The expansion model of concrete due to Alkali Silica Reaction (ASR) was proposed basing on the damage theory and introduced to the three dimensional finite element method. By comparing with the uni-axial restrained experiments, the expansion strains due to ASR, which depend on the difference of the reinforcement restraint were predicted accurately. The proposed model was applied to the ASR damaged specimens reinforced in multi-axial directions with different reinforcement ratio in order to evaluate the concrete expansion and strain localizations near the bent corner of reinforcement. Then, by comparing with experimental results, it was confirmed that the proposed model was effective in predicting the ASR damages of RC structures.

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This research clarified the effects of microscopic thermal stress caused by the difference of coefficients of paste and aggregate on mechanical properties of early age concrete subjected to high temperature history.
When concrete was subjected to high temperature history like steam curing, compressive strength of concrete whose water to binder ratio was 30% was much lower than that of cement paste without aggregate. When water to binder ratio was 50%, the difference of coarse aggregate affected mechanical properties of concrete so much, which was caused by microscopic thermal stress. The effects of microscopic thermal stress was remarkable in concrete using ground granulated blast-furnace slag. Under high temperature history, effects of fine aggregate were also observed. A possibility was suggested that crushed sand of limestone had an effect of increasing strength due to chemical reaction with cement paste.
When concrete was subjected to high temperature history at 7days, the effects of microscopic thermal stress were small.

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Recently, new types of artificial lightweight aggregates with extremely low water absorption have been developed. The use of these high-performance aggregates can assist in creating the structural lightweight concrete with high-strength and high-durability. However, the shear carrying capacity of RC beams using this concrete decreases due to the increase in autogenous shrinkage and decrease in fracture toughness. Hence, the authors performed the loading tests of high-performance lightweight concrete beams with a combination of synthetic fiber and shrinkage-reducing admixtures, and clarified the combined effects on improvement of the shear carrying capacity.

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Asphalt roadbeds are widely used for ballasted tracks to prevent permeation of rainwater into subgrade and to reduce the growth of track irregularities. In the conventional design method of asphalt roadbeds, thicknesses of asphalt roadbeds have been specified by the resilient settlement at the surface of asphalt roadbed. According to a new performance-based design method as described in this paper, the effect of the number of passing trains considered as well. The effects of the number of passing trains are prescribed by the fatigue criteria of asphalt mixture layer. By introducing the new design method, more rational deigns of asphalt roadbed considering traffic volumes became possible.

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We investigated about a mechanism of pressure loss causing and increasing, when self-compacting concrete flows and passes interspaces of steel bars, based on theological dynamics of thixotropic flow and multiphase flows, and we try to show the theological formulas. In this paper, the model of causing pressure loss mechanism is proposed that a coarse aggregate volume of the self-compacting concrete increases partly; a mechanism of force transmit of the concrete is changed from plastic viscosity flow model to a state of solid particle friction model the influence of it is larger, the apparent yield stress of concrete increases, then, the pressure loss increases, we consider. Then, we try to investigate the suitability of the mechanism model, a flowing test to measure pressure loss and visualization test to grasp the state of coarse aggregate movement inside a model formwork, using model self compacting concrete, it includes the artificial lightweight aggregate, viscosity agent and water. As the result, the theological formula of pressure loss mechanism is proper generally, the theological value and the result of the experimental pressure loss value are similar in the case the experimental pressure loss value is lower than about 200Pa and no coarse aggregate blockage near steel bars.

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A theoretical equation to express the relationship between pressure and mercury volume intruded into the pore space was derived from the energy equilibrium on thermodynamics. The equation has the form:

V =	V0Upc	,
	1+Upc

where p_c and V are pressure and mercury volume obtained by mercury porosimetry, respectively, V₀ is the total pore volume, and U is the constant reflecting the characteristics of the pore structure. The equation can be used to express the mercury intrusion process in various cement materials with extremely high precision. This makes it possible to characterize the pore structure characteristics of cement materials based on the mercury intrusion process.

