Concrete pour - water cleanliness question

[otlski]

When pouring readimix concrete, how clean does the water have to be? I will be pouring a slab well away from access by truck. The water I hope to use is rain water collected off a roof and stored several months in an enclosed white poly 550 gal container. The water is relatively clear but has small amounts of algae in it. Otherwise there are some organics (leaf pieces) but no sediment. To give an idea, when transferred into a 5 gallon bucket, the water may be ever so slightly tinted with green specks and occasionally a wisp of algae the size of a 1/2 paper-matchstick. Will the fact that the water is not clean affect the strength of the concrete?

Dan

 

[crash325]

It should hve little or no meaningful effect. Use it with out worry;

 

[jaotguy]

ditto

 

[Cord]

The water needs to be "potable". In other words, it should be clean enough to drink. That's not say that it's bacteria free. If I saw that water being used on one of my jobs, I'd reject the pour.

 

[CalG]

The water needs to be "potable". In other words, it should be clean enough to drink. That's not say that it's bacteria free. If I saw that water being used on one of my jobs, I'd reject the pour.

For what reason?

Organic material is not wanted, but really? What difference does "green" make. I would use rain water and would accept large amounts of mineral sediment.

But, no leaves twigs, or frogs ;-)

(well, a frog or two would be cute.)(

 

[oosik]

I used rain water on a pour in 1967 and its still strong as ever. The water was stored in a whiskey barrel and DID have a little alcohol in it. Happiest concrete I ever worked with.

 

[Gary Fowler]

For what reason?QUOTE]

Well for one ACI (Code for concrete construction) states water for concrete is to be potable water. Now would rain water that was strained of all extraneous matter would be ok, most likely, although I don't know what the green algae would do. It may make the concrete off color or bleed white powder after curing like alkali water does but likely wont affect the strength.
Water that is slightly alkali will cause concrete to continually bleed white powdery residue for years when used on a wall, seen that many times in Saudi Arabia although I don't think it affects the strength. You can wash it off but it comes right back.

Why not use that barrel, clean it out and then fill with potable water and take that to the site for use.

 

[otlski]

Thanks guys. I found some info this morning. It was just a matter of finding the right Google keyword. http://www.engr.usask.ca/classes/CE/898/t2/b/notes/PCA/Chap.4/Water.pdf

http://pbadupws.nrc.gov/docs/ML1215/ML12153A326.pdf

It looks like I should switch over to tap water. I have no idea how to judge 1000 parts per million of algae. Testing it seems like it would only be valid the day you had it tested. I'll need to transport about 150 gallons up a rough trail about 1200 feet with a 350 foot elevation gain. All this will be 12 gallons at a time in my Bush Hog side-by-side.

Dan

 

[Texasmark]

I know "washed sand" vs straight deep pit sand makes a difference in the compressive strength of concrete. So I'd say that bad water would too; depending of course on amount of contamination and what.....anything that can come between the portland (glue) and the aggrigate.

While we are at it, ensure that your rebar is in the concrete, not under it which is easy for the contractor to let happen if you don't stay right there and supervise; especially when the mix has to be wheelbarrowed in and the crew is tired. The barrow pushes it down into the cushion sand and you have to stay on their .... to get it pulled back up.

I had to do that on my shop which has a 5" floating slab inside a pole barn; no perimeter beam. With our drought and all, and being heavy clay below the "select fill" brought in, packed and leveled for the slab, as the clay sub soil shrank, the slab cracked over about 40% of the surface. Had I not insisted on the rebar be inside the crete, I guarantee you the sections would be sliding apart leaving gaps. as it is, I just have a hairline crack and I don't have a problem with that, knowing that the soil is "unsuitable for dwellings and roadways" per the Civil Engineering report we got when we put in out community water well. On that we installed a 100' stand pipe on an 8' (that's foot) thick slab. Been there since '85 and no problems yet.

Mark

Mark

 

[k0ua]

Maybe make a filter out of a couple thickness of bed sheet stretched over another barrel? Transfer water from the first barrel to the second thru the sheets. The would get rid of any larger particulates, and a lot of the algae. I would give it a try.

 

[Professor Marvel]

What are you making with the concrete? That could make a big difference.

 

[crash325]

What are you making with the concrete? That could make a big difference.

You got it.

A little algae is going to have less effect than how much water you use & how well its mixed.

Does not sound like some really critical, high strength job is needed.

Wet soupy mix reduces the strength.

 

[wrenchrider]

You can most likely strain the dirty water like k0ua said, and it should be ok. The organic stuff (leaves, grass, twigs, bugs, and even frogs) will eventually decay leaving open 'pockets' in the concrete. Algae does the same on a smaller (almost microscopic) scale. The algae and dirt will hinder the portland cement's ability to stick to the aggregate (rocks) as mentioned earlier. I'd strain it really well and use it. Rusty rebar is not a good idea either, may want to pack a wire brush up the hill with yer water. Happy pouring!!!

