The present study deals with the influence of surface coatings on the scaling of the concrete surface by the freezing and thawing action. The freezing and thawing tests were performed on concrete specimen some of which were treated with coating materials. For this purpose five different water repellents were used. The influence of the curing period of coating, the strength of concrete and the condition of concrete surface were studied. The obtained results show that the resistivity of concrete against the scaling increases when treated with water repellents. However the success of the concerning treatment can be optimized by the use of the adequate surface coating material.
Size effects of RC beam without shear reinforcement is well known as in the shear strength. However, there are few studies concerning the size effect on the out-of-plane shear failure of RC panel. In this study, the size effect on the shear strength of RC panel was investigated by the out-of-plane shear test on RC panel specimens in various sizes including large-scale ones. As a result of the test, the size effect was not clearly identified, because the shear span to depth ratio of the specimens was small and concrete around the loading plates, forming the tied-arch mechanism, was failed in compression zone. The 3D FEM analysis turned out to be effective to estimate the shear strength of RC panel including large-scale specimens.
In this study, 3-D numerical simulations on responses of three kinds of reinforced concrete (RC) beams subjected to standoff detonation loads have been carried out to establish a numerical simulation method for predicting responses of RC members subjected to blast loads. Effectiveness of the numerical simulation method used in this study was discussed in terms of reaction force histories, strain histories of reinforcing bars, and damage of the RC beams, comparing analytical results with corresponding experimental ones. The main result is that by assuming a proper value of tensile failure pressure of concrete, responses of the RC beams subjected to standoff detonation loads would be simulated relatively well with a simple material model based on static material properties.
This study relates to the development of a manufacturing machine of artificial coarse aggregate which excels in grain shape and grading. The experimental results of coarse aggregate produced by the kinetic energy of many chain rotating at high speed in the presented stone crusher are reported. In this investigation, a total of 24 specimens are made for three kinds of stones which used now for raw stones in our country, and the grain shape and grading of produced coarse aggregate are examined. The results show that the presented stone crusher can produce coarse aggregate with excellent grain shape and grading.
It is important to know initial performance of the structure in urgent measure on damages due to earthquakes and the control of maintenance. In this research, the vibration test at the same time construction step of the structure to grasp an initial performance of the structure to use a continuous Arch-culvert structure that used precast members was executed, and the natural frequency of the structure was understood. The reference value to evaluate the performance of each material that secured safety was examined by confirming the validity of the design technique of the structure by using the result, and forecasting the change of the value by the analysis in an initial value to receive damage due to the earthquake etc. while the structure was using it in being do the maintenance management of the structure in the future.
The purpose of this research is to clarify the influence of construction works on variation in concrete quality, and to establish estimation method of quality variation considering construction conditions (mix-proportions, re-bar conditions, cover concrete depth, etc). In this research, variation in concrete quality obtained by the experiment was quantitatively evaluated using neural network. As a result, the influence of construction conditions on the variation in concrete quality could be clarified quantitatively and the cover concrete quality and its variation could be estimated.
This study reports the suppressing effect of fly ash incorporated as the part of fine aggregate on the expansion of mortar due to alkali-silica reaction (ASR). In this study, 3 types of fly ash were tested according to 2 types of accelerated mortar bar test. As a result, the larger the replacement ratio of fly ash became, the less the expansion of mortar. The effectiveness of fly ash on expansion due to ASR was different according to the chemical composition and particle size of fly ash. More quantities of fly ash are required in Danish method than JIS method to suppress expansion due to ASR. It was revealed that the suppressing effect of fly ash was affected by the contents of amorphous silica and calcium and the specific surface area of fly ash.