In this study, we aimed to evaluate the structural changes of stratlingite, which is formed in Roman concrete and cement materials with clay, and stratlingite is considered to contribute significantly to strength and durability of concrete. Specifically, changes in the bonding state of atoms and Al coordination number of stratlingite before and after heating, and dehydration behavior were analyzed and examined. As a result, XRD and Ft-IR showed that the bonds in the main layer are cleaved by heating at 150℃, while those in the interlayer remind. Dynamic TG results indicated that stratlingite undergoes dehydration in three steps：the water molecules in the structure are desorbed, followed by the hydroxyl groups in the main layer, and then the hydroxyl groups in the interlayer.

There has been recent interest in understanding the mechanical properties of 11Å tobermorite, arising from the relevance of tobermorite to concrete durability. In this study, the uniaxial tensile and compressive behaviors of 11Å tobermorite in crystalline and amorphous states have been investigated using molecular dynamics simulations. The uniaxial tensile simulation clarified that 11Å tobermorite has three different deformation mechanisms：the first is a layer peeling deformation, the second is the deformation with bond breaking, and the third is a deformation that only disrupt the structure without bond breaking. The simulation also clarified that the maximum stress of the layer peeling deformation shows the small temperature dependence compared to those of other types of deformation. In the compressive deformation, the simulation shows a rotation of crystal orientation due to slip without disrupting the crystal structure. Other deformations in which a wide range of structures collapses simultaneously are also observed. For the amorphous state, since the structure is already disordered before deformation, no difference in mechanism appears depending on the direction of deformation in both tension and compression.

The structure of the C-S-H gel, the distribution of mobile water in the pores, and the amount of chemically bound water in hydrates in hardened cement paste vary with external relative humidity （RH）. In addition, hysteresis due to drying history exists, so that the properties of virgin-dried and subsequent re-humidified systems differ even when they are in equilibrium at the same RH. In this study, hardened cement pastes which was virgin-dried at RH 60％ and those re-humidified at RH 60％ after RH 23％ and D-dry drying were measured with ¹H NMR Relaxometry, water vapor adsorption isotherm, TG, and XRD. It was confirmed that the decrease in interlayer distance due to RH 23％ and D-dry drying was not recovered by subsequent re-humidifying. In addition, the formation of new gel pores was observed after those drying processes. Changes in gel water and interlayer water content and AFt content due to drying and re-humidifying were quantitatively evaluated.

In this study, the effects of alkanolamine on the hydration reaction of calcium aluminoferrite with different compositions were examined under various conditions in which calcium hydroxide and calcium carbonate coexist. As a result, alkanolamine promoted the hydration reaction of calcium aluminoferrite, and the reaction-promoting effect was especially pronounced in ferrites with high Fe₂O₃ ratios. Among alkanolamines, triethanolamine, which had a remarkable effect of increasing the degree of Fe and Al elution, was confirmed to accelerate the reaction rate of calcium aluminoferrite in particular. The reaction acceleration of alkanolamine was similarly confirmed in the system with calcium hydroxide and calcium carbonate.

During the first drying, microstructural change in hardened cement paste （HCP） accompanies irreversible alteration, even subsequent re-humidification. This study applied T₁-T₂ correlation measurements using ¹H NMR relaxometry to explore microstructural reorganization in HCP after re-humidifying. Based on T₁-T₂ correlations, diagonal features along T₁/T₂≈1.7, including ¹H in interlayer space and gel pore in C-S-H, and capillary pore, were observed for sealed HCP. This is the fact that the observed relaxation time of ¹H in the pores of HCP is due to pore size, described by the fast exchange between the adsorbed pore surface water and bulk pore liquid. After the re-humidification, increasing in water contents of interlayer space and gel pore with increasing in exposed relative humidity was confirmed in diagonal peaks at T₁/T₂≈1.7, while the new off-diagonal peak at T₂≈131us with T₁/T₂≈12.3 was consistently detected at all re-humidify conditions. Comparing T₁-T₂ correlations between sealed or re-saturated HCP and re-humidified HCPs, this off-diagonal relaxation component is likely derived from a part of irreversible C-S-H alteration under the first drying. This irreversibility cannot be recovered by re-wetting even at 95％RH other than re-saturation under water. Presented two-dimensional T₁-T₂ interpretation of microstructure of HCP indicated the new insight on unique pore structure change under re-wetting, including the part of irreversible change.

In this paper, ¹H-NMR Relaxometry is applied to carbonation phase and analyzes changes of chemically bound water content, mobile water content, and total water content in hardened cement paste with the progress of carbonation. The results showed that calcium hydroxide and C-S-H were carbonated at 20℃ and 85％RH. From the measurement of transverse relaxation time T₂ by CPMG method, it was confirmed that the transverse relaxation time of Interlayer and Gel pore increased with carbonation. There was a positive correlation between carbonation degree of calcium hydroxide calculated by thermogravimetric/differential thermal analysis and decreasing of chemically bound water measured by Solid echo method, confirming that chemically bound water in calcium hydroxide changed to mobile water due to carbonation. Regarding mobile water, the water content of Gel pore increased and that of Interlayer decreased in C-S-H during the initial stage of carbonation.

