Cost: $6 for the mold and then 5 cents a lb.
Project time: maybe an hour per plate plus dry time
Difficulty: It's just mixing cement for the most part so not very hard at all
- Small shovel or trowel to mix and spread cement
- Scissors (to cut tape)
- Saw or serrated knife (to cut plastic mold)
- Wood saw and drill (optional, if you make the wood frame)
- Empty Spray Bottle (optional but useful to spray water)
- Caulk Gun (if you decide to use caulk and you buy caulk that needs the gun)
- 80 lb. bag of Quikrete cement mix (I used the "just add water" yellow and black bag mix)
- Duct Tape (optional but a cool addition so I recommend it)
- 2 inch diameter PVC pipe
- Round storage bin or oil pan or other round plastic container with a 15" diameter
- Caulk (optional, you could use tape, I think)
- Few handfuls of dirt
I cut this video down to the essentials so I won't explain the whole project step by step here, just watch the video. However, I will make a few notes below; things I didn't have time to elaborate on in the video.
A TEMPORARY SOLUTION
To me this isn't a permanent thing. Concrete is simply not as strong as we want compared to metal plates which are basically indestructible under normal use. Though concrete has high compression strength, the way forces would be applied to a plate on a bar being aggressively set down on a heavy deadlift would no doubt break the cement over time. Concrete also is not as dense. This means it will take up more space on the bar and result in less weight you can fit on your bar. It's basically like half as heavy as iron plates. So a 45 lb. concrete plate would be the same size (at least) as two 45 iron plates. That means if you could cram 800 lbs. of iron plates onto your bar, you could only cram 400 lbs. of concrete plates.
Also, I do not suggest you use only concrete plates. If you don't have any weights I do not recommend this as your solution, unless you don't plan to pull off the floor, meaning deadlifts or power cleans or rows, etc. I don't trust cement to be strong enough to handle the stress of setting down a heavy deadlift.
I suggest you have at least a pair of 45 lb iron plates, as well as the smaller increments, 25, 10, 5, and 2.5 lbs. You can make smaller increments out of wood or industrial washers. I made a post about that, look at the Project Index for it. I personally bought one of those 300 lbs. weight sets from the sporting goods store. I think that's a decent starter set. When it costs like $200 you do get a bar that will last at least a year, plus the 255 lbs. of iron plates, including all the smaller increments. So these concrete plates make a decent temporary addition to an iron set.
Eventually though you want to find some cheap used iron plates because concrete weights are not a long term solution in my opinion. Even if they hold up, you'll eventually run out of space on the bar. Now I suppose you could probably get something like 500 lbs. on the bar using a combination of iron and concrete weights. So if you never intend to deadlift more than that I guess it might be good enough.
But to me this is a temporary solution until I hit the motherload of rusty 45s from someone on craigslist or a garage sale whom doesn't care about lifting and just wants me to take the stuff away for like 50 bucks.
This I am ashamed of. I didn't put quite enough thought into it before I started the project. I basically decided on a size, a thickness, and then I poured my plates to that thickness. As a result, the two plates I poured probably aren't the same weight. Nor are they a specific precise weight. I was roughly intending them to be 35 lbs. I think they will be a little more than that after they cure. And if they both end up being the same weight it would be pretty lucky. Since I know how to do this right, I'm ashamed that I didn't do it this way. It didn't occur to me until I was already done.
I recommend you weigh out your dry cement mix. So if you want a 35 lb. plate dump 35 lbs. of dry mix into your mixing bucket. As a weightlifter I can only assume you have a somewhat accurate bathroom scale. At the very least it will be consistent so both plates will be the same. By doing this you will ensure that all the plates you cast are as close to the same weight as you can get them. This is what I should have done but I just didn't think of it in time.
As a result, though my plates will be roughly the same size, they are probably not going to be exactly the same weight. It won't be a big deal since I can just add micro plates to compensate when they are on the bar. My plates are also probably going to be a bit more than the 35 lbs. I was intending. Again not a big deal. But it's just easier if you weigh your mix. That way you'll only have to mix it up once and pour it into the mold. You will not have to mark your mold either. For what it's worth, 35 lbs. will be somewhere around 2.5 inches thick, just an FYI. I like this thickness because cement doesn't have a high tensile strength so having it thick is a good thing. I don't really recommend making light plates out of cement for this reason. They won't be as strong if you make them thin and if you make them thick but light you just waste space on your bar.
The way PVC is labeled is by the inner diameter. So when I tell you to use 2 inch diameter PVC pipe that is what it is labeled in the store. The actual outer diameter is more like 2.25 inches. So the hole it leaves in your cement plate will be 2.25 inches, which is more than big enough to fit on the bar. We make a better fit with a duct tape ring. See the video for that. I just wanted to clarify that 2" pipe is what it will be labeled as, and it will have an outer diameter of 2.25 inches.
THE EXTRACTION PROCESS
I made wooden frame to help me take the plate out of the mold by myself easily. I had the scrap wood and tools so I spent no money on it. If you don't have this stuff you don't have to make it. I'm sure there's something around the house you could use to support your plate as you tip the mold upside down. If the inner PVC pipe holds tight to the cement like it did for me in the video you might even be able to just pull the plate out using the PVC as a handle of sorts. The PVC did not hold to the cement like this when I cast me first plate though. Anyway, it's not rocket surgery here. Point being, you don't have to spend money or time making that "extractor" if you don't want to. I only did it because I had the stuff and I was bored and figured it would make things really easy, which it did.
Also, when I cast my first plate I sprayed the mold first with some oil. The idea being that it would help release the concrete. The second plate I cast I did not do this. It doesn't seem to matter. The concrete will not stick to the plastic mold. However, I did have a hell of a time getting the PVC pipe out of the second casting. This may or may not have anything to do with not oiling it. The pipe also was a little wiggly (i guess the caulk didn't hold as well) the second time, so it may have set slightly off kilter, which is what I'm betting on. Point being, you don't need to oil it or use any kind of mold releasing agent. But if you want to spray it down with some WD-40 it won't hurt anything.
MARK YOUR PLATES
Once you let your plates cure for a few weeks I would suggest painting their weight on them. This is especially true if you messed up like I did and both plates don't weight the same amount. Mark their weight on them so you know exactly what they weigh.
In the video I show you how to line the inside of the plate with duct tape to protect your bar and give it a better fit. Since then I realized there is another option. The PVC pipe you used to cast the center hole is the perfect size to slide over the bar sleeves on an Olympic bar. So you could cut down a length of that PVC the same thickness as your plate, then hammer it into the center. It will fit very tightly. As you saw in the video I had a hard time getting the pipe out of the plate when unmolding. I had just a hard of time hammering in the new shorter length of pipe. I'm not sure how this will affect the plate in terms of the concrete expanding. But it fits beautifully on and off the bar with ease.I would say the PVC core is nicer, assuming it doesn't have some unforseen negative impact on the expansion of the concrete.
That being said, using concrete plates is a temporary solution so you want the price to be as low as possible. I had the scrap PVC so decided to try it out.