concrete floors and load

[ScottV]

I just had a core sample taken in my proposed brewery site and it showed a 4", very lightly reenforcement, slab over packed earth. I was told by a engineer that this would not hold the weight of full 40 bbl tanks.

Has anyone been faced with this problem, and how did you deal with it. I don't want to have to rip up the floor and lay down a new reenforced slab, and I don't want to add a 4" slab on top of the existing slab if possible.

Does anyone have pricing on this type of excataing work?

I figured 1250 gallons of beer @ 8#/gallon spread over 4, 6" feet. Adding in 5000 pounds for the weight of the tank this would give me 7460# per square foot. Does this sound right?

thanks for any help and advice
Scott

[Diamond Knot]

Well........

Scott,

What makes it tough is the fact that your tanks will put a point load at each foot location. The way I see it:

1250 Gal x 8 lb/Gal = 10,000 lb

10,000 lb + 5,000 lb = 15,000 lb

15,000 lb / 4 ft = 3,750 lb per Fermenter foot

6" DIA foot = 28 sq-in area = .1944 sq-ft

4 x .1944 sq-ft = .7776 sq-ft total

15,000 lb / .7776 sq-ft = 19,290 lb / sq-ft

However: 19,290 lb / sq-ft and 144sq-in / sq-ft = 134 lb / sq-in [psi]


Though non-structural concretes can be as low as 2,500 psi in compression, you still run a big risk of cracking due to bending loads if the substrate is not fully compressed. Literally, the slab bends under the weight and cracks. Concrete is awsome in compression but terrible in bending and tension.

A couple of options might be:

1.) Place large steel plates below the tanks to disperse the load over a greater surface area.

2.) Drill out piling cores at each foot location down to a couple of feet each. Make them about 1' x 1' square. The 2 ft depth may be overkill.

3.) Consult a concrete contractor / engineer and show him the data. They may deem the installation safe as is, but will really quiz you on the substrate.

Good luck!

[Moonlight]

Been there. I agree with Diamond Knot's suggestions...and in the end it's probably cheaper and easier to rip it out and do it right...especially if there are any regulatory agencies watching you.

[mike2brew]

dont risk it

I have seen installations with 30 bbl tanks on 4in concrete and it held up. As a brewer I didn't like it. Think of the guys standing next to the tanks. And to be repetitive Diamond Knot layed it all out for ya.

[ScottV]

concrete beams

My engineer decided that the best way to go would be to excavate 12" wide beams in the existing slab and to repour 24" deep, reinforced concrete. I think it seems a little thick, but he is the engineer. The only draw back is i had to sit down and figure out the distance bewteen the legs of as many different brands of fermenters as I could find so that i can excavate beams for future tanks.

thanks for all the help. I'll let you know how it turns out.

Scott

[BrianU21]

wow, this is the first time my engineering background actually paid off for a beer related question. Diamond did a great job explaining, so no point rehashing it all.

As for the 12" strips, you might be better served to excavate and pour an entire new slab, say 10'x10' or something. Point being, you had better make sure you get the legs of your tank to line up right directly with the beams otherwise.

If you can make a larger excavation area then the leg location variable is more acceptable and your brewhouse layout can vary a bit easier over time. I don't know how many tanks you are dealing with though, so this may be impractical for many reasons. Of course you can always go through the exercise again in the future if more tanks, or bigger tanks are brought in.

[cpelz]

We're experiencing similar problems. We've got a 4 in floating slab that stood up under 30 bbl tanks, but is settling and cracking under 60 bbl. I think we've also had some water related subsoil consolidation under the slab where water has penetrated at the joint between the footers and the slab.

We're planning to cut up much of the slab this Fall and repour with curbs along the walls. I'll try to re-post as the details develop.

[ScottV]

Construction Has Begun

Well today was the day. We began the saw cutting of the floor and jack hammering it out. My engineer decided that a 24" slab would be over kill. I will say that 4" concrete with wire mesh is not as easy to get rid of as I had hoped.

