Working mechanism of a poly-beta-naphthalene sulfonate (NS) and polycarboxylate (PC) superplasticizer (SP) types was studied from the point of cement characteristics, i.e. solution chemistry of cement paste and initial hydration of cement. It is shown that the complicated dispersing performances of SP can be represented by two parameters, which are the critical dosage (CD) and dispersing ability (DA). When used at lower dosage than CD, SP does not affect the fluidity of paste. However, beyond CD value, the fluidity of paste shows a linear increase with SP dosage. DA is defined as the fluidity increment per unit of SP dosage. CD is closely related to the initial hydration heat, which corresponds to the surface area of initial hydrates. For NS type, CD is affected by the absorption ratio of NS into initial hydrates. The absorption amount into hydrates is decreased by increasing the sulfate ion concentration supplied from the alkaline sulfate in cement or by delaying the addition of NS. In the case of PC, the absorption amount into hydrates is negligible. DA of pc is related to the sulfate ion concentration. SP adsorption on the surface of hydrates is in equilibrium state with SP concentration in solution phase. Furthermore, sulfate ion and SP show a competitive adsorption on hydrates. More sulfate ion in solution phase changes the adsorption equilibrium of SP to a lower adsorbed state. The decrease of adsorption amount of SP decreases the paste fluidity.

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 The reaction ratio of fly ash in hardened cement mixture is determined by insoluble residue, which increases with age. The consumption amount of calcium hydroxide per unit weight of fly ash, due to pozzolanic reaction of fly ash, is constant and independent of the curing temperature, water powder ratio, and replacement dosage offly ash.
　Clarifying the mechanism of the pozzolanic reaction of fly ash is important to determine the effect on increasing strength and durability due to the pozzolanic reaction. The knowledge leads to rational decision-making on choosing appropriate mix proportion of concrete. A regression model of the reaction amount of fly ash is shown, which includes the cumulative temperature, mix dosage of fly ash, and water powder ratio. In addition, some basic models of the pozzolanic reaction are proposed to confirm the reaction. As a result, the higher the curing temperature or the higher the water powder ratio is, the higher the reaction ratio of fly ash. The reaction amount increases little when the replacement dosage of fly ash exceeds 40%.
　There are two types of pozzolanic reaction models. One is FA+CH→C-S-H, and the other is FA+C-S-H→C-S-H in the case of a decrease of Ca/Si mole ratio. The former model can explain the pozzolanic reaction up until 1 year of age, because the consumption of calcium hydroxide (CH) due to the reaction is constant.

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 Comparison of fresh concrete properties, slump, air content, and hardened concrete properties, compressive strength, Young's modulus, flexural strength under steam curing between the Eco-cement and Normal Portland cement are described in this paper. The performance of Eco-cement concrete is the same as Normal Portland cement concrete in both fresh and hardened concrete under steam curing. However, with Eco-cement concrete the amount of admixture required to obtain the same slump and air content is about two times that of Normal Portland cement concrete. And the slump loss of Eco-cement concrete with time is higher than that of Normal Portland cement. It is necessary to adjust the amount of admixture for optimum working conditions to produce sufficient handling time for fresh concrete.

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 Normal type of eco-cement (EC) which is made with urban refuse incinerator ash as raw material has been developed. As the chloride content of this cement is under 0.1%, applications of this cement to reinforced concrete will be expected. In this study, properties of fresh concrete and strength of concrete with EC of different chloride contents (150, 540, 860ppm) were compared with those of concrete with ordinary portland cement (OPC), and the influence of chloride content on properties of concrete were discussed. With in the scope of this study, the following results were obtained:
(1) Influence of difference in chloride contents of EC on the properties of EC concrete were not recognized.
(2) Unit water content of EC concrete is larger than that of OPC concrete.
(3) Bleeding of EC concrete is less than that of OPC concrete.
(4) Setting time of EC concrete is delayed compared with OPC concrete.
(5) Water-soluble chloride content of EC concrete is similar to that of OPC concrete.
(6) Compressive strength of EC concrete is lower than that of OPC concrete at the same W/C, the same strength can be obtained by decreasing W/C by 5% compared with OPC concrete.
(7) Relationship between compressive strength and static modulus of elasticity of EC concrete is similar to that of OPC concrete.

