凍結融解作用を受けたモルタルの水銀圧入法による空隙構造評価

Abstract

Concrete structures and members show performance degradation due to materials deterioration through their service life. In particular, frost damage due to freeze-thaw cycles causes deterioration of concrete structures in cold regions. Chloride of deicing agents accelerates the deterioration due to frost damage under freeze-thaw environment. It is generally known that phase changes of hydration products, such as formation of Friedel's salt and ettringite, occur due to penetration of chloride ion into cement hardened matrix. Ettringite formation leads volume expansion and cracks. Thus, alteration of pore structure in cement matrix could be shown with propagation of micro cracks. It is considered that connective pores can be indicated in a result of mercury intrusion porosimeter. In this study, as for mortar samples subjected to freeze-thaw environment, alteration of pore structure was investigated by using information of pore connectivity shown in depressurization behavior after mercury intrusion. As the results, it was confirmed that residual strain, cumulative pore volume and pore diameter increased due to expansion of original pores influenced by freeze-thaw cycles and chloride ion from deicing agents. In addition to absolute amount of pores presented in mercury intrusion, residual mercury and mercury evacuation volume shown after depressurization of mercury were indicating geometric characteristics of pore structure, such as inkbottle pores and pore connectivity.