Recently, there is a need for accurately determining the heat properties of mass concrete structures, because these properties are required as input data for numerical analysis. Although great efforts have already been made, as yet, there are no reliable methods for evaluating the heat properties.
This paper demonstrates that a back analysis method, proposed by the authors, is very capable for evaluating thermal and boundary characteristics of concrete dams. And this method also allows to estimate heat transfer coefficients from results of field measurements of a concrete structure structure or a simple test in the laboratory. The variation of the heat transfer coefficients is discussed in relation to the several curing conditions of concrete.

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Concrete is normally considered to have high watertightness, but it is microscopically porous material. The migration and diffusion of oxygen, water, chloride ion and so on causes corrosion of steel embedded in concrete. Accordingly the improvement of durability of concrete is considered to make concrete itself voidless.
In this paper, electrical resistivity was measured so as to estimate the permeability of mortar and concrete. Besides, three methods of electrical resistivity measurement were compared. Complementally experimental methods adopted were water permeability test, chloride penetration test and porosity measurement. Test results indicated that electrical resistivity had correlated with chloride penetration and provided reliable indicator of the permeability of mortar and concrete. Furthermore, mix proportion and addition of admixture had an influence on the permeability of mortar and concrete.

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The compressive fatigue tests for about 240 concrete cylinders were carried out and the following items were investigated. That is, i) the form of probability distribution in fatigue life, ii) the effects of specimen size, concrete properties including static strength, and frequency of loading on the fatigue strength.
Test results indicate (1) the distributions of fatigue life conform to the logarithmic normal distribution and 3-parameter Weibull distribution. (2) if fatigue tests on specimen with the ratio of specimen diameter to maximum size of aggregate being 5 or more are conducted under the frequency of loading ranging from 0.1 to 15Hz, the factors such as concrete strength, specimen size, and frequency of loading hardly affect on fatigue strength but the scatter in static strength significantly affects on the scatter in fatigue life.

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Pysical properties of mortar change due to carbonation. An accelerated carbonation test, a wet-dry accelerated test, and a cyclic accelerated carbonation and water-spray test were performed to investigate the change in compressive strength of mortar. The depth of carbonation, the amount of calcium hydroxide and calcium carbonate, pore volume, and the compressive strength of mortar were measured. The compressive strength of mortar is increased due to carbonation. Pore volume depends on the amount of calcium hydroxide and calcium carbonate. The change in the compressive strength of mortar due to carbonation can be predicted by the use of the amount of calcium hydroxide and calcium carbonate as a parameter.

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Usage of an epoxy-coated reinforcing bar has been one of the most effective methods that prevent corrosion damages. It may happen that flaws are made on coating surfaces during transportation, handling, or bending of an epoxy-coated bar. This study examines the effects of flaws on the coating upon the corrosion of an epoxy-coated bar intensively. Epoxy-coated steel bars were embedded in concrete test pieces with 2cm and 4cm of cover, and the area of corrosion on the bars were observed for 400 days. The coated bars showed much higher preventive ability under a corrosive condition than the uncoated ones, even if there are some flaw on coating. However, the experimental results suggest that, under a severe corrosive condition, a flaw should not exceed 1mm², the area of the whole flaws should not exceed 0.013% and 0.054% for 2cm and 4cm of cover, respectively.

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Concrete overlaying is one of the repairing methods of the slabs in the steel girder bridges. However, overlaid concrete may separate from the old slab because of the shear stresses caused by the heavy load such as trucks or trailers. Therefore, experimental research has been conducted to clear the mechanical behavior of the slabs with concrete overlay. Analytical way using non-linear finite element method is also developed and compared with the experimental data.Furthermore, this analysis is applied to the models of real bridge slabs to estimate the shear stresses at the boundary of overlay and slab, and it is shown that overlaid concrete will not be separated from the slab by the traffic loads.

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The relationships between the pore solution composition and the corrosion intensity evaluated by electrochemical measurements for the steel electrode embedded in mortars containing a reactive aggregate and chloride are experimentally discussed in order to reveal influences of the alkali-silica reaction on the corrosion of steel reinforcement in mortars. The alkali-silica reaction promotes the chloride-induced corrosion of steel bars embedded in mortars containing a reactive aggregate and a chloride. The extent of the promotion varies with the type of chloride. The relationships between the corrosion intensity and Cl^-/OH^- ratio in the pore solution in CaCl₂-bearing mortars are very different from those in NaCl-bearing mortars.

