This is a very simple mod that reverts Factorio 2.1 changes to hazard concrete and refined hazard concrete recycling.

This mod is for all your existing Fulgora bases that paint your concrete to void it quickly. If you update to 2.1 and don't install this mod or the other one before you load your old save, your concrete recyclers will be full of iron ore and stone bricks and your belts will be full of useless concrete.

There was already another mod by Techjar that does the exact same thing. However my mod can be installed before you have updated to Factorio 2.1 and will sync/update automatically whenever you get around to updating Factorio to 2.1 and reload your save. I don't want to remember to install a mod later. (Yes, it's tested and working in 2.0.77 and 2.1.7)