Moisture-Controlled Concrete Masonry Units Removed from ASTM C90 

by Sheldon Wolfe, RA, CSI, CCS, CCCA

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Absent from the new ASTM C90-00 are the Type definitions found in earlier versions of the standard. The terms "Type I, Moisture-Controlled Units" and "Type II, Nonmoisture-Controlled Units" no longer appear. As would be expected, Table 1 - Moisture Content Requirements for Type I Units, and the map of mean relative humidity are also gone.

Assuming there is a need for moisture-controlled CMU, the specifier has two options: make sure that references to ASTM C90 indicate an earlier edition, or add moisture control requirements to the specifications. Without correct specification of moisture content by one of these methods, contractors will be free to provide units that would be rejected under many current

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