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To clarify the effect of vibration on the roller compaction of concrete for RCC, time subsidence curves of concrete were measured under various vibration conditions. Also, plastic viscosities and yield stresses of mortar and concrete were measured by a pulling up sphere type viscometer during vibration.
When the acceleration or kinetic energy supplied to mortar and concrete increased and exceeded a certain limit, the plastic viscosity of mortar and concrete decreased remarkably, resulting in increased liquefaction and compaction. Thus, the compaction behavior could be expressed by the acceleration or kinetic energy of such mortar and concrete.

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Research work was devoted to the study of carbonation as one of the major causes of concrete deterioration. Big amount of field data and accelerated carbonation, in laboratory control tests, was collected. This led to many formulas describing the carbonation rate. However, most of them contain water/cement ratio and time as the only parameters affecting carbonation. Intuitively, carbonation should be affected, also, by CO₂ concentration and environmental conditions. Hence, in this research, the effect of CO₂ concentration on carbonation rate of concrete is clarified through experiments. This, besides a comparative study on the data available in the literature led to the introduction of new equation for the carbonation rate. This equation considers, as its parameters, the concentration of CO₂ and temperature in addition to water/cement ratio. The equation is employed in correlating accelerated and natural carbonation and shows good performance.

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Bending tests of lightly reinforced concrete beams were carried out and the failure characteristic of the beams was investigated. The size effect on the flexural strength of concrete was taken into account in estimating the cracking and the yield strength of the lightly reinforced concrete by considering the tension softening of concrete. The failure process of the reinforced concrete beams in experiments was able to be explained through the proposed simple calculation model. The unstable fracture process after cracking was also explained using the relations between the load-deflection curves of beams and the loading conditions. The failure modes of the reinforced concrete beams were classified into three types according to the relations among the cracking, the yield and the ultimate strengths of the beams.

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In order to generate the dynamic response of reinforced concrete structures by means of visual manner without doing vibration test, a simulated dynamic response visualization system was successfully developed by utilizing computer controlled video tape recorder in the pseudo-dynamic test. By playing back the tape, the visual dynamic response behavior can be observed in the real time scale although the experiment has been done by using pseudo-dynamic test. The visual dynamic simulation of four types of reinforced concrete columns under a severe earthquake were carried out by using this system. This system was quite useful to realize the characteristics of ongoing seismic failure of those columns.

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Hybrid structures with steel plates and concrete have considerable potential for use in offshore facilities. In those structures, steel plates will be seen either on one surface only or both surfaces of structural members. For the hybrid structures, adequate shear reinforcement is required to obtain appropriate mechanical properties. Flexural and shear resisting mechanisms have to be developed. This paper presents the results of flexural and shear loading tests on hybrid beams with newly proposed shear reinforement. Furthermore, load carrying mechanisms against shear and flexural forces are investigated and their design methods are established based on the test results.

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It is very important to take the influence of human error into consideration in order to assure the structural safety. New probabilistic model by which the influence of human error is taken into consideration is proposed. In the new model, occurrence of human error is assumed to have something to do with the quality assurance level of structural material or member. Furthermore, the influences of quality assurance level or the distribution of load effect on the structural safety of RC columns subjected to axial load are numerically examined by use of the proposed probabilistic model.

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Experiments were carried out to develop a new x-ray non-destructive inspection technique for concrete using contrast media and sufficient results were obtained. A contrast medium that was in accord with the purpose of the investigation was selected by comparison tests among many contrast media in the medical field. Using the technique, patterns of fine cracks were detected forming in concrete around deformed bars of axially tensile specimens, lapped splice specimens and beam specimens. The patterns of cracks on x-ray films were compared with those obtained by red ink injection method. Three dimensional figures of cracks in concrete and influences of aggregate size on crack's pattern were also examined.

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Concrete is considered as an aging linear visco-elastic material. Hence, the creep behavior of concrete under the constant sustained stress is represented by either creep coefficient or specific creep, both of which are based on an assumption of the linear relation between creep strain and externally applied stress. What is in doubt, however, is the upper limit of this relation. In terms of the stress/strenght ratio, an upper limit between about 0.23 and 0.75 has been observed. The purpose of this study is to clarify the nonlinearity of creep strain of concrete under the constant sustained stress. We verify the significant difference among the creep coefficient of concrete which is under the various constant stress level. Furthermore, we propose a non-linear creep prediction equation which can represent the results of creep experiment.

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This paper discribes the results of the data analysis of the pavement condition survey conducted in Kyushu. Since most of the pavements were repaired before their ultimate failure stage in warm regions, the transient performance model of asphalt pavement distress was formulated by applying the Weibull distribution function to the surveyed data in order to evaluate the distress performance during the life of asphalt pavement. Reliability and survice life were evaluated by means of the Markov transition probabilities calculated by this model.

