In order to estimate the rebar corrosion rate in carbonated concrete, reinforced concrete specimens acceleratedly carbonated were subjected to a 5-year exposure test. In concrete specimens, rebars were arranged in lattice direction. Test results showed that the average corrosion rate of the lower part of lattice rebars was abut 0.002mm/yr. Based on the above-mentioned test results and the past references, deterioration prediction of concrete structures was carried out. As the result, it was considered that bearing capacity of concrete structures is not seriously hampered by rebar corrosion. However, the possibility of deterioration such as the spalling of cover concrete is rather high, as carbonetion precedes.

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Reinforced concrete structures such as a containment vessel, a support structure of the reactor, piping systems and facilities for storing high level radioactive waste in nuclear power plants are designed assuming the conditions that those structures are exposed to high temperature conditions. In the previous papers, the author elucidated the temperature dependence of the properties of concrete and reinforcement and the influence of differential thermal expansive strain between concrete and reinforcement on the behavior of reinforced concrete tension and flexural members in order to contribute to the rationalization of the design method. In this paper the influence of high temperature conditions on the flexural behavior and strength capacities of RC members with axial force were made clear and those estimation methods were suggested.

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The purpose of this study is to investigate influence of using the recycled fine aggregate on properties of concrete and discuss its cause. From experimental results, it was found that the slump of concrete using recycled fine aggregate decreases, because recycled fine aggregate had a bigger volume of fine particles than natural fine aggregate with same grading in weight. There is a correlation between strength, depth of carbonation or shurinkage per unit volume of cement and a ratio of cement to total water. The total water is a sum of water content and total water absorbed in aggregate. This means that water absorbed in aggregate influences porosity of hardened concrete.

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The applicability of recycled asphalt concretes, with the waste materials obtained in construction works of airport pavements, to airport pavement surface courses at taxiways was verified through this study. In laboratory tests on asphalt concretes with the maximum recycling rate of 70%, the recycled asphalt concretes are almost equivalent to new ones, regarding both flexural properties and anti-stripping properties, and the changes of properties due to accelerated aging actions become less as the recycling rate increases. The properties of full-recycled asphalt concrete is similar to those of recycled asphalt concrete with 70% recycling rate. Through the field observation on airport asphalt pavements with recycled asphalt concretes, the difference in properties between recycled and new materials is negligible.

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The formula for calculating the shear strength of a reinforced concrete member is based on the result of a test under symmetrical concentrated loading at two points. In a spread foundation or multiple-pile footing of an actual structure, loading is distributed or applied at multiple points along multiple lines. For effective design of structures, therefore, establishing a shear strength calculation method that produces satisfactory result even for such loading distribution is important. Then, a method was proposed to calculate the shear strength of a beam while considering the mutual effects of the distances from the bearing and from the load. Verifications were made using the existing results of tests under symmetrical or unsymmetrical loading at multiple points. It was revealed that the proposed method reproduced the test results fairly accurately.

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Time-dependent flexural deformation of prestressed reinforced concrete members made of high strength concrete subjected to sustained load is investigated experimentally, comparing with that of normal strength concrete members. Compressive strength of the former and that of the latter are approximately 100N/mm² and 45N/mm², respectively. The effect of autogenous shrinkage is incorporated into the creep analysis model. Furthermore, a new model for tension stiffening is presented, which is owing to the contribution of tensile stress of concrete at cracked sections as well as that of bond stress between concrete and reinforcing steel. The comparison of experiment and analysis shows the validity of the present method.

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In this study, constitutive equation of reinforced concrete element was developed based on Lattice Equivalent Continuum Method. Lattice Equivalent Continuum Method is a technique to construct a constitutive equation by using the concrete and reinforcement main lattice system to express the flow of force in RC elements and shear lattice system on crack surface to evaluate shear rigidity. In addition, the objective of this study is to develop a more robust and powerful analytical tool from the view point of constitutive equation and algorism. The validity of the proposal constitutive equation was examined by analysis of RC panel. The validity of proposal analytical toll was examined by evaluating the post peak behavior of RC beam failing in shear including snap-back instability.

