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<p>This report was investigated about accuracy of phase composition of cement and cement hydrates in mortar samples when the heavy liquid separation was applied as sample preparation and then the samples were determined by XRD/Rietveld analysis using the internal standard method. Amount of amorphous phase as a part of hardened cement pastes in mortar samples with the heavy liquid separation were compared to mortar samples without the heavy liquid separation and hardened cement paste samples. As a result, it is found that the heavy liquid separation improved accuracy of phase composition of cement and cement hydrates mortar samples.</p>

DOI： 10.2472/jsms.69.416

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<p>Sulfate attack is known as one of the deterioration phenomena of concrete structures. According to previous researches, it has been suggested that the presence of carbonate ion may promote secondary ettringite formation and expansion；however, the details of this hypothesis have not been confirmed by experiments. The purpose of this research is to examine the effects of mixing amount of monocarbonate and curing temperature on thaumasite and ettringite formation. Synthesized monocarbonate and the materials required for thaumasite formation were mixed with deionized water in order to hydrate in the suspension, after which the solid phases after hydration were analyzed. As a result, when a mixture of portlandite, calcium carbonate, amorphous silica, gypsum and a large amount of monocarbonate was mixed and hydrated at 5, 20, 40℃, the amount of secondary ettringite formation was increased with the rise of curing temperature. In particular, the amount of secondary ettringite formation was increased significantly when a large amount of monocarbonate was mixed. It was suggested that the secondary ettringite formation from monocarbonate is strongly affected by the dissolution of CH and the formation of C-A-S-H in the suspensions.</p>

DOI： 10.14250/cement.73.18

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<p>The purpose of this study is to consider the effects of addition of Al and Mg on the formation and crystal of tobermorite. The samples were synthesized in different conditions of curing （autoclave curing or hydration curing at 80℃） and additional materials （gehlenite, akermanite, and gehlenite-akermanite） which are known as industrial by-products. Therefore, this study will contribute in terms of developing sustainable society. As a result, 1.1nm tobermorite which was including Al was generated by addmixing gehlenite or gehlenite-akermanite under high pressure and high temperature condition （autoclave curing）. In addition, the large amount of Al in gehlenite or gehlenite-akermanite replaced Si at bridging site in 1.1nm tobermorite. Furthermore, the interlayer spacing of 1.4nm tobermorite got narrower to 1.1nm without strong drying after 80℃ hydration. This was due to replacing Si to Al in gehlenite, and SiO4 tetrahedra at bridging site was tied together and interlayer spacing got narrower. This result is great step to realize a material design to produce 1.1nm tobermorite in concrete at low temperature. On the other hand, the amount of 1.1nm tobermorite increased by admixture akermanite under high pressure and high temperature condition. But akermanite was hard to react at low temperature condition such as 80℃.</p>

DOI： 10.14250/cement.73.2

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<p>Three-component concrete, in which silica fume is mixed with blast furnace slag cement, has been reported that chloride penetration resistance is greatly improved. Its spread is desired. In this study, silica fume slurry is post-added to a track agitator and the concrete was mixed. The fundamental properties of this concrete were examined. As a result, even if the slurry was added, the decreases in the slump and the air content of the concrete were small. Furthermore, there was no decline in the compressive strength and the coefficient of variation was also small. The bubble spacing factor also shows a sufficiently small value, which suggests that it is possible to add a silica fume slurry with a track agitator to produce a three-component concrete. Furthermore, it is suggested that it is possible to adjust properties of fresh concrete by post-addition of super plasticizers and AE agent.</p>

DOI： 10.14250/cement.73.459

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DOI： 10.3151/jact.17.5.260

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DOI： 10.2472/jsms.68.55

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<p>The purpose of this research is to discuss that the effect of pretreatment drying of monocarbonate and coexisting substances on secondary ettringite formation. As a result, when monocarbonate simple substance was hydrated using an aqueous solution Na₂SO₄, ettringite was not generated. However, when monocarbonate and C-S-H was mixed and hydrated using an aqueous solution Na₂SO₄, the amount of ettringite was increased. And when monocarbonate and C-S-H with a low C/S ratio mixed, it was shown experimentally that amount of ettringite was greatly increased. And from the result of ²⁷Al NMR measurement, the presence of tetracoordinate Al was confirmed only when monocarbonate and C-S-H mixed. Therefore, it was suggested that the change of the chemical form of Al from 6-coordinate of monocarbonate attribution to 4-coordination of C-A-S-H attributed to the formation of ettringite was affected.</p>

DOI： 10.14250/cement.72.33

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DOI： 10.3151/coj.57.11_876

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<p>In order to realize the recycled cement, we are aimed to organize the cycle composed of highly reactive β-C₂S and amorphous C-S-H with a high C/S ratio. By using Double-decomposition method, amorphous C-S-H with C/S＝2.0 were synthesized from sodium-ortho-silicate under the samples which might not contain sodium or natrium in the solid phases. Therefore, this study was performed to reveal the hydration mechanisms of C₂S, derived by heating amorphous C-S-H samples with a high C/S ratio at low-temperature（600℃）. As a result, it was succeeded to obtain amorphous C-S-H not containing CH through the hydration at 80℃, which were similar to the original sample synthesized by Double-decomposition method. Furthermore, another pattern of amorphous C-S-H samples without CH were composed in the case of using sodium-meta-silicate as a starting material. In this process of hydrations, Wollastonite was hydrated because of its high pH in the solution and high specific surface by N₂-BET.</p>

DOI： 10.14250/cement.72.18

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<p>This study was conducted from the viewpoint of chemical composition and Al bonding state of the sample in order to clarify the promotion mechanism of the secondary ettringite formation due to the coexistence of C-S-H. As a result of mixing the synthesized monosulfate and the various coexisting materials using sodium sulfate solution, when C-S-H coexisted with monosulfate, the amount of the secondary ettringite formation remarkably increased regardless of drying conditions. This promotion phenomenon of the secondary ettringite formation due to the coexistence of C-S-H did not occur when the calcium hydroxide and the amorphous silica coexisted at the same C/S ratio as C-S-H. On the other hand, only when C-S-H coexisted, the peak of the four-coordinate Al indicating the formation of C-A-S-H was confirmed in the ²⁷bAl NMR spectra. Therefore, when a similar experiment was carried out with C-A-S-H coexisting sample, it was confirmed that ettringite was formed the same amount as the case of C-S-H coexistence, whereas a large amount of monosulfate remained. From these facts, it was considered that ettringite is likely to form from four-coordinate Al and C-S-H promotes the secondary ettringite formation in order to convert six-coordinate Al to four-coordinate Al by substituting Al in the silicate chain.</p>

