Old Block

[allseason]

I was in a commercial/warehouse today, concrete block and brick. One section date unknown but the owner has been in business 70 yrs. The other half built in the 1970's.

The block walls in the older section have a lot of small divets, most appear to be from the interior face of the block, not from fasteners or mechanical damage for the most part. I have seen in some old block where iron in the aggregate will rust and pop small spots. Any ideas? This side of the building was also the victim of a fire at some point, likely prior to the 1970's addition as that is unscathed. Could that have affected the block?

Otherwise the walls are plumb and solid, very few cracks.

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[Marc]

My backyard 'cajun fire pit' uses concrete blocks and they last perhaps a dozen fires before they crack into pieces.

That kind of concrete doesn't take very well to high temperatures.

I think you knew this about block already though.

Marc

[mjr6550]

It could very well be iron deposits. I see that often in old block. Concrete based products can spall when exposed to fire because the concrete contains water that can turn to steam and build up pressure.

[John Kogel]

Cinder blocks. They used real cinders in them days.

Try searching here for previous discussions. No serious issues AFAIK.

[Marc]

Cinder blocks. They used real cinders in them days.

As in pyroclastic rock?

I've always wondered where that term came from.

Marc

[Chad Fabry]

Cinder blocks. They used real cinders in them days.

As in pyroclastic rock?

I've always wondered where that term came from.

Marc

No, as in coal cinders. The practice consumed industrial waste.

How long have you been sitting on "pyroclastic"?

[Marc]

Cinder blocks. They used real cinders in them days.

As in pyroclastic rock?

I've always wondered where that term came from.

Marc

No, as in coal cinders. The practice consumed industrial waste.

How long have you been sitting on "pyroclastic"?

'Bout ten minutes. Mr. Google offered up pyroclastic rock when I inputted 'cinder'.

So...they put coal in the form of cinders in concrete?

Spill the beans.

Marc

[ghentjr]

The blocks were made from leftover cinders (cinder block) from incinerators. Leftover organic matter, over time, "popped" the block from the creation of small pockets of methane gas. A very common thing in CT especially around the Bridgeport area but I assume it occurs anywhere cinders were used to make block.

[Jim Baird]

I agree with the cinders theory. I had a guy bring coal cinders from a big coalfired heating plant to put on my driveway because he got them for no cost. They are often light and airy and could well be like sponges when mixed in the block making slurry.

The only other thing that occurred to me was bullet holes. Don't suppose there could ever have some tommy-gun firing sessions there?

[Marc]

Ok. Another round with Mr. Google and 'cinder' was originally fly ash, the ash that results from the burning of coal. Over time, it came to include 'clinker' which is industrial waste materials such as slag, etc.

This ties in with the OP in that the industrial waste could have been the culprit that caused in the spalling during the fire, as Mark R and others have opined.

Marc

[allseason]

There are areas where rust stains are present below the holes that leads me to the iron.

When one of my brothers ran track in high school he ran on cinder covered tracks.

[John Kogel]

Here's a thread on that other website. The pics show similar rust stains. Speculation runs rampant. Nice pic of a Tommy gun.

http://www.inspectionnews.net/home_insp ... cause.html

[Les]

Cinderella? anyone ever hear of her? Huh?

[hausdok]

The heat from the fire did it. I've seen the face of concrete blocks spall in many a fire pit once exposed to heat. Sometimes the divots pop off with a lot of force and send embers up into the air and scare the crap out of everyone.

ONE TEAM - ONE FIGHT!!!

Mike