 

[adirondackmtnman]

The water needs to be "potable". In other words, it should be clean enough to drink. That's not say that it's bacteria free. If I saw that water being used on one of my jobs, I'd reject the pour.

The company I work for has 9 concrete plants, some on municipal water, some on drilled groundwater wells, and some on pond water, with the municipal supplies being the only potable source. Personally, I wouldn't think of any water supplied through a ready mix plant and then into a truck and out the hose in the back 'potable,' as those are for sure not a sanitary system...take a look in the sight tube of the water tanks on the next ready mix truck that shows up on your job site, reject said truck due to the water, and see if another truck from that company shows up to your job...then call the next supplier...you'd be out of business in a week...
To the OP: You should be just fine with collected rainwater, as long as it's free of too much sediment, our ponds are basically the same thing, probably dirtier yet than your system.

Sent from my LGL35G using TractorByNet

 

[otlski]

I'll be pouring a 12 X 16 foot slab for a small cabin. I plan on wire mesh plus some rebar (one corner is compacted fill).

 

[EddieWalker]

For a cabin, with load bearing walls, I would want the maximum strength I could get from the concrete, which means I would use clean water. If I'm not willing to drink it, it's not clean water. But for a lot of projects around my place, I'll use pond water to mix concrete without a second thought. Especially for fence posts!!!!

Be careful on the wire mesh, it is impossible to pour and keep it in the middle of the slab. Even when you pull it up, you walk on it again and it goes straight to the bottom of the pad and sits on the dirt. In 100% of every slab that I've worked on where there was wire, it's always at the bottom of the slab, sitting on the dirt or plastic.

Rebar on chairs is the only way I would do it for myself or for my clients.

Eddie

 

[boggen]

there are folks that make decorations, out of concrete, and on purpose, mix in leaves, twigs, algae, etc... the effects give little "pot holes" per say, to more of a old aged look to the concrete. more so after everything rots away and just the concrete is left. with that said, i would want to keep large chunks of stuff out. or rather stuff that would rot over time.

==========
with above said...
12 x 16 concrete slab, and trying to manually use ready mix bags, and a 2 bag or so concrete mixer. i think you are over estimating, how much labor is involved. and how much actual time you have to work the concrete before things cure to much.

i would say you would be better off ordering a concrete truck, and either having it pumped, or wheel borrowed from truck to area. or other. trying to do it yourself and some friends *shakes head no* not that much concrete. i doubt a trailer of pre mix would be able to hold enough for size you are talking about.

 

[Cat_Driver]

I'll be pouring a 12 X 16 foot slab for a small cabin. I plan on wire mesh plus some rebar (one corner is compacted fill).

ALWAYS use either stainless steel fibers or other fibers in concrete. I poured a test sample of 2" concrete on compacted beach sand and I drive a 10K skid steer on it all day long and never a crack. I had a contractor pour a slab with no fibers and it's full of cracks. Yes still use the rebar, just *** the fibers, the cost is cheap and the benefits are AMAZING.

 

[crash325]

On1 thing for sure, in answer to a question like yours. The replies will be from "Go for it" to OMG don't do that.

Eddie Walker is probably the best builder on the site. Very meticulous & work above the ordinary.

With that said, it would be nice if you can tap into your tank a few inches from the bottom. Most everything that is in your tank will either settle to the bottom or float on top. Nice clean, drinkable water in the middle.

Once the slab is poured, set up & finished, cover it with the empty cement sacks & keep them wet at least 1 day, longer is OK. The slower it cures the less chance of it cracking.

Your mixer is about 2 wheel barrow loads, & a slab your size should be poured in sections. Depending on how much help you have about 6'X6' would be good for 2 real busy people.

Don't claim to be any kind of expert, but have mixed concrete since about 14. Grandad as a contractor & we had an old "Hit & miss" engine powered mixer. I was so lucky I got to feed it & truck (wheel barrow) the mix.

I poured a slab about the same size with 1 helper. Much larger sections will start to set up before your pouring is done.

 

[farmer2009]

I must agree with crash in the post above.

Bacteria in the rain water may make it unsafe to drink but won't affect the structure of the Crete. Now if the algae is bad it could. Add some bleach to kill the algae. Then if needed some Alum this will drop everything to the bottom of the barrel. You should have nice clean water on top. Do this a couple of days prior to pour.
If your barrel has a bottom spicket skip the Alum and steal your wife's pantie hose and filter as you drain into a bucket.

The size of your pad isn't bad as long as you have time. On a 12x16 pad look at a 6x8 pour. This will let you do 4 even pours. It will be a lot of work but is do able.

Post some pics.