DOI： 10.14250/cement.72.25

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<p>Sulfate attack is known as one of the deterioration phenomena of concrete structures. In particular, there is a serious problem with expansion due to Delayed Ettringite Formation（DEF）. Recent researches had indicated the possibility that CO₃^2－ promotes DEF expansion. Therefore, we focused on understanding carbonate ettringite, in which ettringite substitutes SO₄^2－ for CO₃^2－, despite it has never detected in hardened cement. Our purpose is to discuss the relationship between the secondary formation of ettringite and Al bonding state, by comparing ettringite and carbonate ettringite.<br/>From the experimental results, thermal dehydration converted carbonate ettringite into amorphous carbonate ettringite, as shown by XRD, while Al coordination of dehydrated carbonate ettringite was 4 and 5. In addition, water adsorption isotherm of dehydrated carbonate ettringite showed a sharp rise at RH60-80％. It is possible that carbonate ettringite formed as a secondary carbonate ettringite when Al coordination number was 4 or 5, and up to 6, by water supply. Therefore, it is concluded that dehydrated carbonate ettringite has large potential of swelling compared to carbonate ettringite.</p>

DOI： 10.14250/cement.72.40

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DOI： 10.3151/jact.16.587

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DOI： 10.2472/jsms.67.884

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Nowadays, high-durability has been required in concrete structures that assume long term-service. Therefore, generation of tobermorite in the concrete has been important for the material design of high durability concrete. The purpose of this research is to evaluate the effect of the addition of high volume CaO-MgO-SiO2-based materials with autoclave curing for the generation of tobermorite, and to clarify the generation mechanism of tobermorite from the view point of the hydration reaction of materials at heating process in autoclave curing. As a result, generation of tobermorite was increased by using high volume CaO-MgO-SiO2-based materials. It is because that C-S-H with high CaO/SiO2 ratio was maintained, since the reaction of the α-quartz at heating process in autoclave curing was suppressed by substitution of CaO-MgO-SiO2-based materials.

DOI： 10.2472/jsms.66.199

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DOI： 10.3151/coj.55.3_217

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DOI： 10.2208/jscejmcs.73.82

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<p>The purpose of this study is to evaluate the water vapor adsorption and desorption of hardened cement paste by water vapor adsorption and desorption model based on Calcium silicate hydrate（C-S-H）. The relation between the composition and water vapor adsorption and desorption was investigated using C-S-H and various cementitious materials. In this results, it was clarified that water vapor adsorption and desorption of C-S-H is affected by Ca/Si ratio. In addition, the water content of adsorption and desorption in low relative humidity was not same values, and showed the hysteresis. The water vapor adsorption and desorption of hardened cement paste also showed the same tendency.<br/>Moreover, the water vapor adsorption and desorption model of C-S-H was proposed. The model has been considered the difference of Ca/Si ratio, and has been divided into interlayer water, surface water and gel water. The calculated value of water vapor adsorption and desorption evaluated by the model was good agreement with former research's results. To verify the applicability and the accuracy of model of C-S-H, the model was compared with the water vapor adsorption and desorption of dried hardened cement paste on various relative humidity. In this results, the calculated value of water vapor adsorption and desorption evaluated by the model was good agreement with the experimental value of hardened cement paste in the low relative humidity and high relative humidity. Furthermore, the scanning loop of water vapor adsorption and desorption can be estimated by the proposed model.</p>

DOI： 10.14250/cement.70.154

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<p>Electrochemical non-destructive inspection of steel corrosion need to use electric equivalent circuit model. But, electric attribute of hardened cementitious materials changes according to changes in the materials and compounding, and relationship between electric equivalent circuit model and materials and compounding has not been clarified. Therefore, this study was performed to find out effects of pore structure and ion composition of pore solution on electric equivalent circuit model of hardened cementitious materials. We examined the effects of the pore structure and the ion composition of the pore solution on the electric equivalent circuit model of hardened cementitious materials.<br/>There was the difference between electric resistivity of extracted pore solution and that of pore solution in paste specimen. We showed that this difference can be evaluated by the pore structure and the ion composition of the pore solution. Charge transfer resistance and electric double layer capacity on the interface between the rebar and the liquid phase are affected by the area of the interface between the rebar and the liquid phase and the ion composition of the pore solution. Therefore, we showed that the charge transfer resistance and the electric double layer capacity could be evaluated by the pore structure and the ion composition of the pore solution.</p>

DOI： 10.14250/cement.70.185

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<p>It is necessary to evaluate the chloride attack environment for durability design and maintenance of the structure under marine environment.<br>The amount of salt penetration into the concrete structure is influenced by weather conditions and neighboring topography. Chloride attack environment also depends on the shape and the dimension of structures. However, these effects have not been clarified.<br>Although many researches about chloride attack caused by airborne salt had been conducted in past time, most of those were related to macro environment. Then we have not done so many studies focused on the shape and the dimension of structures. Under such circumstances, the exposure test using thin plate mortar specimens was conducted on the wheel guard in each span and the beam of a bridge which is located in the coastal area.<br>As a result, it is confirmed that amount of airborne salt penetration into the structure is influenced by neighboring topography and weather conditions, and it can be evaluated that the deterioration condition of each span of the structure by short term exposure test using the thin plate mortar specimens. By the thin mortar exposure test, micro chloride attack environment can be evaluated, and that qualitative trend can be evaluated by analysis of wind field.</p>