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In order to clarify the extensibility of fresh concrete with fly ash of type IV that substitute for sea sand, visual inspection and ultrasonic method of nondestructive testing are performed to evaluate width and depth of settlement cracks of normal concrete and concrete with fly ash of type IV. As results of this experimental study, it is observed that the average of settlement crack width of concrete with fly ash of type IV become as half as one of normal concrete in same covering. It is confirmed that settlement cracks penetrate relatively closer at the position of reinforcement bar, as covering thickness become thinner regardless of the season placing concrete, the sort of cement and the replacement ratio of fly ash.

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Failure of concrete subjected to uniaxial compression is localized, which governs structural behavior of concrete, especially in the post-peak region. In this study, compressive cyclic loading tests were conducted to formulate the hysteresis loop of concrete in compression taken into account the localized failure. As a result, the proposed formulas in this paper can represent the experimental stress-strain curve with good accuracy, which have been obtained from specimens with various height to depth ratio H/D and cross-sections.

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Evaluation of the mechanical characteristics of RC structures during earthquakes by using the lattice equivaent model is the main purpose in this study. To apply this analytical model to cyclic stress field, maximum 4 directions of orthogonal crack, non-orthogonal crack model is developed and static cyclic and non-linear dynamic analysises are performed. Comparing those analytical results with the experimental values, the valuation of the behavior in post-peak region and the validity of the model and the parameter of the model are investigated.

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This paper discussed the test results of fresh properties of highly-flowable steel fiber-reinforced concrete carried out in the laboratory. The main subjects are the influences of volume fraction of steel fiber, unit volume of coarse aggregate, and dosage of viscosity agent. Flowability and seregation resistance of the concrete, and mortar properties were examined. As the results, it is possible to design mix proportion of highly-flowable steel fiber-reinforced concrete with adequate segregation resistance and adequate combination with volume fraction of steel fiber and unit volume of coarse aggregate.

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This paper describes the chemical and mineralogical features of reactive aggregates and their alkali-silica reactivity, which are collected over the Hokuriku district. Various test methods, which include JIS A1145, JIS A1146, ASTM C1260 and Danish mortar bar method, were carded out to clarify the alkali-silica reactivity of about 80 aggregates in the Hokuriku district. The compatibility between the test methods was discussed with respect to the expansion behavior of mortar bars containing reactive aggregates. Furthermore, by taking out the cores from the concrete specimens, and then by measuring their expansion behaviors in accelerated curing condition of the immersion in 1N NaOH solution or the saturated NaCl solution, the rapid test method for the evaluation of the alkali-silica reactivity of concrete itself was proposed.

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This paper describes results of the research on the problems of concrete strength estimation by rebound hammer tests. The relationship between the rebound number and the concrete hardness obtained by the experiments almost coincides with the one theoretically derived. Accordingly, the rebound number expressed hardness, including the experimental error that affected by the random change of the impact energy loss in concrete. The energy loss can cause increased error of hardness in high strength concrete. It was also shown that the hardness was approximately proportional to compressive strength, which means the hardness was a possible index to evaluate compressive strength of concrete.

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Reinforced super lightweight aggregate (SLA) concrete beams with controlled density of concrete were experimentally load-tested. The test results showed that the shear capacity decreased as the density of concrete decreased. The conversion term from general normal-weight concrete to SLA concrete for calculating the shear capacity was proposed based on the test results, which is expressed as a function of the density of concrete. Furthermore, the shear transfer mechanism of SLA concrete at the surface of a crack was experimentally investigated. It was concluded that the existing formula for calculating the shear transfer capacity of high strength concrete is applicable to SLA concrete by using the same coefficients..

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Pore structure characteristic of a hardened mortar is quantified as a pore structure coefficient (PSC) that is defined and calculated in this research using an effective diffusion coefficient obtained from a migration test. PSC is composed of porosity and tortuosity. PSC was found to be controlled partially by the amount of pores ranged from 100nm to 2μm in the diameter. Potassium ion as a tracer ion in the migration test provided reasonably consistent PSC as well as chloride ion.
Larger tortuosity of fly ash mortar resulted in lower PSC despite larger porosity. The PSC for fly ash mortar appeared to account for part of micro pores that may reduce ionic diffusion. An electrical effect of the micro pores would seem to restrict the movement of diffusing ions.

