Quantitative evaluation of accelerator property and performance-based evaluation of shotcrete have been required with JSCE concrete codes changing to performance-based codes recently. So in this paper, the effect of accelerator on shotcrete performance was evaluated quantitatively and prediction method of shotcrete performance with any mix proportion was developed, using three models established in view of hydration; hydration degree changing model of cement paste with accelerator, plocter penetration resistance development and compressive strength development model. And then performance-based evaluation system of shotcrete was recommended by integrating the three models.

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There are various standards and proposals to inspect re-bar corrosion in reinforced concrete structures with half-cell potential measurement, however, it is uncertain whether they are applicable to carbonation-induced corrosion. In this study, to make sure of the applicability of half-cell potential measurement to inspect carbonation-induced corrosion, the promoting carbonation test using RC specimens was carried out. The results indicate that carbonation-induced corrosion occurs at more positive potential than standards and proposals based on chloride-induced corrosion and it is possibly caused by the difference of boundary of concrete and re-bar.

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SHIRASU, which is one of pyroclastic flow deposits, contains many minute particles and exists in South Kyushu so much as unused resources. Authors are doing the research and development which use SHIRASU as fine aggregate for concretes. In this study, authors tried to develop the design method of mix proportion of self-compacting concrete with SHIRASU experimentally. As a result, fundamental idea was proposed in order to design the mix proportion of self-compacting concrete with SHIRASU particles by mortor test.
Furthermore, production and the examination of precasted PC bridge which used SHIRASU concrete were performed, and the applicability of SHIRASU concrete was checked.

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Dam concrete with highly replaced fly ash (Fa) based on ordinary portland cement (OPC) was investigated, in which the study of the characteristics of strength, adiabatic temperature and durability was performed. In spite of highly replaced Fa, it's early and long-term strength were higher than those of Dam concrete with moderate heat portland cement which Fa-replaced-percentage was 30% (MPC30%). Compared with MPC30%, adiabatic temperature of these Dam concrete with the same σ91 were lower and the durability against freezing-thawing repetitions and carbonation were almost same. The C/S ratio of OPC40, 60% were a little lower than that of OPC30%, but it was almost same.

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The shear carrying performance of prestressed concrete girder using external tendons was studied as contrasted with that of girder using internal tendons. As results of static load test of T-section girders, the girders using external tendons showed large shear capacity by remarkable increase of tensile stress in external tendons and the tensile stress in concrete at shear span was restrained. Based on these results, the comparative design for continuous girder bridges was conducted and the factor which improving shear capacity was found in shear span, and was not found at nearby intermediate support. The results revealed that it was conservative that we estimate shear capacity of girder using external tendons following to the design method of girder using internal tendons.

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Concrete is easily affected by material segregation because it is composed of several materials (such as cement, water, aggregate, etc.) that have different properties. Material segregation greatly affects the durability of concrete due to steel corrosion. Since steel corrosion in concrete is an electrochemical process, therefore, acceleration of the electrochemical reaction depends on temperature. However, there are only few researches dealing with above subjects. Therefore, the objectives of this paper are as follows; (1) to evaluate the influence of material segregation on concrete property, (2) to evaluate the influence of material segregation on corrosion rate of steel bar in concrete and (3) to evaluate the temperature dependency of corrosion rate of steel bar in concrete affected by material segregation.

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In this paper, the durability performance evaluation of surface coating, which is widely used as a repair method of concrete structures, applied to cracked concrete was experimentally examined. As a result, it has been understood that the thicker the coating material is, the better the mechanics performance of coating material is. The influence of crack generated in coating material on the corrosion of steel reinforcement due to combined deterioration (carbonation and salt damage) was also conducted. In case of the cracked coating material, chloride content of vicinity of steel reinforcement was higher than that of other area due to carbonation and cyclic wet-dry condition. Therefore, the distribution of chloride content and the corrosion of steel reinforcement were quite different according to whether the crack was generated in coating material or not.

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It was experimentally studied to find an effective method for the reduction of the autogenous shrinkage of 150 MPa ultra high strength concrete, and the following results were obtained; 1) The use of an expansive agent, a shrinkage reducing agent and an artificial light-weight aggregate can reduce the autogenous shrinkage respectively. Moreover, the combining usage shows an accumulative effect. 2) The light-weight aggregate used can be an effective and economical answer considering the adequate content to avoid the excessive strength loss and the combination with other two additives tested for the sufficient shrinkage reduction.

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This paper described the time-dependent failure characteristics due to creep and fatigue of FRP rods with glass and aramid fibers and proposed an estimating method. At first, the results of creep and fatigue test of fibers themselves confirmed that the characteristics were strongly affected by the level of creep and fatigue and could be analyzed by the theory of failure probability by Weibull. Moreover, the simulation model on the destruction of FRP rods was constructed considering the time-dependent characteristics of fibers themselves and matrix resin. The simulative and experimental results provided the good agreement between them. Consequently, the simulation model developed here made it possible to evaluate the time-dependent failure characteristics of FRP rods.

