weight of concrete

[Chain Bender]

Today I made a balast weight for my L3200. I used 7 1/2 80# bags of ready to use concrete mix. I figure I added about 2+ gallons of water to each bag.

NOW......here's the question. How much weight will a gallon of water add to the concrete when it has dried. I know some of the water will evaporate through the top while it is drying, but the mix is in a plastic drum.

As I mixed each bag of concrete mix and poured it in the barrel I also threw in some busted up chunks of a slab made out of the exact same mix. I estimate I threw in about 100# of the chunks. I also think the internal welded frame and the barrel weighed about 40-50#'s.

I think the barrel will weigh in some where between 700 and 750 pounds. I have a 27" piece of 3/4" cold rolled round stock for lift pins. If I keep the lift arms pulled/pushed against the barrel as close as I can, will the 3/4" pins be strong enough? I know it's a little late to ask now, but I've been thinking about it since the minute I walked away from the barrel this afternoon.

thanks for your time.

CB

 

[ruren]

Cured concrete weighs about 145 pounds per cubic foot. My gut feeling is the 3/4" stock should be plenty strong enough if done correctly, but that is just my opinion.

Rich

 

[k0ua]

Well I dont know about the 3/4 cold rolled, probably be ok, but I used a commercial drawbar from TSC. of course it is 7/8 on the pins. It was 26 dollars. Now as to the water , almost all of the weight stays in the form of hydrates locked into the concrete matrix.

James K0UA

 

[Shmudda]

Well, lets calculate the load the pins can take....

Pin material say has a yield stress of 18,000 psi, ultimate stress 36,000 psi.

Area = Pi * Radius squared

Area Pin = 3.1412 * .375 squared

Area Pin = .442 inches squared

.442 inches squared * 18,000 psi = 7956 lb

Each pin can withstand 7956 lb with a safety factor of about 2. So that means that (2) pins can hold 15,912 lb with a safety factor of 2.

Needless to say, I bet your tractor doesnt weigh that much......

Edit: Tractor weight (4WD Hydro) = 2623 lb

You are fine!!

Craig

 

[Chain Bender]

Well, lets calculate the load the pins can take....

Pin material say has a yield stress of 18,000 psi, ultimate stress 36,000 psi.

Area = Pi * Radius squared

Area Pin = 3.1412 * .375 squared

Area Pin = .442 inches squared

.442 inches squared * 18,000 psi = 7956 lb

Each pin can withstand 7956 lb with a safety factor of about 2. So that means that (2) pins can hold 15,912 lb with a safety factor of 2.

Needless to say, I bet your tractor doesnt weigh that much......

Edit: Tractor weight (4WD Hydro) = 2623 lb

You are fine!!

Craig

XXXXXXXXXXXXXXXX

Tractor also has an LA524 on it.

The internal frame is 2X2X.250". Inside of the 2X2 cross bar or draw bar I put a full length (side to side) piece of 1" EMT and the cold roll runs through it. I think with a 3/4" bar 27" long I'll have about 3.5" of pin sticking out of the barrel. With a clinch pin hole at about 3/8" from the end of each end. SO, my lift arms have about 1.5" of ball width. That will make the usable length of the pins about 3". I have kept rolling the 3/4" bar so it won't stick to the concrete. It is very possible that if the 3/4" bends I can cut it off at the barrel and punch it out either side and replace it with a 7/8" piece. Hopefully that won't be necessary. (fingers crossed)

CB

 

[swick1]

Well, lets calculate the load the pins can take....

Pin material say has a yield stress of 18,000 psi, ultimate stress 36,000 psi.

Area = Pi * Radius squared

Area Pin = 3.1412 * .375 squared

Area Pin = .442 inches squared

.442 inches squared * 18,000 psi = 7956 lb

Each pin can withstand 7956 lb with a safety factor of about 2. So that means that (2) pins can hold 15,912 lb with a safety factor of 2.

Needless to say, I bet your tractor doesnt weigh that much......

Edit: Tractor weight (4WD Hydro) = 2623 lb

You are fine!!