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Concrete structures have been constructed without priorly considering their maintenance, because they have been long considered as permanent structures. However, a deterioration of marine facilities due to chloride damage has become conspicuous in recent day. It has come to think that those structures should be periodically inspected and preperly maintained to keep their performance level.
In this paper, optimum inspection interval is sought by choosing piled piers as a target structure. The problem is defined as a trade-off problem between inspection cost, repairing cost and loss cost. The optimum interval is determined so as to minimize total expected cost. Expected repairing cost and loss cost are obtained based on reliability theory. A deterioration model is defined examining inspection data on existing piled piers.

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Most of widely-used creep analysis methods of concrete are on the basis of principle of superposition, and the creep coefficient used in the analysis is constant irrespective of subjected stress. Hence, the non-linear phenomena of creep are frequently neglected in the actual design. We clarify that the creep strain of concrete under the various stress histories is non-linear phenomena strongly affected by the maximum stress. When we treat creep as non-linear phenomena, we need creep hardening rule to calculate the creep strain under the changing stress. Many creep hardening rules have already proposed. For example, there are strain hardening rule, time hardening rule, work hardening rule and so on. These creep hardening rules are proposed for metal materials not for concrete. We will propose the creep hardening rule which can be applied to creep problem of concrete under any condition.

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Glass fiber reinforced concrete (GFR concrete) were produced by premixing method. Changes in mechanical properties of GFR concrete have been investigated up to the age of 5 years. Reductions in strength and toughness were observed at relatively early ages, compared to GRC produced by spray method. Differences in time-dependent changes in mechanical properties between specimens stored in various conditions were not clear. These tendency may result from the dispersion of strands into individual filaments and/or loosening of strands. Loosening of strands enables hydration products to deposit easily at the interfacial zone and within spaces among filaments. Therefore, effects of aging mechanisms on the reduction in mechanical properties GFR concretes produced by premixing do not appear at the same age as in those by spray method.

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The influence of both compressive and tensile lateral stresses on the bond strength of deformed bars were studied. The test specimens were devised so that the frictional restraint induced by loading plates for pull-out load and lateral stress were reduced. The major variables used were the lateral stress and concrete cover. The bond strength increases with increasing compressive lateral stress up to about 30% of concrete compressive strength. However, beyond a concrete cover of 2.5 times of test bar diameter this trend disappears. On the other hand, the bond strength rapidly decreases with increasing tensile lateral stress. Taking account of these results, the emprical equations for bond strength under lateral stress were derived.

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The effects of the voids caused by bleeding under the bottom of coarse aggregates to the mechanical behavior such as cracks and compressive strengths were investigated in dam concrete with coarse aggregates of less than 150mm of maximum size. Rectangular concrete specimens which have several model aggregates made by mortar with the shape of circle and rhombus were tested in order to grasp the behavior of cracks and compressive strengths. In addition to the experimental study, the analysis using finite element method also was conducted for verifying the results of experiments. It has been cleared that the voids under the aggregates of large size deteriorate the compressive strengths in dam concrete greatly.

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The problem of double peak tensile strength distribution for CERP rods, 8), is investigated. First, single carbon fibers were tested in tension and the strength distribution was obtained. Consequently, a model for tensile failure of CFRP rods was proposed, assuming ideal matrix properties. The actual behaviour of the rods was compared with the ideal one in order to determine the deviation in behaviour. The reliability of the measured strains was ensured through two types of experiments, that led, also, to characterisation of the loading system. The picture was completed by testing the binding matrix together with two other matrices for comparison and the results of all the previous experiments were analysed. The analysis assures the importance of the large matrix strain capacity for maintaining rods high strength.

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System identification using Kalman filter was applied to an in-situ reinforced concrete bridge to identify its modal properties. A field vibration test was conducted to obtain vibration response data for the purpose of the identification. Using a step-by-step parameter identification technique based on modal analysis of a linear multi-degree of freedom system, the estimation of the modal parameters, which are the dominant natural frequencies and the corresponding damping ratios, was examined. The results from the system identification are presented and compared with those obtained from spectra analysis.

