Small-angle neutron scattering（SANS）of autoclaved aerated concrete（AAC）which is mainly composed of 1.1nm tobermorite（5CaO・6SiO₂・5H₂O）, one of the calcium silicate hydrates, were performed to clarify the location and behavior of water molecules in tobermorite. The solvent contrast variation with a mixture of heavy water（D₂O）and light water（H₂O）showed the disappearing of the（002）diffraction peak of tobermorite at a certain D₂O-H₂O mixture ratio with 50wt％ and 6wt％ water content, respectively. Tobermorite crystal has a stacking structure consisting of CaO-SiO₂ layers connected by SiO₄ pillars in the c-axis direction, with interlayer water molecules. The disappearance of（002）diffraction peak indicates that the D₂O-H₂O mixture replaced periodically into the interlayer structure of tobermorite, i.e., a matching contrast between the CaO-SiO₂ layers and the D₂O-H₂O mixture replaced the interlayer spaces. Considering the samples with 6wt％ moisture content were prepared in D₂O-H₂O mixture vapor atmosphere, the content water should exist as adsorbed D₂O-H₂O molecules. The significant increase in adsorption at low relative pressure in the water vapor adsorption isotherm of tobermorite previously reported also should be due to the penetration of water molecules into the interlayer. This method can be applied to the other calcium silicate hydrates such as cement hydrates（C-S-H）and is to be a powerful tool for analyzing the microstructure including water molecules.

Simultaneous small-angle neutron scattering（SANS）and water vapor adsorption measurements with heavy water（D₂O）were performed on 1.1nm tobermorite（5CaO・6SiO₂・5H₂O）, a calcium silicate hydrate, to clarify the location and behavior of water molecules during adsorption measurement. Tobermorite crystal has a stacking structure consisting of CaO-SiO₂ layers connected by SiO₄ pillars in the c-axis direction, with interlayer spaces containing water molecules under room temperature and humidity. In the initial stage of adsorption at very low relative pressure range, the diffraction peaks corresponding to the stacking direction of tobermorite disappeared as D₂O adsorption progressed, directly indicating the penetration of D₂O molecules into the interlayer spaces. This means a matching contrast of scattering length density between the CaO-SiO₂ layers and the D₂O molecules intruded into the interlayer spaces, i.e., indicating D₂O molecules intruding between the CaO-SiO₂ layers of tobermorite in adsorption measurements. The significant increase in adsorption at low relative pressure（p/p₀～0.0079）also should be due to the penetration of water molecules into the interlayer, and the amount of interlayer water molecules was estimated from the decreasing behavior of（002）peak intensity. This method can be applied to other calcium silicate hydrates, such as cement hydrates（C-S-H）, for dynamic and simultaneous observation of the water molecule conditions affecting various physical properties.

The strength of concrete is closely related to the calcium silicate hydrate（C-S-H）produced by the hydration of ordinary poltland cement. Since the structure of C-S-H is reported to be similar to that of 1.1-nm tobermorite which is a kind of natural minerals, the relationship between concrete strength and 1.1-nm tobermorite have been actively researched. Although there are several experimental and theoretical studies based on classical molecular dynamics have been reported, few theoretical studies focused on bonding states have been conducted. Under these circumstances, in this study, the electronic states and mechanical properties, including bonding states, of 1.1-nm tobermorte have been investigated from tensile and compressive simulation using ab initio molecular dynamics simulation. From the atomic charge distributions obtained from the simulation, Si atoms have two different sites, one with the Si atoms bonded to O in OH group and the other with that bonded to O without H atom. For O atoms, there are three different sites, one with the bridging O atoms, the second with the nonbridging O atoms, and third with the O atoms bonded to a H atom（O atoms in H₂O）. From stress-strain curves and atomic configurations in tensile deformation, the stress drop is caused by delamination of layer of 1.1-nm tobermorite. In compressive deformation, additional Si-O bonds are formed across the layers, resulting in a structure more resistant to compression. In this process, the fivefold-coordinated Si is generated.

In this study, microstructure of Calcium Silicate Hydrate（C-S-H）agglomeration, so-called C-S-H gel, formed during cement hydration, and that of synthetic C-S-H was compared by ¹H NMR T₁-T₂ correlation measurements. Based on T₁-T₂ correlation maps, C-S-H gel in hardened cement paste（HCP）showed all the relaxation components were on-diagonal at the same T₁/T₂ ratio, which is the measure of mobility of ¹H. However, ¹Hs in interlayer/gel-sized pores of synthetic C-S-H decayed at different T₁/T₂ ratios, similar to the result of layered clay minerals. From the viewpoint of ¹H relaxation mechanisms in porous materials, experiments indicated microstructures of C-S-H gel in HCP and synthetic C-S-H are different. Synthetic C-S-H shares some similarities with layered clay minerals, indicating ¹H in interlayer/gel-sized pores likely exhibits different mobility compared to those in bulk regions. On the other hand, C-S-H gel in HCP is more disordered and contains interlayer and gel between neighboring CaO layers. According to these assumptions, the length along the a-axis/b-axis of the pore having some fixed size in c-direction inside C-S-H gel may tend to be shorter than those in synthetic C-S-H. This can be the possible explanation for the difference in the microstructure of C-S-H gel in HCP and synthetic C-S-H.

In this study, white cement paste powder with particle sizes less than 75μm was utilized to investigate the effects of carbonation on cement hydration products. The T₂ relaxation time was measured using ¹H-NMR relaxometry, which enabled the evaluation of changes in the distribution of mobile water and the total specific surface area within calcium silicate hydrate（C-S-H）due to carbonation. Additionally, powder X-ray diffraction（XRD）measurements were conducted to quantify the phase composition, providing insights into the degree of carbonation of C-S-H. These analyses were crucial for understanding the carbonation process and the subsequent alterations in the pore structure of the cement paste. Experiments were conducted under natural carbonation conditions with relative humidity set at 60％ and 95％. It was observed that, after a carbonation period of 14 days, the extent of carbonation in C-S-H was approximately the same for both humidity conditions. However, the study revealed that relative humidity levels significantly influenced the speed of the carbonation reaction and the changes in pore structure post-carbonation. Specifically, at a relative humidity of 60％, the carbonation reaction progressed more slowly, and the resulting changes in the pore structure were less pronounced compared to the conditions at 95％ relative humidity, where the reaction occurred more rapidly, leading to more significant alterations in the pore structure. These findings indicate that humidity plays a critical role in the carbonation behavior of C-S-H and its physical properties.

