conservation of sugaring marble by...
TRANSCRIPT
Conservation of sugaring marble by hydroxyapatite: Conservation of sugaring marble by hydroxyapatite: some recent developments on producing and treating decayed samples
Enrico Sassoni1,2, Gabriela Graziani1, Elisa Franzoni1, George W. Scherer2
1 Dept. Civil, Chemical, Environmental & Materials Engineering (DICAM), University of Bologna, Italy2 Dept. Civil & Environmental Engineering (CEE), Princeton University, USADept. Civil & Environmental Engineering (CEE), Princeton University, USA
[email protected], Website: https://events.unibo.it/hap4marble/
BACKGROUND
HELP!
Architectural decorations and sculptures made of marble,
when they are exposed outdoor, deteriorate because:
In 2011, we proposed the use of hydroxyapatite
(HAP) to preserve carbonate stones [1]
HELP!• Temperature variations
cause the opening of cracks
between calcite grains, so
HAP can be formed directly inside marble and
over marble surface, from the reaction between
calcite and an aqueous solution of diammonium
• Rain causes the dissolution
between calcite grains, so
that grains detach and fall
calcite and an aqueous solution of diammonium
hydrogen phosphate (DAP) in mild conditions
• Rain causes the dissolution
of calcite grains, so that the
marble carved surface is lost
The products currently available are not
effective and/or durable in preserving marble effective and/or durable in preserving marble
against these deterioration causes
RESEARCH AIMS
1
Accelerated ageing
2
Treatment parameters
4
Protection
3
Consolidation
1 2 43
To study the consolidating efficacy of the
HAP treatment, artificially aged samples
with characteristics similar to naturally
The treatment parameters need to be
optimized to reduce the porosity of
the HAP layer, increase the surface
The ability of the HAP treatment to
prevent the dissolution of marble
surface in rain, by formation of a dense
The ability of the HAP treatment to re-
establish cohesion between calcite grains
and restore the strength of weathered with characteristics similar to naturally
sugaring marble (i.e. micro-cracks more
diffused near the surface) are needed
the HAP layer, increase the surface
coverage and prevent the formation of
soluble calcium phosphate phases
surface in rain, by formation of a dense
coating with low solubility, needs to be
investigated
and restore the strength of weathered
marble, without causing over-
consolidation, needs to be investigated
MATERIALS AND METHODS RESULTS AND DISCUSSIONMATERIALS AND METHODS RESULTS AND DISCUSSION
1 Ageing was produced by
heating samples over a hot
Heating at 200 °C for 20 sec
was predicted to cause an ∂T
∂=
∂
∂k(x, t)
∂T
∂
T = temperaturet = timex = distance from plate
UPPER 1 cm
ExperimentsTheoretical model
d
1heating samples over a hot
plate, the temperature and
time of heating being
calculated by a theoretical
was predicted to cause an
average ΔEd = -35% in the
first 1 cm from the surface,
leaving the rest undamaged.
200 °C for 20 secbefore ageing after ageing
∂t=
∂xk(x, t)
∂x t = timex = distance from platek = thermal diffusivity
UPPER 1 cm
% o
f in
itia
l E
d
UP
PE
R 1
cm
LOW
ER
1 c
m
calculated by a theoretical
model. Damage was assessed
by measuring the modulus Ed
leaving the rest undamaged.
Experimental results
confirmed the predictiontravelling time t1 → Ed1 time t2 > t1 → Ed2 < Ed1
LOWER 1 cm
% o
f in
itia
l E
Distance from the plate (cm)
UP
PE
R 1
cm
LOW
ER
1 c
m
2 Ethanol addition favors
marble surface coverage and
The influence of several
treatment parameters
travelling time t1 → Ed1 time t2 > t1 → Ed2 < Ed1
Organic additions
pHcontrol
SE
M2marble surface coverage and
helps reduce the porosity of
the HAP layer, as it weakens
the hydration shell of the
treatment parameters
(ethanol addition, pH control,
double treatments [2]) was
investigated and the effects
additions
Ca2+ ions additions
control
e-
3
the hydration shell of the
phosphate ions in solution
investigated and the effects
evaluated by SEM-FIB
The increase in marble 3 Double application of the
HAP treatment with 10 vol%
ethanol was able to fully
The increase in marble
cohesion after consolidation
was assessed by measuring
after
consolidationconsolidationbefore
consolidationHAP inside
cracks
10 vol% EtOH
ethanol was able to fully
restore the Ed, thanks to
HAP formation inside cracks
formed by artificial ageing
was assessed by measuring
the increase in modulus Ed
and observing the new
phosphate phases by ESEMtravelling time t1 travelling time t2 < t1
from t1 → Ed1 from t2 → Ed2 > Ed1
cracks
4
formed by artificial ageing
The HAP coating was able to
reduce marble dissolution,
phosphate phases by ESEM
The resistance to dissolution
was assessed by measuring
pH measurement
from t1 → Ed1 from t2 → Ed2 > Ed1
10 vol% EtOH4reduce marble dissolution,
even if cracks appeared after
the test. The orientation of
the underlying calcite grains
was assessed by measuring
the increase in pH vs time
of an aqueous solution of
HNO initially at pH=5
HNO3 solution
initially at pH=5
the underlying calcite grains
influences the film durability
HNO3 initially at pH=5
(simulating slightly acid rain)
REFERENCESACKNOWLEDGEMENTSCONCLUSIONS AND FUTURE WORK
[1] Sassoni E., Naidu S., SchererG.W., The use of hydroxyapatite as
a new inorganic consolidant for
damaged carbonate stones, J CultHerit 12 (2011) 346-355 [2] Graziani
This project has received funding fromthe European Union’s Horizon 2020programme through the Marie
Skłodowska-Curie HAP4MARBLE
The developed model allows to produce
samples with a desired level of damage.
The addition of ethanol is effective in
Ethanol has a competitive effect, as it weakens the
hydration shell of the phosphate ions in the solution
but it is adsorbed on calcite surface. Herit 12 (2011) 346-355 [2] GrazianiG., Sassoni E., Franzoni E., SchererG.W., Hydroxyapatite coatings for
marble protection: Optimization of
calcite covering and acid resistance,
Skłodowska-Curie HAP4MARBLE
Project (Multi-functionalization ofhydroxyapatite for the restoration and
preventive conservation of marble
The addition of ethanol is effective in
promoting HAP formation and reducing the
film porosity, thus allowing to achieve a good
consolidating and protecting ability
but it is adsorbed on calcite surface.
Future research will be aimed at identifying by NMR
possible alternative solvents that may weaken the
hydration shell without being adsorbed on calcitecalcite covering and acid resistance,Appl Surf Sci, 368 (2016) 241-257
artworks, grant agreement No 655239)film porosity, thus allowing to achieve a good
consolidating and protecting ability
possible alternative solvents that may weaken the
hydration shell without being adsorbed on calcite