Effects of thermal expansion of enclosed medium and direction of pressure bearing plane of metal tubes on pore pressure measurements in cement-based materials under elevated temperatures

Abstract

This paper investigated effects of thermal expansion of enclosed medium, air or silicone oil, and direction of pressure bearing plane of metal tubes on pore pressure measurements in cement-based materials subjected to elevated temperatures. To this end, heating tests on mortar slabs with metal tubes and thermocouples embedded at different depths by different angles were designed and conducted. Test results showed that the pressure due to the thermal expansion of enclosed medium in a metal tube could make a contribution to the total measured pressure. The additional pressure contribution did not exceed 10% of the corresponding total measured pressure in the cases where the total measured pressures were higher than 0.4 MPa. The maximum real pressures reported by metal tubes embedded at the same depth by different angles to the direction of vapor movement did not synchronize and were generally different. The maximum real pressures measured by tubes with pressure bearing planes perpendicular to the vapor movement direction were higher than those with pressure bearing planes parallel to the vapor movement direction.