This paper presents the reduction of quality of self-compacting concrete incorporating ground granulated blast-furnace slag that has frozen at early age and the effects of the countermeasure to the frost damage. As the experimental results, the self-compacting concrete incorporating ground granulated blast-furnace slag attacked by initial frost damage showed the remarkable reduction of both the strength development and the resistance to freezing and thawing. Especially, the resistance to freezing and thawing of the self-compacting concrete became much lower than that of the normal concrete. Furthermore, it was recognized that the strength and the resistance to freezing and thawing of self-compacting concrete could not completely recover to the quality of concrete not subjected to initial frost damage, even if countermeasures such as water curing and heat curing after initial frost damage were performed.

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Elderly people often cause an accident according to slip on a walkway. However, skid resistance of walkway pavement materials has not been studied enough. We investigated walkinng properties of elderly people and studied porous properties, surface texture and skid resistance on several surface conditions of kinds of walkway pavement materials.
We found that an average inclination reflects surface texture of pavement materials; surface water absorption and surface texture of pavement materials have a strong correlation with skid resistance; and O-Y·Pull Slip Meter is a good skid resistance testing device of walkway pavement materials. Finally, we considered coefficient of friction and proposed anti-slip pavemennt materials.

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The stiffness of PC box girder bridge with steel web reduces as compared with the stiffness of normal PC box girder bridge with concrete web. Therefore, beam section must be reinforced by cross beams in order to maintain sectional form. This paper shows a calculation method for sectional deformation of box girder with steel web. This method is based on foldet plate theory. An definite example is shown due to examine a behaviour of box girder with corrugated steel web.
Finally the symplified calculation method for corrugated steel web is proposed.

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There is a method to place thin cement concrete overlay on an asphalt concrete pavement as one of the rehabilitation methods for improving an existing asphalt pavement. However this method doesn't become popular at present. In this research, to begin with, applying the theory of a beam on Winkler foundation, we will investigate the stress analysis procedure of pavement slabs. Next, we will investigate the model of composite structure that consists of a thin cement concrete layer and an existing asphalt pavement layer, taking the degree of bond between these two layers into consideration. We will combine the results of these two investigations and establish the design procedure of the thin layer cement concrete overlay as a composite pavement.

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The experimental and analytical study on the autogenous shrinkage of cement paste, of which mechanism is assumed to be creep phenomenon due to the transition process from the unstable stress state to the stable stress state, were performed. In the analysis, the autogenous shrinkage model which is assumed to be creep phenomenon was developed and then the developed model was introduced to the coupled model with the liquid and solid phase of cement and concrete as a two phase porous permeable material. The applicability of the developed models was estimated compared with the experiment results. In the experiment, the autogenous shrinkage tests with the parameter of the atmospheric pressure (1.0atm, 0.5atm and 0.3atm) were performed and then the effect of the parameter on the autogenous shrinkage was discussed.

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In this study, compressive fatigue tests of totally about 200 high-strength concrete specimens with about 60-80N/mm² of compressive strength were carried out, in order to investigate the effects of compressive strength of concrete, test environment and type of coarse aggregate on the fatigue characteristics in compression. The fatigue strength of high-strength concrete decreased when compared with that of normal strength concrete with normal aggregate. On the other hand it was almost same as that of normal strength concrete with normal aggregate, when high-quality artificial lightweight aggregate was used as the course aggregate.

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In this paper, the quantitative evaluation was carried out on the effect of mix-proportion and material condition on the characteristics (thickness, pore ratio) of transition zone (T. Z.). At first, the thickness of T. Z. was evaluated using Wall-effect Model. Using these values and experimental results (pore volume of T. Z.), the pore ratio of T. Z. can be evaluated. To compare the analytical results with experimental results, prove that the thickness and pore volume of T. Z. that were established from several assumptions was reasonably. Using these results and King's model, the model that calculated the coefficient of mass transport of each phase in hardened cement was established. As a result, the coefficient of mass transport of T. Z. was bigger than that of paste.

