Al G
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Cocina mortar...Foam panel stucco
This question spans 2 threads...one general one construction.
So I hope this will not be consider hijacking.
I have read about Stranded fiberglass being added to mortar/ grout...1 part portland cement...1/4 part lime...3 part sand and 1 part 1" cut fiberglass
strand.
I am thinking this could replace re-bar in counter tops and two 3/8 coats each side should be enough to reinforce 6" foam panels in house
construction. I have read and seen this in use, but do not remember much about it. Can some of our contractors or researchers enlighten me on the
possible/probable uses.
Albert G
Remember, if you haven\'t got a smile on your face and laughter in your heart, then you are just a sour old fart!....
The most precious thing we have is life, yet it has absolutely no trade-in value.
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Ken Bondy
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Al G
The use of synthetic fibers is a big deal in concrete technology today. Most of the fibers being marketed are polypropylene. Fiber-reinforced
concrete has significant advantages, the most important are:
1. The fibers don't corrode
2. The fibers, properly mixed, are uniformly distributed throughout the concrete member and eliminate placing problems inherent with steel
reinforcement.
3. The fibers are generally less expensive than the metallic reinforcement they replace.
They have found application in slabs-on-ground and concrete slabs in composite metaldecks. In my opinion fiber-reinforced concrete could be used
effectively in the applications you cite, countertops and the cementitious coatings on both sides of the foam walls.
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Ken Bondy
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Larry
If the reinforcing steel is continuously protected by contact with the alkaline concrete environment, there is no strength loss with time (due to
corrosion). Corrosion in steel requires contact with air and the presence of moisture. Cracking can allow ingress of both air and moisture, and
produce corrosion in the steel. The corrosion process is expansive (the corrosion product occupies a larger volume than the non-corroded metal), and
can produce spalling of the concrete surface which produces more corrosion. Strength loss in reinforcing steel is measured by metal loss. A sample
of the steel is taken, and sectioned in a laboratory. Measurements of the cross-sectional area of the bar are made and compared with the original
specified size. I have been involved in many corrosion investigations in existing buildings and have seen some cases where a large bar is corroded
down to just a thread of bright metal.
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Cypress
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Ken Bondy!!! Not only are you a world class underwater photogapher, you know one heck-of-a lot about cement/concrete/grout/rebar etc.  Thanks for sharing your knowledge of both.
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shari
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Rebar is super expensive here...so where can I get some of this fiberglass strand stuff??? Is is sold in bags er what? Will it hold up in
earthquakes??
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Gadget
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I'd like to add to Kens very informative and technically accurate information regarding structural and pre-stressed concrete done professionally here
in the States. The inspection and material specifications for these structures are very carefully regulated to achieve the desired resuts and
performance over the engineered life span on the design, less of course certain failures which Ken out lined, water intrusion, cracking, spalling etc.
But....what I think should be considered for construction in Mexico and specifically Baja is the construction procedures and materials. Consider the
mixing of concrete on the ground, potential for salty or brackish water to mix with, un-washed sand etc. and you have a recipe for not such a great
product.
I also agree the stranded fiber reinforcement has great potential in very limited applications such as thin and decorative coatings etc. You wouldn't
want to see the guys building the bridge abutments pouring sacks of fiber glass into the concrete mixer and no rebar in the forms would you? 
[Edited on 5-29-2007 by Gadget]
"Mankind will not be judged by their faults, but by the direction of their lives." Leo Giovinetti
See you in Baja
http://www.LocosMocos.com
Gadget |
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Ken Bondy
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Larry corrosion is not a problem in those environments if the concrete is designed and built to be sufficiently impermeable and crack-free, so that
the water doesn't get to the steel. This is generally done by supplying a low water-to-cement ratio and increased cover to the steel. The reason
that cement is so tough on your skin and so beneficial to preventing corrosion in steel is the same, very high alkalinity.
Gadget thanks for your comments which are right on. I should have mentioned that fiber reinforcement, to date, has been used only for non-structural
applications such as shrinkage and temperature reinforcement. Some testing has been done (interestingly, at Virginia Tech) that indicates it might
have structural capacity in certain applications (i.e., used to resist applied exterior dead and live loads), but that has not yet materialized
(pardon the pun).
shari I think it is going to be some time before fiber reinforcement will be available to the general public, sorry. We're all gonna be stuck with
rebar and mesh for awhile.
Thank you Cypress!! Underwater photography has been my avocation/obsession. Structural engineering (specializing in concrete) has paid the bills
.
++Ken++
[Edited on 5-29-2007 by Ken Bondy]
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Mexitron
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We'd had fiber available in Southern California for many years at building material stores like Larry's Building Materials in Costa Mesa, and also
most ready-mix concrete companies offered it as an option.
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Al G
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| Quote: | Originally posted by Shari
Rebar is super expensive here...so where can I get some of this fiberglass strand stuff??? Is is sold in bags er what? Will it hold up in
earthquakes?? |
Shari...I do not know the answer, but my hope is it is at least as strong. if not I am very sure it will reduce the use of steel greatly. As a
guess...enough can be transported by pickup truck for a entire house. Another great use is stucco the outside of a weak block wall and double(??) the
strength'
I would think that would be good for your area. I think you paint the wall with a bonding agent and the apply the stucco or finish coat in the color
you want.
