Flippanarchy

Not a concrete expert, but dead bodies. They decompose, can create pockets of pressurised gas, and leave a hollow cavity of no structural strength.

Source: Me. I made it up, but seems plausible.

There's two broad categories of ways that concrete can get messed up: things that apparently ruin a batch on the spot, and things that compromise the resulting structural integrity in ways that might not be readily apparent.

The biggest things I can think of for the first category are water and time. More water means more "workability", so it flows better, but it means the overall strength goes down. You basically want to use a minimal amount of water you can get away with. More water also means more time to set, so concrete workers will add water to the mix in the truck to slow it down if they need to. You can always add more water, but you can never take water out (or add more cement/aggregate on site). Concrete trucks have a water tank on board to add water, and also clean off equipment after pours because job sites often don't have water. If enough water is added to the concrete in the truck, the batch is ruined. I'm sure there are compounds that could ruin a batch, but the water is right there.

Time also hurts because there is a ticking clock for getting the mix out of the truck once it has been made, particularly if the batch plant is far from the work site, and weather is hot. If the site is not completely prepped and ready to go when the truck gets there, enough delays will force the whole batch to be scapped before it ruins the truck. A lot of work goes into getting forms set properly and squared, and the underlying gravel compacted, so that is all delicate before the truck gets there.

The second category, things that compromise the integrity over time has a lot of potential, but there is no guarantee that strength will be compromised enough to cause failure, and there's a lot of potential for collateral damage if it's in a bridge, building, or something people could be on/in. The first things that come to mind here are stuff that will decay over time resulting in voids, like woodchips. I know there's been research into woodchips as an intentional additive, but I'm sure there's more science that goes into that than just tossing it it. Something that causes oxide jacking would also really increase failure rates. This is when a material like steel rusts and expands, splitting concrete apart. This happens often if rebar is not fully encased in concrete. This does happen eventually to any reinforced concrete, which is why modern concrete structures have design lifetimes unlike Roman concrete which lasts indefinitely, but has to be much more massive. Adding a bunch of nails or something like that to concrete would probably speed up the process, but enough nails/woodchips to make a difference would most likely be noticed by the people doing the pour (which could actually be a benefit).

If you wanted it to be unnoticeable, you would probably want to get a roll of rebar tying wire, and figure out a way to get it placed in the prepped site in such a way that it would be exposed to the elements after the final pour without being easily noticeable by the people doing the pour. Bonus points if the effort is focused on areas of stress concentration like corners or joints in the concrete.

Well what you could do is put calcium chloride into the concrete and that'll fuck up the chemical composition of Portlandcement and most steel reinforcements found in concrete.

So instead of sugar, use salt.

2 pounds of sugar is not the same as 10 kg of sugar.

The secret ingredient... is crime

So if you want to sabotage a building, the idea would be to get a job where you're assigned to haul the wheelbarrow full of concrete to the back of the jobsite or drag the end of the chute to where it's going to dump out, so you know exactly where that ton of concrete is going. Then you surreptitiously pour out a couple pounds of sugar from your orange vest or fake beer gut and stir it around with a trowel without arousing suspicion. Zoidberg takes notes: "surrep...titiously..."

It might not sound like much, but the French people who committed the prison concrete sabotage weren't ordinary people who showed up with sugar in their pockets, they were a well organized group that had also broken into offices to steal construction plans. One of their documents describes sabotaging the concrete as "a simple matter" of adding sugar, but that's all - it doesn't say whether they added it to a running truck (which would be quite a trick because everybody on a truck crew knows who's in the crew) or mixed it dry with sacks of concrete in a storeroom, or what. It also doesn't mention observing any actual results. People's vision of how this would work is way too simple - "Just toss a 50-lb bag of something into a truck!"

In Guantanamo Bay for now.

AFAIK, the whole point of adding sugar and sand to a gas tank is that they clog up the filters, and that can result in the in the engine stalling... after an indeterminate amount of time.

The idea being if you can add enough, stealthily, now the car fails without an immediately apparent time-proximal cause.

Do that to an entire motor pool, or a good chunk of it, and you can functionally force a decision between a significant amount of logistics and repair costs, and fleet downtime... or, deal with a random number of vehicles failing randomly.

Sand is... probably better at clogging up fuel pump filters faster than sugar, and if any actually gets into the actual engine, can cause more damage there.

Water, on the other hand, is more likely to rapidly cause an ICE vehicle to either sputter or stall... but you have to use a good bit more water than sand or sugar.

Anyway, back to my jam.

Are they only coffee can sized now? My buddy did a stint as a grunt with an engineering firm where all he did was load those things into a crusher and document how they broke, and the logs were more like human torso sized.

Either it’s bullshit, or the amount of concrete in question was less than an inch thick.

Though sugar spread in front of the concrete would prevent it from adhering to surfaces, so maybe that was the goal. The wood forms they use to hold concrete in place are coated with a sugar and oil mixture so they come off easy. So that would make sense.

Right? That seems to be the biggest missing piece in this 'advice' to sabotage things. You can't just dump the sugar on top after they've already poured it, and when is a concrete truck just left at the construction site unattended?

Just looked it up again... Pictures suggest that it wasn't that much volume:

https://www.independent.co.uk/news/uk/home-news/victoria-line-cement-flooding-fixed-workers-used-sugar-to-stop-spilled-concrete-from-setting-9082206.html