On RC columns, it was assumed that the shear failure is caused when Mohr's stress circle drawn by using the axial stress of concrete and the confining stress of hoops touches Coulomb's criterion. And, the predicting method of the shear strength and the deformation capacity on RC columns based on Mohr-Coulomb's criterion, that was a reasonable method of considering the state of the stress in concrete, was proposed; then it compared with the experimental results in the past. As a result, the shear strength and the deformation capacity could be predicted more accurately than the methods of the past.
This paper describes the results of laboratory experiments of injecting epoxy resins into concrete cracks using cylindrical specimens and concrete flat plates (JIS standard) with controlled crack width, in order to study the factors affecting the injection behavior of crack repair materials. As the result, it was confirmed that the areal velocity of an injection material into a crack is proportional to the square of the crack width, to the injection pressure and to the reciprocal of the material viscosity, as has been shown by past research. Furthermore, the results show the possibility that injection velocity is affected by crack surface roughness, and the degree of influence is also affected by crack width. In addition, it was found that the loss of injection pressure in the injection system is an important parameter in order to predict injection velocity.
Supercritical water, a solvent with a very high decomposition efficiency, is especially applicable to waste treatment, requiring no organic solvents or incinerators. This paper discusses the technology to remove asphalt from the asphalt mixture by using Supercritical water as well as the promising applications of the recycled aggregates for the manufacture of cement concrete. In this experiment, the strength and durability (drying shrinkage, carbonation and freezing and thawing) tests of concretes using recycled aggregates produced by supercritical water treatments were conducted to evaluate the applicability of the aggregates to cement concretes. The results reveal that the strength and carbonation behavior were similar to using virgin aggregate, however, the drying shrinkage and the scaling of the concrete with high water cement ratio tended to increase as compared to the use of the virgin aggregate.
In cold regions such as Tohoku and Hokkaido districts, many RC structures are suffered from frost damage. While a frost damage risk map produced by S. Hasegawa has been widely used to evaluate the required durability performance for concrete against frost damage, the capability of resolution is quite limited and engineers can guess only briefly the risk of the frost damage. Another shortcoming is that the correspondence of the map to the damage in existing structures is not sufficiently proved. In order to overcome the shortcoming of the currently used map of frost damage risk, the local climate condition was taken into consideration and a detailed map of the frost damage risk with 1km square mesh was produced. Based on the detailed map, it has become possible to quantify the risk of the frost damage on the site where RC structures of electric power plant are located. On the other hand, a series of site investigation on the existing RC structures of electric power plant was carried out. Many of them were damaged by frost action, though it was difficult to clearly quantify the rank of damage by the currently used assessment diagram that is composed of five ranks determined with a set of five levels of damage development and four levels of damage extension. To avoid the shortcoming of the currently used assessment diagram, a new one was proposed in this paper. It is composed of twenty ranks, each of which is determined by a set of a single level of damage development and a single level of damage extension. Therefore the damage rank of the investigated RC structure is clearly quantified. All data of the assessment of frost damage by the site investigation on totally 2,246 components in 176 structures were collected and also the risk of the frost damage on the site was quantified. For the sake of relating these two variables, a theoretical model developed by authors was introduced and the coefficient of a function in the theoretical model was determined by data fitting with the obtained values of two variables mentioned above. Finally a detailed frost damage risk map was produced by the obtained function.