What type of cement to use to make my own dumbbells?

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Old 03-26-20, 08:07 AM
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What type of cement to use to make my own dumbbells?

I want to make my own dumbbbells since the gym is closed and i'm on a budget.

I saw youtube tutorials and they used cement. Now i went to the store and saw they have different types of cement. Sand cement mix and instant cement. The sand cement mix was only $2 for a 55 lbs bag which is a great price.
However the instant cement cost $8 per 45 lb bag. This is a lot pricer if i want to make multiple dumbbells.

Question 1: What cement type is the best to use to make dumbbells? I need the cement to become rock solid. Can that be done with a sand-cement mix or is that too soft when it dries up?

Question 2: Will adding small rocks inside the cement mix, make the ''weights'' heavier? I can buy a 55 lbs bag of small rocks. So i figured if i add it in the cement mix, it might become heavier and i can save on cement.



Question 3: How heavy will a 45 lbs bag of cement be once mixed up? Will it still be 45 lbs when the entire bag is used up? I'm hoping to make 66 lbs dumbbells.

I'm trying to make something that looks like this:



Final question: Can i use a regular hand saw (used for cutting wood), to saw through this galvanized steel
pipe? The store wouldn't cut it for me.



I'll be really thankful if someone could help me in the right direction.
 
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Old 03-26-20, 08:40 AM
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I would use concrete mix which is a mix of stones, sand and Portland cement. If using pipe for the handle I would drill a hole through each end and insert a big nail or bolt to help key the handle into the concrete.
 
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Old 03-26-20, 09:07 AM
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A 40 0r 60 lb bag of cement should be pretty close to final weight once the water evaporates. as noted keeping a good connection between the handle is probably your week link.

Personally I would just find something around the house to lift or get into push ups, dips, pull ups, seems like a lot of work for short time of need!

 
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Old 03-26-20, 09:20 AM
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As to the last part of your question.
No you cannot use a regular hand saw.
You need a hack saw or something designed to cut metal.
 
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Old 03-26-20, 02:03 PM
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Thank you everyone! I did more research and indeed, concrete is the way to go. I will also make sure to put in a screw with bolts or 2 nails tied together with elastic bands to keep it more secure (as seen on youtube)

I willl return the metal pipe since i don't own a hacksaw. Thank you for making me aware of that.
-----------

Now i have a few final questions.
I plan to use stone grids inside the concrete mixture to make this heavier, and also because this way i need to use less concrete.
But how much is the max ratio of stone grid to concrete?
If i use a lot of stone peddles, will this make it more weak? Or will the layers of concrete keep it all together and keep it strong? I don't want it falling apart.

And if i use a plastic hollow pipe. Can i add the concrete mixture inside this hollow pipe, let it dry. And then turn it into a solid pipe that's strong enough to lift the concrete weights attached to it, once i make those afterwards?

You guys are truly amazing. I'm really glad i found this forum. Really nice helpful people. I appreciate it a ton!

 
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Old 03-26-20, 03:50 PM
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Concrete and stone are probably very close to the same weight!

You know, you can find dumbbells on Craigslist for cheap, then resell afterwards and cost is nothing!
 
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Old 03-26-20, 03:54 PM
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I didn't know it was almost the same weight. However i know a place where you can find a ton of pebbles for free. So i figured, adding those in the concrete mix would save me some money on concrete. I could also find some old tiles and smash those into pieces with a hammer and use that as filling as well.
I'm planning on making a lot of dumbbells and i'm a broke student, so every little bit helps.

As for craigslist. Right now every gym is closed due to the corona virus. And almost every dumbbell set is either sold out, or raised in prices incredibly much due to the supply and demand factor. Unfortunately i can't spend $100 for a pair of 25 lbs dumbbells. I want to make some heavier ones for myself too which would definitely be unaffordable right now, so i figured this would be a good way.

Ps: Do you think this pipe is strong enough to withold 16 lbs of concrete on each side? I want to make a 32 lbs dumbbell but i worry the pipe will snap.
If it's not strong enough, i can always fill the inside with concrete mix as well and hopefully that will make it more durable.

 

Last edited by cementnoobie; 03-26-20 at 04:46 PM.
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Old 03-26-20, 06:39 PM
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You should be able to find galvanized nipples (pipe) in the plumbing section. They are different lengths, I would probably choose a 3/4" diameter and 10 or 12" in length. The galvanized pipe will be quite strong enough to support the two ends. You could always add an elbow or something at the end to keep it embedded in the cement. The store might even have reject pipes that have had the threaded ends damaged that they'll give to you at a discount.

Plastic pipe filled with cement might work. Plastic has a tendency to shatter though, so I probably would stay away from using it.

Even a 1" wood dowel would probably work.
 
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Old 03-26-20, 06:58 PM
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The problem with galvanized pipes are 1. i don't own a hacksaw and i'm already on a budget so it would suck having to fork out extra money for it. And 2. i wanted to make a lot of dumbbells, and the galvanized pipes are twice as expensive as the plastic ones.

