Concrete Admixtures

[Kodakjello]

Hey everyone,

I'm getting ready to start building my house this spring and I'm trying to nail down the type of concrete that will work the best for my concrete piers. I'm coming 36" up off the ground and using CB88 brackets for the house beams. However, the piers will be in either water or frozen ground for at least 5-6 months of the year and I'm a little worried about how they will perform :-/

Right now, I'm planning on using standard 3000psi concrete with an admixture for waterproofing and some synthetic reinforcement fibres.

Admixture - Cementaid - Everdure
Bar Fibers - Elasto Plastic - Barchip "Shogun" for reinforcement
Fibers  - Propex - "Novomesh" for early and long term crack control

Does anyone have any suggestions on what I should use or does anyone have any experience with either of theses products? Should I go with 5000psi concrete? Keeping in mind that I don't have any steel rebar in the 12" piers, will these fibres be enough?

Thanks,

Kodakjello

[skiwest]

I'm no expert but from the stuff I read I bought the freezing admixture , the one that adds micro bubbles .  And used rebar.  I'm the same in the 36" top of concrete off of grade.  I went threaded rod route.  16" above top of concrete and 20" embeded.  A couple of nuts and a peice of angle embedded.

[MountainDon]

No steel? I'm not a concrete expert either but any concrete work I've needed to get permitted has always been required to include mesh or rebar.   :-/  

[Kodakjello]

Yeah, I though rebar was pretty standard stuff but the Ontario Building Code doesn't call for any rebar in concrete piers. In fact, the building inspector told me that I'd have to get an engineer's stamp if I added rebar to the piers in the plans. Very strange stuff indeed.

The CAN/CSA A23.3-M guide to designing reinforced concrete is what I'd need to use if I wanted to workout the rebar requirements myself but I can't find any hint of it on the Internet...

Any tips anyone?

[John_C]

Plan A   Forget the steel.  Lots of small houses are sitting on concrete blocks or a pile of stones.  A solid piece of concrete would be an upgrade.  No big deal to replace a pier if there is a problem.


Plan B  If there is a foundation inspection put the steel in after the inspector is over the horizon.  Once encased in concrete it's not really there   By far the dominant force on the pier is compression.  In that case the steel doesn't do much work.  It's there to keep the pier from crumbling if the concrete cracks. Four #4 bars and a couple cages should be plenty.  If a pier cracks it will need to be replaced, steel or no steel.


Plan C  If there is no foundation inspection do whatever you want and once poured .....


Most of my concrete experience was in S FL, so freezing wasn't an issue but isn't the admixture just to protect the concrete from freezing during the curing process?  If you are doing this in the summer it may not be necessary.  Water getting into any cracks in the concrete and freezing there is what causes cracks.  Some sort of waterproof coating might help.  Glenn might know.

[skiwest]

I have seen that in the code too. guess some reason for it.  I think steel in the footing would be worth while.

I put in steel , well I was able to get and well I could as there are no inspectors out here.

[Kodakjello]

John C: Thanks for the insight. The only reason I was contemplating not using rebar was due to the pier's design. I figured that a round column of concrete with synthetic fiber reinforcement would be more than strong enough to resist the compression forces and the slight uplift forces. Am I right in thinking that the uplift forces for a 24x32 cottage with 15 piers that's 3 feet off the ground won't significantly strain it's piers? I can't imagine how high the wind would need to get just to counteract the weight of the house let alone test the uplift capacity of the piers.

skiwest: Steel in the footings should fall outside of the realm of "piers" so I wouldn't be technically going against code   I think I will follow that advice.

[glenn-k]

I started to put a posting yesterday but think I crashed my computer.  

Rebar is cheap.  You have freeze -thaw flood cycles to deal with also if I recall.  The steel would be good insurance.  Concrete has compressive strength but not much tensile strengthe to hold things together.  Steel has high tensile strength.

