In this paper, alkali silica reactivity of chert and siliceous slate was investigated, and petrographic examination of these rocks was carried out. Petrological characteristics, JIS A1145 chemical method and mortar-bar method were examined on chert rock and siliceous slate which were included in the ASR damaged concrete structure in Aichi Prefecture. In the expansive test method of mortar and concrete, storage environment was changed in various types of conditions. The results of the chemical method became innocuousness, when the crystallinity index measured with X-ray diffraction exceeded 7.5. And in the JIS A1146 mortar bar method, the expansion of mortar made with chert and siliceous slate exceeded 0.1% in 2 months, and in comparison with both rock, the expansion of mortar using siliceous slate was higher than that of mortar using chert. Furthermore, the expansion of the mortar bar of the mixing use of siliceous slate and chert was higher than that of the single use.
This research showed the expansion behavior of prestressed concrete beam deteriorated by alkali-silica reaction under long term exposure test by the follow-up survey over about four years. The main results are as follows. Expansion of the cracks became remarkable at the time of the high temperature of summer, and it was almost changeless in winter. Compared with the strain of concrete surface of upper edge of axial direction, strain of vertical direction and upper edge of right-angle direction was large. The strain of the stirrups exceeded a yield strain greatly. The compressive strength of the test piece of concrete deteriorated to about 80% of the maximum, and the elastic modulus deteriorated to about 30% of the maximum.
A large number of bridge piers in Japan, which were mostly constructed in the 1970s or 1980s, are suffering from serious damages caused by alkali-silica reaction (ASR). The concrete using reactive andesite successively expanded for more than 30years, leading to the serious damage of structural elements of bridge pier. In the case study of Kashima Bridge in Ishikawa Prefecture, the degree of deterioration of bridge pier due to ASR was investigated by both visual inspection of cracking and non-destructive testing. Furthermore, the mechanical properties of concrete and the degree of fracture of steel bars were examined for the purpose of strengthening design of bridge pier. Based on the classification of ASR deterioration level of each element, the steel plate bonding was adopted for the column, after the pillow beam had been totally reconstructed. This paper describes the mineralogical properties of reactive andesite used in concrete and the mechanical properties of concrete cores taken from bridge pier. Furthermore, monitoring and strengthening methods applied for Kashima Bridge pier are introduced together with non-destructive testing by means of ultrasonic wave inspection. In the maintenance of this bridge, a monitoring using crack sensors has been successfully applied in order to ensure the daily safety of bridge.
This paper presents the results of long term outdoor exposure of specimens made of reactive aggregate and ASR expansion control by various surface penetrant methods, surface coating methods and injection methods. All methods have been able to control the ASR expansion of specimens. Especially, silane penetrant method can control the ASR expansion even if the surface layer removed. And this paper deals with the basic investigations on the amount of impregnated silane in addition to the impregnation depth by applying differential thermal analysis (TG-DTA) of samples obtained from different depths in concrete. A good linear relation between the exothermic peak area of the heat flow curve and the content of silane was confirmed.
Recently, lithium ion pressurized injection method has been spotlighted as the repair method of concrete structure which deteriorated by ASR. In applying this method to established structures, it is important to set up suitable pressure and suitable period according to the degradation grade of concrete. Then, it considered that the fall of compressive strength or modulus of elasticity was the degradation grade of concrete, and authors proposed the calculation formula which presumes a injection period from compressive strength or modulus of elasticity. This method was applied to the retaining wall. After applying this method to the retaining wall , the concrete core was extracted and the promotion expansion examination was carried out. Consequently, it was shown by injecting in lithium ion in suitable pressure and a suitable period that the effect which controls expansion is expectable.
When the utilization volume of industrial wastes and by-products in cement plants are increased, it is necessary to control the adiabatic temperature rise of cement containing a large amount of the interstitial phase. As previously reported, we produced an adiabatic calorimeter in order to evaluate the adiabatic temperature rise using about 30mL of mortar sample only. In this study, we investigated the influence of interstitial phase composition and ground granulated blast-furnace slag on the adiabatic temperature rise of the cement mortar using the advanced calorimeter. Changes in adiabatic temperature rise were negligible even when the amount of interstitial phase of cement was increased from 18mass% to 21mass%. It was confirmed that the adiabatic temperature rise of cement containing the interstitial phase of more than 21mass% was improved by a 20mass% replacement of blast-furnace slag.
