Which cement should I use?

[Reborn]

Hello,

Here comes some information about the project:
The renovation in the laundry room is almost complete. Now I need to cast a platform for the washing machine and dryer, and I don't know what type of cement to buy that is suitable for my project.

The floor is made of concrete, and I plan to put some screws in the concrete floor and tie a mini reinforcement mesh to them to anchor the platform to the floor, then I will apply floor primer. Am I thinking correctly?

The platform should be about 135 cm x 65 cm, with one side about 3 cm high while the other should be about 5 cm (due to floor inclination to the floor drain).

A friend who has worked in construction was unsure about which cement I should use and said, go to the building store and buy a few bags of K47 (costs 450:- / each 25kg) another said buy Grovbetong (costs 59:- / each 25 kg)

Here are my questions:
What type of cement should I use?
How many 25kg bags will I need for the dimensions I mentioned?

Thanks in advance!

 

[Raskus]

You get 12-13 liters of finished concrete, so 3 bags of this: https://www.byggmax.se/finbetong-25kg-p0102

 

[Reborn]

You get 12-13 liters of finished concrete, so 3 bags of this: [link]

Nice, very cheap, do I understand the text correctly that only about 3 liters of water is enough for a 25kg?

I want to take the opportunity to ask another question...

I'm going to build a wooden frame for casting and don't know what to have under the frame for sealing between the frame and the floor so the concrete doesn't leak underneath or do I need to have something there?

 

[ArneTW]

Depends on how uneven the floor is.

It shouldn't be necessary. But a little sand or other backfill can be good.
If it seeps out a little, it probably doesn't matter as it can be removed when dismantling the form and before it sets.

Remember to anchor the form downward with weight or other anchoring.
Wood floats in concrete and then everything runs out...

/ATW

 

[Raskus]

Nice, very cheap, do I understand the text correctly that only about 3 liters of water is enough for a 25kg?

Thought I'd take the opportunity for another question...

I am going to build a wooden frame for casting and don't know what to have under the wood for sealing between the frame and the floor so that the concrete doesn't leak underneath, or do you need to have something there?

Simply follow the instructions on the bag.

 

[roli]

You should not buy cement (an ingredient in concrete) without some type of ready-made concrete mix to which you only add water. There are many variants available in hardware stores. Exactly which one you should buy depends a bit on the area of use and casting thickness. You mentioned a thickness of about 30-50 mm. In this case, a fine concrete should be suitable, where they recommend a casting thickness of between 25-100 mm.

Remember to "roughen" the surface you are casting against and saturate the surface with water so your old concrete doesn't absorb the moisture from your new casting, as that will cause it to detach from the substrate. The wetter your old concrete, the better, but make sure there is no visible water surface when casting. After casting, make sure to cover your casting with plastic to reduce water evaporation. The slower the concrete cures, the better the result, especially with thin overlays. Then lift the plastic and spray your newly cast surface often during the first few days, as the concrete "consumes" water during curing. A dry surface cures faster and is more prone to cracking.

 

[Reborn]

You should not buy cement (a component of concrete) but some type of ready-made concrete mix where you only add water. There are many variants in the building trade. The exact one you should buy depends a bit on the area of use and the casting thickness. You mentioned about 30-50 mm thickness. In this case, fine concrete should be suitable where they recommend a casting thickness of between 25-100 mm. Make sure to "roughen" the surface you're going to cast against and saturate the surface with water so that your old concrete does not absorb the moisture from your new casting; otherwise, it will detach from the substrate. The wetter your old concrete, the better, but no visible water surface when you cast. After casting, make sure to cover your casting with plastic to reduce water evaporation. The slower the concrete cures, the better the result, especially with thin overlays. Then lift the plastic and spray your newly cast surface often during the first few days, as the concrete "consumes" water during curing. A dry surface cures faster and is more prone to cracking.

OK, do you mean that the variant Raskus recommended is suitable? https://www.byggmax.se/finbetong-25kg-p0102

 

[roli]

It will work perfectly fine.

 

[Reborn]

It will work perfectly fine.

Nice, I'm going now to buy the stuff

 

[ArneTW]

Since I don't like plastic, I have used rag rugs instead.
Easy to keep damp, just water with a watering can, and if you're lucky that they are made of rags with water-soluble dye, you can add a little life to the concrete surface.

/ATW

Ps I guess it would work with a couple of old bath towels too... ds

 

[Reborn]

One last question before I go...

Is this the right primer?
https://www.byggmax.se/primer-puts-betong-v-p197000#722=14527

 

[roli]

Well, rag rugs or bath towels are indeed easier to water, but they dry faster and then draw moisture out of the concrete. The purpose of the plastic is to "trap" the moisture so that the concrete doesn't dry out too quickly. It might work but requires more attention than using plastic, as the surface needs to be wet.

 

[roli]

One last question before I go...

Is this the right primer?
[link]

What are you going to do with it? It will take some time before you can paint your newly casted plinth.

 

[Reborn]

What are you going to do with it? It will take some time before you can paint your newly cast plinth.

Oh, I thought you would need to apply primer before the concrete, the floor is painted, I know nothing about it, if you don't need it then I'll go without

 

[slacker]

Always Primer for adhesion! As someone said - Roughen up the surface/remove paint before primer for even better adhesion of the concrete cake.

Good luck!