How to bust out Concrete Pedistle

I'm not really sure how to describe this other then a 3'x3'x3' concrete block or pedistle, believed to originate from the 1930's (when the house was built).
I'm looking to break it down to a hight of 6" to 8" in hight. Once down to this hight, I'll level it off and fill in the voids to make the whole corner level at the 6" to 8" above the rest of the floor (corner us not level, so I can't go right down to the ground). Once it's down and level, I can move my water softener and DHW tank to the corner and free up some wasted space.

Over the holidays (one day with no kids and a box of beer), I tried drilling 5/8" holes, about 6" deep, 4" apart in a grid pattern vertically. On the horizontal, I did the same, lining up the horizontal holes with the verticle. Did this to the top 1/4 of the block. Figured a couple good whacks with a hammer should knock off manageable chuncks. Total fail.

Under the painted surface, I noticed there was steel rods, almost like rebar, but couldn't confirm it was. The concrete was mixed with larger stones under the surface and did contain some sort of rope mesh, almost like drywall tape type mesh.
Once the top surface was removed, the inside was very sand like, crumbling pretty easily.

So... my idea of using the pilot holes as fault lines was a fail. Any other suggestion for busting this thing down?

Here is the block before I attacked it.

 

A pro concrete cutting company could cut it into manageable chunks with a water jet but if you want to to do it yourself rent an electric pavement breaker (AKA jack hammer).

 

Since you have bore holes all you need are some explosives...

I would probably rent an electric jack hammer. First I would put a sheet of plywood between the pedestal and your water softener to protect the equipment. Then get or build something secure to stand on so your feet are at about the same height as the top of the pedestal. Put on safety glasses, ear plugs and a mask for the dust and plan on a boring, tiring and sore day.

 

Man, I wouldn't mess around with trying to cut it down... I'd smash it with a sledgehammer and then form up a new one. The old one surely isn't one solid block. Looks like a job for when all the kids are over and you are out of beer. LOL

 

I was thinking of dragging the air compressor out of the garage and using the air hammer. Would leave the compressor outside while working and run the air hose through the near by window.
Would be slower then a full out jackhammer, but a lot cheaper as I have the tools and bits.

Using the air hammer on the pre-drilled holes might do the trick.
Definitely going to put up a protective wall to protect the softener and other equipment from flying rock. I had laid a scrap piece of wood against the softener to protect it when I tried the sledgehammer, but couldn't go all out with it as I was still sending small 1" chunks flying.

This is not a time sensitive job as I don't have all the pipe fittings and other components to relocate the DHW tank and install the new plumbing.

I'm still very interested to see if it's solid concrete, or if the center is filled with large rocks (common from what I have seen of that time).

 

Do yourself a very BIG favor, and just pick up a small amount of S-mite. Or similar product with different brand-name, as there are quite a few of them out there. Best source would be a concrete supply place. It's an expanding cement used for non-explosive concrete demolition. Mix it up to a thick cream consistency, pour it into all of the vertical holes you drilled, and then wait a few hours. You'll be pleasantly surprised at how cracked and broken up your chunk of concrete will be--just throw the pieces into a wheel barrow and haul away. No mess, no fuss, no dust. Back in my DOT days, we used it to break up boulders the size of a VW beetle that had fallen off steep slopes onto the roadway below--they were too big for our biggest rubber-tired loaders to move.

 

I remember stuff like that when I was the IT admin at a concrete and aggregate company. Now that you mention it, that makes perfect sense.
The physical labor bit doesn't bother me, but the mess of beating concrete is a PITA.

Thanks.

 

I thought I would post a quick update in this thread.
Picked up a small pail of expanding concrete (can't remember the brand). It's temp range was 50'F to 77'F and was highly recommended at the retail store for the concrete company I use to work at a number of years ago.
Without breaking the bank on equipment and bits, I used 5/8" drill bit and bored out the holes described in the OP.
With the cold snap here, the basement was close the the 50'F mark (thanks to the -35 to -45'C weather outside).