The expansion due to gypsum formation was examined by immersing hardened alite in sulfate solution at 20℃ and 30℃. At 30℃, a significant expansion was observed compared to 20℃. At each temperature, ettringite and gypsum were found as reaction products. Ettringite was formed in an equivalent amount regardless of temperature, whereas gypsum was formed in approximately twice the amount at 30℃ as compared to 20℃. Based on the results of the expansion and the reaction products, it was indicated that the difference in expansion behavior at 20℃ and 30℃ was dominated by the formation of gypsum. From the results of this study, it is considered that reducing the amount of calcium hydroxide, which is associated with gypsum formation, contributes to the suppression of expansion, and that reducing the amount of C₃S/C₂S in Portland cement improves sulfate resistance because it reduces the formation of calcium hydroxide.

In this study, we investigated the effect of carbonation products on the volume change of β-C₂S carbonated by dry or wet methods. The volume change by carbonation was evaluated based on observation of particle morphology by electron microscopy and quantitative values of the rate of volume increase by various analyses. As a result, it was thought that through carbonation, silica gel was produced from the particle surface to the inside to maintain the shape of the β-C₂S particles before reaction. On the other hand, it was thought that calcium carbonate was generated externally from the particle surface, which increased the particle volume. Therefore, the strength development by carbonation of β-C₂S was considered to be caused by filling the pores only with the calcium carbonate.

The purpose of this study is to clarify the effect of moisture conditions of hardened cement paste on the carbonation process of hydration products. Cement pastes with three types of water/cement ratio（w/c＝45％, 55％ and 65％）were prepared and dried under different relative humidity levels（40％RH, 52％RH, 70％RH and 85％RH）to obtain the samples with different moisture conditions. The samples were carbonated under accelerated conditions（5％ CO2 concentration and 25℃）at the same relative humidity levels. Phase assemblages over carbonatation time were measured using a combination of XRD/Rietveld-PONKCS method and mass balance equations. PONKCS method allows for the quantification of silica gel content in carbonated samples. The polymorphs of calcium carbonate varied depending on the relative humidity levels. Calcite and vaterite were observed at 70％RH and 85％RH, while aragonite and vaterite were precipitated during carbonation at 40％RH and 52％RH. In the early stages of carbonation, the formation of amorphous calcium carbonate was indicated at 40％RH. C-A-S-H content was determined by calculating the mass balance equation between reaction products and formation products. At lower relative humidity, the carbonation of portlandite was slower, whereas C-A-S-H was continually carbonated. The relation between the amount of consumed hydration products and CO₂ uptake revealed that the carbonation process of portlandite and C-A-S-H is determined by relative humidity during carbonation and is independent of water/cement ratio. Additionally, C-S-H decomposition and silica gel formation occur early under slight CO₂ uptake at lower relative humidity.

In this study, the hydration promoting effect of α-C₂SH prepared from waste concrete powder was examined in terms of the reaction rate of C₃S and heat of hydration. In addition, the fractal dimension, a measure of the complexity of the hardened cement paste surface, was calculated for the prepared samples and analyzed in relation to the hydration promotion effect as a measure of the complexity of the C-S-H generated by the hydration of C3S on the particle surface. The results showed that the addition of α-C₂SH prepared from waste concrete fines shortened the induction and acceleration phases in the early stages of hydration. In addition, regardless of the specific surface area and average particle size of the additive, the surface fractal dimension Ds in the initial stage of hydration increased rapidly, especially for the additive that showed an accelerating effect on hydration.

In this study, the effects of triisopropanolamine（TIPA）on the compressive strength and hydration reaction of ordinary Portland cement（OPC）mixed with limestone powder（LSP）and blast furnace slag powder（BFS）were investigated. The compressive strength at 28 days of age was improved to the same level as that of OPC by using LSP and BFS together. Furthermore, the addition of TIPA resulted in compressive strength higher than that of OPC. Therefore, it can be said that the LSP＋BFS＋TIPA system is effective in increasing the small amount of mixed components. In addition, the addition of TIPA to the combined LSP and BFS system improved the reactivity of aluminates（C₃A）, ferrite（C₄AF）, and CaCO₃ at 28 days of age. On the other hand, no change was observed in the reactivity of BFS. In addition, the formation of monocarbonate（Mc）and hemicarbonate（Hc）increased. This was attributed to the increased reactivity of C₃A, C₄AF, and CaCO₃, and the supply of Al^3＋, Fe^3＋, and CO₃^2－ into the system by the addition of TIPA. Therefore, the increase in compressive strength at 28 days of age in this study was suggested to be due to the increased amount of hydration products in the pore phase such as Mc and Hc, which filled the voids more.

This study examined changes in BFS reactivity with varying powder degree and anhydrite additions in a blast furnace cement Class B（BB）system with blast furnace slag fine powder（BFS）of lower basicity than the current system. The reactivity of the low-basicity BFS at the early 7 days of age could be improved to the same level as that of the current BFS by controlling both the fineness of the BFS and the amount of anhydrite added, as well as by increasing only the powder content of the BFS and the amount of anhydrite added. The reactivity index of BFS with low basicity was also improved to the same or higher than that of the current BB by controlling both the powder degree and the amount of anhydrite added, indicating that not only the reactivity of BFS was improved by controlling the powder degree of anhydrite and BFS, but also the reactivity of BFS was improved by adding It is suggested that this is due to the formation of ettringite（Ett）by the addition of anhydrite. The addition of anhydrite also decreased the amount of CH in the BB paste, which was presumably due to the fact that the amount of CH consumed by the BFS also increased as the amount of anhydrite was increased.

