DIY Concrete Dumbbells

I made this 10 kg (23 lbs) dumbbell out of really cheap and recycled materials. It does the job really well, except it's very large compared to a regular dumbbell.

I hope you'll find it useful, enjoy.

For a single dumbbell you are going to need

Materials

• Two 3 liter containers. I used 6 liter water bottles that I cut to size.
• 50cm (16") long metal pipe 3/4" in diameter
• Two 10cm (4") bolts 10mm in diameter and 4 accompanying nuts
• 25 kg (50 lb) bag of cement
• Pipe insulation or a pool noodle

Tools

• Drill
• X-acto knife or a box cutter

To learn how tall 3 liters would up to be I poured 3 liters of water in the bottle and marked the water level with a sharpie.

I started pouring 500 ml of water into the container and gradually added 2.5 liters of cement. This ratio might vary for you so start with a little bit first and go by feel.

You need it to act as an anchor so that the pipe won't slip out and smash your skull while you're doing triceps extensions.

To secure the rod in the center I cut out the hole in the cap of the bottle and slid the top portion of the bottle onto the rod. Then I secured it with a sticky tape. I let it get hard enough so that it would support the rod in the center, after which I took the top section off and let it cure overnight.

I had cut out the vent holes in the top portion of the bottle beforehand.

For the other half I did the same process. Except this time i had to slid the top part of the bottle onto a rod before I would insert it into the other half of the dumbbell. I propped it up in the corner so that the halves would stay parallel to each other.

For the handle I wrapped the rod with a pipe insulation and secured it with a strip of electrical tape on either ends.

• I would definitely make the handle 8-10 cm shorter. I didn't consider the indent on the bottom of the container which made the whole thing even longer. Now it's a bit awkward to do alternating bicep curls with it but for the other exercises that I do it's totally fine.
• The walls of the bottles are thin and flimsy and the mixture warped it. Which is not a big deal, it doesn't really interfere with the balance of the whole thing but it's kind of annoying. To avoid warping taping the whole mold with duct tape might be a way out.