As the title states, I'm designing and building a concrete fence.  This will be reinforced concrete posts and rails, cast in the back yard and built with slave labor (mine and my boys).

I'm started on building/designing the forms right now, about to build the rails forms.  If there is any interest I'll do a 'build thread' for it.



Update 1-

The engineering design of the posts.

As has been mentioned in this thread already, the big problem with the concrete fence posts I've seen has been the spalling of concrete once the rebar begins to rust.  The single best way to prevent this is to keep the rebar completely covered with durable concrete, but eventually the concrete itself will carbonate and allow the rebar to corrode regardless of the integrity of the concrete.

So...To keep the bar from rusting I'll have to keep the concrete cover.  To do this I have to make sure the cracks that form are small enough to prohibit water and air from reaching the bar.  This is both a problem for the physical design and the concrete mix.

Physical design will use a 5"x5" concrete post with #3 rebar (3/8") in all 4 corners.  It will be 6'6" long and will have sockets cast into the concrete to allow the rails to slide in.

Mix design is a little complicated.
Air content is measured as entrapped and entrained.  Entrapped air is of no value, but entrained air creates micro pockets throughout the post where the post can expand and contract in temp changes to allow movement without causing cracking.  Entrapped air is large bubbles that you can see, no value and the lower the breaking strength.  Entrained air is typically achieved with chemical additives.
Another problem I face with the mix is that I need to control shrinkage cracking, which occurs when the surface dries faster than the center.  Because I have so much surface area I need to pay close attention to shrinkage.  My mix design will use as little water as I can get away with, probably incorporating a plastisizer to help the concrete flow through the form with less water.  I'm also using 3/4" minus gravel (most structural concrete is 1" minus, or 95% of the aggregate is less that 1" in any direction) and a fiber reinforcement.  Breaking strength should be about 3,000lbs.  The harder it is the longer it will last, but even a weak mix will outlast me and I don't mind if my kids have to replace some posts in 70 years.

I'll post pics of the forms and design drawings tomorrow, as it's too late now.



Update 2 near the top of page 4.  Link to pictures of nearly complete forms on page 4


Update 3

Discussion on beam failure here

Work on ties and filliing voids on blocks



Update 4

Update here, first rail cast.


Current design questions yet unsolved-
1- I'd like to lock the rails into place once they are set in the posts.  It would be good if I could slide the rails in (or out) when I want to, but have them locked into place the rest of the time.  Grouting the sockets is one option, but doesn't let me unlock them very easily.  
2- I'd like to provide the easy ability to add an electric fence wire.  I purchased some insulators on lag screws that I can set into the post, but I'd like to have an imbedded attachment point on the post where the option of an electric fence insulator can be added.

Yes, definetely.   Please post.

I'm interested in a thread about this.

I would. No plans to do it myself but I enjoy watching those kind of threads.

Me too.

Yes        




 

Pun intended?

I'd be interested.  

Heck yeah, get after it!

Doooo  eeeeeet!

Yes, taggage

I would love to see this! Concrete rocks!

Yes please.

Posted Via AR15.Com Mobile

Yes.  And I request an IM letting me know when you post it.. so I don't miss it

Does a bear shit in the woods?

Yes, please.

I'm interested in pictures as I have no clue what a concrete fence is. Does it differ from a wall? Is it concrete cast to look like a picket, split rail, or other type of fence?

Hell yeah!

In for sure

Sounds like it would be an interesting pic thread, but why in concrete?

Hell yeah!

Love these types of projects and pics!

Subscribe here, I'll update this one tonight.

I would love to see pics of this project.

Yes.

I am interested in pics too.  BTW, make your boys mix the concrete by hand with a hoe so they understand why they should stay in school.

In for the hernia surgery sure to follow.

Yes.

Phase 1 will be smooth rails, either three or four rails high.  Each rail will be 8' long for this first phase, then hopefully out to 12' once the bugs are worked out.

Think of an Abe Lincoln style split log fence.  In concrete.

I'd like to see it.

#1- I'm a structural engineer
#2- my 'thing' is concrete
#3- I really hate fencing,
#4- I really hate doing maintenance and
#5- I really really really hate animals getting out of the pasture.

Sorry, we don't serve your kind here, '07er!

Just kidding, will update tonight.

Very interested, please do a thread. Thanks!

Officially tagged.

This should be great. Please take lots of pictures during the build so the non-engineers amongst us don't have to fill-in the gaps.

Like this?

http://www.landscapingnetwork.com/products/fencing-gates/precast-walls.html

or this?

http://www.smooth-on.com/a74/Concrete-Fence-Exhibits-Detail-Never-Seen-Before/article_info.html


Subscribed.

Farm not too far from us has concrete  fence that my FIL helped build years ago. There must be several miles of this fence. it is very cool.

Here is a link to their farm and a pic of the fence

Fence

Good Luck!

Edit for spelling

Neither.

This is not a panel fence/wall, this is a rail fence like the vinyl fences you see falling down after 10 years, only this one eventually will have Charlton Heston IV ride past it on a horse and start screaming about the fools did it....

And hopefully keep my horses, cattle and chattle in the pasture.

Yep, keep us updated.

I like concrete. I don't quite get what your fence plan is, but since you have experience with concrete I'm sure it will be decent. Concrete can look very good when properly used. For a fence, I would like the look of a rough sawn board form. Horizontal planks would work, and when you get as high as you like, top it off with a stone slab and drip edge.

If you're not doing a major quantity, the cost to add color (pigment) to the concrete is not that high. I've also built walls with white sand and cement, and marble aggregate, that looked like finely tooled stone when finished.

I've used precast concrete as  major portions of buildings, they came out pretty good.

Sounds interesting. Do you know what you're doing?

Yes, do it.

Too many words.  Repost when you get pics.

Yes

Nice. Now I'm definitely in.

Are you going to take into account corrosion of the rebar in the fence. I have seen several concrete fences around here that are starting to fail due to spalling of the concrete due to rust on the rebar.

Yes

tagged

OST

If it's for zombies then yes. If it's some made up reason then no.

How long of a run are you doing?

In for pics of your posts.