Easy. Fill it up with scrap rebar.

Some of the media for sand blasting is iron or steel which can replace the sand in the mix to add weight.

....or it could be made in cast iron instead, perhaps?

Heavy aggregate can be obtained but it is expensive. It is used for radiation shielding in hospitals and laboratories. I have used multiple steel plates for counter weights in the past, it is so much easier to adjust when changes are made.

In North America, the heavy aggregate comes from Canada.

How heavy must the weight be? Do you have a space/volume restriction?

Supported? Suspended?

There are no space/volume restrictions as such, they will be concrete segments used as part of an energy storage devise (Pat pending) It is not simply a very big Grandfather clock, there,s more to it than that as you might imagine and I need the heaviest cost effective material per cube metre that can be cast into a pre determined shape.It would be supended.

I have no pearls of wisdom for you. Use the heaviest filler you can afford, I guess.

Good luck!

This is the second time this subject has come up, so better hurry with those patent filings!

The concern that i have with adding materials is that they might chemically change, resulting in greater volume, and create internal ruptures and or spalling. So put in a heavier matrial that will not further react with the concreter. As i posted on the other thread, steel scale (oxide) is added to concrete for counterweights on the power shovels we see on construction projects. I know, because I sold it by the barrel from my shot blasters to the company making the weights.

milo

Many thanks for your post.

I will know who to come to for materials now as long as it's not coming from half way round the planet. As I said earlier ,weight is only a very small element in my machine but as you rightly commented you can't be too carefull with the protection of inovation.

All comments thus far should be taken into account. Special consideration regarding the compatibility of embedded materials with basic chemistry of a concrete is very important when considering longevity of this counterweight. You might wind up casting your weight with materials that will begin corrosion cell formation immediately. As mentioned, internal stresses could cause big problems in very short order.

If the actual weight [and keeping it constant] is a factor, you will need to waterproof the concrete once cast. Depending on the size of your weight, absorption of moisture will cause a significant fluctuation in the weight. Waterproofing the concrete will reduce moisture and oxygen content, thereby removing two of the four ingredients required for corrosion of ferrous metals encased in a concrete. This will go a long way toward a reasonable service life of your weight if that is important to you?

Well thought out and articulated answer.

milo