The mechanism of CO₂ bound by carbonation of β-C₂S was investigated. The carbonated β-C₂S analyzed in this study had constituent phases consisting of calcite, aragonite and silica gel containing a small amount of calcium oxide. Through TG-MS, it was observed that decarbonation started at around 400℃, which is lower than the decarbonation temperature of typical calcium carbonate. This phenomenon was thought to be caused because calcium carbonate and silica gel coexisted in the carbonated β-C₂S, and silica gel acted to lower the decarbonation temperature of calcium carbonate. Because the components of the carbonated β-C₂S were calcium carbonate and silica gel, CO₂ was bound as a form of calcium carbonate in the carbonation of β-C₂S. Therefore, it is expected that once bound, CO₂ will not be released into air and remain stable for a long period of time.

In this study, we focused on the structural changes and phase composition of Calcium aluminate silicate hydrate （C-A-S-H） before and after carbonation to confirm its transformation by carbonation in the medium humidity range and its subsequent change after contact with liquid water. Based on the results of NMR, SEM-EDS analysis, and liquid phase composition analysis of the synthesized C-A-S-H, the structure was identified from the Ca/Si, Al/Si, H/Si, and Na/Si ratios and a schematic model was presented. After carbonation, the formation of vaterite, calcite, and aluminosilicate gel were confirmed. Unlike synthetic vaterite, vaterite of carbonated sample did not undergo a phase transition at 450℃. Thermogravimetric analysis demonstrated that carbonated sample’s vaterite undergoes a phase transition at 450-600℃. The vaterite underwent a phase change after immersion in the liquid phase and was confirmed to be all calcite. The aluminosilicate gel was found to have compositions of Al/Si＝0.16, Ca/Si＝0.09, and Na/Si＝0.09.

Various analyses were performed on C-A-S-H carbonated by dry or wet process. In case of dry process, C-A-S-H was almost completely carbonated, and vaterite, aragonite, calcite, and silica gel were formed. Electron microscopic observations showed that the calcium carbonate and silica gel were not clearly separated, but were present in a fine mixture. In case of dry process, C-A-S-H was almost completely carbonated, and the phases were calcite and silica gel. Electron microscopic observations showed that the calcite had a size of several micrometers and was clearly distinguishable from silica gel. The decarbonation behavior was different between the two processes, and the C-A-S-H carbonated by dry process showed more significant decarbonation in the lower temperature range （around 400 to 600℃）.

In this study, we investigated the effect of the combinate addition of synthesized calcium carbonate （CC） and calcium nitrite （CN） on the hydration and strength of high sulphate slag cement （HS-BFSC） containing 1-3％ ordinary Portland cement （OPC） and 15％ gypsum. The addition of CC increased the initial hydration of the BFS up to 7 days, however, tended to reduce the long-term strength elongation. On the other hand, the addition of CN, in addition to improving the significant reduction in strength at 3％ OPC, can complement the long-term strength when CC is added. The use of CN for accelerator may produce low-carbon cement with the same level of strength as Portland blast furnace slag cement class B and C （JIS R 5211）, but with significantly reduced CO₂ emissions.

We investigated the structure of solidified sodium silicate solidified with cement using Raman spectroscopy, X-ray diffraction measurements, and ²⁹Si solid MAS NMR measurements. Raman spectroscopy and NMR measurements confirmed that alite was consumed in the early stage of the reaction, and sodium silicate promoted the reaction, resulting in an intermediate phase consisting of a chain structure containing Q². Furthermore, X-ray diffraction halo analysis revealed the formation of an amorphous solid derived from tobermorite.

In this study, the effect of triisopropanolamine （TIPA） on the development of initial strength, the stability of long-term strength and the behavior of hydration products of ordinary Portland cement （N） or moderate-heat Portland cement （M） or low-heat Portland cement （L） containing limestone powder （LSP） were investigated. The addition of TIPA to N containing LSP increased the amount of hydrate at 7days and improved compressive strength as the hydration products filled voids. On the other hand, the addition of TIPA to M or L containing LSP did not increase the amount of hydration products at 7days. The reason why the amount of hydrate of M or L did not increase by the addition of TIPA at the initial age is that the amount of the amorphous hydration product decreased. For this reason, hydration products did not fill the voids, thus not increasing the compressive strength of M-LSP system or L-LSP system. At 28 and 91days, the addition of TIPA to N, M or L containing LSP increased the amount of hydration products, and the compressive strength was enhanced by filling the voids. And the addition of TIPA also suggested the formation of amorphous aluminate hydrates and a change in the composition of C-S-H.

The low burning-temperature type clinker with an adjusted mineral composition is expected to save energy in the burning process in cement production, but at the same time, reducing CO₂ emissions from raw materials generated by decarboxylation of limestone is also an issue. In this study, concrete sludge, which is an industrial waste, was used as a calcium source for a part of clinker raw materials, and we investigated the influence of concrete sludge on the clinker mineral composition and the quality of cement for a low burning-temperature type composition. As a result, it was confirmed that, in the system under study, even when concrete sludge is used as part of the raw material for the low burning-temperature type clinker, it is possible to reduce CO₂ emissions originating from the raw material by 22.9％ while maintaining the properties of cement.

The mechanism of hysteresis generation in pore structure analysis using thermoporometry is discussed. The pore size distribution during the melting process was similar to that obtained by the mercury intrusion method, in which the sample was dried in the pretreatment process. This indicates that the hardened cement paste is dried during the freezing process in thermoporometry, resulting in changes in the pore structure. This well explains the previously pointed out change in pore structure due to treatment before measurement, indicating the necessity of measuring the pore structure considering the environment to which the hardened cement paste is exposed. The analysis of the measured data with varying water content confirmed the existence of two types of C-S-H gels in the hardened cement paste, LD C-S-H （outer C-S-H） and HD C-S-H （inner C-S-H）, as indicated by Jennings et al. and Goto et al. Furthermore, it is found that LD C-S-H has an ink-bottle pore structure with an entrance pore corresponding to a 2nm gel pore that is frozen by homogeneous nucleation.

