Support for the Big Dig comes from Cure Alzheimer's Fund, which supports foundational scientific research

into the causes of Alzheimer's disease, because research is the only path to a cure.

Learn more at cure ALZ.org.

When did you first realize there was something weird going on with the concrete that was going into the big dig?

Mix 404-291.

I remember doing the work on it and I didn't like it.

It was setting up too quick and I remember talking with the boss I said well you know what's going on here you know this stuff is just tightening up very quick setting up quick and he said it's that new mix we decided to use.

And then thinking, oh no, this is not going to go well.

Dan Johnston was a quality control technician for aggregate industries, the largest

supplier of concrete for the big dig.

But I have to say he's not what I would have pictured. Johnston has long hair down past his shoulder

blades. The shelves in his living room are filled with Stephen King, classic sci-fi, with the books propped up by statues of

dragons and gargoyles. I might expect to find him at a Magic The Gathering tournament, more

than I would a concrete plant.

I ended up in construction first through the trades painting.

I was the worst cop until you ever run into.

Scare the hell out of the nails.

Never could hit it twice. So I ended up meeting some

friends who were in the testing business. Testing materials for construction. I had a friend who was working for this

company, said, come on down.

This was in 1997 just as the big dig was entering its peak construction years. Essentially you look at all the ingredients.

And Johnson's job was to check the concrete.

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