CHANGES OF ROCK PROPERTIES BY ARTIFICIAL WEATHERING TESTS

To investigate the variation of physical properties of rocks due to weathering, artificial weathering tests such as freezing-thawing, acid immersion, and salt crystallization of NaCl, KCl, CaCl₂ and Na₂SO₄ were carried out. Samples of granite, limestone, marble and basalt were collected from six localities in Korea and prepared for artificial weathering tests. All tests were performed up to 30 cycles. During the tests were measured physical properties of rocks such as apparent specific gravity, porosity, absorption and P-wave velocity after experiencing every 10 cycles, and before and after full tests were measured uniaxial compressive strength and slake durability index. After salt crystallization test, SEM(Scanning Electron Microscope) analysis were carried out to observe recrystallized salts in the cracks of rock samples. Salt crystallization test resulted in relatively greater change of rock properties than freezing-thawing and acid immersion tests. In salt crystallization test, limestone, marble and basalt samples showed relatively greater change of physical properties than granite samples. Some rocks were severely deformed and then burst after repeated salt crystallization and in the early stages of salt weathering, recrystallized salts filling pores and cracks in rocks could be an important factor affecting rock properties. The variation trends of rock properties due to artificial weathering were too variable to draw generalized conclusions but it can be concluded that weathering agents have different effect on the rock properties depending on natural circumstance and time.