It was a chemical to speed up grout curing. I don’t know which one. I looked up a few and they were corrosive petrochemicals with like 20-letter-long names and an acute health exposure rating of 4 on the MSDS. They also didn’t provide PPE or instructions on what PPE was necessary. And have you ever gotten any significant amount of gasoline on your skin? It burns and it is not safe. Here’s a list of chemicals in common gasoline mixtures: Gasoline, Toluene, Hexane, Xylene, Octane, Ethanol, Trimethylbenzene, n-Heptane, Pentane, Cumene, Ethylbenzene, Benzene, n-Hexane, Cyclohexane.
Even if it was just the water in the tunnel — how about you try 8+ hours of heavy work in steel toed boots with damp feet, let alone standing in ankle deep water filled with corrosive chemicals. Even standing still in clean water, your skin basically turns to paste after not too long.
With the way the job market is trending in tech, you might have the opportunity to find out one day while someone sitting in a Herman miller chair in a climate controlled office building dismisses your pain as petty griping.
Those kind of chemicals (including gasoline!) are in all the most common products like Watco Danish Oil floor finish that you can buy from home depot and use inside your home (and burn in your car for everyone to enjoy). They speed up curing. I don't recommend them! But they're very, very ordinary. If you want a product without them, you have to go out of your way to get it, unfortunately. (I recommend Tried and True Danish oil, which you'll find is significantly more expensive, and takes far longer to cure, but has no ill health effects)
These chemicals are being sprayed at high enough pressure to splash them, all day long, in enclosed spaces, in the presence of lots of other people. Even if it was bleach, that would require significant effort to protect the people in that environment from injury. They didn’t do that, the workers are human beings that deserved that, and that shouldn’t be minimized.