In order to reduce CO₂ emissions from the cement and concrete industry, carbonation curing of Ordinary Portland cement containing a large amount of blast furnace slag（BFS）has been studied. In carbonation curing of high volume BFS cement, mixing a CO₂ fixing admixture（CFA）with it is considered to increase the amount of fixed CO₂ and strength of concrete. On the other hand, it has been reported that relative humidity（RH）during carbonation curing greatly influences the carbonation reaction rate of components in cement paste. In this study, influences of CFA and RH on chemical properties of the microstructure of hardened high volume BFS cement after carbonation were investigated. The thin hardened cements cured in water were carbonated, and the amount of CO₂ and states of carbonation products in them were analyzed by inorganic carbon measurement, XRD, FT-IR, and scanning electron microscopy（SEM）. The reduction of C₃S, β-C₂S and CH due to carbonation of high volume BFS cement was slightly higher at 95％RH than at 66％RH. The amount of fixed CO₂ and calcium carbonate were significantly increased by mixing CFA. The carbonation products of CFA in high volume BFS cement were vaterite, calcite, and silica gel containing small amount of Ca. It was suggested that the calcium carbonate produced by carbonation of CFA contributed to the densification of a microstructure of hardened cement.

The paper has investigated hardened cement paste, lime sand mortar, and river sand mortar with coupled analysis TG, dilatometer and X-ray diffraction while heating from 100℃ to 1000℃. The goal was to understand the influence of aggregates on the mortar character, particularly the mineral composition and the phase transition during heating at high temperatures. TG and dilatometer analysis showed shrinkage occurred when C-S-H transformed to β-C₂S and β-C₂S transformed to α’_L-C₂S. Besides, mass loss and shrinkage resulted from the phase transformation of C-S-H to β-Wollastonite. The high-temperature XRD in-situ analysis showed that C-S-H transformed to β-C₂S at 600℃ and β-Wollastonite at 780℃. These transformations are significant as they indicate changes in the structure and properties of the mortar. In the high-temperature XRD in-situ analysis with corundum（α-Al₂O₃）as an internal standard, which is non-reactive against the sample during heating. The mass ratio of the minerals to corundum was determined at elevated temperatures. According to the result of XRD/Rietveld analysis, the β-Wollastonite mass ratio to α’_L-C₂S in the river sand mortar was higher than in the hardened cement paste at 980℃. This result indicated that in the river sand mortar, Silicon in the aggregates was consumed during the reacting process of C-S-H to α’_L-C₂S and β-Wollastonite. When studying concrete at elevated temperatures, it is essential to experiment with specimens including aggregates, not just the hardened cement paste.

The effect of triisopropanolamine（TIPA）on the early strength development and hydration reaction of cement made with low-burning temperature clinker（LTC）was investigated in comparison with that of ordinary Portland cement（OPC）with TIPA. The addition of TIPA to LTC improved the strength development of LTC after 3 days of curing. When mixed with limestone powder, LTC showed a particularly good strength enhancement effect at 28 days of curing with the addition of TIPA compared to OPC. The results of the hydration analysis suggest that the mechanism of strength enhancement by TIPA addition is due to the increased reactivity of the ferrite phase. It was also suggested that different types of calcium aluminate hydration products may influence the strength development.

Carbonation of concrete can lead to not only a decline in the pH of pore solution due to the formation of calcium carbonate, but also the volume change associated with decalcification and decomposition during the carbonation of calcium silicate hydrate（C-S-H）. This study investigated the effect of the decalcification of C-S-H and silica gel formation on the carbonation shrinkage of hardened cement paste. Cement pastes samples with three types of water/cement ratio（w/c＝45％, 55％ and 65％）were carbonated under different relative humidity levels（40％RH, 52％RH, 70％RH and 85％RH）in accelerated conditions（5％ CO₂ concentration and 25℃）. Carbonation shrinkage, CO₂ uptake, IR spectrum and the quantity of silica gel formation were measured over carbonation time. Results show that carbonation shrinkage increases over carbonation time, and the shrinkage strain was highest at 52％RH and/or 70％RH after 182 days of carbonation time for all three w/c types. In the case of same CO₂ uptake, carbonation shrinkage strain was found to increase at lower relative humidity during carbonation. The change in carbonation shrinkage due to relative humidity was attributed to micro-structural alteration of carbonated C-S-H, based on FT-IR results of Si-O stretching vibrations. The relation between carbonation shrinkage strain and silica gel content appears to be independent of w/c types of sample and relative humidity during carbonation. From these results, it was indicated that the decalcification of Ca^2＋ between the calcium silicate layer and silica gel formation due to decomposition of calcium silicate layer progress simultaneously at a certain Ca/Si ratio.

The purpose of this study was to clarity deformation behavior of cement paste at high temperature environments to better understand the thermomechanical properties of concrete. The water binder ratio of the cement paste was set at three levels：W/C＝50％, W/C＝30％, The water binder ratio of the cement paste was set at three levels：w/c＝50％, w/c＝30％, and w/b＝18％. And Silica fume was added to the cement paste with W/B＝18％ at a ratio of 10mass％ to cement. The results, the deformation behavior of cement pastes at high temperature environments due to dehydration was revealed. Cement pastes with W/B18％ and W/C30％ turned from expansion behavior to shrinkage behavior near 100℃. Furthermore, the temperature dependence of the rate of thermal shrinkage with cement paste was confirmed, and it was found to vary in four stages depending on the dehydration.

