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Cite this document
Material deterioration in historic masonry structures is typically diagnosed by field investigation and material testing. Detailing and specifying effective repairs requires understanding deterioration mechanisms and how to apply modern standards to archaic materials and construction. In 2008, the United States Army Corps of Engineers considered dismantling the 87-ft-tall Grant Hall Clock Tower that had stood sentinel over Fort Leavenworth since 1908. Falling masonry prompted an inspection that identified heavily coated, crumbling brick in the tower walls, but did not identify a cause of deterioration. A theory developed that the tower was constructed using the inconsistent-quality, prisoner-made brick, prevalent throughout the garrison and thus was at the end of its life. The architectural and engineering consultants hired to evaluate the tower and develop treatment recommendations considered this theory as they undertook a thorough examination of the tower’s exterior and interior condition. Based on direct close-range observation and limited destructive investigation the A/E team theorized that the deterioration was not caused by inferior brick, but to decades of unchecked water penetration, unexpectedly hard original mortar, and coatings that prevented drying. Together, these conditions allowed moisture to saturate the full thickness of the walls. ASTM C67 [Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2007] analysis of the brick supported this theory, but ASTM C1324-04 [Standard Test Method for Examination and Analysis of Hardened Masonry Mortar, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2004] analysis of the mortar did not. The A/E team questioned the mortar analysis because the results were contrary to their direct physical experience with the mortar. Based on knowledge of historic mortar materials, the team relied on their field observations. Although the quality of the primary structural material was verified, the exterior wythe of brick was heavily coated and damaged. The A/E team was challenged to specify an innovative replacement of the entire exterior brick wythe in the three- and four-wythe structural masonry walls. The repairs needed to be constructible, compatible, and safe for the workers and occupants in the offices below.
brick replacement, masonry rehabilitation, masonry evaluation, mortar testing, archaic masonry construction, ASTM C1324, ASTM C270, ASTM C216, ASTM C1713
Mathias Manglitz, Julia E.
Project Manager, Treanor Architects, P.A., Topeka, KS
Vance Kelley, K.
Principal, Treanor Architects, P.A., Topeka, KS
Professional Engineer, Dudley Williams and Associates, P.A., Wichita, KS