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A study was made, by nonlinear analysis and static load experiments, into the ultimate bending behavior and failure mechanism of continuous prestressed-concrete girders in which simple girders of an existing highway bridge were joined by a no-joint construction method and reinforced with external tendons. It was found that because of the improved flexural capacity due to the increased external tendon stress accompanying the deformation of the structural members, the moment redistribution that occurs with the deformation of the plastic hinges of the intermediate supports predominates, the load-carrying capacity of the girders is improved, and safety against flexure is satisfied. Also, an analysis method is proposed that makes use of secant stiffness to directly reproduce the structural system in the plastic region.

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An experimental study was carried out to find out the threshold value of chloride ion and hydroxy ion ratio (=[Cl ]/[OH]: mol ratio) for the onset of reinforcing steel corrosion in concrete. After the application of electrochemical method (desalination and realkalization), a five-year follow-up survey on the specimens was carried out in order to check the performance of the rehabilitation method.
The experimental results showed that when the pH value was 12 or more and Cl/OH ratio was 1 or less, the reinforcing steels were not corroded. The rehabilitation using the desalination and realkalization method increased the pH value to 12.6-13.2 and decreased water soluble chloride content to 0.47-0.56 kg/m³ around the reinforced bars in concrete of existing structures. During the 5-year-follow-up survey, re-diffusion of chloride ion into the concrete around the reinforced bars had been hardly recognized, and also the presence of clear shadow spot surrounding the reinforcing steel had not been recognized.

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This study has investigated the characteristics of massive concrete which has been suffered temperature history by heat of hydration. The study through the mortar specimen and concrete specimen which have cured under artificial heat treatment simulated to the heat of hydration, reveal that influence of temperature history on mechanical characteristics and durability of mortar and concrete. The block specimen, which simulated to actual massive structures, was investigated and the test results shows that the compressive strength as well as the penetration depth of chloride ions and carbonation depth was degraded by initial temperature history during at least 6.5 years after casting.

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In the investigation of the existing Prestressed Concrete structures on the deterioration, the several examples of the defects of PC grout have been reported.The quality improvement of PC grout has been requested. In this study, the formulations that predict the bleeding and the efflux time for flow from J14 funnel have been done for PC grout made by adding the quenched blast furnace fine slag and the superplasticizer. Through the formulated equations, the parametric study has been carried out for the effect on the bleeding and the the efflux time of PC grout. Moreover, the mix proprtion design to improve the quality of PC grout has been investigated.

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In this paper, a new method to use Carbon Fiber Reinforced Plastic (CFRP) Sheets which are prestressed before they are bonded to the concrete surfaces based on the concept of prestressing technique is developed. An experimental program is carried out to verify the reinforcement effects of RC beams with prestressing CFRP sheets such as on the improvements of flexural strength, ductility, stiffness and crack resistance. An effort is made to investigate the different reinforcement effects for various RC beams with different, ratios of flexural and shear capacities and structural optimization of reinforcement is also discussed in the paper. Finally, the adaptability of existing RC beam theory for calculating the flexural capacity of structures strengthened with prestressing CFRP sheets is examined.

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We investigate bond behaviour between fiber sheets and concrete by the experiments and non-linear finite element method. Moreover, we estimate bond strength between fiber sheets and concrete. In these experiments, we investigated the bond strength by the influence of the different types of sheets, the different compressive strengths of concrete, the different bond lengths of sheet and the different bond widths of sheet. We discuss only the failure due to sheet peeling from concrete surface because we think this failure pattern is the best bond function. In the results of these experiments and these analysis, the bond strength between fiber sheets and concrete depends on the compressive strength of concrete. The effective bond length exists because the bond strength becomes constant over a certain value of the bond length. In the results of these experiments, the bond strength is not proportional to the width of the fiber sheet below a certain value of the width of the fiber sheets. The lower the width of the fiber sheets below a certain value is, the higher the bond strength per unit width is.

