! 1000 year concrete longevity technology

For me, the collapse of the Surfside Condo in Miami, FL started an industry wide focus on the susceptibility and degradation in moisture rich and salt laden environments of our modern concrete.  Contrast this with some of the Roman structures that have survived hundreds of  years and there is now a big focus on concrete admixtures that increase the strength, create some self repairability, and make it completely impermeable and waterproof such that there should be zero degradation over time.   The major problem that is causing concern is the sometimes 25 to 35 year lifespan for major hi-rise and commercial buildings... same as smaller residential structures.    The government  has already studied and determined almost that any expense is worth building bridges that dont collapse with age.   I personally have been adding the "latex" admixtures that tile layers use for their portland cement when they make shower walls and floors ....  to my concrete mortar mix when I make outside steps and porches  with bricks.    I also have found  cheap mis colored Home Depot paint mixed with  Portland cement and painted on top of some old outbuilding asphalt roofs to be life extending ( so far for 14 years )    The point is that there is a big science right now in admixtures being added to cement to dramatically increase the lifespan and or strength and or water proofing etc.   Think about the shot crete walls of swimming pools?   Why cant we have that kind of waterproofing in foundations ?    I dont think a homeowner should ever be told that their house is now depreciating instead of appreciating because   cheap building components.   What do you think ?

Scott, I think you are way off the mark.
I am a Civil Engineer with an interest in this subject, I remember the incident and followed up on what happened.
From Wikipedia
"A contributing factor under investigation is long-term degradation of reinforced concrete structural support in the basement-level parking garage under the pool deck,
due to water penetration and corrosion of the reinforcing steel.
The problems had been reported in 2018 and noted as "much worse" in April 2021.
A $15 million program of remedial works had been approved before the collapse, but the main structural work had not started.
Other possible factors include land subsidence, insufficient reinforcing steel, and corruption during construction.[13][14][15]
The National Institute of Standards and Technology (NIST) is investigating almost two dozen potential causes for the collapse.
It is likely they will determine several factors happened simultaneously to cause the collapse.[16]"

From memory the pool cracked for some reason, reinforcement corroded and lost its tensile strength.
Resulting in catastrophic failure.
I doubt admixtures or similar caused the issue.
I would not be surprised if bad design, sloppy construction and haste also added to it. failing.

Additionally from the same reference
"A 2018 inspection performed by the engineering firm Morabito Consultants pointed out a "major error" in the construction of the pool deck, whereby the waterproofing layer was not sloped.
Rainwater that collected on the waterproofing therefore remained until it could evaporate.
Over the years, the concrete slabs below the pool deck had been severely damaged by this water.
The report noted the waterproofing below the pool deck was beyond its useful life and needed to be completely removed and replaced.
The firm wrote that "failure to replace waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially",
and that the repair would be "extremely expensive".
The ceiling slabs of the parking garage, which sat below the pool deck, showed several sizable cracks and cases of exposed reinforcing bar or rebar from spalling.[23]
Also
"On July 3, 2021, The New York Times reported that investigators had found less rebar than specified in the building's construction plans in its footing neck and starter columns.
The report cautioned that some may have been dislodged in the collapse, and that reduction of rebar alone would not necessarily cause failure because steel requirements can change during the construction process,
and designs often specify more than is strictly needed as a safety precaution.[182]
Construction contractors using less rebar than required is a very common cause of structural failure.[182]
There is some evidence that proper inspections were not performed during and after construction.[158]

On June 27, 2021, the Miami Herald reported on the consensus of six engineering experts it interviewed.
Based on publicly available evidence, the experts believed that a structural column or concrete slab beneath the pool deck likely gave way, causing the deck to collapse into the garage below.
This formed a crater beneath the bulky midsection of the tower, which then caved in.
This is a type of progressive collapse, in which one structural part gives way, destabilizing and removing support from other parts, which in turn collapse and rapidly remove structural support.
Evidence includes the report that moments before the building collapsed, a resident of a fourth-floor unit called her husband to say that a crater had appeared in the pool deck.
She went missing in the collapse and was later found dead.[192][193] A surviving resident also stated that part of the pool deck and street-level parking area had collapsed into the parking garage minutes before the collapse"

I had not heard about the Surfside condo collapse so I ask google.

I seems that this event took place in 2021:

A contributing factor under investigation is long-term degradation of reinforced concrete structural support in the basement-level parking garage under the pool deck, due to water penetration and corrosion of the reinforcing steel.

https://en.wikipedia.org/wiki/Surfside_condominium_collapse

So according to the article it is believed this was caused by the water penetration and corrosion of the reinforcing steel rods.

