Using Sea Sand in concrete mooring.

[oldjags]

The way we do it in the islands is to get a polypropylene 55 gallon drum and fill it with concrete. Make 2 or 3 u-shaped loops out of heavy rebar to extend all the way to the bottom of the drum for the chain to attach to. If you need extra weight, you can add pieces of iron or steel to the concrete.

At low tide, roll the drum down to the water's edge and attach a couple of empty 55 gallon drums to the rebar loop. At high tide, the drum will be floating, and you can tow it out to the mooring location and cut the line to drop it in place. No need to break your back trying to manhandle 1,100 pounds of concrete!

For this, beach sand is fine, as it doesn't need to be as strong as if you were casting a concrete beam, for example. The poly drum will never rust or deteriorate, and the heavy rebar seems to last forever. I think the concrete helps protect it somehow.

For a bigger boat make 2 or 3 drums and chain them together.

[jmschmidt]

Cheapo rock wall builders use beach sand for their mortar. Not good, it is finer and under a magnifying glass you has round edges. Man-made sand and some inland sands have sharp edges which binds better.

[Falbala60]

If your mooring is in 20ft OK, but if in a 8ft area some monohull will hit them. I prefer large surface and flat pieces of concrete that, even if they loose 1/3 of their weights in water, will with time produce so much succion that the will be unmovable... forever. With time they will be flush with the bottom.

[tkeithlu]

Falbala60, you are technically correct, but the coastal sand in Florida and Georgia usually started life as granite in the Piedmont, and sorted out to be largely quartz by the time it gets inside our Tevas.

[PhilC]

Two issues here. 1. Using sand and 2. The salt on the sand.
1. Standard concrete uses a mix of sand and crushed gravel to maximise the strength and minimise the amount of cement needed. Because you are just using sand grains (note needs to be free of silt and clay) you might need to add a bit more cement (sand will have more voids than a graded gravel/sand mix) but you don’t need a particularly night strength so no issues there.
2. Salt is only a problem for corrosion or reinforcement not the concrete. So oversized the steel you cast in to allow for corrosion.

[captlloyd]

Originally Posted by Sea Q

Used a old truck engine block once

Many people use this method. I believe it was in Chapman’s that I read that a rowboat in a good blow can move a V8 engine block. Flotation, isn’t it great ?

[Tillsbury]

Sea sand is no good. In a past life our company used to sell sand to the Arabs, as the saying goes. All their sand is rounded off by the actions of sea or wind, and doesn’t give decent strength to cement. Builder’s sand has been crushed.

We never managed to sell ice to Eskimos though, sadly.

[Mike Banks]

It requires so much washing in fresh water to remove the salt, or neutralizing it with silver nitrate, that it is simply not worth doing. Buy some river sand or crusher fines and cast it properly, or your mooring eye will simply corrode and split the concrete.

I would not be using beach sand with any reinforcing--and that included the mooring eye.

[a64pilot]

I read an article the other day about illegal sand mining in India, it’s apparently a big deal there
River sand is I believe the go to for construction sand
https://www.nationalgeographic.com/e...-mining-mafia/

[dbaublis]

Seabed sand, beach sand and river sand are not suitable for concrete or cement. Construction sand has sharp, jagged edges. Beach sand is smoothed over. In a similar vein, seawater is no good for concrete due to the salt as others have said. I think the salt remaining on seabed sand would be insignificant if the concrete was made with fresh water but the smooth sand would be a no go. Even desert sand is no good for concrete. A desert full of sand and it is necessary to import sand for construction.

[Neeltje]

Aside from there being more coquina than silica in Florida's sand, the idea of using concrete as an anchor makes no sense. Concrete is a very strong but relatively light support material that can withstand compression no end (or almost), but it if it were heavy enough to make anchors, they wouldn't be making hulls out of it.

One of the most effective ad-lib mooring anchors I've seen is not an engine block, but a differential (rear axle). It weighs about as much, can be rolled on and off over the bow of dinghy, and sinks in with a lower but larger foot-print.

[a64pilot]

Originally Posted by Neeltje

Concrete is a very strong but relatively light support material that can withstand compression no end (or almost), but it if it were heavy enough to make anchors, they wouldn't be making hulls out of it.

My anchor is steel. I think there maybe a few of the larger vessels that their hull may be steel too.
Concrete obviously is a viable material, just dimensionally need more of it. I’d assume a few 55 gl drums full of it and chained together with a large steel eye set into each drum may be a pretty good anchor.
Materials easy to get and relatively inexpensive and you ought to be able to sink them one at a time and chain the mass together afterward.

Although I have a heart ache about “private” moorings myself.

[krissteyn]

The best mooring I ever saw was a steel plate 10mm thick , full size sheet approx 4 feet x 8 feet - 3 large hoops welded (properly) equidistant , to the top side.
Attached were 3 large chains meeting a large ring in the center. Mooring point.
When it was dumped at the desired site it gradually sank and the suction effect made it impossible to shift !
It held successive larger boats thru many storms and hurricanes. SXM , before snoopy island was developed - it’s still down there under the development.

Mushroom moorings rely on suction , but on a much smaller scale...

[4deckdave]

Henry Flagler built the Original bridges "keys viaduct" in 1916 using sea water and local sand, the cement was imported from Germany. The amount of cement and curing is key to its durability, along with the fact that no steel was used for reinforcing. Those bridges are still standing today.