The authors reported that employing lithium nitrite in cementitious materials was advantageous under severe low-temperature conditions, such as exposure to freezing temperatures immediately after construction. This compound can be added in large amounts, effectively lowering the freezing point. However, because of the recent price hike of lithium against the backdrop of the global supply-demand imbalance, there is a demand for the development of low-cost anti-freezing agents that do not depend only on lithium nitrite to avoid the lithium supply chain risk. In contrast, calcium nitrite is commonly utilized as the main component of nitrite-based accelerators in cold-weather concreting, and its raw material cost is lower than that of lithium nitrite. Furthermore, calcium nitrite accelerates the hydration reaction of the cement and improves its initial strength development. However, its freezing point-lowering effect is limited because increasing the amount of calcium nitrite causes a decrease in flowability, and there is a problem in developing strength at freezing temperatures. Therefore, by combining lithium nitrite, which has excellent freezing point depression despite its high material cost, and calcium nitrite, which is inexpensive and promotes the hydration reaction, we aim to develop an anti-freezing agent that exhibits both freezing point performance and economic efficiency.Based on this background, this study investigated the fresh properties of cement paste containing lithium nitrite and calcium nitrites and the strength development after curing under freezing conditions immediately after mixing.

Supplemental Cementitious Materials（SCMs）are essential to the decarbonization of the cement sector, as they significantly reduce the carbon footprint associated with conventional Portland cement production. However, the industrial by-products such as fly ash and blast-furnace slag from the thermal power plants and the steel industry, which are widely used for SCMs now, are forecasted to become less available in the future due to the decarbonization of their sectors. Therefore, it would be necessary to investigate natural rock powder（NRP）, such as natural pozzolan, which are abundant in reserves, for use as SCMs. This paper aims to clarify the properties of mortar when 15 different NRPs replacing 25wt.％ of ordinary Portland cement（OPC）, comparing mortars with OPC and with fly ash. Fresh properties, compressive strength, chemical reactivity measured by ASTM C 1897（R³ test）, and expansion due to Alkali Silica Reaction（ASR）measured by ASTM C 1567 in these mortars were experimentally evaluated. The result indicated that the setting time of all mortars with NRP satisfied the limit value defined for fly ash in the Japanese Industrial Standards（JIS）R 5213. Nine mortars with NRP of zeolite, andesite, porphyrite, tuff, granite, sandstone, shale, limestone, and crystalline limestone met the criteria for fluidity and activity index of fly ash for concrete as defined in JIS R 6201. Furthermore, some mortars with NRP were also found to have an inhibitory effect on ASR expansion. Observations revealed that mortar using NRP with a higher specific surface area tends to have lower flowability and higher water demand. Additionally, higher reactivity according to the activity index and R³ test of NRP was linked to lower expansion due to ASR.

For understanding the swelling behavior of cement-based materials, dried hardened cement pastes were immersed in purified water or aqueous chloride solutions, and measured the change of microstructure and mineral composition using proton nuclear magnetic resonance（¹H-NMR Relaxometry）and powder X-ray diffraction. As a result, it was confirmed that the swelling behavior caused by immersion in a chloride solution after drying is not due to mineral precipitation, but rather to the reformation of the structure caused by the supply of water to the microstructure that had been deformed by drying. It was confirmed that, depending on the type of chloride, short-term swelling due to penetration of the aqueous solution into the C-S-H pore structure, and long-term swelling occurred with a gradual increase in the pore size of the gel voids in the C-S-H pore structure.

The effects of adding calcium sulfoaluminate setting accelerator（ACF）and PC type superplasticizer（PC）on the fluidity, bleeding rate, and setting time of mortar at 5℃ were investigated. The study compared the use of ACF and PC together versus using ACF without PC. The results showed that adding PC to the formulation with ACF maintained the same flowability as formulations without ACF for up to 60 minutes After the addition of ACF. Bleeding was reduced and setting time shortened with ACF, regardless of the presence of PC, depending on the amount of ACF added. Liquid-phase analysis indicated that ACF additions effectively reduced bleeding and shortened the setting time. It was inferred that the increase in the amount of organic matter（dispersant）adsorbed helped maintain fluidity. Hydration reaction analysis suggested that the increase in ettringite and other substances due to ACF was responsible for the accelerated setting and bleeding suppression.

The effect of methyldiethanolamine（MDEA）on the suppression of carbonation of blast-furnace cement type B and limestone calcined clay cement was investigated. The results showed that the suppression of carbonation was observed in both blast-furnace cement type B and limestone calcined clay cement, and the effect was larger as the addition of MDEA increased. It was found that the addition of MDEA promoted the hydration of C₄AF and decreased the pores larger than 150nm in diameter. Therefore, the suppression of carbonation was considered to be due to MDEA promoting cement hydration and changing the pore structure of the mortar.

A number of equivalent circuit models have been proposed so far. It has been reported that it is possible to understand the porosity and progress of hydration of hydrated cement from obtained AC parameters even in the classical model. In this paper, a multiple parallel equivalent circuit model is proposed, focusing on the number of different time constants that appear in the equivalent circuit, which is assumed to be related to the complexity of the pore structure of the hardened cement. The ultimate goal is to establish a relationship between the number of time constants and the pore structure of hardened cement. As a first step, we measured the AC impedance of mortar sensors to determine the number of time constants. The measured AC impedance of the mortar sensors was approximated by impedance calculated from equivalent circuits with a finite number of parallel circuits. Some of the time constants were retained even when water content changed.

A fundamental study was conducted to establish a measurement method for the fixed amount of CO₂ in the cementitious materials. The fixed amount of CO₂ in the calcium compounds that simulate cement hydrates containing monocarbonate was measured by the TG-DTA method and TOC method, and their values were compared. As a result, the TOC method provided highly accurate measurement values under the conditions of a sample size of 150μm or less and dripping amount of pure water of 4mL/g or more on the sample. The measurement values of the fixed amount of CO₂ in monocarbonate were generally accurate by the TOC method, while those by the TG-DTA method showed smaller values than the theoretical ones.

