I’m not trying to say that mix doesn’t matter, or that I’m not pleased to see that Facebook is doing something a little more noble than surveillance technology, but as with a lot of construction issues, it’s just not that simple.
I wanted to mention that Concrete is far more complex and regional than folks might imagine. The quality of gravel and sand, local impurities - these all contribute massively. It's probably best to think of it like a wine's terroir - except, unlike a bottle of wine, it's prohibitively expensive to ship both the components and the finalized mixture to different areas. If a region's limestone has a massive clay impurity then it may simply be unsuitable for large structures or require extensive filtering to the point of being uneconomical.
It's important to be aware of just how much the local geological mix can impact the viability of building with concrete because while theoretically we could use perfect concrete for every project - at that point most projects would simply be too expensive to consider undertaking. There is a very large field of engineering around establishing the realism required in settling for what you've got for the price you can afford in. It can absolutely mean that the materials required to build a high rise in Philly might be priced starkly differently from the same structure planned in Milan even with adjustments for the labor impact on pricing.
We could do this if it is important. There are mines in Wisconsin the export sand to the middle east because that is known to work well for fracking and they don't want to risk a local sand not working well. (AFAIK they have never tested local sand properties, but it is possible they have and it doesn't work). In this case the value of the "perfect" is well worth the high shipping costs.
It's all a balance. Imagine a scenario where you can ship in specialized materials to build a bridge with an expected lifespan of 100 years and it'll cost 50M - or you could use local concrete that has an expected lifespan of 15 years and materials would cost 5M. This is a vast simplification of the math but, assuming those expected costs it'd be cheaper to build using local materials and just schedule replacement every 15 years. And, of course, there'll be egg on your face if you build the 50M bridge and then suffer a massive tsunami in two years that destroys the foundations anyways.
To paraphrase a Grady quote: "Engineering isn't a study of building the best thing - it's optimizing the quality we can get for the cost outlay."
IIRC the big tests that occur are the cylinder samples that are taken as well of the concrete and allowed to cure to full strength before destructively tested anywhere from a week to a month after pouring.
> Alongside the event, Meta is releasing a new AI model for designing concrete mixes, Bayesian Optimization for Concrete (BOxCrete). BOxCrete improves over Meta’s previous models with more robustness to noisy data as well as new features including the ability to predict concrete slump (an important indicator of concrete workability).
Seems hard to imagine not doing a slump test, trusting AI when it comes to your multi/many million dollar build outs for something so important. But perhaps still useful for planning, as a starting place?
That said, I'm not sure if the value can ever be greater than a slump test just before pouring.
Cutting out a piece of a slab and sending it to a lab is for post-pour validation in serious construction. There are pre-pour tests that are much simpler depending on the seriousness of what you’re building.
The slump test is rather simple, for example: https://en.wikipedia.org/wiki/Concrete_slump_test
It’s basically a cone with handles and a procedure that’s easy to learn.
This issue here is mainly that it's very expensive to ship all the components of a Concrete in the volume necessary in an economical manner. Some areas of the world just lost the lottery when it comes to having resilient building materials.
Corruption absolutely is an issue as well - I don't mean to downplay it - but even if we remove it as a factor there are just a lot of variables involved in making a reliable Concrete... finding a good mix is an artform and if, for instance, your limestone quary suddenly hits a more clay-laden amalgamation then your Concrete that was reliably lasting for three decades under certain conditions might suddenly lose a decade off the expected lifetime. That change in material quality can also be difficult to detect so there are real quality assurance issues in Concrete mixtures outside of just corruption and cutting corners.
But yeah, there are concrete plants that cut corners and try to save on cement (the most expensive part of the mix), which depending on the project may bite them in the ass when they have to pay to fixing it.