What type of cement is used to make, for example a polished cement sink, or bath?

Question

It seems some magazines call it polished cement, others refer to the type of sand mixed with the cement and also some mention cement and plaster mix. See links to pictures;

http://www.pauldaviesdesign.co.uk/polished-concrete.html
http://www.koncrete.freeserve.co.uk/gallery/worktops/hollandpark/gallery_1.htm

I would like to buy and make this myself, as opposed to buying ready made products featured in the pictures.

Answer 1

If you decide to go the DIY route you will need to mix up several batches of the concrete that you decide to use. Concrete is a mixture of Cement, Aggregate, additives (if desired), and water. Cement comes in several different types and qualities. There is white cement, and there are several different types of gray cements (portland, plastic, etc.) Aggregate can range in size from very small sand to softball sized rocks, the smaller the ag the finer the concrete, the larger the ag the stronger the concrete. additives can be used to modify curing times (faster or slower), increase flexibility, increase strength, or change the color. Water sets off the chemical reaction that allows the cement to harden, the more water you add (to a point) the easier it is to work, the less water you add (to a point) the more waterproof it will be. For a sink you will want to use a relatively dry mixture, with small gravel and sand for the aggregate, some plasticizers for additives, plus some coloring agents if desired. for cement selection, white cement gives a glowing look to the concrete and allows for purer coloring, while the various grays give a more substantial, opaque look that yields grayish hued colors. To achieve a smooth surface you will need to spend hours working the surface of the concrete to make it perfectly polished and burnished, you will then need to let the concrete cure for at least a week, a fortnight would be better, all the while keeping it moist to prevent cracking. after it has cured for sufficient time you can either add a sealer to it to achieve a shiny surface or leave it unsealed to develop stains and mottling from use.

Addendum: I left out the part about using a suitable substrate to provide the needed tensile strength. Concrete has amazing compressive strength, you can weigh it down with tons of weight before it cracks. But, if you pull on it, it breaks down almost immediatly. To prevent this you must have some sort of support frame work that the concrete is shaped around. The popular choices are rebar (difficult to shape into a basin) or various sized steel meshes. I think that the perfect size mesh for a project like this one would be one that half of the large aggregate would be able to fit through if you were using it like a sieve.

Answer 2

You'll understand it much better if you put in the form of a table of ratio of volumes: Cement Sand Concrete 1 part 4 parts Cement+sand=5 prts Cement: 1/5 of concrete Sand: 4/5 of concrete (After dividing parts of cement and sand by total volume (parts of concrete) Therefore if x barrels of concrete made, Volume of cement used =x/5 barrels Answer is A Moreover as some of others said answer A and E ARE NOT THE SAME! X/5 MEANS x divided by 5 1/5x , I suppose was initially written as 1 --- 5x in your paper, this means 1 divided by (5x) Hope I've been helpful and you're not confused...

Answer 3

As well as the above you're going to need to figure out how to wet polish it, it would probably be worth making up a few sample "slabs" to test out your techniques. Flat surfaces might be ok but the concave bowl shape is likely to be problematic.

i notice that all the example pictures on the first site are flat surfaces, so it seems like even the professionals haven't figures out poliching a bath shape. I think a square bath would be uncomfortable.

The concrete needs to be re-enforced as shock or tensile stength is not its strong point.

Answer 4

Used to be a product called 'Marble-lite'.
(spelling could be wrong)
It is used to form swimming pools. Curved interior walls steps and so on are not a problem.
Usually applied by a skilled plasterer.