Craig

I know this is splitting hairs, but since the top of the pin is in compression and the bottom is in tension, wouldn't the maximum load be less than that? You're only assuming axial loading right?

I always thought it would be best to treat the pins as if they were loaded in shear. Correct me if I'm wrong here, but my understanding of the process is to find the shear stress at the neutral axis, where it will be greatest in the part and use that as the limiting factor for the load.

The formula for the maximum shear stress in a solid cylinder is:
s = (4F)/(3*pi*R^2).

Rearranging to find the force, the equation now becomes:
F = (3/4)*pi*R^2*s

F = (3/4)*3.14159*0.375^2*18000 = 5677.8 lb per pin

 

[JB4310]

Today I made a balast weight for my L3200. I used 7 1/2 80# bags of ready to use concrete mix. I figure I added about 2+ gallons of water to each bag.

NOW......here's the question. How much weight will a gallon of water add to the concrete when it has dried. I know some of the water will evaporate through the top while it is drying, but the mix is in a plastic drum.

thanks for your time.

CB

The answer is almost exactly what the water weighs, 8.3 pounds per gallon.
It a crazy thing called hydration that turns water into a solid form. Goes against what we imagine happens to water to all other scenarios.
The water is chemically converted to a solid and stays there forever :confused2:

I tried to find a simple link that could explain it but couldn't.
It's complicated, I've worked with masonry all my life and I always thought the water just evaporated, till I learned about hydration.

JB.

 

[GPintheMitten]

The bottom line I think is that it weighs what the inputs weighed. Unless too much water was used, then some will evaporate. But not much.

The water chemically bonds with tricalcium silicate in the portland cement. In this chemical reaction both the inputs are changed and you are left with a different compound. While some water may be left this would be due to hydration being complete for all the available portland cement. It is a specific ratio of water to cement.

That water is not a solid form of water but the new compound is solid.

The equation for the hydration of tricalcium silicate is given by:

Tricalcium silicate + Water--->Calcium silicate hydrate+Calcium hydroxide + heat

2 Ca3SiO5 + 7 H2O ---> 3 CaO.2SiO2.4H2O + 3 Ca(OH)2 + 173.6kJ

Here's a link:

Concrete: Scientific Principles

 

[tcartwri]

Today I made a balast weight for my L3200. I used 7 1/2 80# bags of ready to use concrete mix. I figure I added about 2+ gallons of water to each bag.

NOW......here's the question. How much weight will a gallon of water add to the concrete when it has dried. I know some of the water will evaporate through the top while it is drying, but the mix is in a plastic drum.

As I mixed each bag of concrete mix and poured it in the barrel I also threw in some busted up chunks of a slab made out of the exact same mix. I estimate I threw in about 100# of the chunks. I also think the internal welded frame and the barrel weighed about 40-50#'s.

I think the barrel will weigh in some where between 700 and 750 pounds. I have a 27" piece of 3/4" cold rolled round stock for lift pins. If I keep the lift arms pulled/pushed against the barrel as close as I can, will the 3/4" pins be strong enough? I know it's a little late to ask now, but I've been thinking about it since the minute I walked away from the barrel this afternoon.

thanks for your time.

CB

I used virtually the same amount of material in my rain barrel / balast. I used 3/4" threaded rod, and haven't broken or bent it yet. It's actually a little on the light side because the barrel sits tight in between the wheels, and has little mechanical advantage. It is nice and compact though, and I use the open area above the concrete as a chain and tool carry all. This is on a CT235.

 

[Chain Bender]

I used virtually the same amount of material in my rain barrel / balast. I used 3/4" threaded rod, and haven't broken or bent it yet. It's actually a little on the light side because the barrel sits tight in between the wheels, and has little mechanical advantage. It is nice and compact though, and I use the open area above the concrete as a chain and tool carry all. This is on a CT235.

I left about 8-10 gallons out of the 190 litre barrel for the same thing. I'll try to take some pictures tomorrow and post them.

So an 80 pound bag of readi-mix, mixed, should weigh 100# +/- a few when dried. How many cubic feet does a gallon of liquid take up?

thanks to all.....
CB