Recent efforts to reduce the burden on the environment have directed our attention toward the use of deicing chemical in preventing the corrosion of steel used for concrete, and the use of deicing chemicals for this purpose has now started. This study compares how the degree of scaling deterioration varies according to the types of deicing chemicals used. The types of deicing chemicals used were chlorides and acetates. The result of this research is as follows. While no scaling was observed on the surface for the specimens filled with pure water, scaling was found to be promoted by all of the types of deicing chemical solutions used. The degree of scaling deterioration experienced with each of the types of deicing chemicals is likely to be affected by the strain generated at the boundary between the concrete surface and the ice, dynamic modulus of elasticity and bond strength between ice and mortar.

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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.

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Recently deterioration of concrete caused by sulfuric acid attack in sewage and wastewater treatment plants has been reported. As a countermeasure of this deterioration, acid resistant cementitious material which contains multiple mineral admixtures has been developed. It is thought that the clarification of sulfuric acid resistance mechanism of this material and the development of a simple evaluation method of the resistance to sulfuric acid for this type of material lead to the development of higher quality acid resistant cementitious material. In this study, a stirring test using sulfuric acid and cement paste powder was performed to know the reactivity of specimens with sulfuric acid and to develop a simple evaluation method of the resistance to sulfuric acid of cementitious materials. Based on the experimental results, the effect of cement compounds and hydration products on the resistance to sulfuric acid attack was discussed and the deterioration due to sulfuric acid attack is predicted analytically. As a result, it was found that the resistance to sulfuric acid could be evaluated by the prediction analysis using the results of the simple testing method. And, it was suggested that the erosion rate is more affected by the pore structure than by the contents of reactive compounds with sulfuric acid.

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Penetration of the deterioration substances like water and chloride ions through cracks into the concrete, generally, induces and accelerates corrosion of reinforcing steel in reinforced concrete（RC）structures. The behavior of RC beams under sustained load is investigated to simulate RC structures in very severe chloride environment. As examination parameters, reinforcement stress with three levels of stress and cover of three different thicknesses are adopted. According to the results, the corrosion initiation time was not influenced by the reinforcement stress level as well as the cover thickness in cracked zone of beams under sustained loading, which as expected, was dependent on the cover thickness for beams without loading. Results also showed that the corrosion crack width became larger as the reinforcement stress became higher as well as the cover thickness became smaller. The time dependent deflection was calculated by using the effective flexural stiffness evaluated, in which the reduction of stiffness due to flexural craking, the influence of creep, and shrinkage with gradient in cross section, were considered. By comparisons between measured and calculated value, It was found that the effect of corrosion on long-term deflection can be observed for the beams with severely increasing of corrosion crack width；while such effect was not found for the beams whose corrosion crack width was less than 1mm.

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The corrosion of steel in concrete structures depends on the chloride ion concentration at the position of steel reinforcement. Therefore, when the corrosion of steel occurs by the chloride supply from the external environment such as the case of wind-conveyed salt, it is considered effective to reduce the chloride ion concentration on the concrete structure surface to delay the onset of steel corrosion. For this purpose wash-away of chloride on concrete surface by the surface water flow by rainfall and so on can be used. In this study two kinds of water effects are examined, i.e., the impact of rain drops and the surface water flow. The influence of those factors on the wash-away of chloride is examined experimentally and the results are summarized for the characteristics and the amount of chloride washed-away. The summary of the test method proposed in this study is given as an appendix.

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Concrete is inherently a durable materials. If concrete properly is designed for environment where it will be exposed, and if carefully produced with good quality control, concrete possesses maintenance-free performance for several decades, except in highly corrosive environment. This implies that the majority of concrete durability issues are focused on the later ages, when the concrete has gained adequate strength. However, the early age shrinkage of concrete induces cracking, which could severely decrease concrete life expectancy；the shrinkage microcracks not only affect the mechanical properties but also increase the permeability and facilitate ingress of aggressive substances such as chlorides and carbon dioxide gas. Hence, the investigation on shrinkage cracking is necessary to control early deterioration for ensuring safety of construction. Fundamentally drying shrinkage is caused by the migration of water in hardened cement paste. This leads to a conclusion that the change in water migration with various external environments, namely water adsorption-desorption isotherm, is of large importance to clarify the mechanism on drying shrinkage. This study focuses on the water adsorption-desorption isotherm of hardened cement paste. The isotherm usually shows hysteresis loop. This hysteretic behavior is often explained by the existence of constrictions or bottlenecks between pores that cause a delay in the desorption process compared to the adsorption. However, it has been reported that the hysteresis loop of isotherm is observed for regular unconected pores, which does not have constrictions and bottleneck pore. A simple phenomenological model, which is proposed by Pellenq et al. and based on a generalized Gibbs surface dividing theory for adsorption and capillary condensation/evaporation in cylindrical meso-pores, can be interpreted the hysteresis loop of isotherm for regular unconnected pore. In this study we extend the Pellenq’s model form unconnected pore to the connected complicated pore system such as hardened cement paste. As a result, it is evident that modified Pellenq’s model can assess the essential migration of water?in hardened cement paste under any ambient?environment. This will be a stepping stone to make clear the mechanism of drying shrinkage.