In this study, we investigated the applicability of a two-electrode method using Ag/AgCl electrodes for the determination of chloride ion content in fresh concrete. We obtained a calibration curve for the amount of chloride ions in fresh concrete applicable from 5℃ to 35℃. As a result of the verification experiment of the calibration curve, it was shown that the chloride ion content in fresh mortar can be accurately estimated regardless of the type of cement, water-cement ratio, and measurement temperature. The two-electrode method using Ag/AgCl electrodes has conventionally been used to measure the chloride ion content of hardened concrete, however this study shows that the method can be used to measure chloride ion content even in ready-mixed concrete.

The surface area and the mean free distance of aggregate particles in concrete were evaluated using the grading curves obtained by the sieve test and the image analysis for the particles that appeared in the cross-section of concrete. The aggregate-cement paste proximity was evaluated by the shell volumes of cement paste near aggregate particles. The number of fine aggregate particles was dominant in the total number of aggregate particles so the surface density of aggregate was almost determined by the fine particles. Therefore, the volume of the interfacial transition zone greatly depends on the presence of the fine particles. The volume ratio of the interfacial zone around aggregate particles to the entire volume of the cement paste matrix is relatively small based on the product of the measured surface density of aggregate and the shell thickness which is comparable to the mean diameter of cement particles. The mean free distance of aggregate particles was much larger than the size of cement particles. This fact suggests that the percolation of the ITZ to cover the entire cement paste matrix is not a realistic phenomenon in concrete. Taking account of the dispersion of many fine particles of aggregate, their random distribution results in both the clusters and the dispersed areas with a few particles. Thus, porous regions such as the interfacial transition zone are present in not only the vicinity of aggregate peripheries but also the bulk cement paste. Therefore, inhomogeneous regions with greater porosity could be considered as the statistical events that depend on the spatial packing density of aggregate and cement particles in the cement paste matrix. It is not necessarily formed on the surface of aggregate particles uniformly.

The wavelengths that affect the slip resistance of concrete pavements were studied for microtextures（＜0.5mm）, which affect the skid resistance of road surfaces. Fourier transforms were performed on the acquired road surface waveforms, and the amplitude and wavenumber of each wavelength were used to examine the areas where the percentage of line length increase, which indicates the percentage of contact with the tire, is large. The results indicated that the wavelength region that contributes to skid resistance is likely to be 0.1mm or less. The addition of sandblast sand with a grain size of about 0.1mm improved skid resistance and texture persistence, indicating that the presence of micro-texture with a wavelength of 0.1mm or less is important after the disappearance of macro-texture during service.

In this study, an evaluation method focusing on the propagation time of elastic waves was investigated for detecting horizontal cracks in RC slabs using the electromagnetic pulse method. Specifically, we set several elastic wave receiving points on the surface of RC slab and confirmed the difference of elastic wave propagation time depending on the presence or absence of horizontal cracks by finite element analysis and specimen experiments when the reinforcing bars inside the slab were electromagnetically vibrated. As a result, it was shown that horizontal cracks, which are difficult to be detected by the conventional method based on the amplitude of vibration response, can be evaluated by focusing on the difference of elastic wave propagation time.

The purpose of this study was to understand the carbonation behavior of stratlingite, which was found to be formed in cementitious materials using sintered allophene. Specifically, we investigated the changes in crystal structure, the amount of carbonate formed, and the molecular bonding state of the accelerated carbonated synthetic stratlingite by various analyses. The results suggest that vaterite is formed by carbonation, and that the decrease in crystallinity is related to the disorder of the double tetrahedral layer. In addition, it was shown that water is supplied to the voids in the crystal structure by the release of bound water due to carbonation.

In this study, we conducted an investigation to clarify the influence of using biomass ash on various properties of concrete, such as fresh properties and compressive strength. As a result, it was found that the influence on fresh properties, including time-dependent changes, was minimal when biomass ash was used in concrete up to 100kg/m³. Biomass ash contributed to the improvement of concrete strength more than fly ash, and it was confirmed that using biomass ash with a high NBO/T ratio, which represents the ratio of non-bridging oxygen and tetrahedral ions in glass, resulted in a higher cement effective coefficient, k. Furthermore, by using biomass ash as a substitute for cement, it was possible to reduce the amount of cement used and confirm a reduction in CO₂ emissions.

In this study, the chloride ion penetration resistance of hardened cement bodies in which 10％ of the cement was replaced with volcanic glass powder（VGP）or silica fume（SF）was compared to that of a non-blended cement body. As a result, a reduction in penetration depth was observed. This reduction was analyzed by focusing on the pore structure and the formation of calcium silicate hydrate（C-S-H）and calcium aluminate hydrate（C-A-H）. It was found that VGP, like SF, increased the amount of gel pores and reduced the size and continuity of capillary pores compared to the non-blended sample. Additionally, when VGP was added, it was observed that the Si and Al within the formed C-S-H were substituted, resulting in the formation of Calcium aluminate silicate hydrate（C-A-S-H）, which contributed to chloride ion adsorption. Furthermore, the formation of Friedel’s salt also played a role in the adsorption of chloride ions.

Exogenous chloride attack due to airborne chloride is one of the main degradation factors for reinforced concrete structures located in coastal areas. The amount of airborne chloride adhered to the structure is affected by wind and rain. Therefore, it is known that the amount of airborne chloride adhered to each structural component is different. In this study, airborne chloride on the pillars of reinforced concrete structures in a coastal area was therefore measured. In addition, tests using water-sensitive paper were carried out to assess the rain exposure of each pillar. Furthermore, wind analysis was carried out considering the topography around the structures. The results of the wind analysis obtained were used to analyse the rain exposure and airborne chloride particles. The validity of the analyses in this study was then assessed by comparing the results of the analyses with the results of the exposure tests. The influence of the analysis model, the minimum mesh size of the wind velocity field in the analysis and the number of airborne chloride particles on the analysis values was also investigated. The results showed that the analysed values approximately captured the trend of the measured values by taking rainfall into account. The number of airborne chloride particles had little impact on the analysis results, and the smallest mesh size in the wind analysis affected the errors in the analysis results.

