In order to improve the prediction accuracy of shrinkage cracking of concrete, it is needed to understand drying shrinkage properties under different relative humidity, in consideration of void structure and internal moisture conditions which affect hydration reactions. In this study, 100mm diameter by 200mm high cylinders of concrete were prepared using ordinary Portland cement, moderate heat Portland cement or blast furnace slag cement type B, and 10mm thick disk-shaped specimens were cut out of them for experimental measurement of drying shrinkage properties under different relative humidity of 12, 33, 59 and 85% and for different curing periods. The results showed that the lower the relative humidity, the larger the drying shrinkage strain was irrespective of the cement type or the curing period, that the difference between the cement types in drying shrinkage strain was more significant in lower relative humidity ranges, and that the relationship between maximum drying shrinkage strain and curing period varied depending on the cement type. It was also found that the relationship between drying shrinkage strain and relative humidity could be evaluated with a unique regression curve. The regression equation based on the present experimental results showed a tendency to be closer to the curve for a 100×100×400mm specimen when the curing period was longer.

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 The objective of this paper is to assess the risk of delayed ettringite formation (DEF) in concrete made with fly ash cements. To achieve this goal, optical and electron microscopic observations were performed. Cements were prepared by adding K₂SO₄ to plain OPC to elevate equivalent SO₃ to 2 or 4%. After that, each of the high DEF risk cements was replaced with 30% fly ash (FA30) or 65% slag (BS65). Concrete specimens were mixed at a room temperature of 27℃, then exposed to a high temperature history with maximum temperature of 85℃, assuming the interior temperature of mass concrete in a warm climate region. An accelerated DEF test was performed in reference to the Duggan test. As a result, DEF had occurred in concrete specimens at several SO₃ levels without fly ash or slag, showing extremely large expansion, with significant cracks including gaps around aggregate particles and random cracks that indicated formation of ettringite. In contrast, no abnormal expansion had not occurred in FA30 and BS65 concretes, suggesting that fly ash would be effective in suppressing DEF. An EDS analysis revealed that low Ca/(Si+Al) hydrates with fly ash or slag were advantageous in fixation of alkalis.

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 Mold-cast pore-free concrete (PFC) with a high compressive strength up to 400 N/mm² has been recently developed and improved by mixing fibers to increase tensile resistance. Steel fibers, stainless-steel fibers and poly-p-phenylenebenzobisoxazole (PBO) fiber bundles were chosen to ensure a sufficient corrosion resistance in the marine environment, and PFC panels reinforced with these fibrous materials were adopted for repairing a coast retaining wall in Hokkaido severely damaged by erosion.
　The aim of this study was to evaluate PFC reinforced with different fibers in comparison with ultra-high strength steel fiber reinforced concrete (UFC) in physical properties, i.e. compressive strength, flexural strength and abrasion resistance, as well as chloride ion penetration depth.
　The results showed that the steel fiber reinforced PFC had the highest compressive strength of about 330～360 N/mm², and its flexural strength and abrasion resistance were also significantly higher than those of UFC. The PFC reinforced with stainless-steel fibers or PBO fiber bundles also showed higher values in compressive strength and abrasion resistance than those of UFC, exhibiting higher resistance to erosion by sea waves. In addition, chloride ion penetration depth was similar between PFC and UFC after one year of immersion in seawater.

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 A new environmental indicator, which considers resource recycling and CO₂ emissions, was proposed to evaluate the environmental impact of materials used for structures. We tried to evaluate the environmental impact of different types of cement used for construction of a bridge by both the proposed indicator and an existing method. The proposed indicator showed that Portland cement had a greater contribution to the environment than Portland blast-furnace slag cements because it uses large amounts of difficultly recyclable resources (wastes), while Portland blast-furnace slag cements use large amounts of easily recyclable resources (by-products). The integrated assessment results by the life-cycle impact assessment method based on endpoint modeling (LIME2), which was adopted as an existing method in this study, also showed that Portland cement had a greater contribution to the environment. Consequently, the proposed new environmental indicator can easily provide environmental impact results consistent with LIME2 for structures.

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 LiMn_1−xFe_xPO₄/C secondary particles (x = 0.2, 0.3, 0.4) were synthesized by hydrothermal method followed by carbon coating and evaluated for electrochemical performance and thermal stability. The prepared LiMn_1−xFe_xPO₄/C secondary particles were attributed to the Pnma space group symmetry of an orthorhombic unit cell. They were spherical particles 10μm in diameter comprised with nanoparticles 100 nm in diameter. The differences of the particle size distributions and the specific surface areas of the synthesized LiMn_1−xFe_xPO₄/C were negligible for evaluation of electrochemical performance and thermal stability. The first discharge capacities of the LiMn_1−xFe_xPO₄/C were 155.3–155.7mAh g⁻¹ at a current rate of 34mA g⁻¹, and they did not depend on the Mn content. The LiMn_0.8Fe_0.2PO₄/C exhibited the best energy density of 596Wh kg⁻¹ at a current rate of 34mA g⁻¹. On the other hand, the rate capability was improved with the decrease in the Mn content of the LiMn_1−xFe_xPO₄/C. The LiMn_0.6Fe_0.4PO₄/C (x = 0.4) exhibited the best rate capability, where the discharge capacity and the energy density were 143.5mAh g⁻¹ and 489Wh kg⁻¹, respectively, at a current rate of 850mA g⁻¹. The cycling performances of the LiMn_1−xFe_xPO₄/C were almost equal. The capacity retentions during the 20 cycles of the LiMn_1−xFe_xPO₄/C were 97.5–98.8%. No change was found during the 20 cycles in the crystal structure of the LiMn_1−xFe_xPO₄/C that could cause capacity fading. The thermal stabilities of the LiMn_1−xFe_xPO₄/C were similar to each other regardless of the Mn content, which was much superior to that of commercially available LiNi_0.6Mn_0.2Co_0.2O₂.

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 Blast furnace slag and steelmaking slag are by-products produced in steel plants and legally approved as slag silicate fertilizers. However, the reliability of their efficacy has been low due to their unstable silicate solubility.
　In this study, granulated and air cooled blast furnace slags were compared for chemical and mineral compositions and silicate solubilities, and some possible reasons for the inconsistent efficacy of the fertilizers were discussed. Solubility improvement was examined by treating granulated blast furnace slag with chemical adjustment and recrystallization and investigating the relationship between mineral composition and silicate solubility. It was found that silicate solubility could be significantly improved by adding MgO to granulated blast furnace slag and reheating it at 1,300 or 1,350℃ for recrystallization of merwinite and monticellite.

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