Does anyone know how to make concrete float? It can be any shape it just needs to float.?

Question

It is for a physics project and we have gone thru a bag of cement trying various shapes and sizes. Any help/suggestions would be appreciated.

Answer 1

just make into a hull like shape that displaces a volume of water that weighs more than the concrete does

Answer 2

The U.S. government made several cargo ships for what's referred to as the Concrete Fleet during the 1940's in an effort to try to save steel for munitions production during WWII. Several were made but the idea was scraped because the idea wasn't very practical. While one of those ships was being towed to sea to scuttled for use as a marine habitat, in the '50, it's tow line broke in a storm and it ran aground at Cape May Point, Cape May, New Jersey. Remains of that ship can still be seen in the water today, just off the beach.

More recently, engineering students at Temple University in Philadelphia, PA made 2 boats and have successfully used them in the Schuylkill River. They keep them in their Boat House in Boat House Row, on the Schuylkill ,where all the schools store their crew team boats. I saw this story during the evening news earlier this fall. It was fascinating. The boats look just like any other crew boat ... they're just made of concrete.

So ... yes, concrete floats. The displacement of the water just needs to exceed the weight of the concrete and it must be bowl or boat shaped in order to keep water from breaching the sides of the object you're floating.

Answer 3

I have been on YA for several months and this is the first question that has perplexed me. What a great question! Anyway, I can only suggest going to some shipyards, industrial waterways or docks and seeing what is out there. Or, call a concrete company ( talk to a boss/owner and not a secretary) and see what they say. I think your answer lies in the design which perhaps should resemble the hull of a ship. I also think for concrete to float you will need to put in salt water and not freshwater.

Answer 4

Think about the problem. Cast a 1" section around a bowling ball for instance.

Do the calcs. The volume of water displaced times it's density has to be greater than the volume of concrete used times it's density.

That is why you learn this stuff.

Answer 5

Is there a way that you can make air pockets in it? For example, could you cast it around wax shapes, making sure each shape included a long wax tube to the surface and then, after the concrete dried, heat the piece, melt the wax and pour it out?

Answer 6

To make any material that is heavier than water float, you need it to make it hollow, so that it displaces more weight of water than the weight of the material

so make a concrete shape like a boat hull, bowl - or even make it hollow to completely enclose an air or styrofoam core

to work out how thin you need to make the walls, you need to make the total weight of the concrete used less than the weight of water that the shape you make displaces. ie the total density of the shape made of concrete needs to be less than the density of water. you' will need to make a form (out of wood or fibreglass) to mould the concrete out of and you'll need to let it cure.

By the way - people make sailboats with concrete hulls. They also make docks from concrete that float.

check this link out for a range of structures made of concrete that float
http://www.vsl.net/downloads/VSL_technical_reports/PT_Floating_Concrete_Structures.pdf

Answer 7

Have you never heard of the concrete canoe contest that civil engineering students participate in every year? Just form your concrete into the shape of a hull.

Answer 8

I know that during WW2 Americans used concrete ships to transport things in Europe.
To make concrete float you have to make it cave, empty.
or you can try adding a lot of (expanded) polystyrene little balls in the concrete.

Answer 9

yes, it just has to displace more water than it weights without letting any into the shape. my uncle has a 16,000 lbs. concrete boat 1

Answer 10

Try using vermiculite instead of sand and make a shape that will displace a large area of water.