Microhardness measurements and EDXA analyses were made in the regions around glass fiber strands embedded in the cement paste to elucidate the effects of curing temperature and mineral admixtures on the microstructure of the interfacial zone between a glass fiber strand and cement paste matrix. The characteristics of flexural strength and toughness of glass fiber reinforced mortars were also discussed relating them to the results obtained by the microhardness measurements and EDXA analyses. Curing temperature significantly influenced the microhardness distribution patterns in the interfacial zone. Both the softest and the hardest region exist within the interfacial zone. The discontinuity in microhardness in the regions in samples cured at a high temperature (38°C) appears to greatly affect the toughness of the corresponding glass fiber reinforced mortars. Overall microhardness distribution patterns were not changed by the addition of the mineral admixtures.

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The roller compacted concrete is the new pavement construction method which can improve the simple and economical technique for the excution work of concrete pavement.
The objectives of this study are to analyze factors which are considered to affect the roller compacted concrete quality and to establish the new design method. In this study the JIS A 1210 and Marshall test instruments are used as the test methods of compaction. It became evident through the compaction tests that compaction mechanism and mix proportion factors are essential in concrete quality control and also the relationship of flexural strength and void ratio is derived for the newly proposed mix design method.

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A non-destractive method based on the ultrasonic spectroscopy is studied for the evaluation of the crack depth in concrete members. A surface method, where both a transmitter and a receiver are attached on the same surface of a specimen, is investigated. Spectral responses are measured by driving sinusoidal waves of sweep mode from a function generator. It is shown that the spectral response due to the sweep mode input is equivalent to Fourier spectrum obtained from a direct signal due to impulsive input. The sweep time is tested to examine the relationship between the spectral response and the Fourier spectrum. To improve the reproducibility of the spectral responses, several coupling materials, which are inserted between the transducer (both a transmitter and a receiver) and the concrete surface, are investigated. Specimens with artificial cracks are tested to study the effect on the evaluation of crack depths in concrete members. Experimental results are analytically examined by the resonance analysis of the finite element method. These experimental and analytical results show that the present method is promising for the evaluation of the crack depth in concrete members.

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This paper presents a new precooling method which reduces the temperature of mixed concrete by mixing it with sand frozen by liquid nitrogen.
The authors tried to clarify the properties of both the frozen sand and the concrete mixed with the frozen sand. The results of a series of experimental studies indicate that the temperature of mixed concrete can be reduced about 25°C, which is a larger reduction quantity than that achieved by conventional precooling methods; and that this method contributes to improvement of the consistency and the compressive strength of the concrete. Furthermore, the advantageous effect of this precooling method is confirmed from the results of laboratory tests using massive concrete members.

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The ultimate purpose of the present study is to evaluate the performance of asphalt pavements containing iron and steel slag base courses. As the first step of the purpose, this paper describes some basic and mechanical properties of slag materials. In the former description, the major emphasis is placed on the introduction of a newly proposed compound slag, namely, a mixture of 50% by weight of steel-making slag, 30% by weight of blast-furnace slag and 20% by weight of granurated slag. This compound slag exhibited more improved hydraulic setting behavior, especially at early curing ages, than the blast-furnace slag itself. In the latter, resilient constants, accumulative plastic strains and fatigue properties of the compound slag specimens are discussed by comparing with those of each reference material, being blast-furnace slag or crushed stone. The regressed equations for these characterization data, regarding some of the number of stress application, stress state and curing age, were verified through the comparison between observed and computed results for each corresponding behavior in pavements.

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Accelerated carbonation test is performed to explain mechanism of carbonation of concrete. The depth of carbonation, the weight loss of mortar, the amount of calcium hydroxide and calcium carbonate, and pore volume and pore size distribution are measured. Water immersion test and air exposure test after accelerated carbonation test is also performed to evaluate the diffusion of calcium hydroxide. The depth of carbonation correlates the amount of evaporated water, and the amount of calcium hydroxide and calcium carbonate, pore volume and pore size distribution depend on exposure duration in the accelerated chamber. The depth of carbonation of mortar decreases due to the diffusion of calcium hydroxide from uncarbonated portion to carbonated portion under wetting condition.
Based on these test results, the diffusion equations for water, carbon dioxide and calcium hydroxide are proposed and the finite difference method is used in numerical analysis. The depth of carbonation of concrete can be predicted by analyzing these diffusion equations.