We are installing 18" wide, 28' long and 12" deep "beams", with two layers of #5 rebar, positioned underneath the feet of the tanks. I had to figure out the foot print of each tank and possible future tanks, and then come up with a suitable distance to space the beams apart to give the tanks the needed support.

We are installing 8 beams, three rows of tanks, and two floor drains. With 3 guys on 3 jack hammers and two guys with wheel borrows and shovels we should have the area ready to rebar in three days.

I will keep you all posted.

Scott

[cpelz]

Good Luck Scott. Do you have any photos to post?

[Diamond Knot]

Yeah..........

Yeah, ScottV, that wire mesh sure makes things a pain to take out! Next to clay and straw (the Eqyptians used this to make brick), concrete and wire mesh must be one of the oldest man-made composites.

You (and your Engineer) made the right call, in my humble opinion. That mesh was probably half way down into the 4" slab at the neutral axis and would have done nothing for you in bending. I've used 1/2" DIA Rebar in our new pad but assumed it would aid in crack resistance and crack growth restraint (i.e., if a crack started, it would keep the new crack-joint tight).

Being an Engineer myself, I spent a month designing the "Brewing Pad" for our new facility. I found that not everything in concrete is science.........or intuitive.

You can see that pour here.

Did you get some fibermesh mixed in with the new pour? It's 3/4" - 1" fiberglass strands mixed in for strength (reminds me of the clay and straw).

Keep us posted...........pics?

Good luck!

[lhall]

We ran into the same problem here, the concrete floor was not level and would not drain properly. The core sample we took hit was 4" deep and had wire in it, but I decided to jackhammer out the concrete in the wet area and repour it with the proper slopes and drains. Boy am I glad we did, because we found that only half of the concrete had wire in it, and that it was only 2 inches deep in some places, and that some of the fill was in fact old cinders from a foundry instead of rock or gravel. But now I sleep better at night not worrying about coming in and finding out that my unitanks are now horizontal tanks. The concrete was not all that expensive in the long run, all of the labor to prepare for the pour is what makes it expensive.

Linus Hall
Yazoo Brewing
Nashville

[cpelz]

Thought I'd posted this last night but it must have got lost in the sauce.

Thanks for the link to the photos Brian. What did you decide on for a slope and what type of floor drains did you install? I also saw mention of sumps on your website. What will you be using them for? TIA for the info!

[Michael Murphy]

perhaps its too late, but you could pour on top of the existing slab adding reforcing mesh. this way you can get your drains exactly the way you want them and not worry about the drains seeping under the base. 8 inch to a 1% slope to middle would work. and you wont have to pay for the jack hammer and clean up work, give it a good epoxy coat and your ready.

[ScottV]

Construction - Day 2

Well day two went well. We cut all the remaining slab, and jack hammered all the concrete. All we have to do now is remove the concrete and about 8" of dirt before we can rebar and repour. Here are some pics.

thanks for all your help. I will post some finished pics next week.

I can't upload the pics, they are to large. If anyone wants to see them just send me an email scottvaccaro@optonline.net.


Scott

[Diamond Knot]

Thought I'd posted this last night but it must have got lost in the sauce.

Thanks for the link to the photos Brian. What did you decide on for a slope and what type of floor drains did you install? I also saw mention of sumps on your website. What will you be using them for? TIA for the info!

Our slope was 1/8 inch per 1 foot of slope. The pour was a single pour, and we used 4 cement trucks during the day. The curbs are 16" high by 6" wide.

We couldn't run a drain trench from the Brewing Pad, which had all our slope for drainage, to the sewer main without going below grade of the sewer. We had a pit put in at the location shown and put a sewer pump in to move the drainage from the Brewing Pad around the periphery of the building to the sewer main. Pretty slick, really. The Pad drains to the pit, which gets pumped out.
We had to do this because the building owner didn't want us heavily excavating the floor. Also, I have had slopes poured onto existing slabs and they crack up over time. The intent of this pour, 6" thick at the thinnest section, was to contain all our wet processes onto a Pad that should never crack (knock on wooden cask).