Using Sea Sand in concrete mooring.

[Popeye2]

Is Using Sea Sand to make a concrete mooring more or less ok if i soak it in warm fresh water to get the salt out?
Could use extra portland cement. Will be in 4 tires with rebard etc.
Will go in mud . It will sink and be undisturbed.

[MNGator]

It can be done but not a great idea. Sea sand tends to be finer and the resultant cured concrete will have less tensile strength. You can rinse the sand, but you won’t get completely rid of the salt further increasing your chances for a weak mix.

[tkeithlu]

In any case your goal is concrete, with actual rocks included, rather than mortar. I'm guessing you're in an environment with lots of sand and no rock, e.g., Florida. For this small job, buy premix, such as Sacrete, which already has the sand and rock included in the bag.

[akopac]

I once made a mooring with a 2 man inflatable raft full of concrete with a chain. The idea was to tow it out and pop it and drop it. I popped it after hanging it from the bow and pealing the raft off, then dropped it. It all went as planned. A year or so later I came out to my my Catalina 30 about a 1/4 mile away from where it started after some heavy winds. Concrete isn’t that much heavier than water relatively speaking. I ended up getting a Door-mor mooring. http://www.dor-mor.com/

[a64pilot]

Sea sand has been polished or rounded and won’t work to make concrete. It will fall apart if you use it.

[tkeithlu]

I used sea sand in my sand blasting cabinet; thought it would be cheaper than bagged stuff. Wrong. It seemed like even glass beads worked better, and the salt made it clot. It is, as a64Pilot notes, rounded.

[David M]

The density of seawater is 1029 kg/cubic meter. The density of concrete is 2400 kg/cubic meter. The density of iron is 7874 kg/cubic meter.

So if you subtract the weight of the concrete from the water you are left with a density of 1371 kg/cubic meter. The concrete will weigh less underwater in proportion to the difference in densities. This is much less than if you you were to use an iron anchor which works out to 7874-1029=6845 kg/cubic meter.

Concrete is cheaper but iron will be much more effective by a factor of 6.65 (6845/1371=6.65) This is solely if you take weight underwater into consideration and not anchor design.

We always use iron anchors for oceanographic instrument moorings off the research vessel for that reason. Some people have wanted to make concrete moorings and we have had to explain why it is not the best idea.


Did I get the math correct, you physicists?

[yalla]

Originally Posted by David M

The density of seawater is 1029 kg/cubic meter. The density of concrete is 2400 kg/cubic meter. The density of iron is 7874 kg/cubic meter.

So if you subtract the weight of the concrete from the water you are left with a density of 1371 kg/cubic meter. The concrete will weigh less underwater in proportion to the difference in densities. This is much less than if you you were to use an iron anchor which works out to 7874-1029=6845 kg/cubic meter.

Concrete is cheaper but iron will be much more effective by a factor of 6.65 (6845/1371=6.65)

Did I get the math correct, you physicists?

assuming your iron anchor is one cubic meter (!!!) of iron...

[tkeithlu]

I'm married to a chemist. You nailed it, David.

I should have mixed my bullet lead into cement when I ballasted my boat, rather than bagging the stuff in tar. Now that would have been a very dense concrete.

[David M]

Originally Posted by yalla

assuming your iron anchor is one cubic meter (!!!) of iron...

The explanation is density, which is weight (or mass) divided by volume.

[Sea Q]

Used a old truck engine block once

[David M]

I have used engine block, wierd iron stuff, railroad wheels and dumbbell weights which were purchased through Amazon Prime, which got them free delivery so they were relatively dirt cheap....not much above the cost of scrap iron. Have used Dor-Mor anchors as well. The nice thing about dumbbell weights is you know exactly how much the mooring is going to weigh.

[Falbala60]

Sea sand is DUST.. calcium dust ! a REAL SAND is from granite, quartz.

[Ken Z]

Don t use sea sand or portland. use premix concrete, saccreat or redi mix that has rock pre mixed, the rocks give the strength, also ther is extra strenght variety I would use. your rebar should be imbedded at least 2” in the concrete

[David M]

I would not use concrete at all. Go to a junkyard and get some iron. Get some smaller pieces with holes in them that you can lift, chain them all together and drop it over the side.