DOI： 10.14250/cement.70.413

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<p>Sulfate attack is known as one of the deterioration phenomena of concrete structure. Especially, expansion due to delayed ettringite formation（DEF）has been serious problem nowadays. According to previous researches, continuous water supply and temperature history above 70℃ are needed for DEF expansion. However, DEF expansion mechanisms are still unclear. Therefore, the purpose of this research is to discuss that behavior of water molecules and structural changes of ettringite in relation to the mechanism of DEF and expansion in terms of dehydration and rehydration of ettringite.<br/>From the experimental results, after dehydration by heating above 80℃ 12 hours, water molecules bonded to SO₄^2- in ettringite structure were removed and dehydrated ettringite was amorphous on XRD；ettringite was converted into meta-ettringite. Furthermore, the amount of water desorption isotherm in rehydrated meta-ettringite was decreased significantly about R.H. 15％. In addition, reduction of density of rehydrated meta-ettringite were observed. Therefore, there were possibility that rehydrates of meta-ettringite possibly have ink-bottled pores of nanometer scale and closed pores.</p>

DOI： 10.14250/cement.70.2

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This study was conducted to investigate the expansion characteristics of mortar specimens during water immersion test, considering "Ettringite (Ett) -generating origin" in cement paste specimens. Specifically, the expansion characteristics of mortar specimens were estimated, suggesting Ett production for each constituent mineral estimated by XRD-Rietveld and selected dissolution methods as an indicator. Results shows that the expansion characteristics of mortar specimens could require not only simple Ett production change evaluation before and after water immersion, but also the evaluation, considering the generation cite of Ettringite and coexisting materials such as C-S-H around Ettringite.

DOI： 10.2472/jsms.64.463

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Calcium silicate hydrate (C-S-H) is a dominant hydration product of cementitious materials. Therefore, its chemical composition and physical properties affect the performance of concrete. The purpose of this study is to investigate the chemical composition (CaO/SiO2 molar ratio (Ca/Si ratio), and H2O/SiO2 molar ratio (H2O/Si ratio)) and physical properties, such as density and specific surface area, of C-S-H. These factors are measured using synthesized C-S-H samples and C-S-H generated from various cementitious materials. Experimental results show that the H2O/Si ratio of C-S-H is proportional to the Ca/Si ratio independent of the mix proportion, curing temperature and type of binder. The density and specific surface area of C-S-H are affected by its Ca/Si ratio. A linear relationship is observed between the Ca/Si ratio and density of C-S-H independent of the mix proportion, curing temperature and type of binder. An inversely proportional relationship is found between the Ca/Si ratio and specific surface area of C-S-H.

DOI： 10.3151/jact.13.275

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This research proposes a future maintenance plan based on the soundness evaluation through the investigation of concrete and steel properties of 15 years old PC road bridge in severe chloride environment. In this research, investigation of degradation situation from the construction, evaluation of the environmental action of chloride by measuring the salinity of the mortar piece stuck on the concrete surface, measurement of air permeability and water distribution near the concrete surface are performed in order to quantitative evaluation of the properties in connection with the durability of this concrete structure. As a result, although this bridge has some problems resulting from material, or construction, and subsequent maintenance, it was clarified that it is possible to operate this bridge continuously through the future strategic maintenance.

DOI： 10.2208/jscejmcs.71.161

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Nowadays, the sulfate attack on concrete structures is one of the serious problems in the Middle East region. On the other hand, rate of C3A and C4AF in cement clinker has increased, related with the increase of amount of industrial-by-product. Therefore, the purpose of this research is to evaluate the sulfate resistance of specimens mixed with C4AF and gypsum after autoclave curing. The influence of C4AF and gypsum on the formation mechanisms of tobermorite also have been examined by X-ray diffraction analysis and FT-IR. As the result of sulfate immersion test, the results of length change ratios of specimens with autoclave curing were much better than specimens with water curing. At low additional ratio of C4AF, tobermorite peak was detected by X-ray diffraction analysis. On the other hand, tobermorite peak was not detected at high additional of C4AF, and the frequency of 980cm-1 and 1,050cm-1 was confirmed by FT-IR. Therefore, improvement of sulfate resistance for the specimens with autoclave curing is due to the generation of tobermorite at low additional ratios of C4AF and the generations of Si structures like tobermorite at high additional ratios. Also, the formation of tobermorite was increased by the addition of gypsum, and the generation of hydroxyl-ellestadite that is intermediate during autoclave curing of tobermorite was suggested at specimens mixed with gypsum.

DOI： 10.14250/cement.69.110

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It has been the problem to control maintenance, and construct civil structures for long-term. It is considered that concrete after long-term exposure decrease performance by changing properties of cement hydrates, however, there are few studies on analyzing the concrete after long-term exposure. In this study, chemical analysis of the cement hydrates in concrete long-term exposure was conducted. And it is difficult to analyze for concrete by aggregate influence, thus a method of aggregate separation that separate aggregate and cement paste was established in order to eliminate the effect of the aggregate in performing chemical analysis for concrete. The method made chemical analysis in concrete sufficiently accurate.<br/>Therefore, using the method, chemical analysis of the railway bridge concrete built in 1923, and long-term exposure was conducted. It is considered that cement in the railway bridge concrete have low C3S and high C2S composition, because the railway bridge built in 1923. From the experimental results, the small amount of calcium hydroxide was produced in the railway bridge concrete. In constrast, calcium carbonate was produced especially in the surface. Hence, not calcium hydroxide but rather C-S-H was carbonated mainly. And in the surface, by carbonation and solar insolation and others, calcium carbonate and dehydrated condensation amorphous silica was produced, therefore specific surface area in paste impaired.

