Toshiharu Kishi

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

In this research, the application of repair methods of water leakage cracks using self-healing technologies for subway tunnels is presented from the Tokyo Metro (Subway) system. From the previous researches, effects of quick setting agents and water-stop agents with self-healing agents were investigated under various crack repair methods such as surface treatment repair method, injection method and V-cut repair method. The results showed that the proposed water leak repair methods using self-healing repair materials were effective under the subway tunnel conditions. Furthermore, experiments of new patching mortars including self-healing agents were conducted for performance estimations in the laboratory and field application. In order to apply these new repair materials in subway tunnels, water leakage cracks with Maximum 1.5 mm width from wall or ceiling of subway tunnels were selected. And then, new two repair construction method using quick setting agents and patching mortars were conducted. From these results, it was also confirmed that the sealing effects of water leakage through the penetrating cracks from these tests could be improved by inorganic repair materials with self-healing capability. Especially, these patching mortars were fully satisfied with the Tokyo metro’s repair materials standard code such as early and long term strength, the higher resistance of mass transfers compare to existing repair materials. Therefore, it is considered that the utilization of self-healing agents has a high potential for one of new repairing methods of cracked concrete under the water leakage for subway tunnels. The long term durability will be monitored continuously and studied.

The Estimation of the Self-healing Repair Technology for Cracked Underground Structures on the Urban Highway System

During the service life, the durability of a concrete structure is always an essential issue in civil engineering. Past researches indicated that the presence of a crack exacerbates the rate of carbonation progress in a concrete structures, leading to the corrosion of embedded rebar or tendons. Such phenomenon may alter the engineering properties, structural capacity, and deteriorated levels, which in turn affect the durability, water leakage, water-tightness of a concrete structure, as well as air tightness to withstand challenges in service. In general, the preferred countermeasure of a large scale underground concrete structure to prevent water passing through construction is waterproof sheet membrane. However, the remedial action to be taken to prevent leakage into crack areas are often inaccessible. In addition, Japan society entered the age of declining birthrates and working age population over a decade, which implied the capital for the infrastructure maintenance and renewal has dramatically declined. Therefore, an appropriate self-healing material for repair, maintenance and rehabilitation tasks is significant undertaking.

Chloride Ion Monitoring in Etched Nanochannels in Glass Using MQAE and Development of Microchannels in Hardened Cement Paste

In this study, nanochannels were prepared on a glass plate and the dependence of the chloride ion transport rate on the channel size was investigated. The nanochannels were etched using acidic etching agents, and the fluorescent reagent N-[ethoxycarbonylmethyl]-6-methoxy-quinolinium bromide (MQAE) was used to measure the concentration of the chloride ions. A decrease of the chloride ion transport rate with decreasing cross-sectional channel size was confirmed. The obtained results are, however, not directly applicable to concrete because glass and concrete have different surface properties. As such, a hardened cement paste (HCP) plate with a smooth surface and an absence of detected pores was prepared by high pressure curing. A microchannel was machined on the plate surface and a glass plate was bonded to this surface by autoclave treatment.

RELATIONSHIP BETWEEN THRESHOLD PORE SIZE AND AIR PERMEABILITY, WATER PERMEABILITY, AND GAS PERMEATION

A new method to measure threshold pore size of concrete was developed. Samples for MIP analysis were coated with epoxy-resin and the maximum slope of the obtained cumulative pore size distribution is defined as threshold pore radius. Threshold pore radius obtained with the new method showed good correlation with surface air permeability and water permeability. Gas permeation was plotted on two lines against threshold pore size and the point of intersection between the two lines agreed with theoretical transition zone of diffusion. The obtained results indicated that threshold pore size governs various mass transfer such as air permeability, water permeability, and gas permeation.コンクリートの物質移動抵抗性を代表する空隙指標として閾細孔径に着目し、検討を行った。まずコンクリートから採取された試料の閾細孔径をより明確に抽出するため、エポキシ樹脂により被覆された試料を用いて水銀圧入法により空隙径分布を測定し、分布の頻度が最大となる点を閾細孔径とした。透水および表層透気係数と比較した結果、いずれも閾細孔径と高い相関を示した。ガスの透過挙動も閾細孔径により整理され、また理論的な拡散係数と同様の挙動を示した。以上は、本論文の検討条件においては、空隙構造による影響が支配的であること、また閾細孔径により様々な物質移動抵抗性の評価が可能であることを示していると考えられる。