What did you buy this week?

[Engineer42]

We used to pour 3k psi building slabs and 2.5k psi flatwork on the same day. All the truck tickets came to me when the pours were done. The slab guy handed me a stack of tickets and I these can't be yours. He insisted they were. Well, I said you poured 2500 psi mud in that slab. 30 days passed and the cylinder break tests read 2600 psi. We waited another month and the test came up to 3200 psi. Conc keeps getting harder with age....

And I would not have paid for the concrete. There's more to the psi difference then break range. If done right you can get 2000psi mix to break above 3k.

Mix designs, how much cement, which stone, sand amounts, add mixes, they all figure in.

Sorry, that would be like drywalling a house with 1/2" and charging for 3/4" fireproof. Looks the same, but not what I paid for.

Bucks is bucks.

 

[scootr]

It wasn't my money or my decision to make but point well taken.

 

[bigtiller]

And I'd would not have paid for the concrete. There's more to the psi difference then break range. If done right you can get 2000psi mix to break above 3k.

Mix designs, how much cement, which stone, sand amounts, add mixes, they all figure in.

Sorry, that would be like drywalling a house with 1/2" and charging for 3/4" fireproof. Looks the same, but not what I paid for.

Bucks is bucks.

Yep, what he said.
Good times brought more and stronger concrete.
When I was a teenager, all DIY'ers around here used a gravel aggregate and 2500 psi. for sidewalks...very few could afford a concrete driveway.

But a decade or two later everyone switched to limestone and 3000 with some at 3500 psi. and were pouring driveways 4" thick.

 

[dodge man]

I can’t remember where I worked ever specing less than 3000 psi and sometimes 4000 psi. I broke hundreds of cylinders over the years. The machine has a cage around it but shards can still go flying. I could tell when a cylinder was going to break high and I’d get as far away as I could. I think I saw break as high as 8000 psi once in a while.

The one time I remember low breaks was when the air content was high. The owner wanted to know why I let them pour it. As an inspector I have no control or authority on the job. I told the contractor the air was really high on that load, they elected to use it anyway.

I personally would never use 4” thick anywhere but sidewalk.

 

[paulsharvey]

FDOT Type-I Non-structural concrete (NS) has a min 28 day break of 2500 PSI. It often breaks at 4000+. Used in sidewalks, driveways, ect. It's also a fairly old school concrete, and although every batch plant has its own mix design to meet the spec; it's more or less just Portland cement, sand, water, and gravel. Less fly-ash, and other ad-mixes than most other "commercial" 3000 psi mixes.

Sometimes simple is best... Not every mix needs super plastizier, or calcium, or whatever, and often, those "fancy" mixes have draw backs for long term

 

[paulsharvey]

Wow, this went further down the concrete rabbit hole then intended; but i was just reading the 25-26 spec book, and RAP (asphalt millings) are now allowed to make up upto 20% of the aggregate in non structural Portland cement concrete. That's an odd choice....

 

[Engineer42]

Wow, this went further down the concrete rabbit hole then intended; but i was just reading the 25-26 spec book, and RAP (asphalt millings) are now allowed to make up upto 20% of the aggregate in non structural Portland cement concrete. That's an odd choice....View attachment 4047518

that's how I would prefer it to be used in Hot Mix, as aggregate with no asphalt value.

I prefer virgin mixes with no rap. I feel that assigned asphalt content in RAP is often rated too high, leading to dryer mixes.

Just my opinion.

 

[grsthegreat]

If i ever poured a new garage floor or parking ribbon id go minimum 6”. Im so sick and tired of concrete cracking.

If i replace the slab where i park my tractor, its going to be 6” with steel plates that allign with tires so the chains wont damage concrete.

 

[ArlyA]

Speaking of concrete. We have a locale co who makes carbon fiber rebar. If you go to road or bridge construction site in many states, they are now required to use coated rebar to keep in from rusting because of road salt.

 

[dnw64]

At the dealer getting a replacement key programmed. $717.69 for the key and programming...

(Porsche)