TY - JOUR
T1 - Hydroxyapatite-based consolidant and the acceleration of hydrolysis of silicate-based consolidants
AU - Naidu, Sonia
AU - Liu, Chun
AU - Scherer, George W.
N1 - Funding Information:
This work was supported by grant MT-2210-12-NC-08 from the National Center for Preservation Technology and Training , a unit of the National Park Service. Its contents are solely the responsibility of the authors and do not necessarily represent the official position or policies of the National Park Service or the National Center for Preservation Technology and Training. The authors also wish to thank the Kress Foundation for financial support. We are also grateful for the use of Princeton University's PRISM Imaging and Analysis Center, which is supported in part by the NSF MRSEC program through the Princeton Center for Complex Materials (grant DMR-0819860). We thank David Boyer, President of PROSOCO Inc., for generously providing the Conservare OH-100 used in this study, and for his advice regarding consolidation.
Publisher Copyright:
© 2014 Elsevier Masson SAS.
PY - 2015/1/1
Y1 - 2015/1/1
N2 - Limestone, composed of the mineral calcite, is susceptible to environmental weathering processes that cause weakening from disintegration at grain boundaries. This paper discusses the effectiveness of hydroxyapatite (HAP) as an inorganic consolidant for physically weathered Indiana Limestone compared to a commercially available silicate-based consolidant (Conservare® OH-100). A double application is also investigated, in which samples are coated with HAP followed by Conservare® OH-100. Finally, a technique to accelerate the hydrolysis reaction of the initially hydrophobic Conservare® OH-100 is also developed. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite. To artificially weather limestone, so that the damage found in nature could be mimicked in the lab, a reproducible thermal degradation technique was utilized. Then, a mild wet chemical synthesis route, in which diammonium hydrogen phosphate (DAP) salt was reacted with limestone, alone and with cationic precursors, was used to produce HAP microfilms to consolidate the grains. The effectiveness of Conservare® OH-100 is investigated by applying it alone, and by following up with an ethanol-water rinse to accelerate the hydrolysis reaction. Samples that were to be rinsed were left to hydrolyze naturally over two and seven weeks before being reacted in the ethanol-water mixture. The dynamic elastic modulus (a measure of stiffness) and water sorptivity of the treated stones were evaluated. HAP was found to be an effective consolidant for weathered Indiana Limestone, as it restored the modulus of damaged stones to their original values and exhibited superior performance to Conservare® OH-100. Rinsing the Conservare® OH-100-treated stones increased stone hydrophilicity significantly, although not to the level of DAP-treated stones, as determined by water sorptivity. The formation of the consolidants in the pores and at grain boundaries was confirmed by scanning electron microscopy (SEM) and energy-dispersive X-Ray spectroscopy (EDX).
AB - Limestone, composed of the mineral calcite, is susceptible to environmental weathering processes that cause weakening from disintegration at grain boundaries. This paper discusses the effectiveness of hydroxyapatite (HAP) as an inorganic consolidant for physically weathered Indiana Limestone compared to a commercially available silicate-based consolidant (Conservare® OH-100). A double application is also investigated, in which samples are coated with HAP followed by Conservare® OH-100. Finally, a technique to accelerate the hydrolysis reaction of the initially hydrophobic Conservare® OH-100 is also developed. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite. To artificially weather limestone, so that the damage found in nature could be mimicked in the lab, a reproducible thermal degradation technique was utilized. Then, a mild wet chemical synthesis route, in which diammonium hydrogen phosphate (DAP) salt was reacted with limestone, alone and with cationic precursors, was used to produce HAP microfilms to consolidate the grains. The effectiveness of Conservare® OH-100 is investigated by applying it alone, and by following up with an ethanol-water rinse to accelerate the hydrolysis reaction. Samples that were to be rinsed were left to hydrolyze naturally over two and seven weeks before being reacted in the ethanol-water mixture. The dynamic elastic modulus (a measure of stiffness) and water sorptivity of the treated stones were evaluated. HAP was found to be an effective consolidant for weathered Indiana Limestone, as it restored the modulus of damaged stones to their original values and exhibited superior performance to Conservare® OH-100. Rinsing the Conservare® OH-100-treated stones increased stone hydrophilicity significantly, although not to the level of DAP-treated stones, as determined by water sorptivity. The formation of the consolidants in the pores and at grain boundaries was confirmed by scanning electron microscopy (SEM) and energy-dispersive X-Ray spectroscopy (EDX).
KW - Calcite
KW - Consolidation
KW - Dynamic elastic modulus
KW - Hydroxyapatite
KW - Limestone
KW - Silicate
KW - Sorptivity
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U2 - 10.1016/j.culher.2014.01.001
DO - 10.1016/j.culher.2014.01.001
M3 - Article
AN - SCOPUS:84921592113
SN - 1296-2074
VL - 16
SP - 94
EP - 101
JO - Journal of Cultural Heritage
JF - Journal of Cultural Heritage
IS - 1
ER -