In this study, the effects of different clinker constituent mineral ratios and curing temperatures on the C-S-H structure were investigated, mainly using FT-IR. In the FT-IR analysis, the second derivative curve of the spectrum was used to evaluate the formation and growth behavior of C-S-H. The intensity ratio of the C₂S-derived Si-O stretching peak to the C-S-H-derived Si-O stretching peak, and the Si-O-Si variant peak width were used as an indicator of the amount of C-S-H formation and as a new indicator of the regularity of the Si chains in C-S-H, respectively. The results indicate that in samples with high C₃S content, the regularity of the C-S-H Si chain is established in the initial stage of hydration, and that the C-S-H may grow with the regularity retained thereafter. On the other hand, in samples with high C₂S content, the regularity of C-S-H Si chains is not established initially, indicating that the regularity may increase with C-S-H growth.

This paper reports on the evaluation interlayer structure of a sample transformed from 1.4nm Tobermorite to 1.1nm Tobermorite with a single chain structure by heat treatment using the isosteric heat of water adsorption calculated from low-pressure water vapor adsorption isotherms. In the isosteric heat of adsorption, there was a difference in the appearance of peaks between the tobermorite and C-S-H samples, suggesting that the regularity of the crystal structure and the uniformity of the Si chain structure affect the bimodal peaks in the heat of adsorption. In addition, an increase in the heat of adsorption was observed in the Mg-added sample, which was attributed to the high-water content and high hydration energy of Mg^2＋ ions.

In order to understand the molecule structure-activity relationship of the admixture to the hydration reaction of C₄AF, the complexation ability of the admixture with metal ions and the leaching degree of Fe and Al from C₄AF were evaluated. As a result, we found a relationship between the complexing ability and the degree of elution and the type, number, and bonding distance of the functional groups of the admixture. The stability of the complexes of Fe^3＋ with admixtures was investigated by quantum chemical calculations, which led to the proposal of a suitable compound for dissolving Fe gel that inhibits the reaction of C₄AF. Based on these results, the effects of five admixtures on the hydration reaction of C₄AF and cement were investigated. The admixture that increased the leaching of Fe and Al promoted the reaction of C₄AF, and in addition, the admixture that did not delay the reaction of C₃S was confirmed to enhance the compressive strength.

The study aimed at investigating on the effects of the crystalline layered sodium silicate on strength development of concrete. The hydration of cement mixed with the powder material was examined to evaluate applicability as an accelerating admixture. The test result confirmed that concrete mixed with the crystalline layered sodium silicate was higher compressive strength at early age than the control concrete without the powder material. Note is that the compressive strengths of the concrete at 28days were almost equivalent in all tested concrete. The reaction of alite in cement was accelerated by mixing the crystalline layered sodium silicate. Cement mixed with crystalline layered sodium silicate indicated earlier and higher hydration heat rate at the second-peak, and indicated higher hydration ratio than control cement paste. In hardened cement mixed with crystalline layered sodium silicate, a pronounced formation of acicular crystal was observed by SEM. Acicular crystal was also observed in the C₃A and gypsum hardened by crystalline layered sodium silicate. The observation confirms that the acicular crystal is ettringite. The study shows the hydration process, which contribute to strength development, of the concrete mixed with the crystalline layered sodium silicate.

An understanding of carbonation reactions is needed to accurately assess the amount of carbon dioxide fixed within cement structures. In this study, the carbonation reaction on the surface of hardened cement paste under atmospheric carbon dioxide concentrations was investigated using infrared spectroscopy （FTIR） with humidity as a variable. By integrating the peak intensities obtained, we were able to semi-quantitatively analyze the change over time of each component and approximate logarithmically the formation rate of calcium carbonate and the decomposition rate of calcium hydroxide at the powder surface. In addition, the decalcification and polymerization reactions of the C-S-H gel could be seen from the shifts in the peak wavenumbers. Furthermore, the humidity dependence of the precipitated polymorph of the calcium carbonate was also determined.

Most conventional studies on carbonation have been conducted in terms of the diffusion of carbon dioxide into concrete and its effect on rebar corrosion in reinforced concrete, with limited research focusing on the carbonation of cement itself. Focusing on the carbonation reaction of cement itself, this study investigated differences in the progress of carbonation of hardened cement paste at CO₂ concentration of 1％ and concentration （about 0.04％） in humid environment （about 95％ relative humidity） by Raman spectroscopy, where the carbonation reaction is most likely to occur. Reaction rate constants were calculated for each cement hydrates assuming a first-order reaction. As a result, the carbonation rate of calcium silicate hydrate （C-S-H） was higher for carbonation at a CO₂ concentration of 1％ in initial stage of carbonation. The carbonation rate of calcium hydroxide （CH） and ettringite were also higher for carbonation at atmospheric concentrations. The pH of pore solution of hardened cement paste varied with CO₂ concentration, and the carbonation of hardened cement paste under atmospheric concentration where the pH of pore solution is higher than that of under CO₂ concentration of 1％ resulted insignificant vaterite precipitation. In addition, the presence of ettringite was a factor in vaterite precipitation.