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This study aims at pursuing the changes in microstructural features and the characteristics of ASR gels composition in reactive aggregate-containing mortars immersed in NaCl solution, relating them to the expansion behavior of the mortars. The alkali contents of ASR gels produced in mortars in NaCl solution were found to be lower than in NaOH solution. Larger expansions in mortars in NaCl solution than in NaOH solution appear to result from the production of ASR gels with relatively low alkali contents in the mortars. A characteristic of microstructural features to be noted in the mortars produced by the use of cement with the higher C₃A content was that ettringite started to be formed within many cracks caused by ASR at a time during the period of 14 to 56 days after immersion in NaCl solution. It is unclear whether the secondary ettringite formation influenced expansion of the mortars in NaCl solution

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It is necessary that the occurrence of the limit states which are undesirable for the bridge systems should be prevented under the consideration of uncertainties in case of seismic design. In this study, firstly, the effect of uncertainties in reinforced concrete (RC) bridge systems on the response of the RC bridge pier and cast in place pile were statistically and analytically studied, and quantitative evaluations of variations in that response were obtained. Then seismic design method was discussed in which such uncertainties were considered in order to keep cast in place pile from yielding. Finally, the horizontal seismic coefficient for cast in place pile was proposed based on the system reliability theory and dynamic analysis for the bridge systems.

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This study was performed to investigate the mix proportion of high strength and self-compacting concrete, which mixproportion strength was more than 80N/mm², and application of the concrete for the underground diaphragm wall. It was confirmed that the concrete, which was consisted of low-heat portland cement, air entraining high-range water reducing agent, would be expected to have long-term development of strength because of very low rise of temperature and could be easily filled into the structure by tremie method And it was also confirmed that the strength of the concrete after filling into the diaphragm wall was the same as the strength of the specimens, which were sampled before filling and cured by standard curing condition.

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It is known that tensile strength of the brittle materials like FRP tendons has wider dispersion, and depends more significantly on size compared with the ductile materials. However, only few reports have been published.
This papar discusses the influence of specimen length on tensile properties of FRP tendons to make size effect clear. The main experimental factor of the tension tests, specimen length, was decided taking standard testing method, actual prestressed concrete structures and so on into account. It was made clear that the longer specimens had smaller tensile strength and ultimate strain.

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Nowadays, premature deterioration of concrete caused by chloride attack has become a severe problem. Desalination, which is an electrochemical treatment of chloride extraction from concrete, has been developed as an essential repair method. Steel bar embedded concrete acts as a cathodic electrode through desalination process and its potential is less than hydrogen occuring potential by electrolysis. Therefore, considering hydrogen embrittlement of prestressing steel bars, desalination has not been applied on prestressed concrete yet. In this study, diffusible hydrogen stored in notched and highly tensioned prestressing steel bars was investigated while desalination was continuously and intermittently applied on prestressed concrete.

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This study aims at investigating the influences of local environmental conditions on the degree of damage in existing ASR damaged concrete structures and proposing a method for predicting the progress of ASR damages in future on the basis of the data obtained in the investigations. The ASR damages in the structures were found to rapidly proceed after the freezing-thawing repetitions due to changes in climate started to increase. It was also found from these investigations that the degree of deterioration in concretes depended on the local environmental conditions such as temperature, humidity and the supply of water from the outside. The combination of the alkalinity of pore solutions extracted from damaged concrete structures and the expansion of concrete cores from the structures by the use of the NBRI test was useful for predicting the progress of ASR damages in concrete structures.

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The analytical method to evaluate easily the ultimate deformation of reinforced concrete columns subjected to cyclic loading was developed, in which the lattice model that can evaluate shear-resisting mechanism clearly was extended. In this study, it was confirmed that the lattice model could evaluate the ultimate deformation of reinforced concrete columns subjected to cyclic loading with reasonable accuracy. In addition to this, shear-resisting mechanism of reinforced concrete columns can be captured by the lattice model analysis.

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The important factor on concrete creep behavior at early age concrete is amount of hydration. This experimental study on compressive and tensile creep has been carried out at condition of the lower temperature in order to inhibit hydration of early age concrete.
As the result, tensile creep became bigger than compressive creep, it was shown that tensile creep mechanisms is different to compressive one.

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This paper describes the deformation characteristics of a base-course material which is a mixture of steel-making slag, blast-furnace slag and fly ash pellet (here called ‘the compound slag B’). The deformation characteristics are investigated by carrying out a repeated loading triaxial compression test: the equations expressing the resilient and permanent deformation behaviour are presented. It is shown that the compound slag B exhibits better deformation characteristics than Hydraulic mechanically stabilized slag (HMS), a standard slag base-course and that the same equations of representing the resilient and permanent deformation behaviour are applicable to the compound slag B as those for HMS and a previously-investigated compound slag.

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