Important Changes to ASTM C90-00

Dick Walter, P.E./CAE, Executive Technical Director

A change to ASTM C90 was recently recommended by Committee C 15 that will have a major impact on design professionals, concrete block producers and mason contractors. This change is one that we have been trying to accomplish for many years: the removal of Type I and Type II units and the deletion of a table for moisture content requirements for Type I units. These changes were incorporated in the standard by the entire ASTM C90 Committee as part of Designation C90-OO.

We have been maintaining for years that Wisconsin block companies produce the best C/M units in the country, with high compressive strength and low absorption. However, we feel Type I, or moisture controlled units, still have the same ability to absorb moisture as do Type 11 units and therefore require the same attention to control joint spacing. This change to ASTM C90 will put crack control design in concrete masonry buildings back in the hands of the design professionals rather than depending on a laboratory test to determine control joint spacing.

The Wisconsin Concrete Masonry Association feels these changes to ASTM C90 are so monumental, they are planning to issue a technical paper that encompasses these changes as well as other information on crack control. Until the TECH is completed, please feel free to contact WCMA with any questions.