The hydration of cement is highly related with the mixing condition. The influence of mixing order to firstly add water or cement and mixing mass on the properties cement paste was investigated. XRD and Rietveld quantification was applied to study the hydration process and NMR is utilized to study the pore structure evolution. The results suggest the change in mixing condition does not intensively affect the hydration degree but affect the pore structure. Changing mixing procedures especially the mixing order exert a long-lasting influence the water distribution in interhydrate and gel pores.

The corrosion of the reinforcing steel in the concrete structure under wetting and drying cycles occurs due to the action of permeated water and oxygen on the reinforcing steel. Therefore, the prediction of the occurrence and progress mechanisms of steel corrosion need to understand the moisture-transport properties of the concrete under wetting and drying cycles. In this study, the degree of water saturation and amount of water absorbed by mortar were measured during the wetting and drying process. Subsequently, the moisture-transport properties of the mortar under this process were investigated experimentally. Based on the experimental results, the liquid-infiltration front position moves with decreasing the degree of water saturation from boundary surface to infiltration front. As discontinuous pores, where liquid infiltration stops, randomly exist in porous media, the liquid in porous media infiltrates with this decrease in degree of water saturation. For the condition of constant accumulated absorption-period, the liquid-infiltration front positions for each condition were approximately same regardless of the wetting and drying cycles regularity. This can be occurred because the effect of drying process on the permeability of mortar is small as the drying period is short and the drying temperature is low in this study. Therefore, this suggests that the moisture-transport property for the wetting and drying cycles containing the short drying-period can be described by that property for wetting process.

The objective of this study was to clarify the effects of synthesis temperature and drying conditions on the formation of products by alkali-silica reaction （ASR）. ASR products were synthesized by varying both conditions, and the products, atomic bonding states, and heating dehydration behavior were evaluated. As a result, no ASR gel was formed at 40℃, but ASR gels were easily formed as the synthesis temperature increased up to 80℃. The ASR gels were also formed under different drying conditions. On the other hand, the formation of ASR gel did not change significantly under different drying conditions, but a change in the peak position of Si-O vibration in the ASR gel structure was observed in the FT-IR spectra. When considered together with the heating and dehydration behavior, it was considered that the water in the ASR gel structure dissipated with the progress of drying, and the state and bond distance of the Si-O bonds changed.

In order to improve strength development in low-temperature environments, high-early strength cement with high C₃A content was prepared in an electric furnace and a test rotary kiln, and early age strength and hydration reactivity at 5℃ or 10℃ were compared with those of High early strength cement. The early age strength in low temperature was evaluated using mortar and concrete, white the hydration of the cement was investigated using Quantitative X-Ray Diffraction, and Isothermal calorimetry. The size of C₃A crystals was evaluated by light microscope. The results showed that higher IM led to larger crystal growth and the higher reactivity of C₃A. In addition, it was found that the reactivity of C₃S was also accelerated along with the improvement of C₃A reactivity, resulting in the improvement of early age strength at low temperatures. Mortar strength of the high-early strength cement with high C₃A content was higher than that of high early-strength cement, in which were increased the blaine specific surface area and added potassium sulfate and calcium nitrite. Moreover, the strength of the concrete of the high-early strength cement with high C₃A content was also higher than that of the high early-strength cement at 5℃. These results indicate that high-early strength cement with high C₃A content has excellent early age strength development in low-temperature environments.

In this study, various physical properties of hardened cement using a large amount of biomass ash were investigated, focusing on the effect of NBO/T, a chemical indicator of ash, on the hardened body. The results of FT-IR and Al-NMR analysis showed that ettringite, C-A-S-H, and monosulfate were formed in large amounts in the hardened cement. This was thought to be one factor in the higher compressive strength. A positive correlation between NBO/T of the biomass ash and compressive strength of the hardened product was confirmed, suggesting that NBO/T may be used as an indicator for estimating the blending strength.

In the context of the energy transition, the conventional supplementary cementitious materials （SCMs） from the co-products of heavy industries may disappear. Therefore, new SCMs should be developed. With the publication of JIS A 6209, volcanic glass powder （VGP） produced from Kagoshima was identified as an SCM. One advantage of producing VGP is that it does not require calcination, resulting in low energy consumption during the manufacturing process. To expand the production of VGP, the Iizaka Silt produced from the volcanic ejecta of Iizaka （Nakano-Hakudo） was tested in this study. The XRD/Rietveld analysis showed that Iizaka Silt has 7different minerals accounting for about 20mass％. Many holes were observed on the surface of Iizaka Silt by SEM, resulting in a large BET-surface area of Iizaka Silt. The isothermal calorimetry showed that the SiltF had a strong filler effect on the cement hydration. The filler effect of Iizaka Silt was quantified by the relationship between the slope of the acceleration period and the total surface of solids. Iizaka Silt exhibited pozzolanic reactivity through the selective dissolution experiment. However, neither of them contributed to the compressive strength. It was found that the gel space ratio decreased with the substitution of OPC by Iizaka Silt, which resulted in low compressive strength.