I also thought i only needed very little concrete and that i could use a lot of gravel as filler, so i would need less cement. (i can get gravel for free).
But someone else told me that it would ruin the consistency of the concrete and therefore make it not work.
I don't know how accurate this is, but if it's true and i'll legit need 30 lbs of cement to make a 30 lbs dumbbell, the cost will add up real fast.

i think i unfortunately have to bail on my DIY project and just do bodyweight exercises until the gym hopefully opens by the end of may or so.

Thank you everyone for your wisdom! I'll definitely remember it in case i ever going to work with concrete.
 
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Old 03-27-20, 04:21 AM
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simple answer: Do NOT make these yourself. Go onto Craig's List or Offer Up and get them for nearly free. Weight equipment can be found very cheap. Lots of folks start working out and quit. . .
Good Luck.
 
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Old 03-27-20, 04:45 AM
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Do not add stones to concrete. It already contains stones and if you add more it will make it weaker. If you try to go cheap the weights stand a good chance of breaking apart when you set them down. By the time you buy pipe for the handle and the concrete there is no way out of spending some money. Concrete is the cheap part and it's per pound price is even less if you buy it in the larger 80 pound bags. If you want to go really cheap then forget about making dumbbells. Start looking around for things that are free and heavy; pieces of scrap metal, logs, rocks. Heck go out in the yard with a shovel and dig a hole. There are a lot of things you can do for strength training that don't use dumbbells or free weights.
 
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Old 03-29-20, 05:53 AM
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Thanks for all the wonderful advice everyone!
I only have 1 last question:

Someone recommended to me, to make my own concrete.
However how difficult is this? And is it really cost effective?

I looked up a youtube tutorial, and they said to mix sand, with stones and portland cement.
However i would have to buy the portland cement of course.
The sand and stones i can get for free. But would this save me a lot of money if i plan to make, say 10 pair dumbbells of 20 lbs each? I need around 400 lbs of concrete.
Which right now. will come down to $4 per 20 lbs bag. So it will cost me $80 if i buy the concrete at the store.

Thank you again! Great helpful people on this forum. I really appreciate it.
 
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Old 03-29-20, 07:17 AM
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This is one of those posts that just screams, don't do it!

I just search my local CL, the best deal was a set of used dumbbell plates, handles, and collars, 200lb for $200.

You have no idea if your construction idea will just fall on your toes, and then what about when the gyms open, then you have a pile of crap that nobody will want and will likely be thrown away.

The used equipment could be sold for $160 so your net cost is only $40, same as what your proposing to spend and you could be working out this afternoon!
 
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Old 03-29-20, 07:38 AM
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you can mix your own concrete if you have sand and stone available a common mix would be 1 part portland cement 2 parts sand and 3 parts aggregate however you can change the mix to add more Portland to get a higher strength concrete but most of what you buy in a premix concrete bag is really just sand and aggregate probably not to difficult to mix in the small batches you would be making for larger amounts you would want a concrete mixer.
might want to look at mortar mixes that does not use stone also would probably want to reinforce the concrete with wire or small rebar and unless you want the weights removable from the bar you will probably want to incorporate some bar through the handle to secure it.
 
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Old 04-01-20, 06:33 AM
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Awesome reply Alan! Thank you for the great info. I'll try it out.

Ps: my very last questions.

Does it matter whether i use cold water or lukewarm water or hot water to mix my concrete?
I was going to use regular cold tap water, but just to be safe, i'll ask about it before i start mixing.

And does it matter if i let them dry in the sun light or should they be in the shades? The end color doesn't matter since i 'll spray paint it, but if it somehow affects the strength of the concrete, then i'll put it wherever it dries up hardest.

Thanks again everyone! I learned a lot from you and i appreciate it a ton.
Hope you all have a great day and stay safe with the corona craze out there.
 
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Old 04-01-20, 08:22 AM
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Concrete will cure faster at higher temperatures. So, if you want it to harden quicker use warm water. I only use warm or hot water when mixing concrete in winter. Otherwise I just use normal cold water.

Concrete can cure and get stronger for many months but 28 days is commonly considered to be "full strength" or close enough to it. If the concrete dries out the hardening can stop but if you keep it moist it will keep getting stronger and stronger. So, sitting the dumbbells in the sun will heat them up so they will cure more quickly but they will also dry out more quickly yielding less strength. I would keep them in the shade and try to keep them damp for a week before using them gently.

I would leave the dumbbells raw concrete and not paint them. If you paint the outer edge where they will sit you'll be scuffing off paint and leaving a mark when you set them down. You can paint the ends or areas that don't touch the ground for identification if you want.
 
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Old 04-01-20, 06:52 PM
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Great reply! I'll take your advice and let them dry in the shade slowly.

As for the painting it, is it a given it willl leave marks even if the paint is fully dried? If so, i'll leave them as they are. Awesome advice! thank you.
 
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Old 05-04-20, 05:05 PM
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Just want to post an update. The dumbbells and plates came out great! Couldn't have done it without your help. Thank you!



 
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