The low-temperature burning type clinker with an adjusted mineral composition is expected to save energy in the burning process in cement production, but there is concern that the long-term strength of the cement will decrease due to the composition change. In this study, we investigated the influence of BaO on the clinker mineral composition and the quality of cement for a low-temperature burning type composition, with the aim of improving long-term strength by improving the hydration reactivity of belite. As a result, it was found that BaO affects the crystal phase composition of belite, and α’-belite is stabilized as the BaO content increases. In addition, it was confirmed that the long-term strength development of the cement tended to improve as the BaO content increased, and it was presumed that this was due to the improvement in the hydration reaction of α’-belite with the increase in the BaO content.

In this study, we carried out burning test using shredded waste plastic as a thermal energy alternative waste of the low burning-temperature type clinker with an adjusted mineral composition by actual kiln. As a result, the low-temperature burning type clinker could be stably burned even if the thermal energy alternative waste was used. Furthermore, it was estimated that the low burning-temperature type clinker was able to be sintered at 1,300 to 1,350℃, which was approximately 100 degrees less than the OPC clinker on the same condition. And the heat consumption rate was able to be reduced around 7.3％ compared with the OPC clinker. It was confirmed that it is possible to use thermal energy alternative waste as in the current OPC, and that CO₂ in the burning process can be reduced by 7.3％ or more. Although the strength development of the trial cement was slightly reduced, it was estimated that the C₃S amount was lower than the target composition, and it was estimated that the strength development was about the same as the trial OPC by setting the same amount of C₃S as the target.

In this study, the hydration reaction of cement pastes using sludge water as mixing water, with or without the addition of sodium gluconate, was investigated. And we also discussed the effect of sludge water on setting and initial strength development properties of concrete with sludge water added from the point of cement chemistry view. The results confirmed that the addition of sludge water, with or without sodium gluconate, promoted hydration of the alite and increased CH production compared to the case without sludge water. It was also suggested that the addition of sludge water may have produced C-S-H with a low C/S ratio. This accelerated hydration of the alite and changes in the composition of the hydrates may affect the setting and initial strength development properties of concrete with sludge water added.

In this study, the effect of triisopropanolamine （TIPA） on the strength development and hydration reaction of moderate-heat Portland cement （MC） or low-heat Portland cement （LC） with limestone powder （LSP） was investigated. Compressive strength of MC or LC slightly decreased at 7 days and significantly decreased at 28 days by addition of LSP. On the other hand, the compressive strength of MC or LC containing LSP increased by addition of TIPA at 28 days, however the compressive strength at 7days did not increase. There was a significant correlation between compressive strength and porosity of hardened cement paste with LSP regardless of the addition of TIPA. In addition, the reaction of alite （C₃S） and belite （C₂S） did not change by addition of TIPA. However, the reaction of ferrite （C₄AF） and CaCO₃ at early stage were significantly accelerated by adding of TIPA. And the formation of monocarbonate in MC-LSP or LC-LSP system was promoted by addition of TIPA.

The effect of limestone fine powder （LSP） on the early hydration products and strength of high volume blast furnace slag cement （HVBFSC） was investigated, considering the increase of small amount of mineral components in ordinary Portland cement as a measure to reduce CO₂ emissions. The compressive strength of HVBFSC and the activity index of BFS can be evaluated by the F value of BFS modified basicity （F value） considering TiO₂ and MnO, even when LSP is added.Blast furnace slag （BFS） with larger F value is highly reactive. By using of BFS having higher F value and higher reactivity, the formation amounts of ettringite （AFt） is reduced and the formation amounts of monosulfate （AFm） is increased in hydrated HVBFSC. But the amounts of AFt is increased by addition of LSP. Without LSP, the Ca/Si ratio of C-S-H in hardened HSVBFSC is 1.34 to 1.39, and when LSP is added, the Ca/Si ratio of C-S-H increases to about 1.38 to 1.50. When LSP is added, the compressive strength of HVBFSC is slightly lower than that without LSP, but the strength of HVBFSC with LSP is not a problem in practical use.

It is known that the reaction of blast furnace slag （BFS） changes greatly depending on the amount of calcium hydroxide （CH） and gypsum （Gyp） added, but there is no study of the changes when used in combination with an accelerator. In this study, the effect of the combined use of Gyp and calcium nitrite （CN） on the hydration reactivity of BFS by changing the amount of the CH addition was investigated. As a result, the following findings were obtained for the reaction control of BFS. In the range of CH 0.5 to 1％, which is a very small amount, the promoting effect of CN alone was not exhibited, and a remarkable effect was obtained by adding Gyp. On the other hand, in the range of CH5 to 10％, the amount of CN added affected the reaction promotion of BFS, and the effect of promoting CN was suppressed when Gyp was excessively added.