[skiwest]

K- builng something similair- 20x30,  3 rows 9 ' spacing, 4 the other way 10'.  Also going 3' off grade.  Per coade piers can be 3 times dia off grade.  So your good but probably knew that.  I just picked it.  So really code says your ok but if you wanted 4' you would need rebar.

for the pier it self , the weight of the cabin all compression so no need of any tension strength.  My thought on rebar was wind.  Basically the all the piers are pushed over and one side might be in tension.  The compression load will probaly be enough so that the concrete never goes into tension.  Your fibres will do the trick.

What are you using for forms?  Big Foots?  


We started out last year thinking wood form of footing then sono tube on top.  ( I would alway put some rebar sticking out of the footing to sono tube)  I didn't use big foots as the biggest one couldn't take the load with my soil.  After putting two with footings I relooked at big foots and in the time frame they made ones with bigger foots.  They had none left in may area so ended up getting Square Foots which are better for putting in rebar in a sqaure rather than cross.

It was a bit of a pain but this is how we did it.  Made up rebar frame  , square with crosses on bottom with 3 1/2" rebar up piers.  Put square foot and sono tube over that and started pouring.  Was using mixer , yes by hand ,  so after first pour which put 4-5" in foot , reached in and pulled rebar to top of concrete.  Didn't set down after that so was good steel seperation off the bottom.

[Kodakjello]

skiwest: I did know the 3X the widest point rule   but it's nice to know that it's used elsewhere. I'm using 12" sonotubes with the BF28 bigfoot...I've doubled the bigfoot size to comply with the high water table requirement.

glenn: I hear what you're saying about the rebar and I agree. I know it's cheap and proven but unless I sneak it in somehow (we're on a Hwy just 4 km south of the building inspector's office ) we're going to have to get it stamped by an engineer.

The problem is that if we get it stamped by an engineer, he's going to need a soil assessment. If I get a soil assessment, I might have to change the foundation plans depending on what they find.  I know the soil will bear the house, it's very firm grey soil and the wooden post I placed in a hole almost two years ago has yet to heave or shift or lean. I just don't want to get caught in an "engineer stamping vicious circle"  :'(

But this gets us back to my first question. "Will these synthetic bars go the trick for reinforcement?" The website states that the Barchip 'Shogun' Structural Synthetic fibres (http://www.elastoplastic.com/english/products.htm) replace welded wire reinforcing mesh and steel fibres in concrete. Their tensile strength is 550MPa (79,770 PSI) which is definitely in the range of Grade 40 rebar. The benefit with this stuff is that I could simply add it to the concrete mix and avoid having to deal with the engineer stamped reinforced concrete issue.

Rebar  + Everdure      :-/ :-/ :-/   Concrete with Barchip + NovoMesh + Everdure


Any thoughts or experiences?

[glenn kangiser]

I didn't realize what you were fighting there - probably didn't read well enough.  

Your optional stuff looks good.  Seeing your problem that would be my choice.

I have only used fibermesh but I like it.

[Amanda_931]

Years ago, a bridge in the Nashville area failed (not dramatically, but still failed) because salting the roads + cracks in the concrete caused the rebar to rust, and as it rusted, swell and therefore cause more cracking problems.  There were a fair number of holes through which you could see the river below.

That might be the reason for the no rebar in piers routine--minor horizontal cracks could become major longitudinal cracks under a building where nobody's likely to check them.

[Kodakjello]

That makes sense...especially if the rebar isn't necessarily needed to keep the column together. But if that is the case, why do we need rebar in a standard frost wall but not in a pier? This is a bit confusing  :-? . Does anyone know the reasoning behind this?

[skiwest]

K- I'm in Canada too so as I have access to Ont building code on net I use that.  All based on Can national building code anyway.  Do  search on texas code with regard to piers.  They spec that there has to be rebar and the size.

I think the rational to the no rebar rule is the residential code is a cook book.  Tables and rules.  No geotech has to be done  no Engineers have to be involved no matter waht the soil conditions.  Its almost if you think rebar is needed you have to make the jump to to main code and Engineer the whole thing.  I would think the fibre in pier will be fine.  If you can put rebar in footing so much the better.  

