Making Weight Plates in Concrete

Industrial weight plates from 10kg and up are out of stock everywhere because of the pandemic, so I set out to make my own in reinforced concrete. The first try was today.

I bought a 30 kg bag of concrete for $8 and a $6 PVC pipe, built a square mold using wooden slats, and simply let the mixture dry for a whole day.

At around 40 cents per kilogram, hard to find anything cheaper. A quick Google search tells me the average weight plate costs 4 times more per kilogram.

Most Youtube tutorials about the topic give similar instructions, but I decided to make things simpler by using a square shape for the mold. It’s easier to find a piece of wood and cut it into four parts rather than trying to make something circular. I might have some balance issues when I try to deadlift—the plates might move around a bit on their axis—but it’s not a deal-breaker for me. Having a mold I can reuse is a big plus though.

Calculating the right proportions for the mold wasn’t too hard to figure out. The concrete I use has a volumic mass of 2000 kg per m3. I wanted to make plates of 10 kg, so I just did a cross-multiplication and obtained I needed a mold with a volume of 0.005 m3. The plate couldn’t be too thick to take less space on the Olympic bar, which forced me to make a square of 40 cm by 40 cm, with a thickness of 3 cm.

The next step is to make more plates (two 20kg, one 10kg, and two 5kg) and add some hooks to the pull-up bar to make it a squat rack.

The advantage of concrete over cast iron, except for the obvious price difference, is that I can leave the plates outside. It won’t budge, no matter the weather. Concrete is less solid than iron, but since I lift in my garden the soft ground combined with the grass acts as a cushion, in case I need to drop weight mid-air.

It’s also quite funny to write my name in the concrete while it’s drying. I’ll try drawing something next time.