With the temp near the bottom end of the temp range... It's like watching grass grow. Took the side closer to the boiler ~36 hours to form a usable crack. Removed the first row and left the rest as is. 4 days later, the second row now has a usable crack.

So... Lessons learned so far;
- Make sure the concrete and surrounding area is not around the lower end of the temp range.
- Larger diameter holes with greater distance between them is better then smaller diameter holes with smaller distance between.
- Use long enough bits to 85% to 95% through what you are trying to break up or it'll be a few month project. I used a 6" bit to keep the chunk size down (easier for hauling out of the basement) and saved a ton on the cost of the bit. Will lose that savings in time spent doing this in stages.
- Not the cheapest method of removal. If conditions permit, air hammer or sludgehammer would be quicker and cheaper. Estimated costs include ~$70CND for 11lb bucket of expanding concrete, $30CND for drill bits (1/4" and 5/8", 6" long concrete bits), ~$100 for a new corded drill (technically unrelated to the project as the drill I was using was near it's end of days before the project started.)

 

If you ever need them, Harbor Freight has an inexpensive set of 12" long masonry bits that is pretty inexpensive. I bought two sets thinking it would be junk but they turned out to be good quality and the two sets was less than the cost of one bit from my local home center.

 

I'm adding Harbor Freight to my list of places to stop at when I go to FL in a few weeks. They have a number of items that are a lot cheaper then what I can get them here.

Here is the one bit I picked up (had the kids, so couldn't shop around, was a quick in and out);
Bosch | Blue Granite Hammerdrill Bit 5/8 In. X4 In. X6 In. | Home Depot Canada

Here is the same bit in the US store;
5/8 x 4 x 6 In. Blue Granite Hammer Drill Bits-HCBG20 at The Home Depot

Keeping in mind, our dollar (CND vs. USD) is close enough to consider it 1:1, it cost me almost 40% more here for the same bit, not taking into account taxes.

 

I suspect you could have shortened the set/work time of the product, considerably, by applying uniform heat to the pedestal with a hot air gun before and after pouring the liquid into the holes. I recall the S-Mite we used (made by Sumitomo Cement Co., Ltd., Japan) being highly exothermic, meaning additional external heat would cause the chemical reaction to happen more rapidly under colder ambient conditions. The paper cups full of the stuff I collected each morning (to make sure the product was working) were too hot to handle bare-handed as they became hard.

 

I tried looking for the S-Mite. I could get it locally and with being off for 2 weeks, I wanted to get working on it as soon as I could. I can't remember brand I bought, but I do remember seeing good reviews online and was recommended at the shop I bought it.

Now that things are warming up again, I'll put the heater aiming at the remaining piece and warm it up before and during the next round. Prior to purchasing the temp range I did, I had confirmed a few times that the ambient temp in the work area was well within the range (~ 60'F to 65'F) without heating.

It is interesting to see the mixture of materials in this thing. I'm assuming it's original from when the house was built in the 1930's. There are rods similar to rebar (smooth finish instead of the standard rebar finish and a lower softer metal), larger smooth rocks (ranging from 1" to 3"), a mess similar to drywall tape, and a couple different types of sand ranging from beach sand a concrete not like Portland which I'm use to. Surprisingly no pea gravel. The outer layer (first inch or so) is very tough. Under this, it's fairly brital and could be brushed away with a stiff brush.

 

Just a quick follow up to this.
Added a heater to the area and the expanding concrete worked like a charm, sort of.

The problem now is, the concrete block is made up of what appears to be one very large boulder, nearly 3ft diameter, and it's a really hard rock. The rock appears to have 4 pieces of rebar holding it in place.
Out of frustration I took a 3 step swing (aka Happy Gilmore swing) with the sludge hammer and barely made a mark on it. The drill doesn't appear to be able to mark it with the bit I listed in post #10.