[John_C]

There were a number of buildings in the FL keys where the steel was rusting, expanding and cracking the concrete, including the local high school.  When they were built in the 50's and 60's it seemed like a good idea to use salt water to mix the concrete.  It didn't work out that way.  The culprit is the salt followed by cracks, large and small, in the concrete.  Steel in concrete is well proven to provide tensile strength to concrete.  

[MountainDon]

This is a bit confusing  :-? . Does anyone know the reasoning behind this?

Wouldn't be proper code if we were able to make sense of it.    As fas as I'm concerned steel and clean water are both nesessary for best concrete.

[glenn kangiser]

The only issue I see with the steel causing engineering to kick in is that this is all part of a good ol' boy system.  A homeowner or contractor is not deemed educated enough to determine if he is using the proper size rebar, hence the college boys in the building department refer you to the college boys in the engineer department to make sure that each of them gets to relieve you of a bit of your money.  

Never mind that you have enough sense to see that a few pieces of steel in the pier will hold things together better than none.

In a case of "not critical" common sense issues it is a college game of "Let's Pretend" designed to keep the entire payola system running properly.  Now - go out and be stupid like you are supposed to. :-/  

Play let's pretend like they want you to.  Lose your common sense.  It is required.  Then you will be able to understand their requirements.  Trouble is you are too smart for your own good and don't understand the purpose of the dumbing down of America.  Follow the money.

[Kodakjello]

Yeah, I'm starting to think it's not my mind playing tricks on me but system-wide push against doing things yourself. One of my original plans was to build one of these tiny houses on my land http://www.tumbleweedhouses.com/houses.htm while I saved up to build my real house. Minimum sqft zoning nonsense stopped that and delayed me about two years.  

Most of the time, the reaction that I get from people when I tell them I'm building a house is just plain shock! How can you build a house? You're not a contractor/construction worker/architect!!!   Talk about brainwashing.

[glenn kangiser]

In the pioneer days those types would have been tarred and feathered and run out of town.

Providing shelter for your family is one of the basic needs.

The system extorts money by exploiting the basic need for shelter, just as it and the Health System extort money from mans basic need for good health.  Both take advantage of need for profit.  The law of supply and demand regulates price, but the rules to regulate shelter have been created to force you to pay the system off before you can shelter your family.

[John_C]

It's a bad day for me to be reading this thread.  I just got a letter from the city about the new  dumpster - trash receptacle permit.   I couldn't make this B.S. up.

When I moved my business from my house to town 15 or so years ago there was no local paperwork.  All I needed then was a sales tax id #.   A year or so later we got occupational permits, a few years after that they added a sign permit in case you wanted to put a sign up for your business, now an additional permit if you want a dumpster or garbage can.  Of course there is a grace period of 60 days.  If you already have a trash can and you file the permit application within 60 days you won't have to pay the fee this year.  No mention of what the fee is - will be next year. The real rub is that this crap gets passed by the city council and I can't vote for those clowns in any case because I don't live in the city.

Not a happy camper here today.
Tarred & Feathered.......   Where do I get the permit to do that?

[MountainDon]

Tarred & Feathered.......   Where do I get the permit to do that?

Those used to be spontaneous events,   no permit required.  

[glenn kangiser]

I already erased a bunch of the stuff I wrote.  I am trying to control myself. :-/

[Kodakjello]

Sorry about taking this thread OT!!

but I hear what you're saying. I decided to build in the countryside south of Ottawa rather than put up with the even more draconian rules and oppressive development fees. I paid $600 in development fees in the Township instead of $7,000   in fees in Ottawa for an equivalent house. One of the problems with building in this area is the size of Ottawa. When it was amalgamated with the surrounding "suburbs" it soaked up ten cities and about a dozen villages. Now Ottawa extends WAY WAY out into the countryside, bringing regulations and taxes to all. It's tough to build outside the city limits and still remain within easy "visiting" distance (no I don't plan on commuting   because that would make me a hypocrite)