It has been experimentally revealed that alkali ions in pore solution are bound to the surface of C-S-H particles and that the degree of ion binding depends primarily on the Ca/Si molar ratios of C-S-H. Based on an assumption that the alkali ions are constrained in the electrical double layer on the C-S-H urface by electrical interaction, the authors developed a thermodynamic model to determine the alkali ion concentration in pore solution under equilibrium with C-S-H of a given Ca/Si ratio, combining the chemical and structural evolution model of C-S-H proposed by Nonat et al. with the electrical double layer model of C-S-H. The proposed model was verified as capable of reproducing the phenomenon that the amount of alkali ions bound to C-S-H varies with the Ca/Si molar ratios. This model assumes a homogeneous system. However, various local reactions take place in real cement hydration which is far from the equilibrium state. The pH of pore solution decreases when supplemental cementitious materials are added. Future improvements on this model should include accurate simulations of these phenomena which influence the pH or alkali concentration of the liquid phase. To achieve this, it is necessary to create models of such phenomena as the local formation of low Ca/Si C-S-H due to pozzolanic reaction and the increase in alkali ion binding caused by the formation of C-A-S-H due to Si-Al substitution.

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 The use of supplementary cementitious materials such as fly ash is one of the most popular solutions proposed to suppress expansion due to alkali-silica reaction. It is known recently that alkalis supplied from the outside accelerate alkali-silica reaction under the saline environment where deicing salt is used. This study aims to investigate the suppressing effect of fly ash on alkali-silica reaction under the environment with externally supplied alkalis. The suppressing effect of fly ash on alkali-silica reaction depends on physical, chemical and mineralogical properties of fly ash. In this study, six types of fly ash which were categorized according to JIS A 6201 as class II were examined by the accelerated mortar bar test (ASTM C 1260). As a result, it was established that the Blaine specific surface area of fly ash was one of the most important characteristics related to its suppressing effect on expansion of mortar due to alkali-silica reaction. The mechanism responsible for this was that alkali ion permeability was decreased by the densification of the hydrated phases produced by the pozzolanic reaction. It was also found that, under a concentrated alkali environment, this mechanism was more effective in suppressing the expansion than the other mechanism where the alkali ion concentration and pH in the pore solution were decreased by the pozzolanic hydrates entrapping the alkali ions and depleting the portlandite in the cement paste.

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 Ductal^Ⓡ involving steel fibers (FM) or PVA fibers (FO) has impressive properties such as high compressive strength, high durability, high tensile strength, high shear resistance, and ductility because of the use of short fibers for reinforcement. Because of these properties of Ductal^Ⓡ, the behaviors of flexural members using Ductal^Ⓡ are so much different from those of conventional concretes. The aim of this study is to clarify the flexural behaviors of Ductal^Ⓡ beams and to clarify the size effect on the flexural strength of Ductal^Ⓡ beams. In this study, we perform bending tests on plain beams using Ductal^Ⓡ. In addition, we also investigate the stress-strain relationship and the equivalent specific length of Ductal^Ⓡ in order to accurately calculate the flexural resistance.

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 According to a report by Japan Ministry of the Environment (2006), organic and inorganic sludge materials account for the largest proportion (32%) of industrial wastes landfilled in Japan. When the landfill contains organic sludge, the landfill stabilization is affected by poor ventilation, reduced water permeability, and extended deterioration of leachate quality such as COD and TN due to continued supply of organic matters. To achieve early stabilization of the landfill containing organic sludge, we evaluated a two-stage improvement plan. This plan consists of two steps: 1) pre-treatment performed before landfilling where water content and properties of organic sludge are modified using neutral solidifier for better ventilation and water permeability; and 2) aerobic treatment by vigorous aeration performed after landfilling for early reduction in the organic and nitrogen concentrations in the leachate.
　Lysimeters (70L) were filled with organic sludge materials and mixtures and solidifiers, and water was sprayed to the lysimeters for one year. BOD was reduced to about 10mg/L which was significantly lower than the landfill termination level for BOD (60mg/L), and COD and TN were also reduced close to the termination levels (COD: 90mg/L; TN: 120mg/L) specified in the Waste Disposal and Public Cleaning Law. These results validate the effectiveness of this two-stage improvement plan in early stabilization of the landfill.

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 Demands for rapid hardening concrete are increasingly high, especially for use in emergency work and routine repair and rehabilitation as well as for the shorting of construction periods. Jet-concrete and One-day-concrete which develop early strengths within 3 hours and 24 hours, respectively, are already in practical use. The difference between the Jet-concrete and the One-day-concrete is in manufacturing process: mobile concrete mixers for Jet-concrete; and ready-mixed concrete plants for One-day-concrete. Facet^Ⓡ concrete we developed has a higher degree of freedom in the manufacturing process which makes it possible to use either mobile mixers or ready-mixed concrete plants for production. We investigated properties of this rapid hardening concrete and tested both means of manufacture.
　This study evaluated the effects of materials, mix proportions and environmental conditions on the properties of the Facet^Ⓡ concrete including the handling time and initial strength. Based on the findings, experimental production was carried out using mobile mixers and an existing ready-mixed concrete plant. Facet^Ⓡ of a two-package system was also tested by adding it to the mixture in a truck agitator at a construction site. With proper dosage of retarder added, Facet^Ⓡ concrete of consistent quality was successfully produced, ensuring both satisfactory workability with a handling time of over 60 minutes and a 12-hour compressive strength over 24N/mm².

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 The recently increasing use of recycled materials often impairs the performance stability of cement kilns and requires complicated control for proper operation. Efforts have been made to solve these problems, with a specific focus placed on stabilization of the preheater temperature. Most recycled materials are used in the preheater system between the kiln inlet and the precalciner.
　It was found in Kumagaya Plant where various kinds of recycled materials were used that variations in the preheater temperature were as large as two times those without recycled materials.
　A new advanced control system was developed to stabilize the bottom cyclone exit gas temperature and optimize the combustion in the precalciner. It is a combination of steady-state control based on process models for handling various recycled materials and non-steady-state control to support the operation of the plant.
　With the plant control upgraded with this comprehensive system, variations in the preheater temperature were reduced by about 38% (76% of changes by recycled materials use) at maximum. The performance was further improved by automating the startup/shutdown operation and problem detection of the recycle material feeders which were previously performed manually.

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 Sintering is one of the important processes in the cement clinker formation. This report provides basic information on the mechanism of sintering, based on previously published material. Both the solid-phase and liquid-phase sintering results in a reduced surface energy. Major benefits of cement clinker sintering are as follows: (1) cement clinker minerals can be formed at temperatures below its melting point; (2) reaction can be accelerated; and (3) cement raw material powder can be sintered without mold pressing. It is known that the melt or liquid phase has critical influence on the whole mechanism of cement clinker sintering, playing important roles in every phenomenon of cement clinker mineral formation, sintering and granulation. The liquid phase properties including surface tension and viscosity vary with the effects of minor constituents on which research will be increasingly needed in future.

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