This study investigated the compressive strength and drying shrinkage of mortar made with recycled fine aggregate carbonated in air or water. Recycled fine aggregate carbonated in air showed a decrease in water absorption and an increase in Oven - dry density. Mortar using recycled fine aggregate carbonated in air showed an increase in compressive strength and a decrease in drying shrinkage. On the other hand, the recycled fine aggregate carbonated in water had the same water absorption and decreased in Oven - dry density. The compressive strength of mortar using recycled fine aggregate carbonated in water decreased and drying shrinkage increased. No clear relationship was found between the water absorption of the recycled fine aggregate and the compressive strength of the mortar, and between the water absorption of the recycled fine aggregate and the drying shrinkage of the mortar.To elucidate the cause, cement paste was carbonated under the same conditions as the recycled fine aggregate and analyzed.The results showed that carbonation in air increased the modulus of elasticity of the cement paste compared to that before carbonation. On the other hand, when carbonated in water, the modulus of elasticity decreased due to leaching of calcium ions. It was estimated that the recycled fine aggregate carbonated in water decreased the modulus of elasticity of the cement paste on the aggregate surface, resulting in a decrease in compressive strength and an increase in drying shrinkage.

In order to prevent communication interference caused by electromagnetic wave interference, there is a need for an easy-to-create, inexpensive, flat-plate shaped wide band electromagnetic wave absorber suitable for mass use in buildings. Therefore, fabricates a wide band electromagnetic wave absorber by vibrating a mortar made of electric arc furnace oxidizing slag and styrofoam beads before it hardens. This wide band electromagnetic wave absorber can be manufactured cheaply and easily with general equipment.
The electromagnetic wave absorption of this mortar is determined by the change in complex relative permittivity and complex relative permeability from radio wave irradiation side to the opposite side. The complex relative permittivity and complex relative permeability of this mortar are affected by the distribution of aggregates in this mortar. The distribution of aggregate in this mortar is considered to be affected by the water-cement ratio, vibration time, density, particle size, mixing ratio of beads and slag, and the amount of admixture added.
In this study, it is clarified the effects of changing the mixing ratio of electric arc furnace oxidizing slag and styrofoam beads, on the flow value, aggregate distribution, and electromagnetic wave absorption.
From the above, within the range of measurement, increasing the ratio of styrofoam beads to total aggregates may make it possible to fabricate wide band electromagnetic wave absorbers with lower water-cement ratios because the aggregates flow more easily during vibration even if the flow value of the mortar is low, for example, mortar with a beads：slags ratio of 6：4 and water cement ratio of 50％ will be a wide band electromagnetic wave absorber, although it has a lower flow value than a mortar with a beads：slags ratio of 4：6 and water cement ratio of 55％, a single-layer narrow band electromagnetic wave absorber.

Calcium nitrite is an additive that increases the reactivity of blast furnace cement, but there have been few studies on the temperature dependence of the reaction of blast furnace cement mixed with calcium nitrite. Therefore, the objective of this study was to clarify the effect of temperature on the reaction of blast furnace slag cement with calcium nitrite. Calorimeter measurements for the initial reaction rate, reaction degree measurements of cement and blast furnace slag by backscattered electron images, and mineralogical measurements by XRD were performed. The results indicated that the initial reaction of blast furnace slag cement was enhanced by the addition of calcium nitrite, but the effect was not high at 35℃ curing. It was also found that the apparent activation energy for the reaction of cement and blast furnace slag in the samples with calcium nitrite was lower than that of the unmixed samples.

Toward the carbon-neutral society, the cement industry is trying to increase the use of mineral admixtures. On the other hand, the amount of blast furnace slag, a typical mineral admixture, is expected to decrease in the future. Therefore, we investigated the properties of mortar and its influencing factors of blended cement using limestone powder as a partial replacement of blast furnace slag cement. The results showed that the mortar flow was improved, setting time was shortened, and short-term compressive strength was improved due to addition of limestone powder, and the 28-day compressive strength and water penetration rate coefficient were similar values when the replacement ratio of limestone powder was up to 10％. The results also suggest that the influencing factor for compressive strength is porosity, whereas the influencing factor for the water penetration rate coefficient is the complexity of the pore structure.

In this study, the influence of calcium sulfoaluminate-based early strength additive （EA） on strength development of steam cured mortar using ground granulated blast-furnace slag （GGBS） was investigated. The test result confirmed that the addition of EA improved the compressive strength at immediately after steam curing. The effect of GGBS replacement rate on increase in the amount of compressive strength at demolding with the addition of EA was not significant. Compressive strength at demolding increased due to an increase in the amount of bound water and an increase in the amount of ettringite in cement paste. The investigation demonstrates that the addition of EA improved the compressive strength at demolding was mainly caused by formation of ettringite. In addition, compressive strength at 28 days tended to increase with the addition of EA in GGBS replacement rates of 25～75％. Due to the addition of EA, the decrease in the amount of the pore volume with a diameter of 50nm or more indicates that the pore structure has become dense.

In this study, the effect of a shrinkage-reducing agent and reactive MgO on the carbonation progress of type C Blast furnace slag cement was assessed under acceleration conditions （5％ of CO₂ concentration）, and the microstructure of carbonated slag cement paste was investigated. Replacing reactive MgO in cement reduced the carbonation depth and shrinkage in the slag-cement paste. The oxygen diffusion coefficient of carbonated slag-cement paste was larger than before carbonation. In contrast, the diffusion coefficients of carbonated slag cement paste with reactive MgO were lower than the OPC cement paste. In carbonated slag cement paste with reactive MgO, aragonite and hydrotalcite were formed as carbonate minerals. It was indicated that the formation of hydrotalcite leads to decreasing the decomposition of calcium silicate hydrate and portlandite during the carbonation process. In addition, coarsening of the pore structure was not observed due to the restrained microstructural change by the decomposition of calcium silicate hydrate for slag cement paste with reactive MgO.

