Carbon Reducing concrete experience...

[Cray Paper]

I have been on a project for the past couple of years that isn't LEED certified via the contract but the enormous attention on it (numerous consultants) obligated us to use carbon capturing / neutral concrete. My experience has been with structural concrete but most of our scope on the project was / is with architectural site work hardscapes. I got the concrete mixes changed for the vertical work ( Arch and owner hated the bug holes and had to change the spec as well as form oil and form plywood) and wasn't managing the flatwork until later last year.

Supt handling the flatwork got shit canned and it became my responsibility in late summer of 2023. There were so many cracking issues, obvious changes needed to be made in jointing (all provided by the landscape Arch and they resisted our company's referencing the spec and ACI standards in said spec) We removed and replaced hundreds of thousands of dollars of in place flatwork do to cracking. Every aspect of the construction process was under the microscope, sub grade prep, QA/QC of the mud before placing, how much water was added before and during placing, curing agents (chemicals = set retarders, water curing?).. The scrutiny was incredible.

We got the owner to change the mix designs about 4 months ago, no slag / fly ash, pure 6 sack cement mix, no reclaimed water and not LEED certified. The supplier really pushed back during the hard conversations about why the concrete was cracking / shrinking, I talked to chemists, QA/QC techs etc. They would not admit the carbon capturing mud didn't perform to the expectation of the owner.

Since the mix designs went back to cement, sand and gravel we haven't had one issue with cracking.

Any concrete guys have experience with this new wave of carbon capturing / LEED certified concrete?

 

[Boat 405]

You want it done right or you want it LEED certified? They are not the same.

 

[Ultra912]

Fly Ash is actually a beneficial ingredient. It increases the workability, strength and improves freeze/thaw cycles making it ideal for placing in cold climate areas to avoid damage due to freeze. It also absorbs abrasion better. It's actually a harder product than Portland Cement.

 

[wzuber]

Where's @ConcreteDr when you need him? He's the resident concrete expert as I recall from his postings...
Maybe he can shed some light? If he's even still participating round here?

 

[4Waters]

Where's @ConcreteDr when you need him? He's the resident concrete expert as I recall from his postings...
Maybe he can shed some light? If he's even still participating round here?

Last seen 3hrs ago

 

[Ultra912]

Where's @ConcreteDr when you need him? He's the resident concrete expert as I recall from his postings...
Maybe he can shed some light? If he's even still participating round here?

I've been a concrete contractor for 32 years. Not Joe Chemist,,,,, but the benefits of fly ash aren't really very difficult for the average Joe to understand. Better workability, dries harder, higher abrasive tolerance, reduces cracking, higher freeze/thaw tolerance. Concrete pump mix designs are always better with higher fly ash content

 

[Racer56]

I've been following the transition to low carbon concrete for the last couple of years, as I know it's going to be forced down our throats.

Thank you @Cray Paper for posting this thread. I've been anxious to hear first hand accounts of how Libtard mud performs. I had a feeling this whole deal was going to be a cluster fuck

 

[JL95]

Let's check in on China

 

[PlumLoco]

Don't know nothing about concrete, but found this pretty interesting.
https://www.sciencealert.com/scient...ing-practical-use-for-leftover-coffee-grounds

 

[Ultra912]

Once dog shit is dry and crystalized it's pretty hard too. Stick with the ash, it's proven itself for over a century. Anything else is a fuckin form of green no matter what it is

 

[Racey]

Build it strong, build it once: bad for the environment

Build it green, build it 3 times: good for the environment.

People need to stop going along with this shit and start pushing back or we will get alot more of it.

 

[76sanger]

This whole carbon thing is so frivolous and full of BS! It's a green agenda RELIGION that has been so brainwashed into people that we are hurting the planet, We are saving the planet, bla fucking bla. Control, control, control!

 

[Sleek-Jet]

I've been a concrete contractor for 32 years. Not Joe Chemist,,,,, but the benefits of fly ash aren't really very difficult for the average Joe to understand. Better workability, dries harder, higher abrasive tolerance, reduces cracking, higher freeze/thaw tolerance. Concrete pump mix designs are always better with higher fly ash content

We sell literal train loads of fly ash that is used for concrete. The cement makers buy every last pound, most of it goes to the West Coast.

 

[Cray Paper]

I've been following the transition to low carbon concrete for the last couple of years, as I know it's going to be forced down our throats.

Thank you @Cray Paper for posting this thread. I've been anxious to hear first hand accounts of how Libtard mud performs. I had a feeling this whole deal was going to be a cluster fuck

I'm just a dumb carpenter that's been working with concrete since 1991 and have worked for very intelligent mentors from the field over the years that demanded to know why things did or didn't work. The LEED / carbon capturing deal with the concrete was new to me. Been on Life Science and big TI projects sense 2010.

The LEED mud placed and finished OK, but the shrinkage and cracking within 12 hours of placing was not something I have seen before. I personally watched the slump testing and only allowed enough water to get to the target slump. Sub grade prep, watering of subgrade, curing hot and cold per ACI standards were all diligently addressed during this time frame. When almost identical 20Ksq' SOG's were placed 5 days apart and the environmental conditions were better for the 2nd pour and the 2nd slab cracked to shit I had enough.

