en Soil Mechanics Classic Soil Mechanics Classic Technical Note Technical Note <p>Bentonite-sand mixture is one of the most important candidates for engineering buffer element in nuclear waste repositoriesso<br> the analysis of its thermo-hydro-mechanical behavior is important for design purposes.An innovative setup of classic oedometer<br> was used for swelling and compression study at high temperatures in this research. A fully calibration program was utilized to<br> include high temperature effects on measurements. This research shows that the elevation of temperature from 25 to 90◦C in<br> 1:1bentonite-sand mixture in distilled water reduces free swelling potential and strain about 20 percent. The required time for<br> equalization of swelling is less in high temperature due to increasing in permeability. Also, the high temperature causes increasing<br> in compressibility rate and quantity for this buffer. For detection of this effect, XRD analysis showed that an increase in<br> temperature causes a decrease in basal spacing. So, the particles can come near to each other more than lower temperatures and<br> the amount of absorbed water in the microstructure of the clay is smaller.The effect of thermal history on behavior of bentonitesand<br> mixture has been showed and tried to clarify it. At similar stress-temperature states, thermal history causes different<br> deformation in samples. The highest temperature that bentonite has been experienced, controls its behavior in the next thermal<br> cycles.</p> Thermo-mechanical behavior, Bentonite-sand barrier, Nuclear waste repository, Thermal history, Environmental geomechanics 162 167 http://ijce.iust.ac.ir/browse.php?a_code=A-10-286-1&slc_lang=en&sid=1 N. Shariatmadari shariatmadari@iust.ac.ir 180031947532846009687 180031947532846009687 Yes Associate Professor, Geotechnical Engineering, Civil Engineering Faculty, Iran University of Science and Technology, Tehran, Iran. S. Saeidijam Saeidijam@iust.ac.ir 180031947532846009688 180031947532846009688 No PhD Candidate, Geotechnical Engineering, Civil Engineering Faculty, Iran University of Science and Technology, Tehran, Iran.