In order to visualize liquid water movement in concrete, changes in the state of concrete when water is immersed on one surface against concrete in a dry state were visualized using a digital image correlation method that can detect minute deformations on the surface of the object. By obtaining the change over time of the principal strain distribution from the amount of deformation, deformations showing drying shrinkage and swelling caused by liquid water penetration in the cement paste section were visualized. Deviations from the linear relationship between water absorption and depth of penetration and the square root of time, indicating liquid water penetration into cementitious materials, were confirmed, indirectly indicating that water movement causes water absorption and swelling of the cement paste, even in concrete aggregate scale analysis.

Recently, the application of near-infrared spectroscopy has been considered as one of the new inspection methods for concrete structures. This method is a nondestructive analysis method that does not require sampling, and can detect deteriorated materials and cement hydrates in-situ within a few seconds using a small and lightweight instrument. This study aims to apply this method to the evaluation of the hardening process of concrete, and compared this method with conventional methods for evaluating the hardening process such as measuring the cumulative heat of hydration obtained using a conduction calorimeter, determination of Ca（OH）₂ content by TG-DTA, setting time test and compressive strength test, using cement paste and mortar as samples. As a result, the near-infrared spectrum of cement paste and mortar showed absorption peaks of H₂O, Ca（OH）₂ and C-S-H overlapping each other. It was also found that there is a correlation between the change over time of the spectrum in the absorption wavelength range of cement hydrates and the change over time of rate of heat liberation and Ca（OH）₂ content. Furthermore, it was considered possible to predict setting time and compressive strength by extracting the effect of absorption by cement hydrates from the spectrum through numerical processing such as statistical analysis.

The salt scaling test was conducted for ordinary air-entrained concrete and superabsorbent polymer （SAP） concrete. Although the SAP concrete of which SAP content was 0.25％ by weight of cement exhibited twice the scaling of the AE concrete, the SAP used in this study was confirmed to greatly increase the resistance to scaling. Using a stereological procedure, three-dimensional particle size distribution was estimated from the particle size distribution of voids on cross-sections of those concretes. The protected paste volume around all the void particles was calculated as sphere shells for the three-dimensional particle size distribution. The ratio of the protected paste volume to the entire cement paste was defined as coverage to evaluate void surface-paste proximity in the concretes. The SAP particles were fewer in number and larger in spacing than entrained air voids in space. To cover the cement paste matrix with the protected paste volume of the sphere shells, the SAP voids were required to protect a greater distance from their surfaces. In other words, assuming the same distance of the protection that was determined by the traveling distance of unfrozen water in the microstructure of cement paste, the cover ratio associated with SAP voids was far smaller than air voids. The mechanism of improving the freeze-thaw resistance by SAP particles was not explained by the conventional mechanism based on the volume and spacing between air voids. The connectivity of SAP voids to the capillary pore network could be related to the frost resistance provided by SAP. Furthermore, the clustering of those voids and the sparse presence of voids also affect the occupation of the protected paste volume in the entire cement paste matrix. The concept of protected paste volume may need to revisit to consider the random spatial distribution of not only the voids but aggregate particles since the distribution of aggregate affects the extent of protected paste volume.

Studies of nondestructive evaluation for detecting defects of post-installed adhesive anchor bolt constructed in concrete structures using electromagnetic pulse method. However, evaluation of newly constructed ones immediately after construction had not been sufficiently examined. Thus, in this study, by defining properly constructed anchor part based on the recommendation for design and construction by JSCE as “complete construction”, and in the distributed range of its corresponding modulus of elasticity of base material, effective evaluation parameter was studied with the use of impact response analysis method by inputting distributed electromagnetic force calculated by dynamic magnetic field analysis, the responses of vibration at the bolt and concrete were obtained. As the result, it was suggested that the ratio of frequency component received at the bolt head was possible to be effective for evaluating construction soundness of the bolt.

In this study, we synthesized three types of ettringite with different crystal morphologies and investigated the changes in crystal structure upon thermal dehydration and rehydration. The XRD peaks of ettringite before and after thermal history were analyzed, the crystal morphology was observed by SEM, and the molecular bonding state was analyzed by FT-IR, TG-DTA, and ²⁷Al-MAS NMR. As a result, it was confirmed that the crystal morphology of the hydrate changed to granular by heating, dehydration and rehydration, regardless of the synthesis method. In addition, the molecular bonding states after heating, dehydration and rehydration changed depending on the crystal morphology, and the degree of change also changed depending on the crystal morphology. Therefore, we conclude that the crystal morphology of ettringite is closely related to the ease of crystal structure change.

In this study, the strength and heat generation properties of concrete using low burning temperature type cement （LTC） with adjusted mineral composition were investigated. As a result, initial strength development pf LTC was same level as that of ordinary portland cement （OPC）, so the compressive strength of normal-strength concrete and high-strength concrete using LTC was almost same value as OPC up to the 3days and 28days, respectively. Although long term strength development of LTC is assumed that calcium aluminate-based hydrates increased due to higher C₄AF content in LTC. Regarding the adiabatic temperature rise, ultimate temperature rise of LTC was lower than that of OPC, which is assumed to cause that LTC contains less C₃A that has relatively high hydration heat and more C₄AF that has relatively low hydration heat compared with OPC. In addition, LTC showed good correlation between the compressive strength and the splitting tensile strength or the static modulus of elasticity, which was same trend as OPC. Furthermore, the autogenous shrinkage of LTC was smaller than OPC.

