Application of synchrotron X-ray to the study of hydrated cement systems
The characteristics of hydrated cement systems are clarified using synchrotron X-ray at the SPring-8 facility in Hyogo Prefecture, Japan. A non-destructive integrated CT-XRD method has been developed and applied to study the physical and chemical changes in damaged and deteriorated cementitious materials. Recovery phenomena such as re-crystallization and densification of the microstructure are also being investigated.
Visualization of microstructure evolution and transport phenomenon in concrete
Using an industrial microfocus X-ray CT (Computed Tomography) system, concrete microstructure can be visualized. From this visualization, the pore structure can be quantified over time by means such as effective porosity, diffusion tortuosity, and the degree of connectivity. In addition, crack geometry due to flexure and splitting tension can be evaluated by the crack width distribution and constrictivity. The transport phenomenon, both in cracked and uncracked areas, can also be visualized and analyzed through the observation of tracer movement.
Utilization of industrial by-products as cementitious materials
Industrial by-products such as fly ash and blast furnace slag are used in place of ordinary Portland cement in order to reduce the embedded environmental impacts of concrete, such as greenhouse gas emissions, as well as enhance the performance of concrete structures under severe climate conditions. Durability, strength development, and crack resistance of concretes utilizing industrial by-products are the primary targets of this studies. In particular, the corrosion resistance of embedded steel due to salt attack and frost damage in fly ash or slag concretes are studied in order to implement improved durability design for concrete structures.
Corrosion resistance of fly ash concrete
Japan is now among the world’s leading coal importers to fulfil its power generation demand. To cope with the expected increase in the generation of coal ash in the future, the increase in its effective utilization in concrete, apart from dams, is one of the important issues under focus. The increase in the utilization of fly ash in reinforced concrete structures like bridges and high rise buildings requires the durability aspect of the concrete to be tested. Specifically, the corrosion resistance of embedded steel subjected to chloride penetration in fly ash concrete is studied to recommend the increase in the usage of fly ash as a partial replacement of ordinary Portland cement to the construction industry. In addition the corrosion monitoring of the real bridge structures which have been in service for many years is also done.
Simulation of simultaneous transport of ions using SiTram
An original computer simulation program, SiTram (Simultaneous Ions Transport Model), was developed and is continually updated for the precise calculation of ionic diffusion and alteration of hydrated cement systems. Unique features of this simulation program include the coupled calculation of the diffusion of chloride and calcium dissolution. Furthermore, the effect of cracks on the transport phenomenon in concrete is clarified considering different boundary conditions that simulate real environmental exposure.