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In order to estimate cracks of concrete in early-age, tensile Young’s modulus of early-age concrete must be evaluated appropriately. Uniaxial tension test were conducted by employing various early-age concrete or mortar; the tensile Young’s moduli were investigated in the present study. The experiments indicated the tensile Young’s moduli are higher than the compressive Young’s moduli in early age of concrete. The present study discussed applicability of composite structural model for tensile Young’s moduli. As the results, tensile Young’s moduli were estimated properly by using the simple model.

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Alkali silica reactivity of andesite has been considered relatively simple regardless of various mineral compositions. The reactivity is considered to be attributed to its volcanic glass and reactive silica such as cristobalite and trydimite. In this study, the reactivity of andesite was evaluated by various accelerating test. Glassy andesite without silica mineral was innocuous in saturated NaCl solution whereas it showed reactivity in JIS A 1145, JIS A 1146 and ASTM C 1260. This is attributed to linkages of mineral composition of andesite and composition of pore solution. The results indicated one possibility that glassy andesite is innocuous even in specific environment where alkalis are supplied from environments such as deicing salt and sea water.

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Large-scaled rehabilitation works with inlay were carried out on pavements of Fukuoka Airport runway under conditions that large aircraft run with high frequency immediately after the end of daily work, without affecting aircraft operation. As the rehabilitation procedure, the following was developed through a series of laboratory tests and experimental constructions. Namely, both modified asphalt and temperature decreasing additive were introduced into asphalt mixtures, with larger maximum sized aggregates having gap grade for binder course. In addition, quick-drying tack coat was also used. As the construction quality control, the pavement surface temperature was set at 60°C or lower one hour before service to operation. This method was verified by inspecting the rehabilitated pavement successively.

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The parametric study using FEM and the experiment of T-beams prestressed with external tendons have been performed to investigate the factors thought to influence on the shear mechanism of externally prestressed concrete beams. The effects of prestressing force and stirrup can be observed as important factors to the failure mechanism. The simplified truss model, having a small number of degrees of freedom, has been modified and proposed by adapting the formulation to predict the angle of concentrated stress flow and the thickness of diagonal compression members for evaluating the shear carrying capacity of externally prestressed concrete beams. The predicted results show the good agreement with experimental results.

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The present study is aimed at investigating the shear behavior of reinforced concrete beams with doubly reinforced rectangular cross-section, with and without steel fibers, affected by distributed cracks. The influence of the distributed cracks was mathematically quantified with the help of a crack density parameter. Monotonic loading tests were conducted on the RC beams and their failure indicated a mixed mode between both diagonal tension and diagonal compression failures. Due to the reinforcement layout, the effect of the longitudinal compression reinforcement on the shear carrying capacity should be taken into account. The distributed cracks were shown to have less influence on the peak load of doubly reinforced concrete beams.

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Crack-induced debonding failures are observed to be very dominant and sometimes unpreventable in concrete members strengthened with externally bonded FRP composites. Many research efforts have been concentrated on developing the debonding predictive models and different models have already appeared in some design guides and codes. However, most models are either lacking of comprehensive under-standing of failure mechanisms (empirical models) or too complex for use in practice. As a complement to our preliminary proposal which has been adopted and included in the current JSCE guideline, this pa-per presents a theoretically reasonable and analytically feasible methodology on how to predict the debonding failure induced from intermediate flexural cracks in FRP strengthened R/C beams. The predictions based on the present analytical model are compared to 180 experimental data collected from existing literature and a close agreement has been obtained.

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This paper presents the results of the laboratory investigations on the corrosion of paint-coated steel plates with defects under laboratory conditions of simulated marine environment and in the field. First, experimental qualitative evidence showing significant similarity of the polarization behavior between divided, which were used for measurement of each potential and macrocell current, and undivided steel plates was established. Macrocell and microcell corrosion were then monitored in paint-coated steel plates with defects under different exposure situations and temperatures. Lastly, corrosion rates in an existing paint coated steel structure in the field were estimated. Results show that values of electrochemical measurements in divided steel plates are almost the same and showed the same trend as the undivided steel plate. Macrocell corrosion occurred between the painted part and the defect part of the steel plates. The exposure condition where high oxygen supply and high temperature exist, provided the most severe environment for corrosion of paint coated steel with defect. Moreover, corrosion rates in an existing steel structure in the field were successfully estimated.

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