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An old standby meets sustainability era

“A product as old as time.” That’s how our cover story subject, Shaw Brick of Nova Scotia, describes its core offering in a 150th anniversary timeline. Market share-driven acquisitions, plant investment, and integrated production and distribution of clay and concrete masonry units have kept the Shaw brand a fixture in North American masonry.

Shaw management also credits company longevity to an ability to demonstrate “success through change, and developing and refining an extensive stable of products and services based on today's needs.” A similar philosophy compels another masonry market fixture, with nearly a century under its belt, to pursue new standards and guidelines for concrete block.

In an effort to keep members’ core product competitive in a construction market demanding more than versatility and structural efficiency, the National Concrete Masonry Association has proposed a key change to ASTM C90 Standard Specification for Loadbearing Concrete Masonry Units: A web area reduction by up to 75 percent from the current standard’s requirements. Results from initial balloting will be reviewed at this month’s meetings of Committee C15.03 on Concrete Masonry Units and Related Units.

NCMA outlines design and production economy rationale in “ASTM C90 – Revisions to Minimum Equivalent Web Thickness.” A change in 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.

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.

Representing NCMA on the C90 proposal is Vice President of Engineering Jason Thompson. He is also responsible for the new NCMA Performance Guidelines For Concrete Masonry Units. It offers commentary on the web thickness proposal, plus the use of mix constituents beyond ASTM C150 cements and C33 aggregates, including recycled glass- or demolition concrete-derived aggregates. Both have potential to impart in finished concrete masonry walls a level of recycled material content conducive to the green building goals of many architects, engineers or their clients. “Performance Guidelines” sets recommended assessment and performance criteria for producers considering the use of alternative materials in block making, and provides background and tools necessary to assess the impact a substantial change in mix materials might have on CMU in service.

NCMA released “Performance Guidelines” and proposed the C90 change fully respecting that certain markets and customers will continue to require CMU with legacy mix constituents and web configuration. Mirroring the National Ready Mixed Concrete Association’s Prescriptive to Performance (P2P) initiative, the NCMA measures are guided by patience, protocol and, above all, sound engineering and construction practice.