We got approval to go back to a non LEED / carbon capturing mix (no reclaimed water, injection etc ), and haven't had a cracking issue since. Guess I am trying to say I and we know what ACI standards are, followed them and in my opinion, the LEED concrete just doesn't perform like what I was accustomed to to. Concrete cracking can be caused by so many factors...when all the environmental factors have been eliminated and it still happens...in my opinion, it's the chemical mix of the concrete, and that is what I believe was the issue.

It doesnt seem to have a problem coming up to strength if the batch plants have their shit together (whole nother story from the same supplier with 3 batch plants over 2 years) but from my experience it doesnt perform well at all for minimizing bug holes in vertical concrete and flat work is a crap shoot with shrinkage and cranking.

Back in my formative years of concrete placement, fly ash was a legit replacement of cement. Slag was not. The carbon neutral mixes of today typically don't include fly ash. I just know what works, cement, fly ash, sand and aggregate of your choice. Using unknown impact ingredients like these and slag in my opinion Leeds to unproven results.

 

[Cray Paper]

We sell literal train loads of fly ash that is used for concrete. The cement makers buy every last pound, most of it goes to the West Coast.

Give Stone Way Concrete a call in the PNW..

 

[Ultra912]

I poured a 37k sq ft parking lot last month. I'm in the High Desert and this time of year we're seeing low 30's to high 20 degree ambient temps over night. Concrete I poured was called "City Mix". Cities, at least up here, require us to use their batch design. It's a 3200psi that does include ash. I added 2% polarset with hot water. I also went with a fiber called F70 that is larger than a micro-fiber at 1 1/2lbs per cubic yard. The cities will NOT let us use fiber when doing work for them. It's the equivalent of WWM,,,,welded wire mesh. Owner did not want to pay to remove native and place a class II base so I talked him into the fiber at $8 a cubic yard,,,,my cost. . This size fiber brooms out pretty hairy but UV and friction eliminate that over time. This fiber virtually removes shrinkage cracking unless workmanship is poor.

 

[Cray Paper]

Fibers work, but don't look good on a finished product. Depending on the fiber "type" the finish can be addressed after finishing with weed burners. Line pumping concrete with fibers is not advantageous and is a legitimate concern, it plugs up slick lines like crazy, which delays pouring and flat out costs money. The fibers absorb water and the only way to counter that from my experience is to reduce the aggregate size and increase the cement which increases the cost of the concrete.

 

[LuauLounge]

Just read the automotive additives, how many are available for concrete?
Better living through chemistry.

 

[Ultra912]

This is for parking lot, not attractive flatwork
No need to burn off
Wears off

 

[snowhammer]

Fibers work, but don't look good on a finished product. Depending on the fiber "type" the finish can be addressed after finishing with weed burners. Line pumping concrete with fibers is not advantageous and is a legitimate concern, it plugs up slick lines like crazy, which delays pouring and flat out costs money. The fibers absorb water and the only way to counter that from my experience is to reduce the aggregate size and increase the cement which increases the cost of the concrete.

Never had an issue line pumping with fibers unless an architect or engineer was involved and specified a ratio outside of normal parameters.

I sense a theme

 

[CMU_LATER]

I make CMU. And I know anyday the type 1 2 we buy in bulk will go to “PL” or what the are calling carbon neutral Portland. Our bagged Portland that we resell already is “PL” but the bulk that we make block with is not yet. As I’m curious to how it performs. From this thread I’m not overly optimistic on anything carbon neutral. Concrete and masonry construction are proven to be long lasting. That seems more carbon neutral than rebuilding multiple times..

 

[Cray Paper]

I poured a 37k sq ft parking lot last month. I'm in the High Desert and this time of year we're seeing low 30's to high 20 degree ambient temps over night. Concrete I poured was called "City Mix". Cities, at least up here, require us to use their batch design. It's a 3200psi that does include ash. I added 2% polarset with hot water. I also went with a fiber called F70 that is larger than a micro-fiber at 1 1/2lbs per cubic yard. The cities will NOT let us use fiber when doing work for them. It's the equivalent of WWM,,,,welded wire mesh. Owner did not want to pay to remove native and place a class II base so I talked him into the fiber at $8 a cubic yard,,,,my cost. . This size fiber brooms out pretty hairy but UV and friction eliminate that over time. This fiber virtually removes shrinkage cracking unless workmanship is poor.

Weed burners

Never had an issue line pumping with fibers unless an architect or engineer was involved and specified a ratio outside of normal parameters.

I sense a theme

I work in commercial construction, architects and structural engineers are always involved and in todays environment they either do not under stand BMPs / ACI or are only focused on LEED points. Portland cement flat out works in concrete, the carbon reducing substitutes do to but have downsides that the suppliers either don't know about or just don't want to talk about.

 

[Cray Paper]

I had a structural engineer on my current project tell us to add 150#s of steel fiber per sack on a mix for a sub slab for a soccer field on top of a structural steel parking garage lid. He referenced an ACI spec, he was so off base it was comical. Try pumping any mix with that amount of heavy steel fibers per yard... probably wouldn't have come down the chute let alone pumped through 500' of 3" line.

 

[NicPaus]

Have you ever met a engineer with on the job site experience or experience in the trades hands on?

Neither have I.