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Reliability-based design of a pavement requires an exact estimation of failure probability of the pavement. In this paper, an estimation method of reliability of asphalt pavement based on T_A method is proposed. The failure probability of pavement is estimated by the second moment formulation and Monte Carlo simulation accounting for the variations of design parameters, such as traffic volume, subgrade and material properties, and accuracy of T_A method itself. The reliabilities of a number of asphlat pavements are estimated by the proposed method. The sensitibity analysis is performed to exploit the effect of the variations of the design parameters on the reliability of asphalt pavements.

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In this study, the material properties, an index to evaluate the control function of heat island phenomenon, an appropriate mix proportion and temperature reduction effect of the porous concrete with 20 to 40% of void ratio used the lapilli which was lightweight and high absorption produced in Akita prefecture were clarified. The mass of unit volume of this concrete was about under half of ordinary concrete and compressive strength was 2N/mm² but it was durable in the drying-wetting cycle test. There existed a paste coarse aggregate volume ratio having the maximum initial evaporation rate which was obtained from relationship between elapsed time and evaporation ratio. From the outdoor exposure test results and heat balance calculation, it was clarified that the temperature in the center of the cross sectional area and on the surface of the porous concrete plate manufactured by this mix proportion was 1 to 9 °C lower than that of ordinary concrete plate and this concrete had temperature reduction effect due to vaporization latent heat.

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Capillary pore structures in cement pastes with mineral admixtures were revealed by a combination of SEM-BSE image analysis and calculations based on the Powers' model. Degrees of pozzolanic reaction were evaluated by the selective dissolution method. In cement pastes with silica fume and fly ash, the volume ratio of large capillary pores to the total porosity were increased. The gel/space ratios of cement paste with mineral admixtures were not consistent with the evolution of compressive strength at long ages. This fact suggests that the compressive strength is influenced by not only the total porosity but also the volume ratios of coarse pores to the total porosity.

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For about 10 years since the mid-1960s, a number of concrete structures were constructed with sea sands from which salt was not sufficiently removed. To establish an appropriate method to maintain these structures, the authors first investigated the results of previous researches to re-evaluated the rebar corrosion rate due to initially-induced chlorides, and then carried out a 5-year exposure test by using a comparatively large-scale specimen. Base on the test and study results, the authors created a formula to calculate the rebar corrosion rate in consideration of cover depth, initially-induced chloride content and water-cement ratio.

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It is, generally, known that when large-sized vehicles like trucks and trailers are turning left, vertical and turning (torsional) load are applied on the pavement surface. However, there is very little information in the literature on the analytical solution of a multilayered elastic structure subjected to torsional surface loading. This paper presents analytical solution based on uniformly distributed circular torsional load. Combination of the solutions for axi-symmetric load (already developed) and torsional load will enable engineers determine stresses, displacements, strains etc at any point within the pavement structure when torsional load acts at the pavement surface.

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In this study, chlirode removal efficiency and repair effect due to applying desalination to chloride contaminated reinforced concrete containing fly ash or blast-furnace slag were evaluated. Moreover, ionic composition in the pore solution extracted from mortar specimens with high-pressure was measured to investigate the influence of mineral admixture on binding of Cl^-, electrophoresis behavior of Cl^- and corrosion environment of steel. As the results of this study, chloride removal efficiency of non-carbonated concrete was decreased by admixing mineral admixture because binding rate of Cl^- was increase and electrophoresis of Cl^- was delayed. On the other hand, chloride removal efficiency was improved by carbonation of concrete because fixed Cl^- was released by the carbonation and such released Cl^- was extracted easily.

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Chloride ions that come flying from the sea are known to be different in different regions. However, there are few reports on the chloride ions on the concrete surface in different areas. In this study, we investigated the chloride ion density on railway concrete structures at 142 places near the coast, and confirmed that the chloride ions on the concrete surface were different in different regions and depending on the distance from the coast. Based on the study results, we proposed a value of the chloride ion density on the concrete surface to be used for durability evaluation.

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Fiber reinforced concrete has been recently employed for tunnel lining in order to obtain higher resistance for exfoliation. The fireproof performance of such concrete, however, is not known sufficiently, e.g. explosion or combustion gas. The present study was conducted for obtaining the fundamental properties of lining concrete against fire temperature. This paper presents the behavior of fiber reinforced concrete from high heating test. Furthermore, the present paper reports the combustion gas of plastic fiber that is often employed for lining concrete. As the results, the combustion gas of plastic fiber was not hazardous for human, and plastic fiber reinforced concrete indicated higher resistant ability for explosion.

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Ultimate shear strength of Perfobond Rib (abbreviated as PBL) in a push-out test was examined using the lower bound theorem of limit analysis under modeling of perfectly plastic material for 3D compressive concrete. Linearized Mohr-Coulomb criterion was applied to yield and fracture of concrete, and discontinuous stress fields were assumed to concrete part within a steel rib hole and on its vicinity. Numerical analyses showed the effect of the hole diameter and thickness on the ultimate concrete dower strength of PBL. Discussion was made on comparison between the numerical results and the existing test ones.

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