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 This paper examines the effect of the combination of strength level in matrix and in artificial coarse lightweight aggregate upon the fracture energy of lightweight aggregate concrete. Fracture energy was determined by three point bending method. Additionally, compressive, splitting tensile, flexural, and shear strength were determined. Our results suggest that the fracture energy depends on not only the strength level in matrix and in aggregate but also the shape of aggregate particles.

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 Recently, the super lightweight aggregates (SLA) have been studied and developed in Japan. The water absorption ratios which greatly affect the handling and durability of concrete are less than 5%. This innovative invention can extend the use of lightweight concrete to existing structures.
　It is known, however, that the shear capacity of lightweight concrete beams is lower than that of normal concrete beams having the same compressive strength. But our test results showed that the shear capacity of the SLA concrete beams has been improved significantly by prestressing.
　According to the JSCE code, the contribution of lightweight concrete for shear has to be reduced to 70% of normal weight concrete regardless of compressive strength and specific gravity. In Eurocode, On the other hand, the tensile strength of lightweight concrete can be obtained by multiplying the corresponding strength of normal density concrete of the same strength class with a factor and the shear capacity of reinforced concrete members without shear reinforcement is rationally formulated using this factor.
　In this study, the authors prepared prestressed concrete beams using the two types of SLA. Each beam had a large cross section of 350mm in width and 1000mm in effective depth. We carried out the experimental study for the shear capacity of SLA concrete beams and verified the effect of the prestressing in improving the shear capacity.

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 Along with maturing our society and revealing various environmental problems, proper maintenance of aging concrete structures has become increasingly important. To evaluate the structural integrity of concrete for maintenance, it is essentially useful to obtain differentiated information on tensile and shear cracks which are commonly observed in the concrete structures.
　For this purpose, the use of an acoustic emission (AE) technique is examined, and then it is found that these two types of crack could be identified by applying two parameters of RA value (rise time/maximum amplitude) and average frequency(counts/duration). In the experiments, AE waves were measured under flexural load where tensile cracking was prominent and also under shear load where shear cracking was prominent. As a result, AE waves observed under flexural load have the smaller RA values and the larger average frequencies. Under the shear loading, the larger RA values and lower average frequency can be monitored.
　To confirm the practical applicability of the identification on crack types based on the laboratory experiments, AE measurement was carried out under live load in an existing reinforced concrete (RC) pier which had been repaired using prestressing bars. Then, the proposed method was proved to be useful for providing information on the development of cracking and crack motions.

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 The aim of this study is to prepare the dense MgF₂ sintered body first by normal sintering combined followed by capsule-free hot-isostatic pressing (HIPing) treatment. LiF was effective sintering aid for MgF₂. The MgF₂ body of 95% relative density was obtained by adding 0.4% of LiF by mass to the sintering above 798K. The relative density decreased above 923K. The MgF₂ above 97% relative density after normal sintering was almost densified to the theoretical density by capsule-free HIPing treatment at 823K under the pressure of 180MPa in Ar atmosphere. The decrease in the relative density at higher temperatures was explained by the growth of pores at the grain boundary according to the grain growth and the evaporation of LiF during sintering. Bending strength, Vickers hardness, Young's modulus and the thermal expansion coefficient of MgF₂ were also measured.

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 Following the end of the legal delay in the enforcement of new Metrology Law, several non-SI units including those closedly related to particulate technology have been deleted from the legal units for metrology. These units cannot be used in practice any more. On the other hand, in the Guide-line for Description of the Specification Format Concerning Powder Materials, which has recently been established by APPIE, several important suggestions are made on the desirable description format of powders including suggestions on the units for metrology. All of these have a close connection with the current movement for the coordination of the domestic standards with the international ones, which is expected to be more and more accelerated. In this report, all of these are reviewed from the viewpoint of a manufacturer of cement and other powder materials.

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