Читать книгу Monument Future - Siegfried Siegesmund - Страница 294

Salt crystallisation tests were in concordance with EN-12370 (1999) recommendations, respectively. 4 cm cubic samples of each lithotype were tested and underwent cycles of saline immersion (14 % w/w Na₂SO₄ solution, at 20 °C for 4 hours), drying (at 60 °C for 16 hours) and cooling at room conditions (20 °C, for 4 hours). Samples were exclusively cleaned at the end of the test (after the 15 cycles). P and S waves were measured before and after the durability test. Every measurement of the P and S waves was repeated three times in order to test the reproducibility of the experiments and the corresponding results. Figures 1 and 2 display, respectively, P and S signals for fresh and weathered samples. They aim to show the evolution of waveform rather than wave velocities because the sample length may vary from samples to sample. Tested samples have a cubic shape and the edge length range from 40–50 mm. Moreover, weathered samples may also suffer superficial weight loss, resulting in a decrease in edge length.