[QUOTE=jasong;489315]Off-topic: I've heard jackhammers can cause nerve damage. Makes me wonder if there's a better way of doing things.[/QUOTE]

Hire someone else to do it :D

[QUOTE=Mark Rose;489324]Hire someone else to do it :D[/QUOTE]

Actually, I've been enjoying doing it myself. And I don't know about nerve damage, but I have callouses on my hands I never had before, and muscles are showing which I didn't know I had!

For context, the attached picture is what I've been doing for the last couple of weeks. When we were building our house the "mixer man" would at the end of the day wash out the mixer, and dump it on the ground.

I couldn't figure out why the grass was refusing to grow, until I started "Hilti'ing" and discovered only about five cm of soil, and then up to 70 cm of concrete! I'm now up to about a five by five meter hole, and I'm not done yet!

[QUOTE=chalsall;489325]Actually, I've been enjoying doing it myself. And I don't know about nerve damage, but I have callouses on my hands I never had before, and muscles are showing which I didn't know I had!

For context, the attached picture is what I've been doing for the last couple of weeks. When we were building our house the "mixer man" would at the end of the day wash out the mixer, and dump it on the ground.

I couldn't figure out why the grass was refusing to grow, until I started "Hilti'ing" and discovered only about five cm of soil, and then up to 70 cm of concrete! I'm now up to about a five by five meter hole, and I'm not done yet![/QUOTE]

Yikes. Not many roots will bust through that!

Why not add a liner to the hole and then you have a pond or pool?

[QUOTE=chalsall;489325]I'm not done yet![/QUOTE]
Keep on! You may find a bunker or something valuable buried there... :razz:
(joking apart, that looks :yucky:, I feel bad for the vegetation in your garden; are you sure is from washing the mixer? it looks like you have found some ancient ruins or stuff... did the Spanish conquerors knew how to make concrete? hihi)

[QUOTE=LaurV;489411]Keep on! You may find a bunker or something valuable buried there... :razz:
<snip>
it looks like you have found some ancient ruins or stuff... [/QUOTE]

At last! Jimmy Hoffa's grave !!

[QUOTE=chalsall;489325]I couldn't figure out why the grass was refusing to grow, until I started "Hilti'ing" and discovered only about five cm of soil, and then up to 70 cm of concrete! I'm now up to about a five by five meter hole, and I'm not done yet![/QUOTE]
Two things come to mind:

(1) Heavy equipment

(2) Dynamite

[QUOTE=Dr Sardonicus;489629](1) Heavy equipment[/QUOTE]For the size that Chris is dealing with I would suggest a skid steer loader with a hammer attachment. That an a lowboy roll-off. It would take about 2-3 hours and would be done. Generally you can rent said device. And the pros would not call it heavy equipment, a skid steer is light equipment. A backhoe is often times not consider heavy equipment.

As far as explosives, you have to get it under or in the concrete. That usually involves a drill or hammer.

[QUOTE=Uncwilly;489638]For the size that Chris is dealing with I would suggest a skid steer loader with a hammer attachment.[/QUOTE]

If I knew the size I was going to be dealing with, I would have hired a backhoe. But I've actually been enjoying the work; very cathartic. Rather than sitting on my sorry ass typing, doing strenuous manual labour makes for a nice change.

Ironically, at the end of the day we're going to have to hire a dump truck, and a backhoe to load it. At first I thought a simple 5 m^3 skip would handle it, but now we'd need at least three! (Linda is not amused....)

[QUOTE=Uncwilly;489638]For the size that Chris is dealing with I would suggest a skid steer loader with a hammer attachment. That an a lowboy roll-off. It would take about 2-3 hours and would be done. Generally you can rent said device. And the pros would not call it heavy equipment, a skid steer is light equipment. A backhoe is often times not consider heavy equipment.

As far as explosives, you have to get it under or in the concrete. That usually involves a drill or hammer.[/QUOTE]
Renting a suitable piece of equipment sounds good to me. Once the disposal problem is solved, there would be the filling-in-the-hole problem. My guess would be, mostly cheap fill dirt, with a layer of relatively expensive topsoil on top. If you re-use the dirt that was there, you might want to add something to acidify it. The concrete may have made it quite alkaline.

Given the structures nearby, I don't think explosives are in the cards. Local laws and codes may not allow their use anyhow. Always fun to think about, though
;-)

[QUOTE=chalsall;489640]If I knew the size I was going to be dealing with, I would have hired a backhoe. But I've actually been enjoying the work; very cathartic. Rather than sitting on my sorry ass typing, doing strenuous manual labour makes for a nice change.

Ironically, at the end of the day we're going to have to hire a dump truck, and a backhoe to load it. At first I thought a simple 5 m^3 skip would handle it, but now we'd need at least three! (Linda is not amused....)[/QUOTE]

Any guess how much deeper you might need to go?
Is the end in sight?

[QUOTE=petrw1;489644]Any guess how much deeper you might need to go? Is the end in sight?[/QUOTE]

It's not the depth that's the issue, it's the breadth. Once I get through all the concrete and hit coral stone, I stop. Unlike all the other Caribbean islands which were formed from volcanic action, Barbados was pushed up from the sea floor.

And, yes, I think the end is in sight. I probably have another 10 square metres or so to deal with, probably to an average depth of about 50 cm. Or, ~12 metric tonnes still to breakup and move. (Ironically, because I'm not lifting the rubble too far, from a strictly physics perspective I'm not doing that much work! LOL)

And to Dr Sardonicus' point, yes, we'll mostly fill the hole with low-grade soil, and then top it off with soil-mix (like top-soil, but with additional organic material). And, yes, concrete is amazingly alkaline. I didn't know this until I did a bit of research, but it can have a pH of 13!