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Present: Larisa Allen, Mark Almeda, Bill Barry, Nicole Benjamin-Ma, David Bliss, Matthew Bronski, Susan Browner, Sara Correia-Eck, Marilyn Fenollosa, Leslie Friedman, David Gallagher, Jack Glassman, Patrick Guthrie, Jeffrey Harris, David M. Hart, David Kelman, David King, Ryan Maciej, Doug Manley, Krista McFadden, Henry Moss, Ivan Myjer, Deborah Robinson, Susan Schur, John Seward, Jonathan Smith, Natalie Wampler, Eric Ward, John Wathne, Sara Wermiel 1. Sustainable Design Topics: The committee again discussed technical topics for which additional research is needed, some of which would be suitable for HRC sessions and some might be packaged for NCPTT research grant applications. The topics that arose were:
2. ASTM C 12.03.03 & Mortars for the Preservation of Masonry: John Wathne of Structures North heads an ASTM committee that is in the final stages of drafting a Standard Specification for Mortars for Use with Archaic Masonry Materials. John's interest in the mysteries of early mortars coalesced when he investigated cracking and failing stone masonry on the tower of the 1870's Immaculate Conception Church in Lowell. The church was built with hydraulic lime and had an exceptionally high ratio of mortar to stone (little if any stone-to-stone contact). John's research into the lime mortar literature yielded little consensus on such matters as materials definition, cure times for test strengths, long-term strength versus time curves, and hard scientific data on comparability of performance between mortars made with hydraulic lime or Portland cement. The ASTM committee includes scientists, manufacturers' representatives, contractors, a few architects, and a few engineers. Our BSA committee is the first outside group to see a draft version of the guidelines. John asked us for comments. John noted the increasing commercial availability of natural cements and hydraulic lime and lime putty (Rosendale cement, Virginia Lime Works). These increase the relevance of an ASTM standard specification for such materials. The standard that John's committee is drafting, ASTM C 12.03.03 is a brand new, stand-alone document, not a sub-section of the current standard, C 270, first issued in 1950 for Mortars for Building Construction; it was drafted to address modern materials. The standard's first section defines its scope. John explained that "archaic" refers to masonry constructed prior to 1947 (when C 270 was introduced) to remind specifiers to think carefully about their buildings. Ivan Myjer emphasized the possible existence of Portland cement mortars in historic structures by noting that he would definitely expect to use C 270 for a 1913 building. John emphasized that C 12.03.03 will be strictly a material standard and not a guide to its application. The standard's second section lists referenced documents, a compendium of ASTM standards for material specifications, practices (mechanical mixing), and test methods. Susan Schur advised that the dates of last adoption be incorporated in references to previous standards. The third section addresses terminology and notation. Susan Schur asked if definitions in C 12 are compatible with American Concrete Institute and Cast Stone Institute usage. Section 4 is devoted to constituent materials. John explained that the standard will reference three groups of natural cement as binders under "Constituent Materials" that are sorted by how they cure: >Group L: Slaked Lime-including: o Type S and SA hydrated limes of C 270 o Types N and NA if shown by test or performance record not to be detrimental to mortar o Lime putty of Specification C 1489, C 5 Specification for Quicklime for Structural Purposes, Appendix 1 and the resulting putty shall meet the requirements of C 1489 >Group HL: Hydraulic Hydrated Lime of Specification C 141 >Group HC: Hydraulic Cements-including: o Portland Cement of Specification C 150 o Blended Hydraulic Cement of Specification C 595 o Hydraulic Cement of Specification C 1157 (Sara Wermiel attributed threshold status to a cement created by Smeaton in the 18th century noting that Portland was called "artificial cement.") o Masonry Cement of Specification C 91 o Mortar Cement of Specification C 1329 o Natural Cement of Specification C 10 [ASTM C 10, Standard Specification for Natural Cement, discontinued in the 1940's was reinstated in 2006 and updated for republication in December, 2007 to describe the material now available as Rosendale Natural Cement through Edison Coatings, Inc. (800) 341-6621. Michael Edison and Ken Urasius restarted production Rosendale natural cement in 2004, about 25 years after the last of the original argillaceous limestone mines were closed. The material was extensively used in early 19th century canal construction, for concrete-filled caissons and granite superstructure of the Brooklyn Bridge (1883), and for Hunt's pedestal at the Statue of Liberty. John said that we could recognize the presence of Rosendale cement in old mortars by the russet hue it contributes. Section 5 addresses mortar proportioning for binder material combinations and binder/aggregate ratios. Ivan mentioned that gypsum was often used as a binder/setting mortar (often for art tile or mosaics) in locations not exposed to weather, and also