In this study, modeling based on Fick's laws of diffusion, hydration reaction formula, and carbonation reaction formula was done to determine the progress of carbonation of hardened concrete and to estimate the coefficient of carbonation rate and the mass change rate, by using concentrated CO₂ under high-pressure CO₂ environment. For comparison of this model, hardened ordinary concrete with different compressive strength, mix proportions and curing age 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, coefficient of carbonation rate, and mass change rate for immobilization of CO₂ by concrete. As a result, it was found that the coefficient of carbonation rate and the mass change 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 addition, the actual test results suggest that the degree of carbonation and coefficient of carbonation rate may decrease as the carbonation progresses, and it is necessary to further study the mechanism of the progress of carbonation under high-pressure CO₂ environment.

In this study, with the assumption that the amount of air in concrete reduces due to the construction processes, the effects on freeze-thaw resistance and scaling resistance when solid paraffin emulsion was mixed in concrete was investigated. From the experimental tests it was observed that, when solid paraffin emulsion was mixed, the freeze-thaw resistance and scaling resistance under the chloride ion supply environment improved. In addition, it was confirmed that the measurement results of the chloride ion concentration after the scaling test varied depending on the conditions of the freeze-thaw cycle.

In recent years, there has been an increasing demand for improved durability and earthquake resistance for buildings. Due to this demand, the strength of concrete has increased and the viscosity tends to increase, and the bar arrangement has become more dense, making it difficult to fill the concrete densely. On the other hand, from the viewpoint of reducing environmental impact and protecting natural resources, air-crushed electric furnace oxidizing slag fine aggregate standardized in JIS A 5011-4：2018 is used to improve the fluidity of concrete and improve the pouring work. We have been studying to improve the quality of the building frame by streamlining and improving workability, and improving filling performance in high-density reinforcement locations. From this, it was confirmed that the amount of electric furnace oxidizing slag used can be used up to 40％ as part of the fine aggregate within the scope of the experiment in this report.

The measurement of majority conventionally is methods to use the accelerometer having wire or cable in order to measure the acceleration on fresh concrete compacting into the form. There is not the measurement of the acceleration on fresh concrete compacting using the RFID （radio frequency identification） tag with the wireless capacitance-type acceleration sensor until now.
In this study, it was carried out the measurement of acceleration transmitted from the outside vibration machines on the fresh concrete compacted in the form of the precast concrete product with help of the RFID tag having wireless capacitance-type acceleration sensor for the first time in the world. The resultant acceleration measured does not depend on value of the slump and slump flow. The resultant acceleration measured was larger as the distance to the position of the outside vibration machine was closer and regardless of differences such as product shape and the filling height. The difference of maximum resultant acceleration by the damping action from the position of the outside vibration.

The microstructure evolution of cement paste along the carbonation depth under different RH conditions （23-80％） was characterized using SEM image analysis, complementing the phase quantification of each depth by XRD. From the microstructure analysis of binarized SEM images used to determine local porosity, a sudden reduction of local porosity occurred from the non-carbonated zone to the carbonated zone, and the lowest porosity was observed at the carbonation front. According to the ratios of macro-pores and microcracks to the total voids along the carbonation direction, calcium carbonate tends to precipitate in the microcracks, which could also explain the lowest ratio of microcracks occurring at the carbonation front. At low RH （23％） conditions, the ratios of microcracks and pores are similar to the non-carbonated zone because of the microcracks newly formed from the connection between the pre-existing microcracks by decalcification of C-S-H and remaining unfilled pores.

In this study, the characteristics of the alkali-silica reaction （ASR） and the suppression effect of fly ash on ASR were evaluated by accelerated expansion test and microscopic observation when photovoltaic panel glass was used as fine aggregate. As a result, cracks caused by ASR are generated by gelation along latent cracks generated during glass crushing production, and the CaO/（SiO₂＋Na₂O） ratio of the ASR gel inside the expanded cracks is 0.2 confirmed to be low. On the other hand, when fly ash was mixed, almost no ASR gel formation was observed in the cracks inside the glass particles, confirming that the expansion was suppressed.

The effectiveness of using fly ash （FA） and blast furnace slag （BFS） as measures to restrain delayed ettringite formation （DEF） expansion has been reported. In this study, paste specimens using high-early-strength Portland cement （HPC）, FA, and BFS subjected to expansion tests were analyzed to discuss the effect of additives from a microscopic and chemical point of view. Compositional analysis using EPMA mapping data was conducted to visualize the distribution of ettringite （Ett） and monosulfate （Ms） in the paste tissue. In the HPC system exhibiting remarkable DEF expansion, pixels containing Ett were scattered at the boundary between lighter C-S-H and outer C-S-H. This nature is consistent with the hypothesis of the DEF expansion mechanism presented in past studies. In FA system, there was no Ett scattering around lighter C-S-H that might contribute to expansion, and Ms and Ett were observed inside FA particles. It was presumed that the released sulfate ions from lighter C-S-H were consumed by FA particles in the vicinity of the cement particles, and DEF expansion was thought to be suppressed by the additional effect. In the BFS system, Ms was stably formed, and no expansive Ett was found in the microstructure around the lighter C-S-H. It is assumed that reactive Al2O3 in BFS contributes to the stabilization of Ms.

