Hav­ing cor­rectly guessed that failed epoxy anchors were the cul­prit behind Mon­day night’s tun­nel ceil­ing col­lapse, allow me to offer some new spec­u­la­tion. If I were a bet­ting man, I would bet that inves­ti­ga­tors will learn that the con­trac­tors installed the ceil­ing anchors over the win­ter. Epoxy won’t cure to full strength when its com­po­nents are much below room tem­per­a­ture. Even if they were pre-heated, the con­crete lin­ing of the tun­nel would act as a mas­sive heat sink and reduce the strength of the epoxy-to-concrete bond.

Of course I’ve always been a lit­tle skep­ti­cal of epoxy con­crete anchor­ing. I use mechan­i­cal expan­sion anchors exclusively.