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VelaCreations

Water tanks are can be tricky to make, especially large ones. Here's an idea I am pursuing to make modular laminated ferrocement panels that get assembled on site to form a water tank. attached is a document with something similar.

LFC has advantages of being faster, higher quality, and using less cement than reinforced concrete or regular ferrocement. These panels could be made easily and quickly by making lots of forms and getting some people to work together. Combine that with a mortar pump, and you could really move, making hundreds of panels a day.

I am planning for my panels to be around 8 feet tall, 2.5 feet wide. They should weigh between 100-150 lbs when fully cured.

A similar system could be used for making roof panels, though you would want a different shape, like a barrel vault.

Dawg

Very creative I think. As I've mentioned here before, I really feel that creative building solutions should be very high on our priority list.

The Dawg

Jason

@VelaCreations

Good topic to bring up. I don't want to hijack your thread, but I've been thinking about modular LFC construction for a while too, and one idea I had was making LFC panels, but flexible ones that aren't yet cured. Imagine if you could just press the mortar into the lath with some type of non-aqueous binding agent, that was activated through either pressure or temperature. That would hold the right amount of mortar onto the sheets, and ideally they'd remain somewhat flexible. Then all you need to do is attach them together and hose them down, and you've got a complete LFC structure, without the mess, labor, or even a high amount of expertise.

VelaCreations

yeah, that might work, Jason, but joining up the panels doesn't seem to be very hard, especially with a bit of acrylic bonding agent.

VelaCreations

I did a cost analysis for a tank I hope to build with 17 8' by 2.5' panels. The cost comes out to be less than $500 for 8100 gallon water tank in materials. The vast majority of building could be done by one person (making the panels), and they come out very cheap, like $.32-.4 per square foot.

I'll be doing a few test panels next week to see what happens....

dorkmo

i like this.

u should start a wiki page. do you know how, i could start you one if you like.

this is the only page i see on the wiki at the moment: http://opensourceecology.org/wiki/Ferrocement

VelaCreations

yes, we should start one on laminated ferrocement, can you do this for me?

the ferrocement wiki page already includes a lot of info from me, and I would be willing to provide the information for a LFC page as well.

dorkmo

k i just stared a basic page.

http://opensourceecology.org/wiki/Laminated_Ferrocement

i also put the water tank and channel roof stuff on there if you want to expand on those too.

i could also add some pages for step by step instructions on how to build them if you want to take on that later?

VelaCreations

yes, I'll document tank construction and get a step by step up

VelaCreations

ok, I made 2 test panels today, hoping to make another one tomorrow.

The panels are 3 ft by 1.5 ft. One test panel had one layer of 3/8" square mesh, and the other had 2 layers of 3/8" square mesh. I made each layer as think as I could, and it came out pretty good, I think. The panels are maybe 3/8" thick.

My mix was just 2:1 sand to cement, no acrylic or anything, as I want to just see what I need in terms of mesh.

I do realize that I need to get a finer screen for my sand, as I had a few small pebbles (1/8" or so) that were popping up every now and then causing issues.

I covered the panels with plastic, just to help with the cure. I'll wet them down this evening or in the morning, if they need it.

Tomorrow I hope to do a panel with the Mexican lath, 4 layers. I don't have access to normal American lath, but I think you could easily do a panel with just one or 2 layers of American lath.

Jason

Whats the difference between American and Mexican lath? How much does Mexican lath cost?

VelaCreations

the difference is that Mexican lath has bigger openings (like 1/2" by 1") and is a thinner gauge (like 20 or 22 ga). Mexican lath costs about $.14 per square foot, whereas American costs about $.38 or more per square foot.

American lathing is much better, no doubt, but in 4 years in Mexico, I have not been able to source it anywhere. So, I've gotta use what I can find.

OmniPhoenix

@Dawg
Yes, effective knowledge should definitely be right up there with shelter, water, food, etc. We should definitely have wiki pages with lists of ways to meet the different needs in different situations and areas. People familiar with the subject can fill the page in with an outline of what they know and the outline can be filled in as research accumulates and it could lead to new open sourced technologies.

@VelaCreations
What is currently commonly used for water storage? How much does it cost compared to the LFC method? If it's significantly cheaper then it could be made into a profitable enterprise, and would be a great chance to document an open source business model.

http://opensourceecology.org/wiki/Open_Business_Model
http://opensourceecology.org/wiki/OSE_Proposal_Enterprise_Models
http://opensourceecology.org/wiki/Development_Strategy#Enterprise_Plans

Just a quick idea.

VelaCreations

well, currently most folks use HDPE tanks, which cost in the range of $.25 - $.50 per gallon of storage.

Another option is a ferrocement tank, but ferrocement is a bit more labor intensive (70%) than LFC, and usually costs around $.15 a gallon (materials only).

I made a metal tank last year with a PVC liner. Total cost was $1800 (including labor), and it holds about 6,400 gallons, which comes to about $.28 a gallon, and we had it built in 5 days.

LFC will be slower, just cause I am probably going to make only 2-3 forms for the panels. Then, there is the curing time (min 7 days). Once your panels are made, however, assembly should take 2 days for an 8100 gallon tank. I am expecting the cost to come in at $.09-$.15 per gallon, including labor.

Ferrocement and LFC get cheaper as the volume increases, but HDPE gets more expensive per gallon past a certain point.

It could definitely be a decent local business, making the panels, and then assembling them on site. I may try it down here in Mexico, because no one really has rain catchment, and everyone is amazed that we have water year round with our system.

I took the test panels out of the forms today, wet them down, and wrapped them in black plastic to cure for a week. They are amazingly stiff, even at 24 hours old and less than 3/8" thick.

VelaCreations

Panel 1 - 1 layer 3/8" hardware cloth, 36.5" X 20.75" - 757 si, 5.26 sf
5/16" - 3/8" thick
Cured for 3 days
17lbs, 3.23 lbs/sf

Panel 2 - 2 layers 3/8" hardware cloth, 36.5" X 20.375" - 744 si, 5.17 sf
3/8" - 7/16" thick
Cured for 3 days
22lbs, 4.25 lbs/sf

Tests - panels were placed on bricks, spaced 14" apart. Weight was placed in center of panel, between brick supports.
Test 1 - 1 gallon water @ 8lbs on 2.25 si, 3.55 psi
Test 2 - 1 gallon water @ 8lbs on 1.5 si, 5.33 psi
Test 3 - human @ 173 lbs on 46 si, 3.76 psi

Results
Test 1, panel 1 - troweled side up - no visible sag or cracks
Test 1, panel 2 - troweled side up - no visible sag or cracks
Test 2, panel 1 - troweled side up - no visible sag or cracks
Test 2, panel 2 - troweled side up - no visible sag or cracks
Test 3, panel 1 - troweled side down - visible sag but no cracks
Test 3, panel 2 - troweled side down - slight visible sag but no cracks
Test 3, panel 1 - troweled side up - extreme sag and panel snapped along brick support
Test 3, panel 2 - troweled side up - visible sag but no cracks

Troweled side has 1/8" less concrete on mesh

Conclusions
Both panels survived psi ratings for tank design (3.44 psi), however because troweled side has less concrete, it is a weaker side of panel in compression. Suggest using formed side as inside of tank, so that the troweled side will be in greater tension (more mesh, less concrete).
Panel 2 with 2 layers of mesh seem to be stronger in all tests.

I think these would do just fine as roof tiles or panels, especially if shaped to take advantage of concrete's compression strength. For a water tank, although they survived the psi required for an 8ft tall tank, I think more testing is required.

I hope to now do a test with 4 layers of the Mexican lathing and compare results.

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