Thesis supervisor: Nikoletta Rozgonyi-Boissinot
Location of studies (in Hungarian): BME, Department of Engineering Geology and Geotechnics Abbreviation of location of studies: BMEGM
Description of the research topic:
One of the characteristic deteriorating phenomena of the as building material used porous stone types is the salt crystallization in the pores. Across the globe, these processes can be observed in a significant part of historical monuments, causing serious questions and problems in restoration works. In many cases, the damage of side by side built in stone blocks is significantly different under the same weathering effects. Exploring the background of this phenomenon is the task of the candidate.
When the salt crystals are formed, the crystallization pressure on the pore walls occurs micro-cracks, which results in the destruction of the rock microstructure. The salt crystallization pressure depends on temperature, humidity, salt type, degree of saturation and shape of the pores. Damage is influenced by rock microstructure, porosity and structure of the pore system.
The candidate must investigate the effect of crystallization of the most common salts in the building blocks (magnesium sulphate, sodium sulphate, sodium chloride, sodium nitrate) on the structure of the high porous building stones. The candidate's task is to crystallize the salts at different temperatures at different speeds. It has to examine the resistance of fine, medium, and coarse grained rock types to salt crystallization and the degree of structure destruction.
The aim of this work is to find a relationship between stone structure, mineralogical composition and the deteriorating level caused by salt crystallization. The influence of the various drying temperatures and drying velocities on the destruction rate from crystallization should be analysed. The candidate has to explore what types of rock materials are resistant for salt damage and develop a method of modelling the damaging effects of salt deposition from the groundwater through capillary system.
After the tests, it is necessary to analyse the degree of saturation of the pores on thin section and the causes of damage to the rock microstructure (thin sections, Scanning Electron Microscope). By mechanical tests, it is also necessary to investigate the loss of strength, to find a connection between the rock properties and the mechanical behaviour. A relationship needs to be found between the salt types, the rock microstructure and the degree of damage. On the basis of its results, the candidate should provide a test method that can be used to model changes in salt crystallization in porous building blocks in the practice too.
Number of students who can be accepted: 1
Deadline for application: 2018-12-20
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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