Slaked lime (Ca(OH)2) nanoparticles were exposed at 33% and 75% relative humidity (RH) to consolidate dolostone samples used in historical buildings. Non-destructive techniques (NDT) were applied to determine the chemical, morphological, physical and hydric properties of the stone samples, before and after 20 days treatment. Morphological and mineralogical characterisation of the nanoparticles was performed. 75% RH favors the consolidation process studied under Environmental Scanning Electron Microscopy (ESEM-EDS), spectrophotometry, capillarity, water absorption under vacuum, ultrasound velocity, Nuclear Magnetic Resonance (imaging and relaxometry) and Optical Surface Roughness analyses. At 75% RH the nanoparticles fill the pores and inter-crystalline dolomite grain contacts but do not favor calcite re-crystallization as it occurs at 33% RH. The ESEM, XRD and TEM analyses under 75% RH reveal the fast transformation of portlandite (Ca(OH)2) into vaterite (CaCO3), monohydrocalcite (CaCO3 · H2O) and calcite (CaCO3), and eventually the physical and hydric properties of the stones significantly improve. New insights are provided for the assessment of consolidation effectiveness of porous carbonate stones with calcium hydroxide nanoparticles under optimum RH conditions combining several NDT.
Bibliographical noteFunding Information:
This study was funded by the Government of the Community of Madrid under the project “Durability and conservation of traditional natural materials in heritage architecture” (MATERNAS CM 0505/MAT/0094 ) and the Spanish Ministry of Science and Innovation as part of the Consolider-Ingenio 2010 programme ( CSD2007-0058 ). We thank C.T.S. S.R.L for supplying the consolidating product Nanorestore®. The authors thank the Marie Curie Fellowships for supporting L. Pinho and the JAE-Doc CSIC contract for supporting P. López-Arce to develop this work. The authors are grateful to Laura Tormo and Marta Furió of the Natural Science Museum (CSIC) for providing the ESEM-EDS photographs and analyses. Special thanks go to Inmaculada Ruiz and Iván Serrano, IGE (Institute of Economic Geology) petrophysics laboratory technicians, to Emilio Matesanz from XRD CAI (UCM) for his help with the XRD analyses and Juan Luis Baldonedo from the Microscopy and Citommetry Centre (UCM) for his support with the TEM analyses.
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- Calcium hydroxide nanoparticles
- Non-destructive techniques