The study on quantitative evaluation with concrete about synergistic effect of penetration of chloride ion and carbonation, is very few. This study was conducted to get information on synergistic effects of penetration and diffusion of chloride ion into concrete and carbonation and to examine evaluation method of synergistic effects of penetration of chloride ion and carbonation. The test results indicated chloride ions in concrete diffused inside by carbonation and chloride ions penetrated for longer term than actual exposure term were accumulated. And so we introduced a coefficient k to consider the effect of carbonation in diffusion equation which is based on the Fick's second law.
Scarcity of natural concrete aggregate is one of the common problems that concrete engineers are facing today. This paper presents the results of a study on a new manufacturing machine of artificial concrete aggregate which excels in grain shape and grading. In the crusher, raw stones are crushed by many chains rotating around a center rod. The number of the rotations is monitored and the mass of raw stones crushed every one minute is changed as experimental factors. A distance between a tip of the chain and an inner wall of the crusher is also changed. Finally, a total of 27 specimens are made and tested. The results show that the crusher can produce fine aggregate with excellent grain shape.
Load-carrying capacity of reinforced concrete (RC) members with lightweight concrete is lower in comparison with that of RC members with normal-weight concrete with the same compressive strength. This phenomenon depends on the fracture behavior of which the lightweight concrete is comparatively brittle to the normal-weight concrete. For the load-carrying capacity of RC members with the lightweight concrete, several reduction factors, which are applied to that of RC members with the normal-weight concrete, have been investigated by some researchers so far. The authors have been studied on the punching shear capacity of reinforced lightweight concrete slabs with the expansive shale aggregate. In the past studies conducted by the authors, the proposed reduction factors were constant values without a multiplicity of uses. In this paper, therefore, the applicable reduction factor to some kinds of lightweight concrete is derived in consideration with the fracture characteristics of the lightweight concrete. Consequently, the proposed method on punching shear capacity of the reinforced lightweight concrete slabs gives appropriate predicting values.
In order to investigate dynamic compaction process in concrete, pore pressure during vibratory compaction is analyzed by the boundary element method (BEM), applying Biot's two-phase theory. In a compactibility test of fresh concrete, variations of pore pressure and mechanical properties are measured. Then, distributions of pore pressures are estimated analytically and compared with experimental results. Good agreement is confirmed, and the distributions of pore pressures during the compactibility test are clarified. Compaction process by means of an internal vibrator is investigated, applying BEM analysis. Thus, it is confirmed that spatial distribution of pore pressure under vibration is closely associated with slump values of fresh concrete.
Waterproofing system in the pavement structures is one of most important functions to keep concrete slab durability, and waterproof material on concrete slab is required to have the sufficient mechanical properties for the wheel load to keep waterproofing function. To be based on concept of performance-based design method, it is important to evaluate mechanical properties of waterproof layer for the wheel load. In this paper, it was directed attention to creep characteristics of waterproof layer and creep characteristics of waterproof layer was estimated by the combination of experimental data, FEM analysis and a Genetic Algorithm metod. The mechanical behavior of waterproof layer applied the wheel load with running and braking was analyzed by FEM with both creep material model and estimated modulus model.
During flaw evaluation of road bridge floor slabs, confirmation of the cracks in terms of width, angle and area is critical. With the thermography method, one of the available diagnosis techniques, it is difficult to evaluate the cracks developed by thermodiffusion by using the heat source from the measuring plane. In this study, correlations of the various crack patterns generated on RC girders and changes in the surface temperature were clarified using the heat transfer of the pavement heat supplied from the floor slab surface during asphalt improvement work, rather than the measurement plane. As a result, it was confirmed that various surface temperature distributions corresponding to crack patterns could be confirmed in heat images from the heat transfer of pavement heat, and that the pattern of developed cracks can be conjectured. Furthermore, in the non-steady heat transfer analysis, the evaluation method of cracks in terms of width, angle and area as well as the reproducibility was also were clarified.