tipping stability - which puts me back to building a Craftsman column (which i like - i had simply planned on a wide column eliminating need for large footing - not realizing the weight or complexity of such a column)

I'd be better off with a Craftsman column from where i am, soil frozen, and say $35 "wasted" (but i'll use it in the craftsman). And being in that bin, a wood 4x4 is not a bad way to go, and can be decorated (ie, mesh and stucco) just as well as a "pole looking column" can be.

SIDE NOTE: I was noticing by intuition i thought "wider is more stable" not realizing that reducing wall thickness to 2" to keep about the same concrete, was not favorable - ie it will not disperse load around the circumference area 2" thickness wall as i hoped - it very well might buckle as if a 2" square column 7' high in some situations. And the mesh? Simply would hold it together long enough to get to the dump.

SIDE NOTE: from what i gleened quicly in structural mech. 101 books on google: i disown euler's column equation as dangerous and for euler's front yard is likely. I can't find a list of columns california tested (i know there's a large somewhere! all i need is a peek!). I favor the molecular model (stick and ball) of balls held together by ElectroNegativity (EN). It's just like Alexandre Gustave Eiffel said: anything pushed (might stretch to breaking) must be supported all the way down - whether it's stick and ball that stretch or trusses! This also means I say that compression of concrete is near infinite: if a column is pressed vertically and shrinks that means it's expanding on horizontally: that's your problem - stretching is pulling apart bonds, it's not the compression. Pressure wise, stone holds pretty tight till it's nearly lava/vapor! Which again means when i designed the column i grossly under-estimated lateral forces. (and wind i should have included and didn't, though where placed the wind would never blow on the roof anyway. a wall added mistakenly by someone not aware: could add hundreds of pounds and topple it.)

THANKS all for bring it to my attention that wide columns (do not disperse force evenly around their 2 Pi (r1-r2)^2 base areas, but would buckle as if all on a a much smaller area.

I'm sure I might have saved time not building it: and certainly had any fool pushed and pulled on such a structure it could fall, if it was windy anyhow :)

Tool Guy - Kg
01-08-2017, 09:42 PM
It would benefit readers for you to visit this link (http://www.johnbridge.com/vbulletin/showpost.php?p=1434377&postcount=4) to learn how to property attribute quotes.

:)

argile tile
01-12-2017, 09:18 AM
Canceled.

If I cannot use self-stable wide column (requires allot of extra material), I need 4x4 with good bases (craftsman style) (not in ground which is frozen, and would maybe require a permit).

I then see for the cost of 4 usable bases and 4x4 I could almost pour a modest 10'x10' concrete floor - which would serve much better in many respects, because if I ever had walls the bases must have extra weight for a modest 300lb windage.

I canceled this project at a loss of the cardboard molds and some mesh trimming. Put up plastic in a room (keep in saw dust), and moved project indoors until time is right for a 4"-6" 10'x10' outdoor concrete slab.