In present paper the applicability of resistivity of concrete for evaluating chloride penetration is discussed. The resistivity of concrete was measured using an AC power source with 15 voltages and 950Hz. Effective diffusion coefficient of chloride ions in concrete was also determined by chloride migration test that is specified by JSCE G571-2003. Normal concrete with varied W/Cs, fly ash concrete and concrete with high strength lightweight aggregate made of fly ash were studied. Theoretical formula was applied to estimate apparent diffusion coefficient of chloride ions using measured resistivity values. In this calculation the transference number of chloride ions in concrete was determined empirically based on the resistivity tests and the migration tests.
Degraded specimens were prepared by mixing expanded polystyrene (EPS) beads with mortar, and sound specimens include no beads. Measurements of compressional elastic wave velocity (Vp) and acoustic emission (AE) were performed using an AE transducer. The relationships between air content and AE parameters were investigated based on the Vp measurements. The changes in AE behavior with increase in strain were measured by a uniaxial compression test and a splitting test. The AE parameters–rise time, count, frequency, average signal level, and event count rate–were evaluated, on average, every ten seconds. The following results were obtained. (1) In the uniaxial compression test, the volumetric contraction of the degraded specimens was small. This is because large volumetric expansion of the degraded specimens occurs with increase in axial strain. (2) It is difficult to measure the degree of degradation due to increase in porosity using only one AE transducer. The degree of degradation can be evaluated qualitatively using two AE parameters (mean value of count and standard deviation of rise time). (3) It is inferred that the area of observation can be recognized as degraded by increase in cracks when the behavior of average signal level and event count rate for monotonic load is similar to that for cyclic load. (4) It is also inferred that the failure type can be determined as either extensive compression or local tension by long-term observation of reverberation frequency and rise time.
The purpose of this study is the development of structural material with its superior strength and durability in historical city landscape. It is thought that reusing of waste colorful earthenware powder as admixture material of concrete is effective to color the concrete. In this study, the mechanical properties and the color evaluation of colored concrete by using the earthenware powder were examined. As a result, the strength and coloring effect of concrete increased with the increase of the replacement ratio of the earthenware powder. Furthermore, the color of concrete using the red earthenware powder was satisfied with the color evaluation of the walls of temples and shrines in traditional area of Kyoto.
Recently, the initiation period of the steel corrosion has been indirectly forecasted by chloride ion diffusion in cover concrete. However, when the chloride ion contents were continuously measured, the concrete structure was damaged by sampling some cores. Based on the above backgrounds, in this study, the system which directly forecasted the corrosion initiation period was constructed by a sacrificial electrode. Especially, the threshold value of the sacrificial electrode itself was confirmed to determine the corrosion initiation period. Here, the sacrificial electrode means “a sacrificial material” and “the Expansion-Ring-System”, which were combined with a dummy steel and a lower-ionization metal. More specifically, when a critical chloride ion permeated an arbitrary position in the cover concrete, the sacrificial electrode could sense the corrosion initiation. In conclusion, the initiation period of the steel corrosion in the concrete could be directly forecasted by some sacrificial electrodes embedded in different cover depths. Also, when the corrosion current density of the sacrificial material was about 0.1-0.2μA/cm2 or more, it was determined that the steel started to corrode.
The Ni40Nb20Ta5Zr30Co5 amorphous alloy membranes were prepared by a single-roller melt-spinning technique. The crystallization temperature of the alloy is 825K in an Ar atmosphere. Hydrogen permeability of the alloy was measured at the temperature of 573∼673K. As a result, it was found that the initial permeability measured at 673K was higher than 1 × 10–8mol·m–1·s–1·Pa–1/2 and that the permeability significantly degraded during the measurement. However, the lower the measurement temperature was, the smaller the degradation of permeability became. The permeability of the alloy measured at 573K was kept constant at 5 × 10–9mol·m–1·s–1·Pa–1/2 during the measurement. Then the hydrogen production by methanol steam reforming was conducted by using the amorphous alloy membrane. As a result, pure hydrogen was extracted by the amorphous alloy membrane from a reformed gas consisting of H2, N2, CO2 and CO and its separation property did not degrade during the experiment for 6h. Moreover, it was found that the amount of hydrogen flux depended on the flow rate of Ar sweep gas introduced into the lower-side chamber of the reactor. From this observation, the hydrogen permeability of the membrane during the methanol steam reforming was roughly estimated. The estimated permeability during the reforming is about 3.4 × 10–9mol·m–1·s–1·Pa–1/2. The value is smaller than that obtained from the permeation measurement with pure H2, which may come from pressure loss caused by the boundary film layer on the membrane surface and from surface contamination such as CO adsorption. The potential of amorphous alloy membranes for hydrogen production has been successfully demonstrated.