DOI： 10.14250/cement.69.257

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Calcium silicate hydrate（C-S-H）is a dominant hydration product of cementitious materials, hence its chemical composition and physical properties also affect the properties of concrete. In particular, the formation of microstructure and diffusion of ion were influenced by the specific surface area of C-S-H. Therefore, to accurately evaluate the performance of concrete, it is important to clarify the specific surface area of C-S-H, which is a dominant hydration product of cementitious materials. Moreover, in the case of use of mineral admixture such as blast furnace slag and fly ash, it is known that Si in C-S-H was substituted for Al. However, physical properties of Al substituted C-S-H have not been clarified.<br/>The purpose of this study is to estimate the relationship between chemical composition（Ca/Si ratio and Al/Si ratio）and specific surface area of C-S-H. The relationship between the composition and specific surface area of C-S-H will also be investigated using synthesized C-S-H, C-A-S-H（Al incorporated C-S-H）and that generated from various cementitious materials. Experimental results show that the amount of adsorbed water and specific surface area of synthesized C-S-H and C-A-S-H are affected by its Ca/Si ratio and Al/Si ratio. The low Ca/Si ratio C-S-H is greatly affected by the effect of Al incorporation for specific surface area. The specific surface area of C-S-H generated from blast furnace slag and fly ash is greater than that from Ordinary Portland Cement. The result of various cement paste show same tendency as that of synthesized C-S-H and C-A-S-H.

DOI： 10.14250/cement.69.37

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Sulfate attack is grouped into two general categories. One is transformation of hydration products, and another is sulfate ion transfer. There are a lot of studies on transformation of hydration products. However, there are few studies on sulfate ion transfer. Considering sulfate ion transfer is absolutely imperative to predict the deterioration rates of concrete. In addition, ettringite that is the principal hydration products of sulfate attack has a large specific surface area, therefore, ettringite has a potential impact on the microstructure of concrete if a large amount of ettringite is generated in concrete. Thus, the experimental evaluation of sulfate ion transfer and the clarification of effects of ettringite on the microstructure are needed for investigate.<br/>In this study, sulfate ion effective diffusion coefficient, porosity, and the amounts of hydration products of hardened cementitious paste after sodium sulfate solution immersion were measured. Tortuosity of sulfate ion, which was an index expressing sulfate ion migration path length affected by the microstructure, was calculated.<br/>From the experimental results, sulfate ion effective diffusion coefficient was decreased by using 70％ blast furnace slag-cement with 10％ anhydrite and 10％ limestone powder. The sulfate ion effective diffusion coefficient was correlated with the sulfate ion tortuosity. The sulfate ion tortuosity could not be estimated using the amount of C-S-H, empty pore volume and the specific surface area of C-S-H. In contrast, it could be estimated using the amount of ettringite and the specific surface area of ettringite, in addition to C-S-H. Hence, it was suggested that ettringite has a potential impact on the microstructure of concrete causing sulfate attack.

DOI： 10.14250/cement.69.417

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DOI： 10.3151/coj.52.399

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The performances of concrete are influenced by the microstructure of hardened cement paste. The microstructure of hardened cement paste is affected by the hydration products. Therefore, in order to evaluate the characteristics of the microstructure of hardened cement paste, the physical properties of hydration product should be clarified accuracy.<br/> The purpose of this study is to evaluate the influence of each relative humidity and temperature on the chemical composition and density of C-S-H. The composition（C/S ratio, the H/S ratio） and the density of C-S-H at each relative humidity and temperature were estimated by using synthesized C-S-H. Two C-S-H samples were synthesized. The target C/S ratios were 1.00 and 1.25. Furthermore, the amount of adsorbed water, the density and composition of C-S-H in hardened cement paste also were measured.<br/>From the experimental results, the water content of C-S-H under high relative humidity is same value independent of the drying condition（50℃ or 110℃）. When the C/S ratio of synthesized C-S-H decreased, the water content at each relative humidity of C-S-H increased. The density of C-S-H dried at 50℃ was higher than that dried at 110℃. The density of C-S-H was increased by increasing in relative humidity. Furthermore, the density of C-S-H at about RH80％ represented the maximum value. From these results, the density of C-S-H was expressed by the H/S ratio independent of the drying condition（50℃ or 110℃）. The change of density at each relative humidity was expected to cause the change of the interlayer structure in C-S-H. As with the results of synthesized C-S-H, the density of hardened cement paste changed at each relative humidity. In addition, the density of hardened cement paste at each relative humidity was evaluated by the amount and density of C-S-H in hardened cement paste.

DOI： 10.14250/cement.67.157

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It is important for durability evaluation of reinforced concrete structure to predict the ions transport in concrete quantitatively. For example, in order to evaluate the durability against salt attack, the model for predicting the diffusivity of chloride ions in the concrete is required. The effective diffusion coefficient of chloride ions is needed in the model.<br/>In general, the migration test and the diffusion cell test are performed to estimate the effective diffusion coefficient in Japan. However, the diffusion coefficients obtained from these tests are not the same. It is considered that the micro-structure and the electrical properties of the pore in hardened cementitious materials affect the effective diffusion coefficient. The authors focused on zeta potential as the approximate value of the pore surface potential.<br/>In this study, the effective diffusion coefficient of chloride ions obtained by the migration test was defined as D_mig, and the effective diffusion coefficient obtained by the diffusion cell test was defined as D_diff, and（1）the effective diffusion coefficient of chloride ions was measured in two ways：migration test and diffusion cell test,（2）the measurement of zeta potential was carried out by the electro-osmosis test.<br/>As the result, the values of D_mig and D_diff were not the same. It was confirmed from the experimental results that the micro-structure and the electrical properties of pore surface affected these diffusion coefficients. In particular the migration test was affected only by the influence of the micro-structure in hardened cementitious materials, the diffusion cell method was affected by both the electrical properties and void structure.<br/>Further, the ratio：D_diff/D_mig was defined as an evaluation index of electrical impact, compared with zeta potential of the hardened cementitious materials.<br/>It was confirmed that the diffusion coefficient obtained the diffusion cell method can be calculated by using the diffusion coefficient obtained by the migration test and zeta potential.