In this study, the influence of calcium hydroxide on the reaction of blast furnace slag with sodium carbonate was investigated. And we also discussed the mechanism of acceleration mechanism of blast furnace slag reaction by calcium hydroxide additon. This study is considered to be important for promoting carbon recycling in cement-based materials and for establishing carbon neutral society.
The reaction of blast furnace slag with sodium carbonate was accelerated by addition of calcium hydroxide and the hydration heat liberation was largely increased. The acceleration or delay of blast furnace slag reaction was related to the formation or decomposition of Na₂Ca（CO₃）₂・5H₂O （gaylussite）. The pH in the liquid phase highly increased by adding of calcium hydroxide to the blast furnace slag-sodium carbonate system. The reaction of calcium hydroxide and sodium carbonate makes calcium carbonate and sodium hydroxide, therefore the pH in the liquid phase rapidly increased. And the fluidity of blast furnace-sodium hydroxide paste decreased due to the increase in pH and high reactivity of blast furnace slag. The relationship between the hydration heat liberation of paste and the compressive strength of mortar was also confirmed.
It is necessary to establish a method for controlling the initial reaction of blast furnace slag-sodium carbonate-calcium hydroxide system in order to use as a binder.

In this study, the influence of sodium carbonate and calcium nitrite addition on the hydration and fluidity of blast furnace slag-calcium hydroxide system were investigated. And we also discussed the effect of combination usage of sodium carbonate and calcium nitrite for blast furnace slag-calcium hydroxide system as alkaline additive. The initial reactivity of blast furnace slag-calcium hydroxide system was largely accelerated by adding of sodium carbonate. On the other hand, the initial heat liberation and the reaction rate of blast furnace slag with sodium carbonate was reduced by addition of calcium nitrite and the mass loss of ignition decreased. In this system, the decrease in pH of the liquid phase were confirmed. The properties of quick setting and low flowability of blast furnace slag-calcium hydroxide system with sodium carbonate was improved by addition of calcium nitrite. due to the suppression of initial blast furnace slag reaction. Also, the long-term reactivity of blast furnace slag was also enhanced by the addition of calcium nitrate due to the nitrite AFm formation. From these results, it is considered that the combination usage of sodium carbonate and calcium nitrite as an additive, is effective for the improvement of blast furnace slag reactivity and flowability of paste in blast furnace slag-calcium hydroxide system.

Strength development at 10, 20, and 30℃ was evaluated and hydration reaction analysis was performed using three GGBS with basicities ranging from 1.63 to 1.90. The hydration reaction analysis was performed by XRD/Rietveld method, chemical composition analysis of C-S-H by SEM-EDS, and pore size distribution by MIP. Hydration reaction analysis was performed by XRD/Rietveld method to determine the hydrate phase, SEM-EDS to analyze C-S-H chemical composition, and MIP to determine pore size distribution. It was found that the strength development of the low basicity GGBS improved with increasing temperature and longer age of the material, and that the strength development of the low basicity GGBS was more temperature-dependent than that of the high basicity GGBS. The low basicity GGBS had a higher proportion of C-S-H in the total hydrates, and it was inferred that the contribution of C-S-H formation to the strength enhancement for the low basicity GGBS cement was significant.

In marine environments, steel corrosion of reinforced concrete caused by chloride attack is a concern. However, it has been reported that the densification of pores in concrete may improve mass transfer resistance and prevent steel corrosion due to chloride attack. Therefore, it is necessary to investigate the mechanism of pore structure change of cement matrix in seawater. In particular, it is rare to study in detail the pore structure change of cement paste using mineral admixture in seawater. In this study, immersion tests in artificial seawater and NaCl solution were conducted to clarify the mechanism of pore structure change of cement paste using ground granulated blast furnace slag （GGBS） in seawater. As a result, it was found that the internal structure of GGBS specimens became denser regardless of the decrease in the CH content due to immersion in salt water. It was also suggested that the alteration of C-S-H by immersion in salt water, with and without mineral admixture, affected the increased pore volume below 20nm.

Reinforced concrete structures are affected by the natural wetting and drying cycles, such as rainfall. Therefore, a closer investigation of the wetting and drying processes of concrete is required because the water and oxygen permeating the reinforced concrete structure leads to corrosion of the reinforcing steel. In this study, the degree of water saturation in the mortar was measured during the wetting process and the drying process, and the permeation characteristics of the mortar were experimentally considered in each process. Moreover, the permeation characteristics of mortar were considered experimentally under wetting and drying cycles. The results suggest that the velocities of liquid movement in the water absorption process and moisture diffusion in the drying process decrease in the case of a low water-cement ratio. The reduction in these velocities occurs primarily because the compactness of mortar enhances when the water-cement ratio is low. In the drying process, the liquid absorbed into the mortar in the water absorption process moves due to the moisture diffusion that depends on the moisture gradient in mortar. Additionally, the mortar under the wetting and drying cycles could have high permeability in case that initial moisture state of the mortar ranges from the absorption surface to the penetration front is in an unsaturation state.

The purpose of this study was to gain knowledge about the changes in electrical properties of mortar during the curing process. The type of cement and the mixing-water content were changed, and the impedance changes were measured in the time range of 0h to 96h. The Cole-Cole plots of normal portland cement was the characteristic of RC parallel circuit. For all mortars, the electrical resistivity decreased gradually from after placing until 3-4h and then increased rapidly. For a water-cement ratio of 0.5, the peak values of relative permittivity at low-frequency （＜5MHz） decreased in the order of high-early-strength, normal, and low heat portland cement. On the other hand, on the high-frequency side （≥20MHz）, the order was reversed. These changes were discussed in terms of the hydration reaction and the ionization of the cement components.

