Rh readings

[rthompson]

(10-13-2008 10:11 AM)dennismck Wrote:  Ray,
Am I right in assuming that the closer the RH of the Concrete and the RH of the Building enviroment( Bldg with HVAC on), the less likely there will be a moisture problem? I know some manufacturers say that the RH should be no more that 70 percent, but isn't it the difference in the Rh of the concrete and the RH of the air the main reason there may be problems?


Dennis McKenzie

Dennis,
The RH probe measures the relative humidity at the apex of the drying curve of the concrete. The ambient RH has a long term correlation between the the RH of the concrete. The lower the ambient RH the faster the moisture dissipates out of the slab. The numbers established by the manufacturers are really the RH moisture content after the slab goes into equalibrium. Each product can only withstand a certian level of moisture content of the slab and the number is the maximum percentage of relative humidity that product can tolerate.
Regards
Rayt