In addition to alkali-silica reaction （ASR）, delayed ettringite formation （DEF） has recently been attracting attention as a cause of degradation due to internal swelling reaction of concrete, and it has been suggested that ASR and DEF chemically interact with each other in the degradation process, but many unknowns remain. In this study, combined degradation of ASR and DEF was experimentally reproduced in concrete specimens, and expansion ratio were measured, and cross-sectional observation and elemental analysis confirmed that the expansion ratio is not necessarily larger in combined degradation than in cases where ASR and DEF occur independently. In addition, there is a correlation between the pH calculated from the alkali concentration and the change in the expansion ratio, and it was confirmed that a gradual decrease in pH causes a gradual increase in the expansion ratio, while a rapid decrease in pH causes a sudden increase in the expansion ratio.

In chloride attack, the passivation film of the rebar is destroyed and the corrosion progresses. In alkali silica reaction （ASR）, the aggregate expands and cracks occur. This study evaluated the corrosion rate of the rebars in concrete with chloride ion and glass cullet, targeting the combined deterioration due to both chloride attack and ASR. That is, when the concrete was mixed, water containing sodium chloride aqueous solution was partially used. In addition, the glass cullet having reactivity was partially mixed with the land stone as a coarse aggregate. Based on these procedures, specimens were deteriorated with independent chloride attack, combined deterioration and Fly ash admixture with chloride attack or combined deterioration. The crack on the concrete was observed and the corrosion rate of the rebar was measured. In addition, the porosity was investigated from porosity test, the amount of oxygen supply was investigated from the cathodic polarization curve, and the formation of an electric circuit was investigated from the concrete resistivity. These were evaluated comprehensively, and the influence of ASR on the corrosion rate was considered. As a result, it was clarified that ASR gel inhibits oxygen supply and suppresses the corrosion rate, and that the addition of FA makes the concrete structure denser and suppresses the corrosion rate.

This paper deals with the effect of the surface treatment of a base concrete by water-absorption-controlling material （WACM） on the chloride ion penetration resistibility of polymer-modified mortar （PCM） coated concretes. PCMs using the EVA and AME emulsions are prepared with the polymer-cement ratios （P/C） of 0 and 5％ as coating mortars for the base concrete. The specimens of the base concrete with water-cement ratio of 57.9％ are prepared, and cured under prescribed conditions for 28d. For preparing the WACM coated concrete specimens, the surface of the base concrete specimens is treated by the EVA- and AE-WACM with the application quantity of 20, 25 and 30g/m² as solids which are the range of the recommended application value of productors. Then the specimens are subjected to dry curing for 1d. For preparing Plain and PCM coated concrete specimens, the surface of the base concrete specimens is treated by wetting with the water or the WACMs with the application quantity of 20, 25 and 30g/m² as solids. After such treatment of the concrete surface, the base concrete specimens are coated by PCM with coating thickness of 2.5mm, and cured under prescribed conditions for 28d. The specimens of base concrete, WACM coated concretes, PCM coated concretes are immersed in salt water. The chloride ion penetration depth of the base concrete and WACM coated concrete specimens is measured at immersion periods of 28, 56 and 84d. In PCM coated concrete specimens, the measurement of the chloride ion penetration depth of the base concretes is started after the complete penetration of chloride ion into the coated layer of PCM during the immersion. The chloride ion penetration depth measurement of PCM coated concrete specimens is conducted at the immersion periods of 28, 56 and 84d from such starting point. As a result, the chloride ion penetration resistibility of the base concrete is improved by the surface treatment by WACM coating. After the chloride ion is completely penetrated into PCM coated layer of PCM coated concrete specimens, the layer still inhibits the chloride ion penetration into the base concrete. The ability of the surface treatment by WACM and PCM coating is increased with an increase in the application quantity of WACM. The chloride ion penetration resistibility of the concrete is considerably improved by the synergy of the application of WACM as the concrete surface treating material and PCM coating for the concrete.

This paper presents the results of several experiments on the chloride penetration characteristics of mortar subjected to continuous compressive stresses inside and outside elastic limit. The following experiments conducted on mortar specimens continuously subjected to compressive stress （stress strength ratio （σ_c/f’_c）＝0, 0.15, 0.35, 0.50, 0.60）to obtain each experiment data. Calculation of apparent diffusion coefficient by salt submergence test, measurement of residual strain, measurement of pore diameter distribution by mercury intrusion porosimeter, and internal void condition by 3D X-ray CT image. The findings obtained are as follows. According to the apparent diffusion coefficient, the diffusion coefficient decreases with increasing σ_c/f’_c until near the elastic limit, after which the diffusion coefficient increases with increasing σ_c/f’_c. Even above the elastic limit, salt penetration resistance is high near the elastic limit, and the salt penetration resistance at σ_c/f’_c＝0.50 is comparable to that at σ_c/f’_c＝0. According to strain, microcracks occur at σ_c/f’_c＝0.30～0.40. According to pore diameter distribution and 3D X-ray CT images, above the elastic limit, the pore volume increases significantly from 100nm to 5μm in pore diameter.

From the viewpoint of CO₂ reduction, concrete structures using blast furnace slag powder or fly ash are increasing. However, it has been pointed out in previous studies that blended cement concrete differs from ordinary Portland cement concrete in terms of the mechanism of frost damage deterioration. The purpose of this study is to quantitatively clarify the factors affecting freeze-damage deterioration using cementitious materials with different types of cement. The results showed that the resistance to freeze-thaw degradation differed among cement types, and that the air content, air spacing factor, and compressive strength could not explain the differences, but the freezing water content and coarse porosity could explain the degree of freeze-thaw degradation.