I'm thinking I'll drag the compressor through the snow to the house and go at it tonight and tomorrow with the air hammer. I'll have to work the concrete around the rock and probably remove the rock as one piece.

 

You could cap it with C4.

 

Trust me Ray, that thought crossed my mind.
The close proximity to my water softener and other gear might make that a really bad idea.
If I could have made a hole in the rock, I could have let the expanding concrete do it's thing. The stuff works great once I got the tempurature regulated.

If I can get the rock loose, a couple of us with straps could get it out. They moved it in by hand back in the 1930's, I'm sure a couple of us could match the strength of the monsters that probably moved it in.
I think I'll attack the corners where the rebar is located. That is concrete so I can get through it. It should also give me a better picture of what I'm working with. There is only 4 pieces of rebar, one at each corner of the rock from what I can see.

 

Isn't this rock in your basement? If so I think the guys in the 30's had gravity on their side. I'd be afraid to put a couple guys and a 1'000 pound rock on a set of wooden stairs.

 

True.
The big thing is to get it out of the way so I can repair the concrete in that area and continute with the Utility room build.
Once the rock is out, I'll have time to figure out what to do with it. Works comes to worse, an engine pull tripod and hoist it out a basement window.

 

Maybe it was there when they dug the basement and they couldn't move it so they hid it. You could have the tip of the iceberg there.

 

That is always possible.

Looking at how the other (older) equipment was setup in the basement, everything was raised up on a concrete pedestal of some sort. I suspect back in the 1930's, they had water issues in the basement as there is a french drain (trench) in the concrete which leads to a drain area in the floor. The pedestals would have saved the equipment from the water they may have gotten down there at the time. There is now a sump pump pit in the basement which would render all these raised areas unnessessary.

 

The last house I bought for a rental has a couple boulders visible in the basement. They poured the floor and built the walls around them. Sort of a neat as an initial "wow" but it would really cause a problem if anyone ever wanted to finish off. Judging by the look of them it's only the tip of the iceberg.

 

I saw the "iceberg" problem originally on This Old House when they were digging a new basement. There was a term they mentioned but I don't remember it. Basically it was bedrock that was closer to the surface then usual. Don't remember the solution so no help, just a warning.

 

In my town is a rather common problem. Even large jackhammers on track hoes are largely ineffective. They will use them if there is only a slight interference with a houses foundation but much more than a little bit and it's blasted. A few holes, some explosives and a heavy blast mat and the problem is solved. Neat to watch but amazingly unimpressive if you've ever seen a big blast at a quarry or pit mine.

 

I don't think I'm dealing with an iceburg situation here.
The rock is very smooth from what I can tell at the exposed areas. This would indicating it's been in water for many, many years before it was covered in Concrete. This would be a very sharp, yet smooth tip of the burg which would be odd for the perfectly smooth finish of it.

I can't however discount the idea as it is still possible (until I dig under it and confirm).

 

I suppose a thermal lance (oxy-magnesium torch) doesn't get hot enough and might be too dangerous in the confined space of a basement.

 

Ya, don't think that will work.
If this was outside, I'd build a hot fire around it, let it burn all day, then hit it with ice cold water. Worked great in the past. Not so much of a good idea indoors though.

 

I'm wondering if a line of holes and then feather and wedges could crack it into more manageable pieces.

 

It's getting the hole(s) into the rock that will be the issue.

You'll see from my first progress picture (attached here) that I had started this in a 6"x6" grid. Using the expanding concrete, it should have created cracks in a somewhat organized pattern.
What through that plan out was I was able to get down 6" around the outside, but not in the center.


Looking closer at the next progress picture, I'm starting to see a glimps of hope that I didn't notice while I was working.
Assuming the rebar visable goes all the way down, this is more then one rock in there.
You'll see the smooth surface in the forground and the one on the left edge closer to the pump, that is rock.