The purpose of this study is to investigate the effect of post-curing conditions on hydration behavior of slag blended cement pastes. Pastes of ordinary portland cement (OPC) and blended cement containing 40% ground granulated blast furnace slag (BFS) were cured at 60℃ for 24 hours and subsequently stored in limewater at 20℃ or subjected to atmospheric curing. Microstructure development in the cement pastes was determined by mercury intrusion porosimetry (MIP), the amounts of calcium hydroxide, carbonates and combined water were measured using thermogravimetric / differential thermal analyzer (TG/DTA), hydration products were analyzed and quantified by X-ray diffraction (XRD)/Rietveld method and the reaction ratio of BFS was estimated by selective dissolution method. Three-day strength of the blended cement pastes was higher than that of the OPC pastes when cured in limewater at 20℃ after the high temperature curing. The hydration ratios of C₂S and BFS increased when the pastes subjected to high temperatures at early age were post-cured in limewater at 20℃. Theoretical volume changes of hydration products obtained by the XRD/Rietveld analysis were consistent with the compressive strength and microstructure development. Vaterite, a calcium carbonate polymorph, was observed in the BFS blended cement pastes post-cured under the atmospheric conditions. This phenomenon was accompanied by a decrease in Ca/Si molar ratio which was likely due to calcium ion elution from C-S-H gel. It was concluded that physicochemical properties of BFS blended cement pastes would vary significantly depending on the post-curing conditions after the early-age high temperature curing.

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 Shrinkage crack characteristics were compared between expansive concrete and plain concrete without expansive additive in this study by investigating crack distribution in uniaxially restrained specimens in which a deformed steel bar was embedded. Furthermore, shrinkage crack control effect of expansive concrete was evaluated by determining relationship of drying shrinkage strain measured in the unrestrained specimens with the number of cracks found in the restrained specimens and also with the cracking coefficient calculated from the number of cracks and crack widths.
　The drying shrinkage strain in expansive concrete was found approximately 15% less than that in plain concrete. Expansive concrete was obviously effective in reducing the number of shrinkage cracks and the cracking coefficient. It was also suggested that the crack control effect of expansive concrete could be approximated quantitatively as the sum of the decrease in drying shrinkage strain and the amount of expansion-induced strain of about 100 to 150 x 10^-6.

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 Ultra high strength fiber reinforced concrete (UFC) has high ductility, high strength and high durability compared to normal concrete. However, these high performances may be lost when steel fibers in UFC are corroded. The objective of this study is to experimentally investigate the tensile performance of UFC with cracks. UFC samples without initial cracks exhibited no corrosion of steel fibers or penetration of chloride ions in the experiment. In UFC samples with initial cracks, the larger the crack width, the more corrosion products were detected on steel fibers near the surface of seawater. In addition, cracks induced by external load propagated into a wider extent and, in UFC samples with initial cracks of 0.5mm or wider, chloride ions were found distributed along the cracks. It was also revealed that corrosion of steel fibers increased tensile stress to be carried by UFC regardless of the initial crack width.

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 Super-low-viscosity prestressed concrete grout is being used increasingly widely for its excellent durability, fill capacity, workability and ease of handling. However, fluidity of grout of admixture type often varies substantially depending on the cements supplied in situ, causing serious problems at construction sites.
　This study investigated the effects of soluble alkali in cement on the fluidity of admixture-type super-low-viscosity grout using polycarboxylate-based superplasticizer and evaluated the performance of premix-type super-low-viscosity grout using melamine sulfonate-based superplasticizer. The results showed that the grout of premix type manufactured using melamine sulfonate-based superplasticizer could achieve stable fluidity, controlling cement-induced fluctuations to a minimum level. Fill capacity was evaluated in a full-size model experiment where good workability of the premix-type grout was demonstrated.

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 Taiheiyo Cement Corporation has developed a new calcium removal technique using ion-exchange resin to solve the calcium scale problem at leachate treatment facilities of landfills. This technique is a completely new calcium separation method based on ion chromatography. A pilot-scale test model was installed at an existing landfill, and its calcium separation capacity was demonstrated in a test run. Unlike the conventional method which uses sodium carbonate, this method uses no chemicals and thus allows for substantial cost reduction which is expected to relieve local governments of the burden of purchasing expensive chemicals.

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 It is generally considered difficult to separate and remove Cs from soil contaminated with radioactive materials. This study aims at developing a heat treatment method for separating and removing Cs from radioactive-contaminated soil by sublimation, thereby reducing the Cs content in soil down to acceptable levels for use as civil work materials. In a simulative experiment using non-radioactive Cs, Cs removal rate was found to increase dramatically with addition of inorganic high-performance accelerators, while being very low in soil with no additives or in soil added only with CaCl₂ as a promoter chloride. Based on this finding, heat treatment tests were carried out using actual contaminated soil samples containing several ten thousand Bq/kg of Cs. With the accelerators added, all samples exhibited successful sublimation of Cs and achieved the target clearance level (100Bq/kg) or lower concentrations. The proposed technique was demonstrated to be capable of removing radioactive Cs from contaminated soil to a level acceptable for civil work materials, allowing for substantial reduction in the volume of contaminated waste that requires long term storage.

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