The purpose of this study is the proposal of an equation for estimating the carbonation depth at the outdoor exposure for the concrete coated by the polymer-modified mortar（PCM）after treating the concrete surface with the water-absorption-controlling material（WACM）. The base concrete with water-cement ratio of 57.9％ is prepared and cured under prescribed conditions for 28d. In the preparation of PCM coated concrete specimens, the surface of the base concrete is treated by wetting with the water or the WACM with the application quantity of 20, 25 and 30g/m2 as solids which are the range of the recommended application values of the productors. Then PCMs using EVA and AME emulsions with the polymer-cement ratios（P/C）of 0, 5, 10 and 15％ are coated with the thicknesses of 2.5, 4 and 6mm to the base concretes. The PCM coated concrete specimens are cured under prescribed conditions for 28d and subjected to the acceleration carbonation test. The carbonation depth of the base concrete is measured at 28, 56 and 84d after the PCM coating layer is completely carbonated. By the organizing the test results, the equation ［6］ with factors as the application quantity of WACM, the coating thickness of PCM and its P/C is proposed for calculating the apparent carbonation rate coefficient of the base concrete coated with the PCM after surface treating by the WACM, namely the PCM coated concrete in the accelerating carbonation test. On the other hand, the estimating equation ［11］ for the carbonation depth of the PCM coated concrete at the outdoor exposure is proposed based on the general equation for estimating the carbonation period of the uncoated-concrete.

The control methods of alkali silica reaction, one of the deteriorations of concrete structure, are control of R₂O content in concrete, use of mixed cement and use of aggregate determined to be non-expandable. However, the deterioration cases are still being reported despite the application of these methods. For the purpose of evaluation of calcium propionate as repair material, this study investigated control of the expansion by addition of calcium propionate after the expansion and the effect on composition of alkali silicate gel, which can control the expansion of alkali-silica reaction by addition at mixing stage of concrete. As a result, expansion due to alkali silica reaction was reduced even when calcium propionate was added after the expansion. Alkali silica gel may have been changed the characteristic about expandability caused by replacement Ca of calcium propionate to Na of alkali silica gel.

The effect of the steam curing temperature on the dimensional stability was investigated on expansive concrete of the ettringite system treated with steam curing and cured in water for up to 5 years. For the expansive concrete with 38％ water-binder ratio in this experiment, the delayed expansion was observed only at the curing temperature of 90℃, and the delayed expansion and strength reduction did not occur below 80℃. Furthermore, the amount of sulfate ions eluted at steam curing temperatures of 80℃ or lower was smaller than that at 90℃. It was suggested that the risk of ettringite decomposition could be reduced by appropriately controlling the steam curing temperature. Even when expanding concrete is used, it is thought that the risk of delayed expansion can be reduced by using it within the R₂O, SO₃, and steam curing temperature ranges specified in the guidelines for controlling cracking of mass concrete. It is true that the SO₃ in concrete is increased by using the expansive additive compared to normal concrete, but the use of the expansive additive can be expected to suppress the water supply in the structure by lowering the hydraulic conductivity, reducing the crack width, etc., and it is not always a negative factor in the delayed expansion. It is considered that proper temperature control without delayed expansion is important for expansive concrete.

Delayed ettringite formation（DEF）and alkali-silica reaction（ASR）need to be carefully distinguished due to their similar macroscopic appearance. In this study, the cement paste matrix of concrete specimens with DEF and ASR potentials was analyzed by using EPMA（Electron Probe Micro Analyzer）. Mapping analysis of CaO, Al₂O₃ and SO₃ was carried out and the results of the analysis were plotted on a ternary diagram, showing that in specimens with DEF potential, the C-S-H composition data groups were distributed extending in the direction of the ettringite composition. When these data groups were plotted on the BSE（backscattered electron）image, the portion of the data groups overlapped the lighter C-S-H microstructure. Lighter C-S-H is a microstructure formed during high-temperature curing and appears lighter in BSE images, and is thought to sorb Al₂O₃ and SO₃ and contribute to DEF expansion. As the specimen lost DEF potential, the lighter C-S-H composition was distributed in the direction of the monosulphate composition. For specimens with combined DEF and ASR potential, ASR expansion occurred first and DEF potential was identified even after the expansion had ceased. It is not easy to distinguish between ASR and DEF, and careful diagnosis using a combination of several methods including petrographic analysis, residual expansion testing of concrete cores and analysis of DEF potential by using microscopic analysis, is recommended to identify DEF potential.

The objectives of this study were to clarify the characteristic changes in the chloride penetration of mortars with DEF expansion and to investigate the effect of chloride penetration on the acceleration of DEF expansion. Mortar specimens with DEF were immersed in NaCl solutions of different concentrations to evaluate the expansion amount, chloride ion profiles, and pore structure. As a result, a trend toward greater expansion due to DEF was shown when the concentration of the immersed NaCl solution was 3％. For specimens immersed in NaCl solutions for 28days, chloride ions penetrated deeper in the mortar specimens with DEF expansion than in the specimens without DEF expansion. Based on the pore size distribution, capillary pores with diameters ranging from 50nm to 4μm were formed in the specimens with DEF expansion. Therefore, the chloride penetration was probably enhanced by the increase in capillary pores of 50nm to 4μm in diameter associated with DEF expansion.

