ASTM Standard Revisions Benefit Historic Restoration Projects
Last December I attended a three-day conference for ASTM. I was on the C12 Committee for mortars and grouts, and we were discussing ASTM standards that affected masonry construction.
Two of the standards most typically used in specifications for mortar are ASTM C144 (Standard Specification for Aggregate for Masonry Mortar) and C270 (Standard Specification for Mortar for Unit Masonry). While these standards cover a wide range of mortars, they do not specifically cover historic mortars used for restoration of historic and older buildings.
Many times when we want to replicate an existing mortar for a historic building restoration project the aggregate gradation and mortar strength falls outside of what is specified in the ASTM C144 and C270 standards. There have been projects where this deviation has become a source of contention and argument with the contractor, who claims as long as they meet the ASTM requirements referenced in the specifications we cannot reject their mortar samples.
These deviations are addressed and accommodated in ASTM C1713 (Standard Specification for Mortars for the Repair of Historic Masonry); however, C1713 is not referenced within C144 or C270. My goal at the conference was to introduce a revision to ASTM C144 and C270 to reference ASTM C1713 for historic restoration projects.
At the completion of the conference the revision to ASTM C144 had been approved. The revision to ASTM C270 was to be submitted for balloting to the membership and was expected to pass.
- Richard L. Applebaum, P.E., SECB