The present study experimentally examined the factors affecting the formation behavior of the alkali-silica reaction （ASR） products. In order to synthesize ASR products using reagents, samples were prepared by varying Ca/Si ratio, K/Na ratio and drying temperature, and the products and atomic bonding states of the synthesized samples were measured. As a result, ASR gels were stably formed with Ca/Si ratio in the range of 0.2 to 0.4. ASR gels were easily formed with high K/Na ratios, while C-S-H formation was predominant with low K/Na ratios. This may be due to the fact that Na-substituted C-S-H is more likely to form in the presence of large amounts of Na with low K/Na ratios. Only ASR gel was observed in the samples dried at 110℃, while crystalline material was also formed in the 50℃ dried samples. These results suggest that the products may change depending on the drying temperature.

In this study, mass changes and length changes were measured using ordinary Portland cement and low heat Portland cement to investigate drying shrinkage properties in hardened low heat Portland cement. The mass change-length change relationship can be approximated by two straight lines, with the changing point of slope corresponding to about 50％ RH. From the change in the slope of the mass change-length change relationship, it can be inferred that only reversible drying shrinkage occurs in the low humidity range, while irreversible drying shrinkage occurs in addition to the reversible one in the high humidity range. The irreversible drying shrinkage of L is large, which we attribute to the larger amount of C-S-H per unit volume and smaller gel-space ratio which is deduced from the difference in Nitrogen sorption and portlandite amount. The C-S-H formed in L cement has larger interlayer space and at a more uniform state. Hence it is easier to make crosslinking between layers upon drying, resulting in higher irreversible shrinkage.

In this study, we evaluated the hydration process and products of cementitious materials made of some clays and alite when kneaded with different concentrations of sodium hydroxide solution in a high-temperature environment. As a result, the formation of C-A-S-H with short silicate anion chains system, 1.1nm Tobermorite that does not have Q³ bonds and N-A-S-H was confirmed in the system using montmorillonite. On the other hand, in the system with kaolinite, C-A-S-H with long silicate anion chains system, 1.1nm Tobermorite that does not have Q³ bonds, and Hydrosodalite were formed. It was inferred that Al at the bridging site in C-A-S-H contributed to the formation of Hydrosodalite as the age of the material increased.

In this study, we evaluated the hydration process and products of cementitious materials made of clay and alite when mixed with aqueous sodium hydroxide solutions of varying concentrations. In both montmorillonite and kaolinite, the results showed that sodium hydroxide solution and calcium hydroxide generated by hydration of alite promoted the decomposition of clay structure. For the C-A-S-H produced, the silicate anion chain structure in the system with montmorillonite tended to be short due to the high Q¹ component, while the silicate anion chain structure in the system with kaolinite tended to be long due to the low Q¹ component.

In this study, the microstructural changes of alkali-activated cement hardeners with blast-furnace slag as binder by repeated drying and wetting cycles were examined by ²⁹Si MAS NMR and ²⁷Al MAS NMR to confirm the structural changes of the products, and by ¹H NMR and MIP to investigate the moisture change behavior and pore structure changes. As a result, no change was observed in the pore distribution due to repeated drying or wetting, but the pore volume decreased significantly. Drying promoted the reaction and increased the amount of Al substituted for C-S-H, resulting in densification of the pores, which were already dense before drying. In addition, drying reduced the water content in the C-A-S-H layer and shortened the width of the interlayer, but it is possible that the width may be maintained by the progressive formation of C-A-S-H. Subsequent wetting may supply moisture to the interlayer and coarsen the gel pores.

This study investigated whether the chloride adsorption performance and diffusion performance could be obtained by mixing calcium nitrite with blast furnace slag cement. As a result, we found that the chloride adsorption power and diffusion performance of the hardened blast furnace cement with calcium nitrite increased, and the reaction degree of the blast furnace slag increased as calcium nitrite was mixed. It is considered that these results are related to the increase in calcium silicate hydrate （C-S-H） and nitrite-type monosulfate （NO₂-AFm） due to the addition of calcium nitrite.

It is known that the strength development of High blast furnace slag （BFS） cement varies greatly depending on the amount of cement （OPC） blended. In this study, we investigated the effect of the combined use of gypsum （Gyp） and calcium nitrite （CN） on the strength development of High BFS cement with different OPC content. As a result, High BFS cement with Gyp15％＋CN2％ added at OPC1-3％ or Gyp1％＋CN2％ added at OPC30-50％ could obtain strength equal to or higher than that of OPC and blast furnace cement type B. In addition, we found the possibility of strength control of High BFS cement by optimizing Gyp and CN addition depending on OPC contents.

The purpose of this study was to change the composition and internal structure of C-S-H, which is the main hydration product in the hardened cement, and to clarify the effect on the linear expansion coefficient of the hardened cement. After mixing with fly ash and crystallization by high-temperature and high-pressure curing, the void structure of the hardened cement was changed to obtain the coefficient of linear expansion and the amount of change in relative humidity. It was clarified that the values of the coefficient of linear expansion and the relative humidity change increased on the high humidity side due to the mixing of fly ash, which is due to the increase in the specific surface area of the solid phase due to the decrease in the C/S ratio. In addition, the formation of tobermorite, the disappearance of voids of 0.1 to 1.0μm, and the decrease in the coefficient of linear expansion were confirmed in the test specimens with a fly ash replacement rate of 45％ that had been subjected to high-temperature and high-pressure curing.