In this study, we investigated measures to improve the frost resistance of plasticized concrete controlled by slump flow, which is manufactured by adding a superplasticizer containing viscosity agent to the slump-controlled concrete. The frost resistance of plasticized concrete controlled by slump flow was lower than that of the base concrete although the frost resistance was improved by adding AE agent afterward during plasticization. The reduction in air volume after hardened relative to fresh concrete tended to be greater for plasticized concrete than for base concrete. This is thought to be because of the defoaming agent contained in the superplasticizer. The use of the AE agent for fly ash concrete and paraffin emulsion improved the frost resistance of plasticized concrete. When general-used AE agents were used, the number of bubbles less than 150μm decreased after plasticization and the bubble spacing factor increased. On the other hand, when the AE agent for fly ash concrete, the number of bubbles below 150μm decreased less after plasticization, and the bubble spacing factor was better. In this experiment, the effect of bubble structure on frost resistance was greater than that of pore structure. These results suggest that the use of the AE agent for fly ash concrete and paraffin emulsion can improve the frost resistance of plasticized concrete controlled by slump flow.

This study aimed to understand the phenomena of segregation and flowability of mechanically-compacting flowable concrete and the physical factors involved. As a result, it was found that “density difference between mortar and coarse aggregate” and “plastic viscosity of mortar under vibration” were the factors of segregation resistance and that the slope a of the approximate equation of “density difference between mortar and coarse aggregate” and “coarse aggregate volume ratio” was correlated with “plastic viscosity of mortar under vibration.” The main factor of flowability is “the volume of mortar that contributes to flow in concrete,” it was understood that the thickness of restraining mortar and the volume of mortar that contributes to flow varies depending on the physical properties of the coarse aggregate and the mortar mix.

Silica fume, which is an admixture for high-strength concrete is currently not manufactured in Japan and can only be obtained by importing it from abroad. Therefore, it is very expensive in Japan. On the other hand, fly ash is produced in large quantities in Japan, and desired to be used for effective utilization. Therefore, in this study, it was focused on ground fly ash for alternative admixtures for high strength concrete, and examined the possibility of obtaining properties similar to silica fume. In this study, by using finely pulverized fly ash in concrete, it was expected to develop strength comparable to that of silica fume. In the experiment, it was examined the fresh and hardened properties of concrete and mortar using finely ground fly ash and silica fume. In fresh properties, it was found that dilatancy properties appeared in concrete using finely ground fly ash. Therefore, the method to suppress it was examined.As a result, by substituting 20％ cement for fly ash pulverized to an average particle size of about 1.5μm, it was confirmed that the concrete show the same level of strength development as concrete with 10％ silica fume replacement, and also exhibit good fresh properties.

Cementitious materials have low tensile strength and are often reinforced internally with steel bars. However, since it is sometimes difficult or impossible to insert reinforcing bars into cementitious materials, the use of steel fibers as a reinforcing material is being considered.Since steel fibers have electromagnetic shielding properties, there is concern that they may interfere with electromagnetic communications when steel fiber-blended cementitious materials are used in buildings. On the other hand, there is a possibility that steel fiber-reinforced cementitious materials can be used as electromagnetic shielding materials to control electromagnetic interference in buildings.In this study, it was clarified that the effects of the amount and shape of steel fibers in mortar mixed with steel fibers on the electromagnetic shielding properties and confirmed its reinforcing effect.Within the scope of the study, it was clarified that the mortar can block electromagnetic waves and inhibit electromagnetic communication by incorporating steel fibers, and that sufficient performance as a electromagnetic shielding material can be obtained with the amount of steel fibers incorporated within the range where the reinforcing effect is enhanced. And it was found that the electromagnetic shielding performance tends to increase with the amount of steel fibers blended and with the increase in the aspect ratio of the steel fibers.

The authors have conducted fundamental research on the load transfer function at transverse joints in concrete pavements with polypropylene fiber reinforced concrete（PPFRC）. From the test results, the relationship between the residual shear strength and the residual cracking width after shear cracking, and the shear stiffness were clarified. However, the specimens used in the previous shear tests were prism specimens fabricated using steel formworks. Then, the orientation and dispersion of polypropylene fibers were limited by the wall effect. On the other hand, concrete pavements having large plane shape compared to the slab thickness are not limited in the fiber orientation and dispersion. In this study, the fiber orientation and dispersion, and the size effect on shear strength were evaluated using prism specimens cut from PPFRC square slabs, and the relationship between the residual shear strength and the residual cracking width, and the shear stiffness were investigated.

In this study, uniaxial compression tests were conducted on high-fluidity ductile-fiber-reinforced concrete using recycled aggregate with different water-binder ratios and material age. At the same time, the effect of the restraint of the loading plate on uniaxial compression tests results was also investigated. The compressive softening behavior obtained from the tests was approximated by two straight lines, and the formulation of the necessary material constants was attempted. As a result, it was found that the bi-linear approximated compression softening behavior can be determined for different water-binder ratios and material ages by giving the compressive strength of high-fluidity ductile-fiber-reinforced concrete using recycled aggregate.

The purpose of this study is to investigate the effect of the application techniques of polymer-modified mortars（PCM）on its flexural, compressive and adhesive strengths in the patching work for the reinforced concrete structure. The specimens for those strength tests are prepared by using PCMs at the set aside time after the mixing of 0, 30 and 60 min with or without remixing. The specimens for adhesive strength test of PCM to base concrete are also prepared at 1, 6 and 24 h after treating the surface of the base concrete by water-absorption-controlling material（WACM）, and at the WACM treating surface having the dry to the touch given by different conditions. As a result, the effect of the set aside time on the flexural and compressive strengths of PCM is hardly recognized. The adhesive strength of PCM to the base concrete is decreased with an elapse the set aside time. However, the effect of the remixing of PCM after the set aside time on those strengths is hardly recognized. The adhesive strength of PCM to the base concrete is decreased with an elapse the time after WACM treating for the surface of the concrete. The higher adhesive strength is given for the specimen prepared by 1h after the WACM treating the surface of the concrete having the dry to the touch. The effects of the conditions to give the dry to the touch of WACM treating concrete surface on the adhesive strength of PCM to the concrete is not recognized.