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It has long been suggested that rationalization of concrete operation can be promoted by utilizing rheological constants obtained by viscosity equation of fresh mortar and concrete. But actually, such studies have been very few.
In this paper, the authors pay attention to the fact that mortar and concrete are a type of high concentration suspension, and the suspension medium in the mortar and concrete are considered to be respectively cement paste and mortar, the suspended particles are respectively fine and coarse aggregate.
This study aims to establish a direct estimate of the plastic viscosity, using the mortar and concrete's viscosity equation with the factors: material characteristics and mix proportions. The authors also show that the plastic viscosity obtained by using this viscosity equation is very accurate, and so very useful.

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Mortar specimens for compressive strength tests were prepared using six kinds of ground granulated blast-furnace slags of various Blame specific surface areas. Water-cement ratio and sand-cement ratio of base mortar containing no ground slag were fixed at 0.50 and 2.50, respectively. Replacement ratios of cement by ground slag were set at 30, 50 and 70% by volume. Both the preparation and moist-curing of the specimens were conducted at a constant temperature; i. e., 5, 10, or 20°C. The results of compressive strength test were analyzed to derive equations, by which the effects of each influential factor could be quantitatively evaluated. New two indices, which are independent on various factors, were proposed for evaluating the activity of ground slags.

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Biaxial compressive-tensile tests were conducted on reinforced concrete plate members. In the average stress average strain curves, steel starts to yield below its yield strength and the length of yield plateau is zero. In addition, the relationships between average tensile stress and average tensile strain on concrete at biaxial compressive-tensile stress states is different from those in uniaxial tensile stress states. Constitutive equations of steel and concrete in reinforced concrete plate element under biaxial stress states are proposed. These equations are then applied to the analysis of torsional behaviours of reinforced concrete members. The experimental and analytical values on the members subjected to torsion are found in good agreement.

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Presently the finite element method (FEM) is largely applied not only to the analytical calculations but also to the actual design. For utilizing FEM to the actual concrete structures, the conventional analytical procedure is unsuitable and the elastic FEM which is often utilized in the design field is deficient in general under the condition of shifting to the limit state design method. Then, this study proposes an FEM model in view of rational and practical application to the actual concrete structures, and its verification was carried out by the experiment using RC and PC beams. As a result, it was clarified that the proposed FEM model could practically execute the calculation of design for the serviceability and ultimate limit states.

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The ability of PC grout to fill voids is an important property which governs the durability of a prestressed concrete structure. It cannot be said, however, that voids are always completely filled in actual constructions, and it is necessary for research work to be done to develop a high-quality PC grout. In the present study, therefore, retarded-foaming type aluminum powder, super-plasticizer, and segregation-inhibiting water-soluble high polymer were used as admixtures, while combinations of various types of cement, flyash, and silica fume were made and the qualities of the mixes were compared.
This report is on the results of laboratory tests which indicate the direction to be taken for PC grout of more complete void-filling capability.

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This study wass made to present a technique for quantification of the heat of hydration evoluation process dependent on the temperature of cement in concrete and provides a general approach for deriving a heat of hydration evolution model capable of conforming with any temperature hysteresis.
The authors show that by using adiabatic temperature rise curves of concretes with different initial temperatures, a more generalized heat of hydration model could be given for cement in concrete even when a conduction type microcalori-meter is not used. For cements in paste and concrete, it is shown quantitatively that the rate of hydration reaction differs greatly at early age because of the difference in dispersion properties of cement particles.

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The tensile cracking of concrete is a major factor contributing to the nonlinear behavior of reinforced concrete elements. This motivated the writers to develop analytical models for the tension stiffening effect.
This paper deals with mechanical behavior of isotropic/nonisotropic reinforced concrete panels subjected to in-plane shear, and its characteristics are examined by numerical calculations as well as by comparisons with experimental results. Nonlinear shear deformation, rotation of principal angles of concrete stress and total strain, influence of bond stiffness, and crack widths and slip are especially discussed.