Frost scaling damage to concrete structures is affected by complex combinations of multiple factors. Therefore concrete scaling mechanism is not yet completely understood. This study examines concrete’s damage exposed to deicing chemicals within dilution water. The existence of the dilution water is greatly connected with salt frost damage. The neural network’s analysis is effective for clarification of the relationship among complicated factors. This study revealed an important relationship between scaling damage and dilution water. A scaling damage evaluation was confirmed using a thermography’s technique. And concrete surface irregularity is grasped by three-dimensional photograph digital measurement systems.

Sendohira Canal Lock is a waterway lock built in 1902. Observation of materials in the mortar used for the joints in stone by a polarizing microscope revealed that cement from the shaft kiln containing many boat-shaped type II belites was used, and the mortar is shown to have been used at the time of construction. Since this cement has a slow hydration rate, the neutralization was suppressed by continuously supplying alkali to the cement paste, but ASR continued for a long time. As a result of EDS quantitative analysis, it was found that the ASR gel still has a high alkali concentration inside the aggregate and has an expansion capacity. However, since there are many large voids in the cement paste, and the ASR gel seeps into the voids, expansion cracks have hardly occurred in the aggregate, so it is considered that deterioration has been suppressed up to the present.

In this study, as a new method for estimating rheological constants of high-flow concrete, we proposed an “apparent aggregate model” that treats mortar that does not contribute to flow in concrete is apparent coarse aggregate. The “apparent aggregate model” assumes that there is mortar that does not deform between coarse aggregates, or that there is mortar that adheres to coarse aggregates and behaves like coarse aggregates.
In addition, we investigated the method of estimating the rheological constant of concrete from the mix proportions and the fluidity of mortar using the “apparent aggregate model viscosity equation”, which is an application of Roscoe’s equation. At that time, the apparent aggregate coefficientα, which is an unknown quantity in the apparent aggregate model viscosity equation, was obtained by machine learning using concrete mix proportions, material properties, and mortar rheological constants as explanatory variables. In addition, we quantitatively evaluated which explanatory variables had a large impact on the apparent aggregate coefficientα by Permutation Feature importance and Partial Dependence Plot.
As a result, the apparent aggregate coefficientα could be estimated with very high accuracy. We were also able to confirm the explanatory variables that affect the apparent aggregate coefficientα. Furthermore, the rheological constants of concrete could be estimated with high accuracy using the apparent aggregate model viscosity equation.

In this study, we compared the properties of “High-flow Concrete Requiring Compaction” and plain concrete subjected to compaction and gap passing effects in a box filling tests. Firstly, coarse aggregate settlement tests and box filling tests were used to evaluate resistance to segregation when “High-flow Concrete Requiring Compaction” was subjected to compaction and gap passing forces. As a result, segregation did not occur in "High-flow Concrete Requiring Compaction" when compaction time was properly controlled. Secondly, the gap pass speed was measured by a box filling test, and the results showed that "High-flow Concrete Requiring Compaction" was significantly faster than plain concrete. Thirdly, the change of compressive strength is evaluated when “High-flow Concrete Requiring Compaction” was subjected to compaction and gap passing forces. As a result, the compressive strength of the “High-flow Concrete Requiring Compaction” did not decrease under the influence of compaction and gap passing forces. Finally, the carbonation resistance of “High-flow Concrete Requiring Compaction” and plain concrete was compared. The results confirmed that the carbonation depth and carbonation rate coefficient of “High-flow Concrete Requiring Compaction” and plane concrete are comparable. Furthermore, the carbonation resistance of “High-flow Concrete Requiring Compaction” was not affected by the compaction and gap passing forces. The same results as above were confirmed for "High-flow Concrete Requiring Compaction" with mixed cement.

Mechanically-compacting flowable concrete with high-volume mineral admixtures can achieve not only the improving efficiency of construction and reducing risks of defects but the reduction of CO₂ emission and usage of natural resources. In order to develop mechanically-compacting flowable concrete with high-volume mineral admixtures, this research was carried out to investigate the basic fresh properties and hardened properties of mechanically-compacting flowable concrete with high-volume mineral admixtures using ground granulated blast-furnace slag with the replacement to ordinary Portland cement ratio of 70 and 80％. Compared with the properties of concrete using ordinary Portland cement, mechanically-compacting flowable concrete with high-volume mineral admixtures also follows the binder-water ratio theory. In addition, the effect of mix design factors such as unit water content and sand-total aggregate ratio on fresh properties for mechanically-compacting flowable concrete with high-volume mineral admixtures is also similar to ordinary Portland cement concrete. Compared between the same nominal strength, unit water content of mechanically-compacting flowable concrete with high-volume mineral admixtures can reduce more 5kg/m³ than that of ordinary Portland cement concrete. Hardened properties of mechanically-compacting flowable concrete with high-volume mineral admixtures is equal to or more than that of ordinary Portland cement concrete except the resistance against carbonation.

In this study, compressive and flexural strength tests were conducted on UHPFRC with steel fibers （SF） and three types of organic fibers （PEF, PVAF, and PBOF） at 1, 3, 7, 28, and 91 days of age to experimentally investigate the effect of matrix strength of UHPFRC on the various fiber reinforcement effects. The results of this study were as follows.
1） Flexural strength increases with compressive strength. Compared to the same compressive strength, the flexural strength of SF and PBOF is greater than that of PEF and PVAF, suggesting that the flexural strength is affected by the elastic modulus of the fibers.
2） It was observed that the compressive strength at which the maximum flexural toughness was reached was different for each fiber type. It was also suggested that even steel fibers typically used in UHPFRC might be at risk of reducing the fiber reinforcement effect indicated by flexural toughness when the matrix becomes ultra-high strength.