DOI： 10.14250/cement.67.378

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It is known that environmental condition affects carbonation progress of concrete. The effects of environmental condition on carbonation rate are not the same in the same structure. Therefore, the depth of carbonation at various points is not same even in the same structure. It is important to evaluate the effect of environmental condition on the carbonation progress.<br/>The purpose of this study is to evaluate the influence of environmental conditions on the carbonation process of concrete structure. Exposure tests of mortar thin plate for 3 months were conducted 4 times a year on various points in two bridges and four structures in water purification plants. The effects of mix proportion and exposure season were studied. After exposure, the amount of CaCO₃ and water content in the plate specimen were measured. The carbonation depth in each part of the structure was closely related with the amount of CaCO₃ in the specimen exposed at the same point. Furthermore, the carbonation depth can be predicted from the amount of CaCO₃ in the mortar thin plate specimen.<br/>The conclusions obtained in this study are as follows. （1）The effect of environmental condition on carbonation progress can be evaluated using mortar thin plate specimen is exposed to the part where is not affected by rainfall. （2）Mix proportion that is higher carbonation rate is suitable to evaluate carbonation progress. （3）When mortar thin plate specimens were exposed to actual environment in period with little rainfall, the accuracy of evaluation of carbonation environment is better than exposure test in period with large rainfall.

DOI： 10.14250/cement.67.370

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Sulfate attack is known as one of the deterioration phenomena of concrete structures. Sulfates react chemically with hydration products of cement pastes and lead expansion or weakning of cement matrix. Deterioration cases of this phenomenon have been reported in a variety of environments all over the world. However, most of studies about sulfate resistance of hardened cementitious materials were mainly considered at 23 degrees Celsius in Na₂SO₄ solution immersion. Thus, this study was conducted to investigate the influence of environmental condition（submerged temperatures：20 and 40 degrees Celsius, and sulfate types：Na₂SO₄ and MgSO₄） on sulfate attack of cementitious materials containing Ordinary Portland Cement（OPC） with Blast Furnace Slag（BFS）, anhydrite（AH：CaSO₄）, lime stone powder（LSP：mostly CaCO₃）, fly ash（FA） and silica fume（SF）, and to design a cementitious material with resistance for Na₂SO₄ and MgSO₄.<br/>From the experimental results, the deterioration by both Na₂SO₄ and MgSO₄ solutions became severe when the temperature of solution was 40 degrees Celsius. Also, the deterioration due to Na₂SO₄ solution was mainly expansion of the paste specimens, while MgSO₄ solution mainly caused mass decrease and scaling of specimen surface. This was considered that hydration products in MgSO₄ solution were different from that of Na₂SO₄ solution because the pH of the sulfate solutions was influenced from the difference of sulfate types. In addition, the comprehensive sulfate resistance was improved by adding BFS, AH and LSP to OPC. The best sulfate resistance was found for BFS/OPC ratio＝70：30 with AH5～10％ - LSP10％.

DOI： 10.14250/cement.67.348

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Nowadays, in the Middle East region where sulfate is abundantly found in soil, the sulfate attack on concrete structures is one of the serious problems. On the other hand, in japan, the utilization of industrial-by-product for cementitious material is required from the viewpoint of environmental protection and forming recycling society. Ca-Mg-Si based materials can be generated from industrial-by-products such as Steelmaking slag. However, Ca-Mg-Si based materials are not being used yet. Consequently, the using of Ca-Mg-Si based materials is contributes to the reduction of the environmental burdens and economical load. Therefore, the purpose of this study was to establish the material design of the high durability of cementitious material using Ca-Mg-Si based materials. In this study, the sulfate resistance of the hardened bodies formed by autoclave curing or underwater curing, using cement, silica powder, and Ca-Mg-Si based materials, such as Akermanite and Merwinite, was examined. Then, porosity, length change ratio from sulfate immersion test was measured. And identification of product materials inside hardened body based on XRD was done.As the experimental results, in the cases of 40％ Ca-Mg-Si based materials substitution ratio with underwater curing, the length change ratios had the values that lower than 0.1％. Furthermore, in the cases of specimens formed by Ca-Mg-Si based materials with autoclave curing, the length change ratios were quite lower values that less than 0.07％. This is due to the generation of tobermorite at low substitution ratio and Si structure like tobermorite at high substitution ratio.

DOI： 10.14250/cement.67.38

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DOI： 10.2208/jscejmcs.70.134

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Recently, the demand for precast concrete have been increased with the object for construction, productivity, quality control and the shortening of a construction period. In addition, the study for compressive strength of fly ash concrete under the steam curing has been investigated. However the effect of various condition such as, temperature history and curing condition（water curing or air curing）after steam curing on concrete performance has not been clarified. With regard to the Fly ash concrete cured in temperature history, the study of compressive strength under long term curing age has not been enough.<br/>From the background, the relation between the phase composition and compressive strength of Fly ash concrete was investigated in this study. In order to clear the effect of the replacement of Fly ash for compressive strength under the period early age between long term ages, the phase composition of hardened Fly ash cement paste was measured. Furthermore, in order to evaluate the effect of the curing condition after the temperature history, the relation between phase composition and compressive strength cured at water curing or air curing were investigated by Gel/Space ratio.<br/>From these experimental results, the compressive strength of Fly ash cement paste cured at water curing after the temperature history was increased until the age of 365 days. The reaction ratio of Fly ash in cement paste cured at water curing was increased until the age of 365 days. On the other hand, the reaction ratio of Fly ash in cement paste cured at air curing was slightly increased until the age of 365 days. A high correlation is observed between the phase composition and the compressive strength independent of the temperature history and type of binder. Therefore, the compressive strength of hardened cement paste cured at water curing and air curing was evaluated by the relation between phase composition and compressive strength. From these results, the compressive strength of cement paste cured at air curing after the temperature history was not increased until the age of 365 days.

DOI： 10.14250/cement.68.156

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The purpose of this study is to clarify the reason of the decrease of the chloride ion effective diffusion coefficient of the concrete using both of blast furnace slag and silica fume, and the effect of the qualities of the silica fume on the chloride ion effective diffusion coefficient. Chloride ion effective diffusion coefficient and oxygen diffusion coefficient of mortar specimens using various silica fume were measured. The porosity, the amount of C-S-H and the C/S ratio of C-S-H were also measured.<br/>From the experimental results, the reason of the decrease of diffusion coefficients of the specimen due to silica fume can be explained by the decrease of the C/S ratio of C-S-H. The effect of silica fume on diffusion coefficients can be estimated the ability to decrease the C/S ratio of C-S-H.