I am hoping someone out there can tell us some do and donut's and maybe a supplier.
I am interested in foam panels that have a chance in a typhoon. I think 16"X16" block pilasters set at 8' o.c. with 8' panels may work. I just need
someone who has done the research and is marketing the panels.
Albert G
Remember, if you haven\'t got a smile on your face and laughter in your heart, then you are just a sour old fart!....
The most precious thing we have is life, yet it has absolutely no trade-in value.
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Ken Bondy
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| Quote: | Originally posted by Mexitron
We'd had fiber available in Southern California for many years at building material stores like Larry's Building Materials in Costa Mesa, and also
most ready-mix concrete companies offered it as an option. |
Mexitron what's it called?? Do you know what dosage is recommended?? Thanks for the info, I wasn't aware that you could get it except through the
ready-mixed concrete suppliers. I know the big fiber manufacturers (SI, Propex, Euclid) sell it mainly to the ready-mix companies.
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tuna stick
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We are using TRIDPANEL construction for our house here in Loreto. Jordan&Associates de Mexico is the distributer, email- AEJNBLW@aol.com, Alan E
Jordan. Jaime Card##as of San Bruno construction is our builder. Our foundation has a lot of rebar and mesh in it. When they poured the slab, they
added fiber to the mix,to prevent cracking.
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Cypress
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Fiberglass mixed with cement works. The finished product has a fuzzy
appearance on the surface, but most concrete slabs are covered with tile, carpet, etc. 
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Mexitron
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Hey Ken--Larry's in Costa Mesa sells SI fiber...don't know what the dosages are but they are probably one bag/cubic yd....I imagine its the same stuff
they throw in the trucks, premeasured bags. I used it occasionally for subbase but didn't like it for finished concrete since the fibers would stick
out once in a while.
While on topic--here's a structural question for you--I started installing flagstone on top of two-inch concrete slabs with mesh instead of the usual
four-inch industry standard for customers who didn't want to pay the extra cost for 2 inches of excavation and concrete. I warned them of them that
it would tend to crack more. But surprisingly the thinner slabs seem to crack less! Any idea why? Only thing I could think of, other than just
getting lucky, was that there was less weight creating shear...that is, the slabs tended to "float" and flex.
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Ken Bondy
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| Quote: | Originally posted by Mexitron
Hey Ken--Larry's in Costa Mesa sells SI fiber...don't know what the dosages are but they are probably one bag/cubic yd....I imagine its the same stuff
they throw in the trucks, premeasured bags. I used it occasionally for subbase but didn't like it for finished concrete since the fibers would stick
out once in a while.
While on topic--here's a structural question for you--I started installing flagstone on top of two-inch concrete slabs with mesh instead of the usual
four-inch industry standard for customers who didn't want to pay the extra cost for 2 inches of excavation and concrete. I warned them of them that
it would tend to crack more. But surprisingly the thinner slabs seem to crack less! Any idea why? Only thing I could think of, other than just
getting lucky, was that there was less weight creating shear...that is, the slabs tended to "float" and flex. |
Thanks Mexitron, appreciate knowing that. Generally the thinner the slab the more tendency there is for restraint to shrinkage
cracking. The slab cracks when the restraint force acting at a slab section reaches the tensile strength of the slab at that section, and the tensile
strength of a slab is directly proportional to its thickness (and some other material properties). I would say this experience with the thinner slab
cracking less is an aberration. Also, the Uniform Building Code limits the thickness of ground-supported slabs to 3.5 inches, how did they get around
that? Mitigation of cracking in hard flooring surfaces is generally done by way of a slip sheet between the slab and the flooring material. Was
there a slip sheet used here? That might explain the apparent lack of cracking in the SOG.
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Mexitron
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Ken--this is for residential applications so flagstone gets laid in anything from one inch of sand to mortar only and so on...at that level its just
what people can afford and what they're willing to risk by not putting in a compacted subbase and concrete of the code's thickness. Thanks for the
consult!
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Diver
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I would guess that the temperature and curing stresses are less in the thinner slab. Faster cure time with less easier temperature distribution across
the thickness of the slab.
Whereas this may reduce initial cracking, it is not a structural base and will crack eventually unless the subgrade is firm with evenly distributed
compaction. If this was in an area where excess rains saturate the subgrade, you will also have problems.
For non structural patios of flagstone or pavers, we either pour a 3 1/2" slab first or lay the pavers on a 4" bed of compacted cement screenings
witht he same material washed into the cracks.
The only good thing about using sand is that it is cheap and you can dig out unlevel areas and fix them eaily. (You WILL eventually have eneven areas
with a sand bed.)
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jimgrms
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back in the 60's some developers trier a affordable housing tract in fontana calit 4 steel corner post and styrafoam walll then plaster .just a
couple were built ,and they diddn't make it thru the wind storms there '
But that was years ago and i am sure the teck is much better
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Mexitron
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Diver--the main problem with flagstone is that folks don't want to see joint lines...so most patios go in on an unjointed slab. Its these instances
where with normal precautions that 3.5" slabs still crack and the smaller ones less so. These were in Irvine, CA on very compacted subsoils by the
developer, not too expansive...excessive saturation wasn't usually a problem.
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