It is the same stuff, that one uses to whiten the churches here in Denmark. Normally it is stored in a specific pile under ground, as it need to be stored for at least 5 years before it can be used. It is highly corrosive in pure form, and there are many stories about someone getting their skin ripped off on the legs, when stepping and sinking into these storage piles.
And I bet that the Romans also knew about the storage part. You burn lime, crush it into powder and store it for 5 years. And if you find a 50 year old storage pile on the church ground, then you will have the absolute best quick-lime imaginable, to paint the churches white with. The longer storage, the longer the church will be white. Basically.... Find the roman quick-lime storage, and you will find the evidence that it was used this way. But in concrete and not to paint with.....