DOI： 10.14250/cement.68.352

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Sulfate attack is known as one of the deterioration phenomena of concrete structures. Sulfates react chemically with hydration products of cement pastes and lead expansion or weakening of cement matrix. Deterioration cases of this phenomenon have been reported in a variety of environments all over the world. However, most of studies about sulfate resistance of hardened cementitious materials were mainly considered at 23℃ in Na₂SO₄ solution immersion. Thus, this study was conducted to investigate the effect of sulfate species（Na₂SO₄ and MgSO₄）and high temperature（40℃）on the mechanisms of sulfate attack of cementitious materials containing Ordinary Portland Cement（OPC）with Blast Furnace Slag（BFS）, Anhydrite（AH）and Limestone Powder（LSP）, and to evaluate the expansion characteristics of specimens immersed sulfate solutions considering "Amount of ettringite", "Ettringite generation rate" and "Ettringite generation origin".<br/>From the results of sulfate immersion test, the expansion was caused due to Na₂SO₄, however not only expansion but also mass decrease were caused due to MgSO₄. This was considered that hydration products in each sulfate solution were different because of pH differences of sulfate solutions were occurred by the difference of sulfate species. And the expansion characteristics of the specimens were not evaluated by only simple amount of ettringite, however it became able to evaluate considering the ettringite generation rate and ettringite generation origin. In addition, the paste specimen of 70％ BFS-cement with 10％ AH and 10％ LSP（BFS 59.5％-OPC 25.5％-AH 10％-LSP 10％）was proposed a material design against sulfate attack.

DOI： 10.14250/cement.68.396

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The purpose of this research is to evaluate the effect of using Ca-Mg-Si-based materials and autoclave curing to the sulfate resistance, and clarify the mechanism of sulfate resistance from the view point of the hydration quantitative analysis, FT-IR and ²⁹Si NMR. As a result, the sulfate resistance was improved by the Ca-Mg-Si-based materials substitution with autoclave curing. In addition, the generation of Mg-tobermorite could possibly contribute to the sulfate resistance in the case of raw Ca-Mg-Si-based materials substitution ratios, while C-M-S-H with low C/S ratio and high-polymerized silicate chains could possibly contribute to the sulfate resistance in the case of high Ca-Mg-Si-based materials substitution ratios.

DOI： 10.14250/cement.68.2

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The electro migration test is commonly used to obtain the effective diffusion coefficient of chloride ion in hardened cementitious materials. Other hands, if the saturated porous material, which has the electrically-charged pore surface, is applied a voltage, the electro osmotic flow is generated in pore. Additionally, surface of hydration products is charged by the reaction of surface complex between ions in pore solution and the surface functional group, such as silanol group. Therefore, it is considered that the chloride ion transport at the electro migration test is affected by electro osmotic flow. However, the influence of electro osmotic flow on chloride ion transport at the electro migration test is not studied by previous research.<br/> In this study, the flux of chloride ion and the electro osmotic velocity generated by the electro migration test were measured. From the results, the electro osmotic velocities between paste and mortars were different. In addition, the electro osmotic velocity had the correlation with gel porosity of hardened cementitious materials. The influence of electro osmotic flow on chloride ion transport at the electro migration test was different for different types of binder, paste and mortar.

DOI： 10.14250/cement.68.360

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The Standard Specifications for Concrete Structures were revised and published by the Japan Society of Civil Engineers in December 2012. This paper describes the major revised points in "Materials and Construction."

DOI： 10.3151/coj.51.493

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DOI： 10.14250/cement.66.167

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DOI： 10.14250/cement.66.182

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DOI： 10.14250/cement.66.189

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Recently great demand for precast concrete members has increased due to the construction ability, productivity, quality control and shortening of construction period. On the construction of precast concrete members, steam curing is the most popular technique to be applied since the process requires high compressive strength at early stage. In this study, fly ash concrete has been used to increase the performance of concrete. Performing the tests on the concrete and the cement paste under different curing conditions, this research investigates temperature control effect, compressive strength and reaction characteristics. The paper concludes that fly ash concrete shows the great advantages under steam curing and it can be used to precast concrete members.

DOI： 10.14250/cement.66.359

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DOI： 10.14250/cement.66.197

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DOI： 10.14250/cement.66.452

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DOI： 10.14250/cement.66.159

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DOI： 10.14250/cement.66.485

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DOI： 10.14250/cement.66.175

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In this study, the diffusion coefficients of oxygen and chloride ions in the hardened cementitious materials using silica fume, granulated blast-furnace slag and fly ash were measured. From the experimental results, the oxygen diffusion coefficients of various mixtures were different depended on the kinds of binder even if the pore volume was the same. In particular, the oxygen diffusion coefficients of the specimen using the mineral admixtures were smaller than that of the specimen using only the Ordinary Portland Cement. In comparison with the diffusion of oxygen gas, the diffusion of chloride ions varies markedly depending on the kind of binder. The chloride ion diffusion coefficients of various materials can be evaluated in consideration of the microstructure and the electric property of concrete.

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C-S-H is a dominant hydration product of cementitious materials. Therefore, its chemical composition and physical properties affect the properties of concrete. However, the composition and the properties of C-S-H, and the relation between both have not been completely clarified. In order to evaluate the concrete performance accurately, the physical properties of concrete should be evaluated accuracy. Therefore, it is important to clarify the chemical composition and the physical properties of C-S-H. <br/>The purpose of this study is to clarify the chemical composition（the C/S ratio and H/S ratio）and specific surface area of C-S-H. The C/S ratio, the H/S ratio and the specific surface area of C-S-H were estimated by using synthesized C-S-H and C-S-H generated from synthesized alite paste. In addition, the specific surface area of calcium hydroxide and calcium aluminate hydrates were estimated by synthesized hydration products. Furthermore, the specific surface area of hardened cement paste was measured.<br/> From the experimental results, the H/S ratio of C-S-H under each relative humidity is proportional to the C/S ratio independent of the mix proportion and curing temperature. From these results, the relation equation between the C/S ratio and specific surface area of C-S-H is proposed. Moreover, the specific surface area of hardened cement pastes can be estimated by the amount of hydration products and each specific surface area of hydration products.

