Rationale

CMU manufactured to meet C90 are machine-made using dry-cast concrete in a similar manner to other dry-cast manufactured concrete products including C55 Concrete Brick, C936 Concrete Pavers, C1319 Grid Pavers, C1372 SRW Units, C1634 Concrete Facing Brick, C1792 Concrete Paving Slabs, C1884 Ballast Units, etc. Currently, only C1372, Specification for Dry-Cast Segmental Retaining Wall Units, refers to Dry-Cast in the title of the specification. In recent years, the carbon footprint of all building materials including concrete products has become a focus of the design and specifying community. Research conducted over the past few years at CMHA has demonstrated that dry-cast CMU have significantly higher natural carbon sequestration rates after they are manufactured compared to wet-cast concrete because the more porous structure of the dry-cast concrete allows carbon dioxide to easily penetrate into the CMU which differentiates it from wet-cast concrete. This result in significantly higher natural carbonation rates which lowers the carbon footprint of CMU. To help communicate the carbon footprint benefits of using dry-cast concrete, this ballot item proposes to include ‘Dry-Cast’ into the title of C90. The changes to the Scope are modeled after C1372. In addition to these changes, a definition for dry-cast is being added under the Terminology section and dry-cast is being added as a Keyword. This definition is similar to the one in C1372 with a few modifications to improve clarity. These modifications to the definition will also be proposed in a separate ballot item for C1372.