Skip navigation
Please use this identifier to cite or link to this item:
Title: Novel Hydroxyapatite Coatings for the Conservation of Marble and Limestone
Authors: Naidu, Sonia
Advisors: Scherer, George W
Contributors: Chemical and Biological Engineering Department
Keywords: acid rain
Subjects: Chemical engineering
Materials Science
Civil engineering
Issue Date: 2014
Publisher: Princeton, NJ : Princeton University
Abstract: Marble and limestone are calcite-based materials used in the construction of various structures, many of which have significant artistic and architectural value. Unfortunately, due to calcite's high dissolution rate, these stones are susceptible to chemically-induced weathering in nature. Limestone, due to its inherent porosity, also faces other environmental weathering processes that cause weakening from disintegration at grain boundaries. The treatments presently available are all deficient in one way or another. The aim of this work is to examine the feasibility of using hydroxyapatite (HAP) as a novel protective coating for marble and limestone, with two goals: i) to reduce acid corrosion of marble and ii) to consolidate physically weathered limestone. The motivation for using HAP is its low dissolution rate and structural compatibility with calcite. Mild, wet chemical synthesis routes, in which inorganic phosphate-based solutions were reacted with marble and limestone, alone and with other precursors, were used to produce HAP films. Film nucleation, growth and phase evolution were studied on marble to understand film formation and determine the optimal synthesis route. An acid resistance test was developed to investigate the attack mechanism on marble and quantify the efficacy of HAP-based coatings. Film nucleation and growth were dependent on substrate surface roughness and increased with calcium and carbonate salt additions during synthesis. Acid attack on marble occurred via simultaneous dissolution at grain boundaries, twin boundaries and grain surfaces. HAP provided intermediate protection against acid attack, when compared to two conventional treatments. Its ability to protect the stone from acid was not as significant as predicted from dissolution kinetics and this was attributed to incomplete coverage and residual porosity within the film, arising from its flake-like crystal growth habit, which enabled acid to access the underlying substrate. The effectiveness of HAP as a consolidant for weathered limestone, alone and coupled with a commercially available consolidant (Conservare® OH-100), was also investigated. To artificially weather limestone in the lab, a reproducible thermal degradation technique was utilised. The dynamic elastic modulus, water sorptivity and coating composition of treated stones were evaluated. HAP was found to be an effective consolidant for limestone, as it restored the elastic modulus of damaged stones to their original values and exhibited superior performance to Conservare® OH-100.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Chemical and Biological Engineering

Files in This Item:
File Description SizeFormat 
Naidu_princeton_0181D_11006.pdf3.96 MBAdobe PDFView/Download
Naidu_princeton_0181D_408/phosphate.nb1.25 MBUnknownView/Download
Naidu_princeton_0181D_408/carbonate.nb670.93 kBUnknownView/Download
Naidu_princeton_0181D_408/marbledissolutionv3.nb509.74 kBUnknownView/Download

Items in Dataspace are protected by copyright, with all rights reserved, unless otherwise indicated.