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I have never used concrete. After you purchase it, how do you mix the components correctly in small amounts?

I only need to mix about 8 ounces of the stuff at a time for an art project. The project requires putting concrete on cardboard sculptures that are essentially cardboard cutouts of a dog. So, the sculpture is pretty thin. What can I do to put the concrete on just the back of the cutout properly? The sculpture is about 20 inches tall and 3-5 inches wide.

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First thing, you should use some concrete. Get yourself some ShapeCrete and follow the instructions to achieve a clay like consistency and try applying it to some test pieces of cardboard. You should be testing how well it will stick to the surface and if it will chip or break off easily once it dries. If the surface of your cardboard isnt right for what you're trying to do, you might try coating the cardboard in fabric before covering it in concrete.

Toga_Dan29 days ago

I would use mortar mix (sand and cement) mixing is as much feel as anything. I would put some wire coat hangers etc on the cardboard. Essentially mini rebar.

For these thin things on paper you should start with a slurry.
Get a bag of cement - that will be just the very fine powder with no and or other aggregates in it.
Also get some primer for tiling works with cement based adhesives - if in doubt ask in the tiling section of your hardware store.
On the cement you find instructions on how to mix it properly - we won't do that for the start but keep it as a reference for the final steps.
Take an old cup or whatever suits to put some of the primer in it.
Brush the cardboard with it and make sure not use too much.
The stuff is like water and the color helps you to see if the cardboard is fully covered.
Make one or two coats and let each coat fully dry.
You now have sealed cardboard that is much harder and stiffer than before and it will take the cement with ease.
Take an old soda bottle and put a cup full of cement in it, add 5 cups of water and shake the living hell out of the bottle once the lid is back on.
Fill in a pot or small bucket and use a big brush to keep mixing it while "painting" a thin layer of cement on the primed cardboard.
Let each coat dry before you repeat the process - the already used cement mix shall be discarded and replaced with a fresh mix.
Depending on the surface structure of your sculpture you will need 3 to 5 layers until it starts to look like a concrete surface.
Once you are there you can use the recommended cement water mix as stated on the bag, if you add sand make sure to get very fine sand, not the usual sandpit or cement mixing type.
Make the mix so it can be formed into balls without cracking or loosing shape.
Now just rub the stuff onto your sculpture with your hands.
To get a smooth finnish wet your hands and use very little pressure.
To prevent cracks keep it covered with a wet towel for at least a day before let it all cure properly.

seandogue1 month ago

Concrete? Concrete has good -sized pebbles in it. Are you using concrete or mortar or sand mix? Concrete will not go very far due to the pebbles increasing a layers miniimum thickness. Mortar and sand mixes are much mroe forgiving in that respect, since their granular sizes are far smaller.

Either/any way...Mix it with water until it has the consistency of a thick milk shake. Add water very slowly to the dry mix (ie less than you think you'll need) and mix thoroughly. repeat as necessary until the desired consistency is achieved. It's easy to add too much water, for which the only solution is to add more dry mix...this can take that 8 oz and make it double in volume in no time... add water slowly...

Once applied, cover with some loose plastic wrap to slow the drying process and occasionally uncover, spray with a fine mist of water, re-cover. It will take a couple of days or more to properly cure.. Make sure to keep it moist as long as possible for best curing.

It sounds like you only need very small quantities overall. In that case, it may be simplest to use the ready mixed type protduct that already has the ingredients in the right proportions. I'm thinking of products like Quickrete, which usually sells for about $3 per 50lb bag at stores like Home Depot. These products sometimes contain small stones that may need to be sifted out with a screen if your final product needs a really smooth finish.

kelseymh1 month ago

Read the directions. Mix in the same proportions (use math to work out how many ounces of each to get to your total of 8 ounces). To pour concrete into a shape, use a mold.

Josehf's recipe will work. Its done by VOLUME

3:2:1

3 gravel

2 sand

1 portland