A model was proposed to evaluate protected paste volumes around air voids. The area where each air void should provide protection was modeled by the Dirichlet tessellation associated with the planar point pattern of air voids. Changes in the Dirichlet tile area distribution due to the random distribution of air voids were represented by Monte Carlo simulations. The distances to achieve a specific volume for enough protection were defined by the area fraction corresponding to an upper confidence limit of 95％ in the simulation. The distances estimated in the proposed model were compared with the proximity of cement paste to the surface of air voids in the conventional models including the spacing factor of Powers. The results showed that the average area protected by the voids was consistent with the volume fraction estimated by the Attiogbe model. The characteristic distance to characterize point patterns in the proposed model was also equivalent to the mean tile area. The Philleo factor was found to overestimate the ability of protection at a given air content so that the evaluated distance was much smaller than that in the proposed model. The distances to cover the most of paste region estimated by the proposed model were almost equivalent to the conventional spacing factor. The conventional spacing factor was found to correspond to the maximum distance covering the local area where air voids were dispersed more sparsely compared to the average density of air voids in random spatial distribution.

Strain measurement of cementitious materials by the piezoelectric effect has been widely investigated；however, the response is less than poled piezoelectric material. Since the piezoelectric effect is caused by charge behavior, there is a possibility to improve the piezoelectric performance by adding highly conductive carbon fiber to the cementitious materials. The goal of this research is to apply cementitious materials themselves as piezoelectric sensors.
In this paper, the influence of carbon fiber on the piezoelectric performance of cement paste and the piezoelectric behavior of cement paste composites with different conductivities are investigated.
In Series 1, the potential fluctuations of cement paste mixed with carbon fiber were measured under cyclic loading and investigated the influence of the carbon fiber volume on the potential fluctuations. From the results, the periodicity of the potential change rate correlates with the loading cycles. Also, the piezoelectric power was affected by the carbon fiber volume and the potential time series trend gradually decreased.
In Series 2, the composites of carbon fiber-incorporated cement paste and carbon fiber-immiscible cement paste were fabricated as to be modelized repaired structures and were measured the piezoelectric potentials. The correlations between strain and potential were observed in the composites；however, the relationships were not linear, and relaxation phenomena could be attributed to carbon fiber and bi-material interface.

Piezoelectric phenomena in ferroelectrics are well known to correlate with elastic strain and power generation of cementitious material subjected to loading has also been reported as piezoelectric phenomena. However, cementitious materials, which are elasto-plastic materials, may become locally plastic at the microscopic even though they are elastic at the macroscopic during loading, or cracks may appear in the interfacial transition zone from the early stage of loading.
In this paper, to investigate the effect of microfracture on power generation, we conducted experiments on the correlation between strain and potential fluctuation, especially on the effects of the interfacial transition zone, which is the starting point of mortar and concrete fracture.
In Series1, the effect of the presence/ absence of interfacial transition zone on the piezoelectric potential was studied by comparing cement paste and mortar.
In Series2 and 3, potential measurements on concrete provided information about the effect of interfacial transition zone when compressive strain is at a minimum and when strain is increasing/ decreasing at a constant rate.
As a result, based on the obtained potential waveforms, we proposed a transient model consisting of a capacitor and a conductor, assuming that the potential fluctuation in cementitious materials is caused by the generation and recombination of electric charges at the shear interfaces.

A pilot study was conducted on the alkali-silica reactivity to evaluate the effect of coal gasification slag fine aggregate （CGS）, which contains a high amount of alkali on alkali-silica reactivity of concrete made with highly alkali-reactive coarse aggregate and high alkali content CGS. The results showed that in concrete prism tests with NaOH added at a total alkali content of 3.0kg/m³, the specimen containing high alkali content CGS showed ASR expansion at an early age, and the amount of expansion exceeded that of the concrete without CGS until one year of age. Polarized light microscopy of mortar specimens made by wet screening from fresh concrete used in the concrete prism test confirmed that the high alkali content CGS itself did not cause an alkali-silica reaction, although the outer edge of the CGS seems to have little reaction. In the pore solution analysis of the mortar specimens, the Na, SO₄^2- and OH^- concentrations tended to increase with the mix of high alkali content CGS. In conclusion, alkaline leaching from the coal gasification slag fine aggregate, which contains a high alkali, induced an alkali-silica reaction in the highly alkali-reactive aggregate.

In recent years, hot-dip galvanized and weathering steels have been considered applicable for reinforcing bars in concrete. The galvanized coatings and protective rust on the surface of these steels are expected to provide high corrosion resistance in the air. However, the effect of the steel surface layers on the electrochemical behavior of steel in concrete is still unknown.In this paper, corrosion rate and corrosion form were evaluated based on electrochemical noise measurements and statistical and wavelet analysis to grasp each steel’s corrosion protection mechanism and corrosion process in concrete based on charge behavior.
Statistical analysis of electrochemical noise showed that hot-dip galvanized steel tended to corrode uniformly, while weathering steel had the lowest corrosion rate among the steels examined in the experiment. Wavelet analysis of electrochemical noise indicated that the current noise energy of hot-dip galvanized steel and weathering steel was lower than that of rolled carbon steel under the same conditions, inferring a lower charge response. This implies that both steels exhibit slow corrosion propagation, and zinc-origin passive film and weathering steel-derived protective rust is possible to contribute to this corrosion resistance.
From the corrosion state and EN analysis results, hot-dip galvanized steel and weathering steel have slower corrosion propagation than rolled carbon steel under the same conditions. They are expected to have corrosion resistance in concrete.

