Characteristics of Ca and Si Eluted from Hardened Cement Paste into Soaking Water

The construction methods for mountain tunnels can be broadly classified into sheet pile and NATM. In the sheet pile method, the arch and the sidewall are constructed separately, which results in horizontal joints and transverse joints. These joints and joints tend to become discontinuous surfaces, and cracking and leakage often become apparent as the service life lengthens. Calcium leaching is a phenomenon in which calcium leaches out of the hardened cement and the area becomes brittle. However, this phenomenon has not been studied extensively because it takes a long time to develop. On the other hand, the Ca/Si molar ratio of calcium silicate hydrate, one of the hydration products of cement, is said to affect the strength of hardened cement. In this study, we hypothesized that calcium leaches out and propagates cracks when cracks with water leakage occur. We have continuously measured the amount of calcium leached into the water by immersing cement paste samples in ion-exchanged water over a long period of time. This study examines the relationship between the dissolution of calcium silicate hydrate and mechanical properties by analyzing the soaking water and samples used for soaking.