I have a similar prolem as did/does? Bob. ?
I have used Cemcrete's Colour hardner on an outdoor patio that has no covering. The concrete was poured on plastic sheeting and is about 100mm thick. I have waited more than a month to apply the sealer. The white powder re-appears after 3 to 4 hours. Will the neutralising action that you discribe, not damage the Cemcrete surface? Will the neutralising be permanent?
Pieter, August 2010