Investigation of New Repair Countermeasure Methods Using Crack Self-healing Technologies for Water Leakage Prevention on Subway Tunnels

Kamei, Katsuhiko; Ahn, Taeho; Park, Jun-Hui; Hashimoto, Tatsuro; Ogura, Norihiko; Kishi, Toshiharu

doi:10.1007/978-3-319-59471-2_30

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“…Another study with the self-healing of ECC in the natural environment have further suggested that environmental conditions such as high rainfall rate facilitates this autogenous self-healing process [24]. Recently scientists of the University of Tokyo have repaired 85% of a 195 Km tunnel with their proposed self-healing cement materials and investigated their self-healing performance in natural environment [25]. Their repairing cement was PC-based systems with CSA-based expansive agent, geo-materials and chemical additive of the carbonate group.…”

Section: Introductionmentioning

confidence: 99%

Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

Qureshi

Al‐Tabbaa

2016

Smart Mater. Struct.

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Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high "N50"and moderately high "92-200") of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 µm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

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Section: Introductionmentioning

confidence: 99%