DOI： 10.14250/cement.65.103

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The purpose of this study is to improve the concrete durability by using silica fume. The apparent diffusion coefficients of chloride ion of silica fume concrete were measured. Silica fume was effective in reduction of apparent diffusion coefficients of chloride ion. The replacement ratio of silica fume 8％ was more effective in reduction of apparent diffusion coefficients of chloride ion than 4％. In order to clarify this mechanism, the diffusion coefficients of oxygen and pore size distribution were measured. There is a good correlation between apparent diffusion coefficients of chloride ion and diffusion coefficients of oxygen. From this result, it was confirmed that the reduction of apparent diffusion coefficients of chloride ion was brought about by microstructural change by using silica fume. Silica fume was effective in reduction of pore volume which had more than 10nm in diameter. The reduction of apparent diffusion coefficients of chloride ion was caused by reduction of the pore volume. In addition, the time to steel corrosion initiation in silica fume concrete was estimated by using apparent diffusion coefficients of chloride ion which was measured in this study. In this estimation, the critical total chloride concentration was calculated using Cl^－/OH^－ ratio, OH^－ ion concentration in pore solution and chloride binding capacity. As a result, the time to steel corrosion initiation in silica fume concrete was longer than the time in OPC concrete.

DOI： 10.14250/cement.65.360

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DOI： 10.14250/cement.64.346

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DOI： 10.14250/cement.64.354

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C-S-H is dominant hydration product of cement. Therefore, the densities of C-S-H are precious fundamental property. For example, the density of C-S-H is needed to calculate the porosity of hardened cement paste. In researches, the values of the C-S-H density are different.<br/>The purpose of this study is to clarify the density of C-S-H formed by hydration of cementitious materials. In this study, synthesized C-S-H and alite paste, blast furnace slag - calcium hydroxide paste were used. Two kinds of synthesized C-S-H were used for the experiment. A kind of C-S-H was contained aluminum and another was not contained. Densities of the synthesized C-S-H and the C-S-H generated by the hydration of alite and blast furnace slag were measured. The densities of C-S-H were calculated based on density and phase composition of hardened cement pastes. Furthermore, CaO/SiO₂ molar ratios of the C-S-H in all were measured. Moreover, Effect of temperature and water to binder ratio were studied.<br/>Density of C-S-H depended on CaO/SiO₂ molar ratio of C-S-H. The density of C-S-H increased with increasing of CaO/SiO₂ molar ratio of C-S-H. The relation between density and CaO/SiO₂ molar ratio was formulated as a linear equation. This relationship was independent of source of C-S-H.

DOI： 10.14250/cement.63.70

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The purpose of this study is to improve the concrete durability by using silica fume. The effective diffusion coefficients of the chloride ions of silica fume concrete were measured. Silica fume was effective in reduction of diffusion coefficient of chloride ions. Over a range of cement replacement ratio of silica fume from 4％ to 8％, the effective diffusion coefficient was independent of silica fume content. Therefore, the replacement ratio of silica fume 4％ is more desirable than 8％ from a viewpoint of cost. Over a range of cement replacement ratio of fly ash from 15％ to 30％, there were little reduction of the effective diffusion coefficient. Therefore, Silica fume was more effective than fly ash. If the effective diffusion coefficients were the same range, the water-binder ratio of silica fume concrete was higher than that of OPC concrete. In order to evaluate the durability of silica fume concrete comprehensively, the adiabatic temperature rise and the autogeneous shrinkage were measured. The adiabatic temperature rise of silica fume concrete was lower than that of OPC concrete when the effective diffusion coefficients were same. And the autogeneous shrinkage of silica fume concrete was also lower than that of OPC concrete when the effective diffusion coefficients were same. The crack risk of silica fume concrete may be expected to decrease when the resistance to chloride penetration is the same as OPC concrete.

DOI： 10.14250/cement.63.414

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It is important for service life prediction of concrete structures to estimate mass transport in concrete accurately. Mass transport in concrete depends on the microstructure of concrete. The microstructure of concrete is affected by addition of mineral admixtures, such as ground granulated blast-furnace slag and fly ash.<br/>The microstructure of concrete is affected by the amounts and kinds of hydration products. C-S-H is dominant hydration products. Ca/Si molar ratio of C-S-H depends on types and replacement ratio of mineral admixtures, water to binder ratio and curing period. Physical and electrochemical properties of C-S-H are affected by Ca/Si ratio.<br/>In this study, the effect of Ca/Si molar ratio of C-S-H on chloride diffusion was studied. Chloride diffusion coefficient, pore size distribution, and the amount of hydration products of hardened cementitious paste were measured. And the zeta potential of hardened cementitious paste and synthetic C-S-H was measured.<br/>'Microstructure characterization factor' which was an index expressing complexity of microstructure was defined. It was calculated from a chloride diffusion coefficient, self-diffusion coefficient and total pore volume. From the experimental results, the relation between 'the microstructure characterization factor' and the surface area of C-S-H per unit volume of hardened cementitious paste which was calculated by the amount of C-S-H and the specific surface area of C-S-H in consideration with Ca/Si molar ratio, was studied.<br/>The tendency that 'the microstructure characterization factor' became large as the surface area of C-S-H per unit volume of hardened cementitious paste became larger was shown. Moreover, the effect of electric property of pore surface on chloride ion diffusion was considered. The zeta potential of C-S-H was changed due to Ca/Si molar ratio. When Ca/Si molar ratio of C-S-H was low, physical and electric resistance increased. Therefore, chloride diffusion coefficient became small. 'The microstructure characterization factor' can be estimated using the zeta potential and the surface area of C-S-H per unit volume of hardened cementitious paste.

