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I have always found concrete to be one of the wonders of the world because of its properties:

If it is poured as dry as possible, it gets harder. However, if it is kept damp while curing, it gets even harder.

There are different ‘slumps’ in the mixture which can change the properties somewhat.

It can cure in 7 days but does not cure fully when it can get it hardest, that time is 28 days. It is time-related and nothing more. Those who say that there is still uncured concrete in the Hoover Dam are full of hooey.

All of its properties are kind of contrary to logic, aren’t they? Concrete is, indeed, curious, to say the least. ;-)

Yes, Contrary to logic.

WPA Concrete seems to be much harder formula than we use today.

I remember a gymnasium floor that was poured locally, being cured for 28 days floated with water. You cannot imagine how hard it is today. My father was the many overseeing the construction company. Not as an employee, but representing the school. We lived directly adjacent to the school.

Dad was a very good contractor, residential and commercial. He was NOT an engineer, but he had good instincts and over built everything he ever touched. He was WWII vet, Belgium, Germany, and CZ. He died 2 years ago at 94. Great man.

Nastiest jobs I ever had was working Concrete.

Setting forms for concrete walls and footers for residential homes or Building Custom Gunite (That’s Cement mixed with sand as the aggregate) for In-Ground Pools, Nasty work all around.

When setting forms for walls we’d occasionally miss the footers we had poured by an inch or less. The pressure from an 8 foot tall six inch wide wall of freshly pour concrete on the “gap” would cause a “Blow Out”. Concrete rapidly flowing outside of where it’s supposed to be.

Someone would Yell “Blowout, Blowout” !!!!
They would halt the pour from the mixer and next you’d hear, “Bucket Brigade, Bucket Brigade” !!!

The closest guy would jump into the hole to stop the blowout with whatever he could use. I’ve seen guys lay out their bodies in an effort to stop the blowout. You never really know how big the blowout can be, so you have to do whatever it takes. Concrete is expensive.

At the same time, all the workers on the perimeter are scrambling to find and throw 5 gallon buckets into the hole. At this point you’d have 2 or 3 guys in the hole scooping up concrete in the buckets and lifting them up to another guy straddling an 8 foot high wall/forms and he’d dump it right back into the form.

At the end of the day, every day, you would be covered in used motor oil and concrete from head to toe. The oil is used to keep the concrete from sticking to the forms.

Oh, and all that is mixed with dirt.

I found a great appreciation for Lava Soap.