Bamboo instead of rebar?

[beatsmyth]

Im doing research on rebar alternatives and trying to keep costs down with DIY for most things. Has anyone had experience with Bamboo as rebar vs steel/iron? I know the concrete is quite alkaline which eventually eats away at the metal rebars, where as alkalinity does not effect bamboo.

[MushCreek]

I'm no engineer, but two things come to mind. One, bamboo is strong, but it's not steel. The design would have to be engineered, with proof of it's strength. Two- re-bar has a lot of little ridges to help the concrete, where bamboo is very smooth except for the occasional node. The concrete has to get a good grip on the reinforcement if it is to do its job. I like your thinking, though!

[beatsmyth]

What about the odd holes her and there for the concrete to grab onto or leech into. Or perhaps twisting iron or barab ware around the bamboo for better grip? I can't seem to find any engineering info on bamboo reinforced concrete. I did find a few studies that say that the strength of bamboo is just slightly less than that of steel poles or rebar.

[rick91351]

Im doing research on rebar alternatives and trying to keep costs down with DIY for most things. Has anyone had experience with Bamboo as rebar vs steel/iron? I know the concrete is quite alkaline which eventually eats away at the metal rebars, where as alkalinity does not effect bamboo.

Most rebar failure comes not from what you are thinking but water entering mostly of the through a conduit such as a piece of rebar touching the soil and moisture wicking in or a crack because of improper fill.  A properly done footing or footer as some say and foundation today will last well past 200 years.

I have never seen any engineering or grading for bamboo used as such.  Myself I think in concrete it would fail miserably.  The bamboo rich countries of Asia I have visited certainly do not use it as such.  I have seen it use for scaffolding on high rise buildings but never in concrete,         

[MountainDon]

Have a read here...  http://www.networkearth.org/naturalbuilding/bamboo.html

excerpts...

Many studies have been done to determine the feasibility of using bamboo to reinforce concrete. The problem is, however, that bamboo soaks up the water in the concrete, causing the bamboo to swell then shrink, the process of which can break the concrete. In addition, adhesion between the bamboo and the concrete is poor. Oscar has experimented with braided bamboo as reinforcement, but it takes an excessively long time to braid.


IF you are working in a code compliance area the inspectors would probably look at you kind of funny too...     

[MountainDon]

And for what it's worth, here a copy of a old US Naval paper...

http://www.romanconcrete.com/docs/bamboo1966/BambooReinforcedConcreteFeb1966.htm

[Squirl]

So far the only thing I have heard of to reinforce concrete is with special glass fibers.  It is also known as surface bonded cement.

Rebar is measured in tens of thousands of pounds per square inch of strength, bamboo not.

[rick91351]

There is a product called basalt roving if I remember correctly that is supper cheap to manufacture.  Glenn and I did a little PM back and forth and I dropped the basalt as it were.  I was going to look into getting some to play with.  OH OH Strike that  -   experiment with.

http://www.monolithic.com/stories/monolithic-ecoshell-built-with-basalt-roving

In the researching that I found companies are now making basalt rebar.  However I have not seen any pricing or availability. 

One more thing about the bamboo if it was used green it would not expand but then still would shrink.  How much rebar are you talking about? 

[beatsmyth]

How much rebar are you talking about?

Well, I was looking at the possibility of building that concrete cave house and noticed the architect never used any rebar. Considering the sq footage of the total amount of concrete used, I realized the added cost of rebar would be significant, and then it came to mind to see if there is substitutes for rebar.

I also found that Roman concrete structures did not use any rebar for their works. And their buildings are still standing thousands of years later.

[Don_P]

In a completely compression structure unreinforced masonry works fine, mosques, aquaducts, cathedrals. There is more to these structures than immediately meets the eye, for one the ancients used mass and buttressing to support their arches and domes. If the masonry goes into tension anywhere it begins to fail. This is when steel with its' high tensile strength is used. It requires less masonry if the thrusts can be restrained by steel rather than mass. We look at an egshell and declare a dome to be a perfect shape. Many modern dome buildings have a wall thickness that is proportionally much thinner than the egg's shell. Domes generally fail by "snapping thru" from the apex of the dome or an unbalanced load causes one side to fail.

We got an email a few minutes ago from a friend who's offices flooded Thursday when a line broke overnight. Furnishings, floors, lower walls, etc, ruined... except, she noted, the bamboo floor in one of the rooms 

I would be comfortable using it in a wattle and daub type wall.

[rick91351]

One of the neatest floors we ever seen was a bamboo floor in the office show rooms of a furniture factory in Shenzhen, China.  No one knew how old it was.  Old part of town and old building.  But it had survived with much use.... with furniture displays and movements in and out.  No one remembered a refinish or how old.

A lot of Roman concrete was rubble construction and not poured as today's cement allows.  Very labor intensive yet fairly light weight by modern standards.  This because the use of pumice and volcanic ash from what I understand.         

[Squirl]

Well, I was looking at the possibility of building that concrete cave house and noticed the architect never used any rebar.

They didn't mention rebar in the article that I noticed, but that doesn't mean he didn't use it.  If he didn't he is either extremely advanced in engineering and concrete or a fool.  I have read 2 books on concrete design, most of ACI-318, and an online course on it.  Not a single one would even consider a flat slab roof that concaves down in the center for that kind of span without rebar.  I believe that is even against ACI-318 standards but I'm not an expert.

Rebar is cheaper than concrete.  The more rebar you use, the less concrete you need for most designs.  You can see it if you play around with the equations I had posted when I had designed a one way slab for a root cellar roof.  Also you can see it in the ICC charts for foundations. http://publicecodes.citation.com/icod/irc/2012/icod_irc_2012_4_sec004_par003.htm?bu=IC-P-2012-000002&bu2=IC-P-2012-000019

It took me a few weeks of playing with the equations to figure it out.  The cost of a 20 ft piece of #4 rebar is $7 while a yard of concrete is $110 delivered.  If you have a 10x10 section of wall at 8" thick with no rebar that would be 2.5 cubic yards or $275, while if you had a 6" wall and rebar 36" O/C, it would be 1.85 cubic yards of concrete or $200 and $14 of rebar.  The 6" wall would be stronger too.

Also higher strength concrete (4000 psi)  is cheaper by design capabilities than lower strength concrete (2500 psi).