Concrete Tank Construction

How on earth can anyone tell you the cost when you don't say where you are?
The entire world doesn't live in the USA , and I expext there will be cost variation even across a country like USA UK or Italy. Central Mongolia could be a tad pricey too.

Del

Since he uses metric length units, he is probably not in USA. Good point nevertheless.

Unless he works predominantly for CalTrans, or a number of other State DOTs. I would however, suspect he is either not educated in or working in UK or India either since he indicated 3000 psi concrete mix and they do not use psi units to describe concrete or reinforcing steel. That mixed system of expressing lengths, areas, masses, and volumes in metric units, and then expressing materials strength in industry standard imperial units is pretty common amongst US State DOTs.

8m L x 5m W x 4m D x.03 = ?Cubic Meters X cost per meter of concrete.

If you are in Iraq the concrete is decent but you have to keep it covered and damp while it cures. This sounds simple;but, last week while I was pouring a clear well it was 121 in the shade (and there wasn't any shade) with a fairly constant 7 knot wind blowing. The burlap was drying almost as soon as it was sprayed with water. I'll be watching your replys with a good deal of interest as I am due to start a concrete water tank in October.

See post #2 for how to calculate material quantities of the components (steel, rebars, waterproofing).

Post #5 is helpful with regards to curing which is an essential step.

But also consider labor costs to erect and remove forms (also material costs for said forms).

Then there are the overhead and profit costs (for the Contractor).

Also include the site costs (time, materials, OH&P) for the excavation, backfill, etc.

I am assuming that this proposed tank is to be "a cast-in-place reinforced concrete tank" (not a pre-stressed concrete tank).

Engineering design and construction costs must be taken into account. These can be 25% or more of the construction cost.

As other posters have commented, more information is required here.

Joozmax6

8m L x 5m W x 4m D >

Is fundamentally Flawed Design.

Should be Cylinder/RIGHT CIRCULAR CONE Vertically--Tapering down to say 3m OD Dish bottom.

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<wall thickness is 0.3m>

A well designed wall thickness will be ~ 0.1m -- may be heavier at bottom dish.

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<how to estimate the reinforcement>

Linked to design. If you must have your rectangular:

with sharp edges IN/OUT-- you will end up needing aTon and still suffer the insult of cracked/leaked mess at CORNERS.

If you go for the Rational Cone/Cylinder/dished bottom-- you could complete the sure-long-lasting job with only 100Kg steel rings prefabricated and kept ready to insert as conrete mix is filled in -- say 100mm vertically apart at Dish OD and 300mm at very top rim.

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< And would ready mix 3000 psi be ok for this tank?>

Trouble with ready mix concrete suppliers is -they give you GENERALLY wanted stuff-ANYTHING!

If you want dense,high strength no-void reliable Concrete, then you should mix your own at site with water-Cement ratio the lowest possible(0.35~ say) using Super-Plasticizers. And then you have control --when which Ring-hoop-prefab rebars to insert at the OD of the Cylindrical/Conical over-the ground portion. If you order Ready-mix--they rush you : "Hurry up Mate - I have other places to go" . Result is you have 'SOME CONCRETE'. not Engineering -is it?

Is all this 'Optimization' Stuff too much for you and CR4 friends?

Well you can end up thinking--'To be -or not to Be"

I mean Concerned about waste.

Wish you all a happy Sunday.

MM

I couldn't agree more with MM. I have a crew on one project now that is attempting to repair a retanglular water tank. The cement was poured too dry by the Readi Mix guy, the crew didn't good good vibration to take care of voids and now we have a leaking tank. Hindsight being 20/20 we should have required a plastisizer in the mix.

Guys

Thanks for all your inputs. CIrcular-conical tank cannot be used for this matter because this is an aeration bio tank.

The tank is for an SBR waste water treatment facility. I now have the cost of cement, formworks, and steel. Kindly give me a good waterproofing system. I'll take one of the recommendations to mix my own cement. ready mix is not applicable because the location is quite remote. By the way I'm from the Philippines.

