Tests on Mechanical Behavior of Cement-treated Masado Under the Influence of Acidic Environment and Temperature
Peng PENG1#+, Feng ZHANG1, Hiromasa IWAI1, Ittetsu OHARA2, Tomoya IWATA1, Keigo TAKAGI1
1Nagoya Institute of Technology, Japan, 2Nikken Sekkei Civil Engineering, Japan

Cement-treated Masado (CTM), as a common cement-mixed geomaterial, is usually only used in ground improvement for temporal structures in Japan. However, in recent years, it has been used for newly constructed permanent structures, such as the supporting ground of pile foundations and direct foundations. The long-term stability of CTM has not been thoroughly investigated, since that it has the risk of exposure to changes in acid environment and temperature, which are very common in volcanic areas in Japan. In this study, to investigate the influence of acidic environment and temperature on the mechanical behavior of CMT, a systematic test program using triaxial tests was conducted on CMT specimens under different conditions of acidic environments, temperatures, and confining pressures. To avoid the extra influence of water on the mechanical behavior of CMT, a special double-cell was designed within the pressure chamber of the triaxial loading device, so that the volumetric strain of the specimens completely sealed with gum sleeve can be accurately measured in triaxial compression and creep tests. Combined with the influence of the initial confining pressure, the influence of the acidic environment and temperature on the strength and dilatancy of CMT is carefully investigated. In addition, the chemical components of all the tested specimens are investigated by X-ray fluorescence spectrometry analysis to identify the calcium leaching in the curing period. Based on the test results, a relation between the stress ratio at the critical state and the influential factors, including the initial confining pressure, acidic environment and temperature, is proposed by regression analyses.