It looked to me like she was creating some sort of teleportation storm like she accendentally did before, after shooting Kuroko. This time she did it purposefully, continuously teleporting pieces of the building probably higher. Since that four tons is her limit, she can't teleport that much material in the end. Four tons of concrete isn't any huge volume. But of course it's enough to wreck a building when done amass. Or when done intelligently, which she wasn't doing.
Anyway, this arc was over, for now, sooner than I expected. Luckily we did get that awesome Accelerator fight. Despite losing some of his powers, he now kicks likely more ass than before because he lost also some of his deluded arrogance and overconfidence. Let's hope Touma doesn't ever need to fight him again...
Kuroko's idealised image of Mikoto was funny as well: Only fights when she absolutely needs to. Doesn't describe very well the Biribiri who attacked every time she saw Touma, who hates to lose even a meaningless fight, and is quite vengeful indeed.