In this study, experiments were conducted to create an evaluation indicator for the visual and tactile tests for concrete with equal slump and slump flow but different fresh properties, which can be used to evaluate flowability and segregation resistance and does not depend on the experience of the evaluators. In order to create an evaluation index that does not depend on the experience of the evaluators, the authors examined styles of expression that do not cause differences in evaluation results and reflected them in the evaluation index. The results of the visual and tactile tests were plotted on the two axes of “flowability” and “segregation resistance”, which can suggest the possibility of understanding the characteristics of concretes with equivalent slump/slump flow.

This paper deals with the compressive and flexural strength properties of the porous concrete using polymer-modified mortars as binder. The applicability of the strength estimating equation for the porous concrete based on the ratio of the strength of the porous concrete to binder strength proposed by the research committee concerning the porous concrete of Japan Concrete Institute （JCI） is also discussed. The polymer-modified mortars using various polymer dispersions for cement modifier and with polymer-cement ratios of 0, 2, 4 and 6％ are prepared as binders for the porous concretes. The porous concretes with the target voids of 10, 20 and 30％ are prepared by using the polymer-modified mortars. After curing under prescribed conditions for 28d, the specimens of the polymer-modified mortars and porous concretes are subjected to compressive and flexural strength tests. The total and continuous voids of the porous concrete are also measured. As a result, the use of the polymer-modified mortar as the binder improves the flexural strength of the porous concrete. The strength estimating equation proposed by JCI research committee is applicable for estimating the compressive and flexural strengths of the porous concrete using various type of the polymer-modified mortar as the binder.

In this study, material analysis of sand plaster and lime concrete excavated from the former Niratsuka Silk Mill was conducted to investigate the material composition and hardening mechanism of lime-based materials. As a result, the sand plaster consisted of plaster and fine aggregate, and the chemical composition of the plaster part was almost exclusively CaCO₃. The binder part of the lime concrete had binding water, suggesting the presence of C-S-H with solid solution of Al₂O₃ and aluminate hydrates by pozzolanic reaction. The use of Asama A pumice （As-A） was inferred for the lime concrete. The calcium hydroxide and As-A paste samples were confirmed to be hardened, and hydrocalumite and hydrotalcite were formed as hydrates in the hardened products.

This study aimed to evaluate the crystal structure of carbonate ettringite, a material in which the sulfate ion of ettringite is replaced by carbonate ions, and examined the bonding state of atoms, changes in the Al coordination number, and dehydration behavior of carbonate ettringite by comparing to that of ordinary ettringite. As a result, it was found that carbonate ettringite showed a difference in the amount of dehydration up to 200℃ compared to ettringite, and that the Al coordination number changed significantly after heating at 80℃ for 24 hours. In the 11％ RH dried sample, the ²⁷Al NMR peak of carbonate ettringite was similar to that of ettringite, suggesting that carbonate ettringite has the same column structure as ettringite and that the dehydration behavior is due to the difference in ionic properties of sulfate and carbonate ions.

This study aimed to understand the effect of C-S-H coexistence on the formation of ettringite from monocarbonate. The results indicated that ettringite formation from monocarbonate may be enhanced when C-S-H coexists with monocarbonate. This was thought to be because when C-S-H coexists with monocarbonate, the dissolution of monocarbonate is promoted to form C-A-S-H. It was also shown that 4-coordinate Al in C-A-S-H can be used for ettringite formation, especially 4-coordinate Al substituted at Q²_b （bridging-site） of C-A-S-H may be preferentially used for ettringite formation.

The previous studies have reported that the water absorption amount with time can be proportional to the fourth root of absorption time. In this study, the water uptake characteristics of hardened cement paste was studied from a viewpoint of fourth root of uptake time. The one bottom surface of cement paste specimen was exposed to liquid water after drying equilibrium at 20, 40 and 105℃. The amount of water absorption was proportional to the fourth root of time as reported in the previous studies. In the case of drying at 105℃, the relationship was bilinear, which suggests that the water can penetrate into relatively large capillary pores and then fine gel pores as two processes. The model to apply different diffusion equations to the assumed capillary and gel pores can reproduce the water uptake behavior of cement paste dried at 105℃ when the constant diffusivities are used for each pore. The diffusion equations were applied to divided pore diameters, respectively when the simple pore distribution was assumed. It was found that the model to use constant large and small diffusivities according to threshold of pore diameter can represent the bilinear relationship between the water absorption amount and fourth root of time rather than the model to use the decreasing diffusivity with decreasing pore diameter.