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Mechanisms of concrete stress transfer were examined and thoroughly understood using the contact density model developed by B. Li and K. Maekawa. Qualitative studies were done on high strength concrete and on structural-deformation-like loading paths involving crack closing or opening with shear slip happening at the same time. The studies indicated that stress transfer mechanisms in high strength concrete crack were different from that of normal concrete due to difference in crack surface configuration. They also showed that the mechanisms in the structural-deformatin-like paths much differed from those in classical crack width constant loading paths due to significantly induced effect of friction and due to unconfined nature of the paths which gave rise to anisotropic property and contact fracturing of a crack surface.

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The model for stress transfer across cracks in concrete with universal applicability is proposed. It is a physical model based upon numerical computational scheme of the original contact density model developed by B. Li & K. Maekawa. Main part of the model which is significant for model non-linearity is the contact stress formulation. The formulation integrates important characteristics of concrete stress transfer behaviors, i. e., significant effect of microscopic friction, anisotropic plasticity of contact stress, and contact fracturing of contact units of a crack plane. Each characteristic is represented by microscopic model which is combined together into the same model framework culminating in the final universal model.

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Verification of the proposed universal stress transfer model is conducted. The model was proposed as the one for stress transfer across cracks in concrete with universal applicability. Thus the verification is done by applying the model on various cases of stress transfer experiments covering the classical cases which are the crack width constant crack deformational paths as well as the mixed mode deformational paths under high confinement, the specialized cases which are the cyclic mixed mode crack deformational paths, and the cases of stress transfer across concrete cracks having distinctive characteristic, i. e., high strength concrete, lightweight concrete, mortar and cracks in construction joints. Verified results are very satisfactory and therefore confirm the universal applicability of the proposed stress transfer model.

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A detailed cyclic micromechanical model based on the micromechanics of granular material is proposed for concrete. In the current study, concrete is idealized to have two kinds of contacts; aggregate-aggregate and aggregate- mortar contacts. The behavior of these contacts is examined and distinguished for both cyclic and virgin loadings. Finally, an explicit formula which expresses the tangent stiffness matrix of the material as a summation of the contributions of all contacts inside any representative volume is derived. Moreover, the nonhomogeniety of the microstructure and the nonuniformity of strain distribution are considered. This is in contrast to Bazant's microplane model in which concrete has been treated as a homogenous brittle aggregate material having a single kind of contact with uniform strain distribution.

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This paper describes a structural design procedure for airport concrete pavements in case that they will be constructed on the reclaimed ground in an expansion project of the Tokyo International Airport. Both the amount of rehabilitation works and their schedules are calculated in two ways. The settlement is considered to affect the behaviors of the pavement as follows: 1) a gradient of the pavement surface deviates from the criterion as the pavement is considered to follow the settlement fully; and 2) distress appeared on the surface exceeds the criterion as the pavement does not follow the settlement fully. In the former, rehabilitation work is found to be three times and in 60% of the whole area at the maximum during 20 years. In the latter. the pavement structures for design periods of 10 years have been determined.

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Bonded concrete overlay has been seldom used in airport concrete pavements in Japan, because insufficient bond between concrete overlay and concrete slab has caused certain problems such as separation between them. As the required overlay thickness varies with bonding conditions between two layers, the sufficient bond between two layers is required when designing especially thinner overlay. Both careful surface treatment with shotblast on the existing pavement and application of bonding medium like cement paste on the surface are necessary to realize it. This bonding technique has been verified through several kinds of laboratory tests. Furthermore, groovings should be applied on edge portion of the slab to ensure the bond. Two series of experimental pavements are constructed to confirm this procedure where Falling Weight Deflectometer is used to evaluate the structural conditions of the overlay pavements.

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As a nondestructive test for pavement structure, its layer stiffnesses are commonly estimated from a set of surface deflection data measured by FWD test. Assumptions commomly made in backcalculation are uniformloading and completely bonded interface between two adjacent layers along with linear elastic theory based on small deformation. In order to judge whether it is important to confirm the assumptions, effects of load distribution and slippage between the layers on backcalculation stiffnesses are examined. BISAR is used for the analysis and Gauss-Newton methed is employed for the backcalculation.

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The strength of the cement treated sandy soil depends on the kind of the soil to be treated and also on the amount of fines, i. e. silt and clay portion, as well as on the kind of the cement used and its amount added. In order to clarify such inter-relationships, this paper intends to study, first, the strength variations of the cement treated sandy soil with different gradings and corresponding bridging state of the cement hydrates in the pores, and secondly the effects of grading with different water cement ratio. The strength of the cement treated sandy soil is found to be affected by the grading of the soil only in case of lean mix. It was also found that with smaller distance between soil particles, the cement hydrate bridging tends to be denser, thereby increasing the strength of the cement treated sandy soil.

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