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Monitoring of travertine changes resulting from thermal load

Keywords: travertine , thermal load , linear thermal expansion , ultrasound velocity , colour change , surface roughness

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Abstract:

Travertines, despite of their unique noble appearance change their properties when affected by ageing like any other building and decorative stone. Some of the most noticeable changes are influenced by temperature fluctuations. From this point of view, the main purpose of presented research was to determine the influence of multiple temperature cycles for travertine from Spi ské Podhradie and Ludrová in temperature range of 25°C to 60°C corresponding to summer period temperature regimes. The weakening of the rock material by heating was determined by non-destructive techniques before and after thermal load. By ultrasound apparatus was observed by means of ultrasonic velocities change, when higher values of ultrasonic velocities were determined parallel to the bedding while the perpendicular direction had slower velocities. The change of colour was specified by spectrophotometer and no distinct visual colour change was determined with increasing temperature. By non-contact profilometer surface roughness data of samples profiles primarily indicate a decrease of roughness during heating. The coefficient of linear thermal expansion acquired by thermodilatometer varied from 4.6.10-3 to 7.8.10-3 mm.m-1.°C-1 for travertine from Spi ské Podhradie and 5.3.10-3 to 7.3.10-3 mm.m-1.°C-1 for travertine from Ludrová. This parameter characterizes the materials response to heating or cooling. The techniques mentioned above are non-destructive and some of them are innovative in laboratory testing.

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