In this study, hardened ordinary concrete is subjected to concentrated CO₂ gas under a pressure of 0.5MPa and 1.0MPa respectively, using a high-pressure injection chamber and evaluated for the carbonation depth. In addition, the mass change during the process of carbonation of concrete was measured continuously. As a result, the relationship between carbonation depth and the mass increase rate of the concrete specimens, it was found that the mass increases linearly with the progress of carbonation and an increase in the carbonation depth. From this research work, it can be concluded that the measurement of mass change rate is an effective method for the evaluation of the progress of carbonation depth.

In this study, hardened ordinary concrete is subjected to concentrated CO₂ gas under a pressure of 0.5MPa and 1.0MPa respectively, using a high-pressure injection chamber and evaluated for the carbonation depth and coefficient of carbonation rate for immobilization of CO₂ by concrete. As a result, it was found that the carbonation rate increased with increasing injection pressure of CO₂ gas and the compressive strength of the concrete also increased due to carbonation. In addition, modeling based on Fick's laws of diffusion was done to determine the progress of carbonation and the coefficient of carbonation rate using concentrated CO₂ under high-pressure CO₂. It was found that the coefficient of carbonation rate calculated by the model was roughly in good agreement with the experimental results, and the carbonation progress can be estimated using the proposed model.

In the process of manufacturing crushed stone, high-quality new materials are used as aggregates for concrete, and unprocessed crushed stone including topsoil and fragile parts are used as roadbed materials. Therefore, it is being considered to make full use of natural resources. As the use of recycled concrete roadbed materials is expanding and the use of crushed stones for roadbed materials is shrinking, it is desirable to increase the choices of applications for the effective use of natural aggregate resources. In this study, it was examined to utilize all the unprocessed crushed stone with a continuous grading of 0mm to 30mm for concrete without partial utilization. As a result, it is possible to ensure the mechanical performance of both strength and elastic modulus. When only unprocessed crushed stone is used as the aggregate, segregation resistance is inferior due to the extreme unbalanced grading of aggregates. It was shown that segregation resistance can be ensured by compensating for the insufficient grading of aggregates.

The heating mortar block system for melting snow, which absorbs radio waves and converts them into heats, requires a strong wide band electromagnetic wave absorber that withstand bending loads caused by walking. And the wide band electromagnetic wave absorber can be manufactured cheaply and easily with general equipment by vibrating mortar mixed with electric arc furnace oxidizing slag and styrofoam beads.
This uses the fact that styrofoam beads have lower density, complex relative permittivity and complex relative permeability than electric arc furnace oxidizing slag, therefore the styrofoam beads and the electric arc furnace oxidizing slag separated by vibration to form a multi-layered electromagnetic wave absorber. Therefore, mortar containing electric arc furnace oxidizing slag and styrofoam beads as aggregate become wide band electromagnetic wave absorber that complex relative permittivity and complex relative permeability gradually increase from radio wave irradiation side by vibrating with table vibrator.
In order to use this mortar as wide band electromagnetic wave absorber in the heating mortar block system for melting snow, it is considered necessary to ensure both strength that withstand bending loads caused by walking and fluidity during vibration. Therefore, we will adjust the strength and fluidity by changing the water cement ratio and the amount of high range AE reducing agents, and investigate the mixing of wide band electromagnetic wave absorber that satisfies the bending strength standard. From the above, within the range of measurements, for the same water cement ratio, the return loss increases with the amount of high range AE reducing agents, except in the case of peaks occurring, and any mixing satisfied the bending strength standard.

This study was conducted on concrete using blast furnace cement Class B and metakaolin-based artificial pozzolan （MKP） as mineral admixture. Two curing methods, water curing at 20℃ and air curing after demolding, were used to evaluate permeability of substances at 1 month, 6 months and 1 year. When the water curing was continued for MKP mixed concrete, sift of pore size distribution into smaller size, smaller chloride ion diffusion coefficient, and smaller water permeation rate coefficient were observed. A correlation was also clarified between the chloride ion diffusion coefficient and surface electrical resistivity in this study.

ABSTRACT：Fly ash, a by-product of coal-fired power plants, has been desired to be commonly utilized as supplementary cementitious material in the concrete industry. However, fly ash is not widely used as a mineral admixture because the concrete using fly ash has lower initial strength. While there are many studies on the reaction of fly ash in concrete cured at high temperature to obtain the high initial strength, few studies comprehensively consider both the strength and the reaction of fly ash. In this study, the effect of curing temperature on the cementing efficiency factor was investigated considering the degree of fly ash reaction as well as degree of alite （C₃S） and belite （C₂S） reaction. As a result, the most appropriate datum temperature for the evaluation of fly ash reaction degree with cumulative temperature is 8.5℃ in this study. Also, the cementing efficiency factor can be evaluated by using that datum temperature for the fly ash used in this study.

This study aims to develop the numerical method for the anomalous liquid water uptake on OPC mortar. The dynamic microstructural change diffusion model with the consideration of the saturation-dependent was proposed to represent the anomalous behavior. The microstructural change, an origin of anomalous behavior, was considered with the pore relaxation that reflects the rearrangement of C-S-H layers during the liquid water uptake process. An Interfacial transitional Zone （ITZ）, which represents the impact of microcracks inevitably occurring in mortar and concrete, was included in the microstructure system. The good agreement of liquid water uptake characteristics （e.g., moisture distribution, penetration depth, and absorbed water amount） with the reference experiment shows the potential of the proposed method for an application on concrete.

