Production of alcohol dispersion containing calcium hydroxide and magnesium hydroxide nanoparticles for dolomite formation and consolidation

Karahan Dağ, Fulya
Dolostone (CaMg(CO3)2 - calcium magnesium carbonate) has been a commonly-used building stone in the construction of many historical structures since the ancient periods. Those structures show deterioration problems in time and need conservation treatments. Repairs with incompatible materials are known to damage the original stone. In the context of dolomite conservation, there is a necessity to develop a consolidation material and treatment method that is compatible with the dolomite. The study aims to consolidate the dolostone by synthesizing dolomite within its deteriorated parts. For that purpose, alcohol dispersion of Ca(OH)2 and Mg(OH)2 nanoparticles was produced from the dolostone itself. This dispersion was allowed to react with CO2 in a desiccator. The carbonation process was followed in petri dishes prior to consolidation treatment. It is found that the carbonation process is affected by relative humidity (RH) and CO2 partial pressure (pCO2) in the desiccator, and Mg:Ca ratio of the dispersion. The most effective dolomite formation is achieved by the carbonation process of Ca(OH)2 and Mg(OH)2 nanoparticles under high RH (90-95%) and high CO2 partial pressure (pCO2 ~ 0.4 atm) conditions in ethanol dispersion where Mg:Ca ratio is ~1. It is important not to disturb that system in the desiccator at least for 10 days for dolomitization. The carbonation products formed in petri dishes were followed by means of XRD, FTIR, and SEM analyses. Afterwards, the deteriorated dolostone sample was treated with alcohol dispersion of Ca(OH)2 and Mg(OH)2 nanoparticles, and kept in a desiccator under high RH and high CO2 partial pressure conditions for carbonation. The formation of dolomite aggregates having 100-200 nm size within the matrix of dolostone was confirmed by SEM analysis. Average UPVdirect value of the treated dolostone sample increased from ~1844 m/s to 2158 m/s. The carbonation products could join two broken dolostone pieces together, which shows its strong adhesion property. The production of this specific nano-consolidation material from the dolostone itself, the description of the consolidation treatment for dolostone, and the success in dolomite synthesis in the laboratory under the appropriate carbonation conditions are expected to provide an important contribution to stone conservation practices


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Citation Formats
F. Karahan Dağ, “Production of alcohol dispersion containing calcium hydroxide and magnesium hydroxide nanoparticles for dolomite formation and consolidation,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.