Can I suggest theat you use whatever waterproofing system you can find in your region but that you augment the waterproofing of the whole system by making the walls 400mm thick and designing to a concrete crackwidth of at least 0.2mm. 0.1mm would be even better.

"BS 8007: Design of concrete structures for retaining aqueous liquids" is our british standard for such design of which you will need a copy. Otherwise, perhaps you have a standard yourself in the Philippines?

Should your waterproofing system fail, and these systems only have warranties of 10 years or so, then your tank will not leak and will not deteriorate the reinforcement either. This does not take away the necessity of replacing the waterproofing system at regular intervals under a well defined maintenance regime.

By the way ready mix concrete can not be poured too dry for a good structure, it can just be poured to dry for the capabilities of the particular concrete crew to properly place and finish. If you utilize the right equipment and crew you can place concrete with less than a 2" slump, this will barely move down a ready mix hopper. Typical commercial/residential construction uses a 4" maximum slump mix, mostly because of constructability and labor cost relative to the product desired. However, drier concrete is always better for almost any structure being constructed, when properly installed it will provide higher strength, better shrinkage characteristics, lower porosity, etc.. It is just that most concrete crews are predominantly comprised of general to semi-skilled labor with minimal specialized equipment to handle placement of harsh concrete mixes. Super plasticizers are definitely advantageous, as well as curing agents (though water curing is the best practice if done properly). You should use a standard mix from a local batch plant as much as possible, as it can provide easier quality control. Batch plants control the water and materials better in the plant, only point that becomes a Quality Control issue is the washout water used by the truck drivers, they sometimes do not flush out all of the wash water and end up mixing more water into the mixes supplied fro the plant in the truck during transport. Any mixes done onsite need qualified quality control inspection onsite as contractors tend to add water to improve constructability and reduce labor time in placement/finishing (also sometimes they attempt to short the materials, particularly cement to save a little on cost). Of course then you need a batch plant with in 90 minutes from point of adding water to placement. As far as cost goes, other things beside labor and materials cost is the scale. Short loads can cost you twice or three times as much as larger deliveries (always try to order as much as you can properly place in a day and can use, as more is better for unit cost). A good resource for all the information you'd like regarding practice standards, materials, design practices, quality control/assurance practice, etc. is the American Concrete Institute. Code manuals like ACI 318, ACI 305, and ACI 308 are quite useful.

As far as the tank goes, I did not notice any mention of earth pressures, bouyancy, foundation bearing pressures, acceptable total and differential settlements, seismic liquifactions/settlement, seismic loads, importance of overlying facilities, maintenance of tank and overlying facilities, etc.. Waste water facilities typically can not accept much settlement and this can be a controlling factor effecting design of shape and size. You design the reinforcement based on the loads applied and the type of structural design. Reinforcement is designed to resist tension loads in concrete structures usually (it can be design to handle a portion of compression in some members). Typically you can imagine the steel as tensile tendons and the concrete working only to resist compressive forces through a cross-section. The basic equation underlying reinforcement design is M_u/φbd². Once you have calculated the reaction, you can use the many available look up tables to obtain the density of steel crossectional area relative to cross-sectional area of concrete inside of the tensile reinforcement members. There are requirements for lateral steel, shrinkage steel, minimum spacing, minimum cover, etc. that also must be met. In a tank you can end up with a earth, hydrostatic, wind and/or seismic load conditions to analyze pushing inwards when empty, and hydrostatic and seismic load conditions pushing outwards when full. Also, and moments or shears depending on wall/roof design transferred from the roof, operational roof loads, and snow loads. Based on the reinforcement requirements, reinforcement spacing, base shears, lateral loads resisted (and vertical loads in some cases), etc. you design the walls in a reiterative process to optimize the amount of reinforcement and concrete required to achieve the structural strengths required including the safety factor based on the importance of the structure,and seismic safety. For a Wastewater facility you will typically have a higher factor of safety for most facilities designed. Alot of the information you would need to analyze a design is available in the international building codes, and reinforced concrete design text books.

cost estimation now, is the easy part, once you have a design, you contact a local supplier or a few, and get a current price for concrete. Contact a few local contractors for there pricing, or you estimate labor, applicable markup for overhead and contractor profits.