A newly developed testing system available to control temperature and the rate as well as applied stress or strain with high quality of extensometer is used to measure the transformation plastic strain occurring in the course of diffusion type transformation (including pearlite reaction). Specimens of six kinds of steels widely used for quenching operation are heated to austenite temperature of 900°C and kept at the steady temperature followed by cooling to lower temperature below transformation finish point subjected to several applied loads. Since the difference in the strain between zero and nonzero stress corresponds to the transformation plastic strain, the value of transformation plasticity coefficient is identified by the ratio of the strain to applied stress. Dependence of the coefficient on the chemical composition is discussed by defining an equivalent carbon content and compared with the data for plastic hardening coefficient.
The impact characteristics of a cue in billiards are investigated for the case where a ball is hit on the right or the left part to give a spin. The efficient computational method developed in the previous paper is extended for this investigation. The extended method is verified with an experiment using a high speed camera, i,e., the ball trajectory calculated with the extended method is shown to agree well with that measured using a high speed camera. It is shown from a numerical simulation that the impact force, the ball velocity, the spinning velocity and the deviation of the ball trajectory from the hitting direction increase with increase in the Young's modulus and density of a shaft. Because the proposed analytical method can predict quantitatively these impact characteristics of a cue, it is useful for designing an easy-to-use cue.
Si3N4/SiC composites in which discontinuous network structure was formed using SiC particles of nanometer size are able to perform both of the electric conductivity and high fracture strength at room temperature. We tried to apply the network Si3N4/SiC composite for paint atomizer (named bell head) of electrostatic rotation paint spraying. If the distance from the bell head edge to ground body could be reduced from 500mm to 10mm distance at the speed of 10mm/s, the ceramics bell head which applied voltage of –60kV was able to restrain spark discharge, which break out at the top edge of current metal bell heads. Moreover, even if Si3N4/SiC bell head was used for electrostatic rotation paint spraying, paint coating efficiency equivalent to a metal atomizer could be able to acquire.
In order to develop new ceramics for a power electric device, alumina/nickel (Ni) nanocomposites were fabricated using the soaking method and the pulse electric current sintering technique. The volume fractions of Ni were 0.5, 1, and 5% in γ–alumina powder. 10mass% α–alumina powder was added as a sintering seed. SEM and TEM observations revealed that the nanocomposites exhibited an intra-granular fracture mode, and agglomerated Ni particles existed mostly along alumina grain boundaries especially for 5vol% Ni. The experimental results showed that the strength and fracture toughness values of the nanocomposites were higher than those of monolithic alumina, and the thermal conductivity decreased slightly with increase in Ni content. Moderate improvements in the strength and fracture toughness seemed to result from the fact that the nano-sized Ni particles dispersed within alumina grains creating dislocations around the Ni particles, which reduced sintering residual stresses in alumina grains and expanded the frontal process zone size. It was concluded that nanocomposites with a lower Ni content had better mechanical, electrical, and thermo-mechanical properties.
The warp deformation behavior for a two-layer laminated body consisting of epoxy resin and FR-4 substrate caused by thermal load from heating to cooling was examined from thermo-viscoelastic analysis based on the linear viscoelastic theory and experiment. It was clarified that the warp deformation behavior for the laminated body was influenced by not only elastic modulus and linear thermal expansion coefficient of the composition materials but also the ratio of the material thickness and bending rigidity of composition materials, and that the warp deformation behavior during heating and cooling processes could be predicted by thermo-viscoelastic analysis that considered the temperature and time dependency of the composition materials.