In this study, the formation of silicate gel when reinforced concrete degradation factors such as CO₂ penetrate the concrete pores were investigated to verify the in-tube cohesion phenomenon and its effect on the water penetration of the hardened cement. In vitro, it was confirmed that the penetration of both degradation factors produced silicate gel. The agglomeration mechanism was attributed to decreased pH in the solvent and increased zeta potential due to an increase in electrolyte. Moisture penetration tests of hardened mortar in which carbon dioxide formed silica gel showed a 77％ reduction compared to the normal hardened mortar. Low-temperature DSC was used to capture the gel non-drying and showed that the silicate gel inhibited water penetration into the pores of the hardened cement paste.

It is concerned that salt damage due to water leakage happens at a RC shield transmission tunnel nearby bay area. To prevent this corrosion, gel composed inhibitor have been developed. By this gel, corrosion inhibitor permeates through the concrete surface and guard reinforcement against chloride attack. This gel, however, is optimized for conventional concrete whose W/C is around 55％. In this study, we developed gel composed inhibitor, which is capable of penetrating corrosion inhibitors into concrete whose W/C is lower such as 35％.

As part of the development of technology to reduce CO₂ emissions from cement production process, tests were carried out using CO₂ capturing pilot plant capable of capturing 10t-CO₂/d to search for operating conditions that would enable the reduction of CO₂ recovery energy, which is the biggest challenge for CO₂ capturing technology with amine-based solvent. It was found that increasing the CO₂ concentration in the cement kiln flue gas and reducing the liquid-gas ratio were effective. Further, it was found that CO₂ loading in amine solvent could be the indicator of CO₂ recovery energy because these two operations increased the CO₂ loading in the amine solvent that had contacted with flue gas. These operations resulted in energy savings of up to 11％ in our pilot plant.

Enforced carbonation of recycled cement paste powder for reuse in concrete requires further research such as the physical and chemical properties of the carbonation products and the chemical change over time of CaCO₃, which includes amorphous calcium carbonate（ACC）, vaterite, aragonite and calcite. In this study, semi-dry carbonated cement paste powder was prepared, and the chemical change over time was investigated in a high humidity environment and in an environment mixed with cement paste. As a fundamental study, ACC was synthesized and analyzed by using TG-DTA and TG-MS, which showed that the metastable phase ACC converted to stable calcite at around 350℃, followed by decomposition of calcite from around 500℃. Semi-dry carbonation of cement paste powder resulted in the formation of ACC and calcite at 20℃, and ACC, calcite and vaterite at 80℃. Vaterite in the carbonated samples did not change to stable aragonite or calcite, while most of ACC was converted into calcite crystal under high-humidity environment for 7 days. No significant decrease in the amount of fixed CO₂ was observed. When the carbonated samples were mixed with cement paste, vaterite and ACC in the carbonated samples were changed to calcite after one day. However, no significant decrease in the amount of fixed CO₂ was observed during 7-day hydration.

In recent years, carbonated concrete has been attracting attention and many research are being conducted around the world. When analyzing carbonated concrete, samples are generally absolutely dried before analysis, and the liquid phase is not analyzed. Therefore, in this study, a dissolution test of carbonated paste was conducted and the liquid and solid phases were analyzed. In the carbonated region of the solid phase, calcite was dissolved as the liquid-solid ratio increased, and Calcite precipitated at pH＝12 and Vaterite precipitated at pH＝9. As a result of the liquid phase analysis, carbonate ions were dissolved from the solid and liquid phases, and a maximum of 24kg/m³ of CO₂ was dissolved. In addition, the dissolution of Ca^2＋ and CO₂ in the immersed water showed a positive correlation, and the dissolution rate of CO₂ increased as carbonation progressed.

We conducted research of carbon dioxide fixation behavior and rate of CO₂ diffusion into hardened cement specimens of different pre-curing period before starting accelerating carbonation curing for ordinary portland cement（OPC）, OPC mixed with ground granulated blast furnace slag（BB）, and OPC mixed with an amorphous calcium aluminate based accelerator（ACC）respectively. We prepared two types of hardened cement specimens, the first was in the case of powder shape hardened cement paste specimen which is designed to avoid carbon dioxide diffusion’s influence as much as possible and to evaluate fixation capacity of carbon dioxide, as a result carbon dioxide content increases with getting pre-curing period longer in any cases after accelerating carbonation curing. The other one was in the case of balky mortar specimens which evaluates carbon dioxide diffusion, carbon dioxide diffusion got slower with getting pre-curing period longer in the case of OPC, BB, however ACC’s carbon dioxide diffusion was almost constant even pre-curing period is different. The mineral composition and hydrate before carbonation differed by difference of cement type. Phase diagram after carbonation was also changed. In fact, more vaterite was formed with getting pre-curing period longer in any case, especially its phenomenon was remarkable in ACC system.

Various CO₂ fixation technologies for waste have been developed to achieve carbon neutrality worldwide. Ready-mixed concrete plants generate large amounts of sludge water from the washing of mixers and agitator trucks. As sludge water is rich in CaO, a compound in cement that reacts with CO₂ to form stable minerals, research on using sludge water to sequester CO₂ is underway. In this study, a method of blowing CO₂ gas in the form of microbubbles ranging in size from 1μm to 100μm into sludge water was investigated to establish a more efficient CO₂ fixation method for sludge. Simulated sludge water with a sludge concentration of 2.5wt.％ or 5.0wt.％ was used in the experiments. The investigated method was found to be able to fix CO₂ in sludge water more efficiently than blowing CO₂ bubbles of 14mm diameter. The factors affecting CO₂ fixation are the temperature of the sludge water and its age（sludge water storage period）. Changes in the amount of minerals and hydration products in the sludge water due to CO₂ fixation were also evaluated by Rietveld analysis. Based on the results obtained, the CO₂ fixation efficiency relative to the amount of CaO in the real and simulated sludge water is inferred to be similar under the same conditions of sludge water temperature and sludge age.