Improved understanding of internal curing processes and how pre-wetted, lightweight aggregate economically increases concrete durability is driving development of an ASTM International standard, WK34078, Specification for Lightweight Aggregate for Internal Curing of Concrete.
“Concrete, especially high performance concrete, is designed to limit permeability and reduce chloride ingress,” says Expanded Shale, Clay and Slate Institute Technical Director John Ries, ASTM C09 Committee on Concrete and Concrete Aggregates member. “Unfortunately, these properties also limit the ability of externally applied curing water to reach the interior of the concrete. The main objective of internal curing is to provide a source of additional water to maintain saturation of the cementitious paste and avoid its self-desiccation.”
Internal curing can significantly lengthen concrete service life by increasing cement hydration, he adds, providing more complete reaction of supplementary cementitious materials and reducing chemical and drying shrinkage. Developed under ASTM Subcommittee C09.21 Lightweight Aggregates and Concrete, the proposed new standard will suit specifications for road and parking lot pavement, bridge and other heavy civil projects. Among prospective users will be the Federal Highway Administration and state departments of transportation.
WK34078 development will be on the Subcommittee C09.21 agenda during ASTM Committee C09 meetings, December 4–7 in Tampa, Fla. Contacts: John Ries, 801/272-7070, [email protected]; ASTM staff liaison, Scott Orthey, 610/832-9730; [email protected].