Concrete block optimization drives NCMA-proposed ASTM C90 revision

Source: National Concrete Masonry Association, Herndon, Va.

By Don Marsh

A change in ASTM C90-prescribed web configuration for concrete block has the potential to lower products’ material use and transportation costs; increase masons’ productivity through lighter units, while reducing fatigue and injury associated with heavier block handling; ease rebar congestion and grout placement in reinforced wall assemblies; and, boost R-values by a factor of 3 to 4, owing to improved thermal properties.

An NCMA-proposed web area reduction of up to 75 percent is in ballot with ASTM Committee C15.03 on Concrete Masonry Units and Related Units, which oversees  C90 – 11 Standard Specification for Loadbearing Concrete Masonry Units. In a typical CMU, three webs of at least 1-in. thickness connect the 8- x 16-in. face shells. C90 could be changed to recognize such units molded with single, ¾-in. thick webs, NCMA contends, positioning the standard to reflect more current block-making technology and wall engineering. Some prescriptive C90 requirements have not changed in more than a half-century, the association notes, thereby failing to pace production technology, design trends and building code demands.

The proposed web area optimization may drive new block-handling recommendations to minimize breakage; alternative grout placement procedures to reduce blowouts; and, changes to design tools that are influenced by unit configuration, including fire resistance, sound transmission and structural resistance. Representing NCMA on the C90 proposal is Vice President of Engineering Jason Thompson, [email protected]; 703/713-1900. Ballot results will be reviewed during C15 committee meetings the week of June 13 in Anaheim, Calif.