These studies were carried out, supposing that regulated set cement is used for cold weather concrete.
By these studies, the strength developing characteristics in the case of freezing the concrete at -20°C at the early age and continuing the freezing and the restored strength in the case of thawing the freezing at -20°C halfway during the age were found.
Further, the relation of the compressive strength at the begining to the repetition of freezing and thawing was clarified. Moreover, when regulated set cement concrete is frozen at the early age, and at the time of thawing, it is brought in contact with water, cracks arise, and the remarkable lowerings of the strength occurs, therefore, its cause was elucidated, and the method of its prevention discussed.

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When designing massive hollow concrete structures under marine, it is important to consider the corrosion of steel bars resulting from the seepage of seawater through concrete cracks. This paper studies the seepage of seawater through cracks and the resulting corrosion of steel bars. The characteristics of seepage and corrosion phenomena are experimentally discussed in the light of long-term permeability tests. In addition, the corrosion process was studied using a new nondestructive method.

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In this study we studied the torsional properties of six model specimens for long breakwater caissons. These specimens were made of steel-concrete hybrid members and prestressed members. Since these specimens had cross sections with upper opening, their torsional capacities were calculated with mixed torsion analysis considering St. Venant torsion and warping torsion. Calculated values were compared with the measured values obtained from static torsional loading tests of the specimens. It was shown that the mixed torsion analysis could evaluate the torsional capacities of these specimens.

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This report describes experimental results on the highly workable concrete for mass concrete purpose, which concrete is made from a ternary blended low-heat generating cement, large amount of lime stone powder and air-entraining high range water-reducing agent. The report also refers to applicability of this type of concrete to mass concrete structure, and it's applicability is confirmed through full size field casting.

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Resin concrete has been widely used for concrete products. It has been pointed out, however that Young's modulus of the concrete is about one-seventh that of cast iron and is inferiored to conventional materials in static stiffness. Therefore, in this paper, a new material named ceramics resin concrete, has been developed for concrete products. This material consists of epoxy resin and ceramics which are alumina, silicon carbide, zirconia or a blend of these. It is concluded from the results that Young's modulus is three times and the compressive strength is two times that of conventional resin concrete. In addition, production methods are established for the ceramics resin concrete.

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Paying the attention to the fracture around coarse aggregates and of mortar, fracture mechanism of plain concrete under uniaxial tension is investigated. The direct tensile tests of plain concrete are carried out. Stress-Strain curves are obtained and broken-sections are observed. These experimental results and some analytical results in plane elastic problem are used to investigete the fracture mechanism. These analytical results are stress singular values at a debonded tip, stresses near the tip and stress intensity factors at a crack tip, On the basis of the fracture mechanism, the direct tensile strength of concrete is discussed.

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FE-analyses of cracks in plain concrete specimens were carried out using the smeared crack model including the concept of the fictitious crack model. For the localized Mode I cracking, the numerical results of this crack model were identical with that of the fictitious crack model. The differences of the numerical results between the localized and distributed cracking were demonstrated. The stress locking phenomenon caused by strain softening was also discussed.

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The mechanics of expansive pressure generation in expansive demolition agents has not been clearly proven to date, although there are a number of theories to explain this phenomenon. It is important to clarify this for not only for the purpose of improving expansive demolition agents, but also in order to develop anchoring method of FRP tendons and chemical jacks. This report examines the relationship among expansive pressure, degree of hydration and pore structure in two kinds of expansive demolition agents at different curing temperatures and wateragent ratios, in order to research the mechanics of expansive pressure.
The results are as follows: The expansive pressure is not determined by the degree of hydration alone. The pore volume decreases as the expansive pressure increases, and this relationship is independent of the types of agents, curing temperature and water-agent ratio. The generation of expansive pressure is generaly explained by using Shalom's sphere model.

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This is to report on the resistance to deformation of fresh concrete when the rearrangement of constituent particles of fresh concrete, i. e., gravel, sand and cement, is introduced. For realizing the simple deformation field in shear, bent and tapered pipe units were adopted in test and stable flow of fresh concrete through them was produced. Herein, the pressure at the inlet of deformed pipes was measured as an indicator of deformability of fresh concrete, which is regarded as the particulate assembly with different sizes. The effect of volume fraction of gravel, sand and cementitious powder on the resistance to deformation was mainly focused in the series of test based upon the multi-phase concept of hydrodynamics. The sensitivity of volume fractions to the total deformational resistance of concrete was of experimental interest to the authors.

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This paper is to propose the liquid-solid two phase modeling for simulating the flow and segregation of fresh concrete with the authors' intention of getting the mathematical background for mixture design concept serving super fluidized fresh concrete. The multi-component structure of solid phase was newly introduced into the frame of conventional liquid-solid two phase model in fluid dynamics. The partial stresses carried by gravel, sand and cement powder were implemented and the compatibility equations derived from experimental works were incorporated in the scheme of formulation for multi-component solid suspended by liquid. For verifying the capability of the physical model concerned, the trial model for particle-to-particle interaction was combined with the entire frame of formulation. It was examined that the model can follow the behaviors qualitatively in terms of the fluidity and segregation of particulate flow.

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This paper is to propose the mechanical modeling in terms of the collisional and frictional interaction of constituent particles for flowing fresh concrete through pipelines. The multi-phase formulation was adopted as the basis of computing the resistant force to the deformation arising in tapered and bent pipes. The effect of cement paste existing in fresh concrete on the particle interaction of sands and gravels was taken into account. Approximately 20 different mixtures of concrete were examined for verification of the numerical modeling. The analytical model was proved to be versatile to wider variety of fresh concrete having 3-27cm by slump and any type of deformed pipe unit with different dimensions. It was emphasized that the pump pressure of concrete being driven through the deformed pipe units can be predicted well chiefly by the particle interaction model of aggregates and the multi-phase scheme.

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