DOI： 10.14250/cement.63.354

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DOI： 10.2208/jsceje.66.1

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DOI： 10.2208/jsceje.66.528

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This paper describes the effect of Ca/Si molar ratio of C-S-H on concrete durability. Concrete durability depends on the physical and chemical properties of concrete. The physical and chemical properties of concrete are affected by the kinds and amounts of hydration products. C-S-H is dominant hydration product. And, Ca/Si ratio of C-S-H depends on types of mineral admixtures, mixture proportion and curing period. Therefore, it is important for estimating of concrete durability to clarify the properties of C-S-H. In this study, physical properties, such as density and surface area, of C-S-H with various Ca/Si ratios were measured. And chemical properties, such as chloride binding capacity and releasing due to carbonation were also measured. From the experimental results, physical and chemical properties of C-S-H depend on Ca/Si ratio. Based on these results, the effect of Ca/Si ratio of C-S-H on concrete durability, such as chloride diffusion and chloride binding was examined. The durability of blended cement concrete can be explained qualitatively in consideration of Ca/Si ratio of C-S-H. © 2007 The Society of Materials Science.

DOI： 10.2472/jsms.56.699

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN CONCRETE INST  

It is well known that mineral admixtures, such as granulated blast-furnace slag and fly ash, control the ingress of chloride ions into concrete. However, the effects of the qualities and the replacement ratios of these admixtures on the diffusivity of chloride ions are not clear. Moreover, the micro-structure of concrete is changed by carbonation and change in microstructure affects mass transfer in concrete. This effect on the chloride diffusivity of concrete using mineral admixtures has not been clarified sufficiently.
Therefore, in this study, the chloride ion diffusion coefficients of mortar specimens containing mineral admixtures were measured, and the influences of the kind of mineral admixture, replacement ratio, and carbonation on the chloride diffusion coefficient were estimated, and the relation between the microstructure and diffusion coefficient was studied. Furthermore, an estimation method of the diffusion coefficient using the pore volume and surface area of the pore system as parameters was proposed.

DOI： 10.3151/jact.4.385

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In this paper, environmental assessment has done for incineration residue by the case study on coal fly ashes. As the result of comparison between each experiment for analysis of materials or leaching tests, there is the problem to using the monolithic model for the chemical assessment of coal fly ashes. By the reason that coal fly ash are mixture of 3 components "Water solubility Part" which soon move after contact with water, and "High surface areas Part" which make absorption or desorption in metastable in any hours, and "Part of leaching availability (eg: after pozzolanic reaction) " which any insoluble part would be changed for soluble part in future. So, we propose: it is necessary to continue the experiment of this study.

DOI： 10.5956/jriet.34.513

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DOI： 10.3151/coj1975.43.3_64

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The quality of Electric arc furnace oxidizing slag aggregate as aggregates for concrete was standardized into JIS A 5011-4. And, "Recommendations for Design and Construction of Concrete Structures Using Electric Arc Furnace Oxidizing Slag Aggregate" was published by Japan Society of Civil Engineers. This paper describes the outline of the recommendation. In this recommendation, the general standard methods were shown on design and construction of the concrete using the electric furnace oxidizing slag aggregate. In addition, the manual for mix design was also made in order to carry out the mixture of the electric furnace oxidizing slag aggregate concrete.

DOI： 10.3151/coj1975.41.7_9

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DOI： 10.2208/jscej.2002.711_73

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This study is aimed to create a model for predicting the chloride ions migration process of concrete due to the compound interaction of salt damage and carbonation through an investigation into the immobilization of chloride ions in cement hydrates and the release of them when degradation of cement hydrates occurs due to carbonation. The available capacity of cement hydrates to immobilize chloride ions and the release of chloride ions accompanying with the carbonation of cement hydrates were determined by artificially synthesized cement hydrates which were immersed in artificial pore solution of concrete. Based on the above experiments, a model for characterizing the process of immobilization and release of chloride ions was established and its validity was verified by comparing calculated data with the data from the tests with cement paste and cement mortar specimens.

DOI： 10.2208/jscej.2002.697_131

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The purpose of this study is to estimate the properties of concrete in consideration of distribution of coarse aggregate quality. The properties of several particles of coarse aggregates and the properties of small specimens, which contain one coarse aggregate each, were measured. In addition, the estimation method of compressive strength and freezing and thawing resistance of concrete was constructed using Rigid-Bodies-Spring Model. The propriety of the estimation method was confirmed qualitatively.

DOI： 10.2472/jsms.51.1079

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An idea for concrete recycling is proposed for the 21st century. When demolished concrete is crushed after heating, aggregate is obtained with satisfied qualities for concrete without destruction of the shape. For produced powder, the chemical composition is presumed. The possibility of recycling cement with reducing of limestone is shown. If thus concrete recycling included cement and aggregate is done, resources and carbon dioxide discharge are reduced. Before long, the external diseconomies like these will be reflected the cost of product. Concrete recycling included cement should be intended for reducing external diseconomies for environment.

DOI： 10.3151/crt1990.11.3_139

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DOI： 10.2208/jscej.1996.532_55

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DOI： 10.2208/jscej.1995.508_33

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DOI： 10.2208/jscej.1992.451_69

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DOI： 10.2208/jscej.1990.414_99

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Language：Japanese   Publisher：日本コンクリ-ト工学協会  

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Language：Japanese   Publisher：Architectural Institute of Japan  

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Applicant：国立大学法人 新潟大学, 電気化学工業株式会社

Application no：特願2012-260258  Date applied：2012.11

Announcement no：特開2014-105136  Date announced：2014.6

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Applicant：太平洋セメント株式会社, 国立大学法人 新潟大学

Application no：特願2006-072092  Date applied：2006.3

Announcement no：特開2007-245007  Date announced：2007.9

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Applicant：新潟大学長, 田辺工業株式会社

Application no：特願平11-053516  Date applied：1999.3

Announcement no：特開2000-246275  Date announced：2000.9

Patent/Registration no：特許第3564481号  Date issued：2004.6

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Applicant：新潟大学長, 田辺工業株式会社

Application no：特願平11-053516  Date applied：1999.3

Announcement no：特開2000-246275  Date announced：2000.9

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Applicant：新潟大学長

Application no：特願平10-300813  Date applied：1998.10

Announcement no：特開2000-128595  Date announced：2000.5

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Applicant：新潟大学長

Application no：特願平10-300813  Date applied：1998.10

Announcement no：特開2000-128595  Date announced：2000.5

Patent/Registration no：特許第3362179号  Date issued：2002.10

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