concrete slab; surface humidity

Hi, So my builder left the slab exposed for 3-4 months after laying it (badly) on a vastly over running build. So now that roof is on its floor insulation time. Weve had heaters and 3 dehumidifiers running 12 hours a day and overnight sometimes. We scrub slab to remove dark mud, clay etc then a...

Having acquired a floor hygrometer (foam box with temp / humdity sensor in it & butyl tape) i've started checking the humidity of a ~ 50 year old ground floor slab. Construction i think is 50mm screed above DPC. not sure what's below the DPC, but i guess another 100mm of concrete. I have...