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Using the hoop tie ratio in the beam as the parameter, experiments were conducted on three specimens that model RC rigid piers. All specimens caused shear damage at their beams after forming a plastic hinge at four locations. It was found that the hoop tie ratio in the beam did not affect the maximum bearing capacity, but had large effect on the deformation capacity. FEM analysis also showed the decrease of shear resistance of concrete due to the increase of deformation.

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To evaluate the durability of a concrete structure, it is important to secure the precision of the cover. In this study, we surveyed the construction errors of the covers of railway RC rigid frame viaducts constructed in recent years, and clarified that the errors in covers were different at different parts and larger with pillars caused by the overall shift of reinforcing bars. Based on the study results, we proposed a value of allowable construction error for the design of railway RC rigid frame viaducts.

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Three-dimensional Cross-sectional joint element to consider discontinuous deformation around RC column base is proposed, and the influence of joint phase to member's response is numerically investigated using frame analysis. The joint element is obtained based on the fiber technique, by assuming that uni-axial stress along member's direction is prominent and plane on relative displacement remains plane. The proposed method is verified through comparison with uni-axis and multi-axes cyclic loading experiments, and multi-axes response at joint are discussed.

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Joint sealing materials, which are joint sealant and joint filler, are used to prevent the rainwater from intruding through the joints. However, the present standards for joint sealing materials might not reflect their required performance because the standard values are different, depending on their ingredients, and test methods for the materials are not specified. Therefore, the rational standards of joint sealing materials are required to reduce the cost for maintenance of airport concrete pavements. This paper describes the results of performance evaluation of joint sealing materials. As the result, it is clarified that temperature, environmental condition and cyclic compression affect on the performance of joint sealing materials.

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Since technical standard was set as a performance-based specification, developing practical measurement methods for individual performance indicators have been urgent. This paper aims to present a framework of pavement performance evaluation methods under the technical standard and to activate discussion and research on specific evaluation methods. According to the contents of the technical standard, pavement performance can be evaluated not only by measuring the pavement in situ with performance indicator but also by using specimens properly substituted for the pavement and/or calculating the performance indicator based on measured values of indicators which correlate with the actual pavement performance.

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The behaviour of thin walled composite (TWC) filled beams with normal (NC) and lightweight volcanic pumice concrete (VPC), is described. Comprehensive series of tests provided information on the loaddeflection response, failure modes, stress-strain characteristics and effect of different modes of interface connections. The strength of the beam is limited by the compression buckling capacity of the steel plate at the top of the open box section. The enhancement of strength of such beams can be possible by stiffening the compression steel plates at the open end of box section with various modes interface connections. The design of such beams should consider local buckling of steel and interface shear bond characteristics.

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Influences of penetrative condition of curing water on properties of cementitious materials were investigated. In a large-size specimen with a low water-cement ratio (W/C), both the mixing water and penetrative water at standard water curing are not sufficient to complete the hydration of the entire specimen. Therefore, curing conditions were studied to improve the properties of the specimens at any distances from the surface during hydration process. When W/C is low, specimens cured with water containing AE-admixture, which has low surface tension, and water under high pressure was able to improve the degree of hydration and strength more than those subjected to the standard water curing.

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The parametric study using FEM has been performed to investigate the factors thought to influence on the shear mechanism of PC slender beams. With the main investigation on the effects of prestressing force with its type of stress distribution, the failure mechanism can be clarified. The simplified truss model has been developed with a small number of degrees of freedom for assessing the shear carrying capacity of PC slender beams based on the equivalent linear analysis. By utilizing the extrapolated inclination of critical stress flow and the thickness of diagonal compression members estimated from the FEM results, the well-predicted results on the shear behavior of PC slender beams without transverse reinforcement can be obtained.

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