This all leads back to my focus on admixtures in concrete that make it waterproof and impermeable to salt and other corrosive elements which then would also preserve the rebar from corroding.  I mentioned Surfside Condo as  at least a major catalyst in my awareness of the short lifespans of present day concrete.  Not only that but some admixtures massively increase the strength.  I dare say that if Surfside Condos were built with concrete modified with a few million dollars of the optimum admixtures ....  the Condos would still be standing today
and maybe for another 20 , 40, or 100 years.   Lets face it, if there is no degradation of material properties then why should it ever come down ?       I am saying that we at Permies can piggy back on this relatively new technology just as the bridge builders are doing.

OK I see your focus now.
In the case presented I doubt admixture would have helped.
If an admixture had been present, with the raw reinforcement bars it may have lasted longer.
We know today, applied waterproofing just does not last, better design methods need to be employed, admixtures may help
the situation if design principles are good.
Admixtures cannot compensate for poor design and construction.

Adding synthetic materials to concrete has its environmental concerns.

The Roman's did not do this. They mixed in sea salt,  sea shell powder and other additives that in effect are "self repairing". They are materials the do, in fact dissolve slightly with moisture but recrystalize to fill in cracks. It's a dynamic chemical response to moisture.

Also, you have to understand the limits and appropriate use of your materials. The Roman's would not have installed a pool above structural concrete. Pools were in- ground and plastered with lime, which is easily repaired from season to season.

Foundations in contact with moist soil were not poured  concrete but stone,  poured concrete being reserved for dry areas like roofs.

Context context context. And maintenance.

There is no benefit to arguing about Surfside Condos.   It is known all over Florida that many buildings build like Surfside and occupants are being bankrupted by the cost to repair ( destroy and rebuild)  All coastal areas especially around the world in salty environments and all the bridges etc.   Which is cheaper, better and most long lasting... stainless steel or composite rebar to prevent corrosion?  What about degradation of concrete?   If they use the same mix with admixtures that is used for pouring gigantic tanks for water treatment plants, the concrete is like plastic keeping everything away from internal reinforcing.   If the rebar doesnt corrode and the concrete which is stronger and doesnt degrade even submerged in salt water you have basically a permante or 1000 year building.   I'm not expert on anything but I have read that Romans had many recipes and one also used Volcanic ash and other weird stuff to make concrete structures that are submerged in Ocean Water for 1000 years.  If you can double triple or more the life of a structure than the extra cost can be justified.    Lets talk about engineering and bad construction practices.  No matter how bad, if a structure stands at all when finished,  it is "good enough"  to stand.   If nothing ever deteriorates then it will continue to stand.    In that way  admixtures could have helped immensely at Surfside.   But its the whole package being looked at.  How bout galvanized rebar ?   How about fiberglass fiber as reinforcement mixed in?   Its always been right in front of us in the portland cement that shower and swimming pool builders use.   Much stronger and water proof.   Driveways are another excellent example of where contractors use cheap concrete  and they break up in 6  to 10 years.   I dont have an axe to grind because when I do research I am finding tons of new info and experiments taking place in commercial and university environments.  Also very intersting are the guys building super strong and waterproof concrete kitchen countertops.   I think I read that the cost of the Surfside Collapse is now over a billion dollars with all the insurance company payments  etc.    That kind of money if known ahead of time would justify stainless steel reinforcement or carbon,  and some super strong water proof concrete etc.  The problem Surfside is just the tip of the iceberg .  Now that we know,  how will we build in the future ?

John C Daly,

Can you shed some light on an observation I had seen some time ago?  I seem to remember hearing that one of the major limiting factors in modern cement is the fact that it is prestressed and reinforced with rebar.  As my recollection goes, the reason for the early failure (compared to Rome) was that the rebar, especially if exposed, rusts and the swelling rusty rod compromises the strength of the cement by pushing out from within.  This further made sense from my understanding on the strength of concrete in that it has outstanding strength under compression, but not when being pulled apart.

I am NOT an expert on concrete/cement, so if you could help confirm or more likely, redirect my line of thinking with regards to cement/concrete, I would certainly appreciate it.



Eric

Eric, your observations are spot on.
Its known as concrete cancer when the rebar corrodes, expands and caused 'spalling' of the concrete.
It can be reto prevented by passing an electrical current into the steel work to prevent further damage.
Thats done often on older structures.
Concrete has great compressive strength but nil tensile strength.
Prestressing does not add to the issue, prestressing can be likened to the effect of holding a few books together in your hands, pushing them together, and lifting them.

Daily check of news from the world of Archaeology -
https://archaeology.org/news/2025/12/11/roman-concrete-ingredients-at-pompeii-analyzed/
and I vaguely remember that the sea shells were heated/burned to produce the quick lime.
When our large concrete water tank sprung a leak, the "solution" recommended was a substance called Krystol, painted onto the inside (yes all the water had to be transferred or perish the thought, wasted) but it worked.  It is something that's used on underground carparks that start to bleed water.