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It is confirmed that excessive expansion of concrete due to alkali-aggregate reaction can be controlled by the use of fly ash as an admixture, but the mechanism of the control is not clarified yet.
In this paper, using eight fly ashes with different alkali content, the deformation of Pyrex mortars containing these fly ashes is studied under the accelerated condition and the influences of chemical and physical properties of fly ash on expansion of the mortar are evaluated. Furthermore, the reactivity of Pyrex as an aggregate in mortar bar is also investigated by measuring the dissolved content of boron in mortar and the influence of the reactivity on the expansion is studied.
The expansion of mortar depends largely on the type and the replacement ratio of fly ash. Alkali content of fly ash has little correlation with the expansion. The expansion may depend on not only the reactivity of Pyrex but also the stiffness of the mortar. The expansion correlates the reactivity of fly ash in alkali solution. Control of the expansion due to alkali-aggregate reaction can be evaluated by the proposed index using amorphous SiO₂ content, mean diameter and the replacement ratio of fly ash.

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This paper describes the effects of stress relaxation on the mechanical behaviour of asphaltic mixtures in ductile zone. Stress relaxation tests were conducted in ductile zone under various loading conditions and examined the effects of stress relaxation on strain at failure, flexural strength and failure envelope of asphaltic mixtures. It is coneluded that strain at failure of asphaltic mixtures increases with stress relaxation of asphaltic mixtures in ductile zone and stress relaxation of asphaltic mixtures have direct effects upon failure behaviour of asphaltic mixtures at various test conditions.

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This paper clarified that reinforced concrete members made of steel fiber reinforced concrete (SFRC) exhibit excellent durability in extremely severe corrosive environment such as marine splashing zone. Based on the results of 5 years of exposure test in marine splashing site, it is ascertained that steel fibers dispersing in SFRC does not corrode except for the ones in the surface layer portion and that corrosion of reinforcing bars embeded in SFRC does not occur, even if considerable amount of chloride may penetrate in these reinforced concrete members. Furthermore, the electrochemical concept explaining of the corrosion protection mechanism of SFRC is proposed.

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This paper shows that condensation of the water-soluble Cl^- in concrete is surprisingly significant in concrete structures submerged in sea water. That is, the Cl^- concentration of the pore solution in the concrete structures can be very much higher than that of the surrounding sea water. In addition, the formation of Friedel's salt is confirmed to be closely related to the binding of intruded Cl^- in materials with cement matrix. The maximum amount of intruded Cl^- bound in the cement matrix materials is also examined. This research therefore provides better understanding of the intrusion mechanism of intruded Cl^- and the induced corrosion of steel in concrete.

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In order to establish the reliable earthquake-proof design for railway reinforced concrete bridges and piers, it is essential to evaluate the ductility of RC members quantitatively. The authors had conducted reversed cyclic loading tests on several RC members which were scale modeled the piers of railway bridges, and derived an equation to evaluate the ductility factor of RC members reasonably. In this report, some nomographs (design aids) which are obtained from the derived equation are introduced. These nomographs can be used to obtain the ductility factor when the dimensions of RC member are given, and also can be used to obtain the volume of transverse reinforcement when the required ductility is given.
Besides the derivation of the equation to evaluate the ductility factor and the presentation of some nomographs, we demonstrated how to use these nomographs in an actual design process.

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The authors developed a stress equation of expansion joint edge of concrete pavement slab based on stress analysis by finite element method (FEM). In this FEM analysis, concrete pavement and its expansion joint were expressed by means of a thin plate-Winkler foundation model and a shear spring model respectively. The elastic constant of the shear spring model was determined experimentally by loading test at a full scale concrete pavement. Multi-regression analysis was applied to the results of the FEM numerical calculation, and consequently, a stress equation was obtained. After the comparison between the calculated results of the equation and experimental results, it was proved that the equation was valid and practical.

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The present paper is to introduce a newly proposed method for nonlinear torsional analysis of precast prestressed concrete member with joint by using the Rigid Body-Spring Model. Particular attention in the analysis is focused on the cracking torque, the ultimate strength and the post-cracking torsional behavior for the whole range of prestressing. And also, this work involves comparison between the theoretical analysis results and the experimental data up to failure with consideration of various factors affecting the torsional behaviors. From these results to domonstrate the applicability of the proposed method, it is found that this method is capable not only of prediction of both the pre- and post-cracking torsional behavior but also of analysis of the failure mechanisms in joint.

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