sometimes incorporated as an additive for accelerated cure. David Gallagher asked about hair and asbestos fibers in mortar. The sixth section of the proposed standard includes an extensive series of requirements for mortars described either by Proportion Specification (prescriptive requirements) or Property Specification (performance-based requirements). Table 1 addresses both methods with requirements for water retention, air content, curing time (samples not in situ), porosity, water vapor permeability, minimum and maximum compressive strengths, flexural bond strength, and initial rate of absorption. John emphasized that water vapor permeability is specifically written into this new standard. This led to an exchange of comments about the relative permeability of even a low permeability mortar, compared to most stones, and the relative permeability of soft brick compared to sandstone, the relative permeability of sandstone or limestone as compared to granite. Consequently, some noted the resultant difficulty of making a one-size-fits-all recommendation for permeability or hardness of mortars in historic masonry. Matthew Bronski noted approvingly that both Preservation Brief #2 and the ASTM C270 standard have thoughtful, similar tables that consider both the hardness of the unit masonry (e.g., granite, limestone, hard brick, soft brick) and the severity of the exposure to the weather (e.g., severe, moderate, sheltered) in recommending an appropriate hardness of mortar for a particular circumstance. The final section defines requirements for test samples and their preparation in similar terms. Table 2 of the draft C 12 stipulates the bulk density of binder materials per cubic foot. Table 3 specifies the storage time in molds for Groups L, HL, and HC. Carbonation depends on exposure to carbon dioxide, therefore the shape and size of test molds is also important. The committee suggested that the document specify that tests be carried out by a "certified laboratory," but left John to describe the necessary certification. John solicited specific suggested changes to the draft standard from our committee as a "user group". Individual HRC members offered John and his ASTM committee the following specific suggestions: Section 1 (Scope): >Clarify explicitly that this spec. is not necessarily pertinent or appropriate for any pre-1951 building. Don't want to give any readers the impression that they should use this standard on any pre-1951 building. ASTM C270 is pertinent and appropriate for many turn of the 20th century buildings. >Several voiced appreciation and approval of the usage statement (1.5) that leaves discretion in use and application of the standard to the user. Section 3 (Terminology and Notation): >Clarify what "pre-dating current codes" means. Does this mean current building codes, current ASTM codes (if so, which?), or does it mean specifically pre-dating C270 (and hence, pre-1951)? Section 4 (Materials): >Perhaps either include gypsum and gypsum-related mortar materials, or specifically say they are excluded and not covered by this standard. If included, need to redefine "Scope" of the document to cover them. >Perhaps include animal hair as "fiber reinforcement"? Or at least note that it may exist in and may be appropriate for some archaic mortars, though not described or specified herein. Same for traditional organic admixtures, such as animal blood or raw eggs. Suggest changing the term "manufactured admixtures" to simply "admixtures", to allow mention or coverage of these traditional non-manufactured organic admixtures. Section 6 (Requirements): >Under the curing time requirements, need to make absolutely clear whether the curing time is for the test samples (like the ASTM specs for curing concrete cylinders) or whether it is the curing time for the in-situ mortar installation (like the ASTM curing requirements for exterior cement plaster/stucco). >Explicitly state the curing regimen and duration. Is it to wrap the mortar in damp burlap or burlene and mist every 4 hours for X days? Is it protect from sun and wind with polyethylene, but no misting, for x days? Is curing of the samples required to mirror the curing conditions of the in-situ installation? Be explicit. 3. H. H. Richardson House, Preservation Awards: Marilyn Fenollosa told the committee about the nomination she had prepared for this year's Massachusetts Historic Commission (MHC) Preservation Awards that concentrates on the generosity, stamina, devotion, and organizational skills of the Hoppins and Alan Galper. Leslie Friedman, who lives in Brookline said she would explore possibilities for presenting the BSA Historic Preservation Award to the same recipients and some of their ancillary advocates at an event in association with the Brookline Historical Commission. 8: 00 a.m., Thursday, March 13, 2008 Featuring Works in Progress: >Wendall Kalsow - Gasson Hall Boston College: Cast Stone >Natalie Wampler (with support from Bill Barry and David Gallagher) - Mt. Auburn Cemetery Preservation Initiative and >Ivan Myjer - Discussion of Current Issues in the Realm of Stone Consolidants
Third Floor The Architects' Building, 52 Broad Street, Boston Henry Moss, Matthew Bronski, and Sara Wermiel co-leaders and scribes
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