In this study, we investigated the impact of CO₂ in high-temperature environment on the chemical changes of C-S-H, and considered the mechanism of concrete carbonation due to fire damage. As a result of heating the synthetic C-S-H, difference of chemical change was not observed between CO₂ and N₂ flow, even in the different two types of Ca/Si molar ratio C-S-H. In the high-temperature CO₂ environment, a dramatic carbonation accompanied by structural change of C-S-H did not occur. The amount of CaCO₃ produced by heating hydrated ordinary Portland cement in CO₂ flow became the highest at around 600℃, which was almost the same as the amount of CaCO₃ calculated from the amount of Ca（OH）₂ before heating. The maximum value of CO₂ fixation due to high-temperature carbonation was almost dependent on the initial amount of Ca（OH）₂.

This paper deals with the effect of surface treatment by water-absorption-controlling materials on the carbonation resistance of polymer-modified mortar coated concretes. Two types of the polymer-modified mortars are prepared with the polymer-cement ratios of 0 and 5％ as coating mortars for base concretes. The base concretes with water-cement ratio of 57.9％ are also prepared, and cured under prescribed conditions for 28d. The base concrete surface is treated by wetting and the water-absorption-controlling materials with the application quantity of 20, 25 and 30g/m² as solids. Then the base concretes are coated by the polymer-modified mortars with coating thickness of 2.5mm, and cured under prescribed conditions for 28d. The polymer-modified mortar, base concrete, water-absorption-controlling material coated concrete, and polymer-modified mortar coated concrete specimens are stored in the carbonation chamber with 30℃, 60％（RH） and CO₂ concentration of 5％. Except for the polymer-modified mortar coated concrete specimen, the carbonation depth of the specimens is measured at storage periods of 28, 56 and 84d. The carbonation depth of the base concretes of polymer-modified mortar coated concretes are also measured at storage periods of 28, 56 and 84d after complete carbonation of the coated polymer-modified mortar layer. As a result, the carbonation resistance of the base concrete is improved by applying the water-absorption-controlling material to the base concrete. The polymer-modified mortar layer still inhibits CO₂ penetration after the layer is completely carbonated. Such carbonation resistibility of the polymer-modified mortar layer and by the application of the water-absorption-controlling materials improve the carbonation resistance of the base concrete coated with the polymer-modified mortar.

In this study, the applicability of the scaling resistance evaluation of concrete by the small piece freeze-thaw test method was examined. First, the same mortar as the ASTM C 672 method was used for comparison with the method, and both tests showed a correlation and a quantitative index that can evaluate the results equally. Next, the concrete was evaluated by the ASTM C 672 method, and the possibility of prediction by the small piece freeze-thaw test alone was verified. In a simple comparison, each result was different. However, it was clarified that if the small piece of mortar has a bubble structure equivalent to that of concrete, the evaluation equivalent to that of the ASTM method can be performed using the results of the mortar.

Average temperatures over most of Mongolia are below freezing from November through March. The lowest temperatures in January are as low as -36℃ to -40℃. However, in the extremely cold climate of Mongolia, it is often executed the concrete works even outside temperature is below -20℃. Therefore, in this experimental work, we investigated the required time span of pre-curing in order to achieve the potential strength at 28 days before being exposed to extremely low temperature（-20℃）, simulating Mongolian weather conditions. Moreover, internal temperature changes and microstructure analyses have been executed. We have found that concrete freezing temperature decreases remarkably from 0℃ to -15.6℃ with increasing pre-curing time, however, depending on the water-cement （W/C） ratio. Our experiments have shown that there was no freezable water after 14 days when the W/C ratio is below 0.39. Our research concluded that concrete should at least be cured at 20℃ for 14 days before being exposed to sub-zero temperatures, in order to reach in fair to middling potential strength at 28 days.

The frost damage resistance of the high-strength concrete using a shrinkage reducing agent was examined based on the amount of air after hardened. Two types of shrinkage reducing agents were used, and the water-cement ratio of concrete was 38％. The amount of air in the fresh concrete was set to 3, 5, and 7％. As a result of the experiment, it was found that all the shrinkage reducing agents showed high frost damage resistance even when the air volume of fresh concrete was 3％. As for surface damage, in principle, the smaller the spacing factor after curing, the higher the frost damage resistance, but the smaller the spacing factor, that is, the greater the deterioration when there is a lot of air in the concrete. It was found that too much air was taken as a weak point in the strength of concrete and caution was required.

On reinforced concrete（RC）road bridge deck in cold regions, highly durable RC road bridge deck with multiple defense concept introduced is proposed as a countermeasure for complex deterioration of salt damage, frost damage and alkali silica reaction（ASR）and its effectiveness are demonstrated. In this study, type IV fly ash and micro sphere made of resin are used in combination with highly durable RC road bridge deck, and the applicability is evaluated using a full-scale simulated road bridge deck assuming construction site. As a result, it was confirmed that the amount of air less than 0.15mm, which is effective for frost damage resistance, was uniformly entrained regardless of the effects of pumping and compaction, and that frost damage resistance was reliably ensured.