jornadas
cidades e desenvolvimento | LNEC, Lisboa, 18 – 20 junho 2012
engenharia para a sociedade investigação e inovação
• Consolidation of stone, plasters and renders: lack of efficient products for calcareous substrates (e.g. limestone and lime-based mortars, Fig.1).
• Nanolimes (colloidal dispersions of calcium hydroxide) should overcome the limitations of traditional consolidants (e.g. limewater), but do not always guarantee a in depth consolidation.
• Research aim: evaluate the effectiveness of new nanolimes (structure, drying rate and kinetical stability). INTRODUCTION
• New nanolimes (conc. 25g/l) synthetized by solvothermal reaction; • Solvent modified using pure ethanol, isopropanol, butanol, water;
• New developed nanolimes applied by capillary absorption (Fig. 3b) on 4x4cm specimens of Maastricht limestone and of lime-based mortars (1:4 lime-aggregate ratio); pore size distribution presented in Fig. 2;
• Nanosize and morphology characterized by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM-EDS).
• Kinetical stability studied by Uv-Vis spectroscopy (absorption at λ=600nm) and monitored over time (0 to 96h);
• Absorption and drying kinetics (50% RH; T=20º) on Maastricht limestone and lime-based mortars.
MATERIALS & TEST CONDITIONS Identification Solvent
composition E25 100% Ethanol (EtOH) IP25 100% Isopropanol (IpOH) H25 100% Water (H20) B25 100% Butanol (BOH)
RESULTS
Fig. 5 - a) Nanosize distribution (DLS) after 1h and 96h of nanolime E25; b) Evolution of the nanosize over time of E25, IP25 and B25 nanolimes.
Ta b . 1 – Mo d ifi ed nanolimes
• E25, IP25 and B25: lack of deposition of lime nanoparticles in depth in the treated material, due to the high kinetical stability of these modified nanolimes. H25: highly instable, nanoparticles end up accumulated at the absorption surface.
• Mixture of solvents appears as a promising strategy to enhance a homogeneous penetration of the nanoparticles, followed by a precipitation of the nanoparticle in the treated substrate.
• Different pore size distributions (e.g. limestone vs lime-based mortar) influence the drying rate of the nanolimes, and therefore the transport of the nanoparticles: it is necessary to optimize the solvent based on the properties (e.g. pore size distribution) of the material to be treated.
CONCLUSIONS
Fig. 3 - Application by capillary absorption of new Nanolimes on Maastricht limestone core specimens.
Fig. 4 - SEM-EDS microphotographs of a,b) E25 and c,d) IP25.
Fig. 8 - Kinetical stability of nanolimes by Uv-Vis spectroscopy; the dotted (Maastricht limestone) and solid (lime-based mortars) rectangles approximately indicate the end of the step I drying of the relative nanolimes, which corresponds to the settling of the lime nanoparticles.
Fig. 6 - a) Absorption and b) drying kinetics of E25, IP25, B25 and H25 and their relative solvents applied on Maastricht limestone.
0 0,5 1 1,5 2 2,5 3 3,5 0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 Ab so rb an ce (a t λ= 600nm ) t (h) H25 E25 IP25 B25
G. Borsoi
a, R. van Hees
b, B. Lubelli
b, L. Colla
c, L. Fedele
c, P. Tomasin
d, R. Veiga
e, A. Santos Silva
fa Heritage & Architecture Sec/on, Faculty of Architecture, Del8 University of Technology, Del8, The Netherlands, G.Borsoi@tudel8.nl
b Division of Structural Reliability, TNO, Del8, and Heritage & Architecture Sec/on, Faculty of Architecture, Del8 University of Technology, Del8, The Netherlands
c Construc/on Technologies Ins/tute, Na/onal Research Council -‐ CNR, Padua, Italy
d Ins/tute for Energy and Interphases, Na/onal Research Council -‐ CNR, Padua, Italy
e Building Division, Na/onal Laboratory for Civil Engineering -‐ LNEC, Lisbon, Portugal
f Materials Division, Na/onal Laboratory for Civil Engineering -‐ LNEC, Lisbon, Portugal
a) b)
c) d)
Fig. 1 - a) Roman stone masonry with l i m e - b a s e d m o r t a r s ( P i s õ e s Archaeological site, PT); b) masonry of Maastricht limestone (Kessel Castle, NL).
• Nanoparticles morphology: rounded to hexagonal shape (Fig. 4a), no significant differences when dispersed in different alcoholic solvents, but quick agglomeration in water;
• Nanosize: nano to submicrometric size (70 to 500nm, Figs. b,c), some bigger clusters of nanoparticles or unreacted metallic calcium (3-5 µm) (Fig. 4d); Nanosize of E25, IP25 and B25 remains constant over time (>96h) (Fig. 5a); H25 instead highly instable and settles in few hours (Fig. 8);
• Absorption kinetics: H25 faster compared to other nanolimes, due to higher surface tension of water (3 times higher then EtOH, IpOH or BOH) (Figs. 6a,b); Nanoparticles of B25 deposit and agglomerate at the absorption surface of Maastricht limestone; nanoparticles of H25 deposit at absorption surface of both Maastricht limestone and lime-based mortars;
• E25 and IP25 penetrate homogenously, but nanoparticles migrate back to the drying surface: the high kinetical stability and volatility of the nanolimes inhibit the phase separation of the lime nanoparticles from the alcoholic solvent.
• Drying kinetics: the solvent of the modified nanolime (E25, IP25, B25) evaporates faster compared to H25 (Figs. 7a,b). 0 0,5 1 1,5 2 -‐ 10,00 20,00 30,00 40,00 50,00 Ab so rb ed l iq ui d / Ar ea (c m 3/c m 2) t (sqrt sec) EtOH IpOH BOH E25 IP25 B25 H20 H25
1st Interna/onal Conference on Science and Engineering in Arts, Heritage and Archaeology, July 14-‐15th, 2015, University College, London
a) 0 0,5 1 1,5 2 0 100 200 300 400 Ev ap or at ed li qu id / Ar ea (c m 3/c m 2) t (h) E25 IP25 B25 EtOH IPOH BOH H20 H25 0 0,4 0,8 1,2 1,6 0,00 10,00 18,97 25,69 30,98 37,95 64,81 As or ve d liq ui d / Ar ea (c m 3/c m 2) t (sqrt sec) EtOH IpOH BOH E25 IP25 B25 H2O H25
Fig. 2 - Pore size distribution of lime-based mortars (red) and of Maastricht limestone (blue).
End of step I drying 0 0,4 0,8 1,2 1,6 0 50 100 150 200 Ev ap or ed li qu id / Ar ea (c m 3/c m 2) t (h) E25 IP25 B25 EtOH IpOH BOH H20 H25
Fig. 7 - a) Absorption and b) drying kinetics of E25, IP25, B25 and H25 and their relative solvents applied on lime-based mortars.
End of step I drying a) b) b) a) b) 0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 0,01 0,10 1,00 10,00 100,00 1000,00 inc re m ental intr usion vo lu m e (% vo l/ vo l)
Pore Size Diameter (µm) Maastricht Limestone Lime mortars 0 2 4 6 8 10 12 0,1 1 10 100 1000 10000 In te ns ity (%) Diameter (nm) E25_96h E25_1h 300 350 400 450 500 0 8 24 48 72 96 Nanosiz e (nm ) t (h) B25 E25 IP25 a) b)
