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Wednesday, May 15 • 2:00pm - 2:30pm
(Architecture) Mortar Mishaps: Testing the Freeze/Thaw Durability Of Common Restoration Repair Mortars

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Many architectural conservators, especially those working far from home, complete a project, take the after photographs and never return. But how many have completed a project and been proud of their work, only to return a year or two later and be disappointed by how poorly the repairs have aged? Jablonski Building Conservation, Inc. has been fortunate enough to work on several multi-phased cemetery projects which have allowed us to see how treatments held up over time. The results have not always been as expected. Since we occasionally work as the contractor, we do not always have control over the products specified, and we have been required to use some patching repair mortars which had faded, cracked, or failed completely within a couple of years. While some repair mortars may be great at filling the larger, deeper spalls often found on architectural elements, they may not be as durable on the thin patches required for many brownstone markers. Other products, made without cement, are perfect for warmer climates, but may not withstand the cyclical freeze/thaw of a typical northeast winter. In an effort to gain a greater understanding of the performance of these mortars, I will be conducting a series of freeze/thaw tests, using a modified version of ASTM C666 Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing. Testing will look at several different commercially available patching materials including a natural hydraulic lime-based, a commercial Portland cement and lime, and an acrylic modified cement and lime material. Custom mixes in Type N and Type O will also be tested. A minimum of three samples for each material will be tested. Testing will include both mortar cubes and simulated patches of different depths on multiple types of stone including brownstone and marble. One set of repair mortars will be mixed, applied, and cured as per the manufacturer’s written instructions. A second set will be mixed with the minor modifications often done in the field to increase workability. A minimum of 50 freeze/thaw cycles will be performed and the patches will be evaluated for weight loss, cracks, spalls, and any visual changes to the sample. While some conservators stress the use of patching materials made without cement, is a small amount of cement required to allow these materials to survive New England winters? This presentation will compile the data and share the results with other conservators.

avatar for Stephanie M. Hoagland-[PA]

Stephanie M. Hoagland-[PA]

Principal, Jablonski Building Conservation, Inc.
Stephanie M. Hoagland is a Principal and Architectural Conservator with Jablonski Building Conservation Inc. where she has been employed since 2003. She has a Master of Science in Historic Preservation from Columbia University’s Graduate School of Architecture, Planning and Preservation... Read More →

Wednesday May 15, 2019 2:00pm - 2:30pm EDT
Salon A1, Uncas Ballroom Sky Convention Center, Mohegan Sun
  Specialty Session, Architecture