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Frost damage, which is the deterioration due to freeze and thaw of pore solution is causes scaling, pop-out and cracks on surface of concrete members, is an important issue in the durability of concrete structures in cold regions. Deicing agents are sprayed in order to prevent frost damage. By contrast, it has been reported that chlorides of deicing agents accelerate the deterioration due to frost damage under freeze-thaw environment. It is generally known that phase changes of hydration products, such as formation of friedel’s salt and ettringite, occur due to penetration of chloride ion. Ettringite formation leads volume expansion and cracks. Since the acceleration of frost damage due to chlorides penetration, the use of deicing agents which is not containing chloride ions, such as potassium acetate and calcium-magnesium acetate, has been proposing. However, it has not been shown that chemical alteration due to penetration of deicing agents influence on increase of strain and decrease of structural characteristic value with frost damage under freeze-thaw environment. Therefore, this study aimed to investigate the influence of deicing agents under freeze-thaw environment on 1）progress of frost damage, 2）phase changes of hydration products and 3）decrease of structural characteristic value. As the results, 1）penetration of deicing agents containing chloride ions influenced on the strain hysteresis and resulted in the increase of residual strain and water absorbing ratio, 2）ettringite formation with displacement and dissolution of monosulfate hydrates was a contributory factor for frost damage acceleration and 3）chemical alteration and increase of residual strain due to penetration of chlorides led decrease of tensile strength, elastic modulus and fractural energy.

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In this study,the frost resistance of concrete applied blast-furnace slag fine aggregate is examined by considering the effect of the decrease in bleeding and an antifoaming agent. The obtained experimental results are as follows：
1）The frost resistance of blast furnace slag（BFS）concrete decreases, but this decrease is not affected by the air content or spacing factor of the BFS concrete.
2）The frost resistance of concrete decreases as the replacement ratio of BFS increases, and the frost resistance decreases remarkably when BFS is used with an antifoaming agent.
3）The increase in the bleeding because of the use of BFS can be controlled by increasing the number of fine particles of BFS；however, the effect of increasing the amount of fine particles of BFS on the frost resistance of concrete was insignificant.
4）The amount of decrease of individual sides of concrete estimated on the basis of the reading of gross checker showed various characteristics according to the variety of materials and admixtures.
5）There are many voids inside BFS grain, and they occupy 2.7% of total volume of BFS concrete, and 1.3% of the voids are open to paste parts.
6）The number of small BFS grains appears to decrease by freezing and thawing test, but the methodology of the test should be examined for a definite evaluation of the frost resistance of BFS.

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Low-heat Portland blast furnace slag cement is the cement which raised a ratio of the ground granulated blast furnace slag and reduced the specific surface area of cement by blaine. When Portland blast furnace slag cement is used by binder, the temperature rise of concrete is lower than that of using ordinary Portland cement. In the case that low-heat Portland blast furnace slag cement is used by binder, the temperature rise of concrete is more low that of using Portland blast furnace slag cement which the specific surface area of cement by blaine is high. In the case of using Portland blast-furnace slag cement which raised a ratio of the ground granulated blast furnace slag, compressive strength and carbonation of concrete are worse than that of using ordinary Portland cement. However, sulfuric acid attack resistance is higher than that of using ordinary Portland cement. And in the case of using blast furnace slag sand together, resistance of sulfuric acid attack is more high. In addition, the drying shrinkage strain of concrete with Portland blast furnace slag cement and blast furnace slag sand is smaller than that of using ordinary Portland cement and crushed sand. And in the case that concrete with Portland blast furnace slag cement and blast furnace slag sand cured in stream, the drying shrinkage strain becomes small more.

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3CaO・CaCl₂・15H₂O is the main factor for the chemical deterioration caused by CaCl₂. In this study, the method for the synthesis of 3CaO・CaCl₂・15H₂O was examined, and the fundamental property of synthetic single crystal was studied through a morphological analysis, X-ray diffraction（XRD）, and Thermogravimetric/Differential Thermal Analyzer（TG-DTA）. As a result, deposition process was found for the synthesis of 3CaO・CaCl₂・15H₂O. The synthetic sample is significantly unstable, and forms a needle-shaped crystal. The heat characteristics and chemical reactions accompanying of heating are explained. Additionally, it was shown that 3CaO・CaCl₂・15H₂O has a strong preferred orientation.

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When hydrated CaO・2Al₂O₃ was mixed to ordinary portland cement, High early strength portland cement and Low heat portland cement respectively, a large amount of two types of hydrocalumite（3CaO・Al₂O₃・Ca（OH）₂・12H₂O and 3CaO・Al₂O₃・Ca（SO）₄・12H₂O）has formed in hardened cement. It was considered that generated hydrate depended because Al₂O₃ and SO₃ amount in cement differently. Amount of portlandite in hardened cement has decreased with increased additive amount of CaO・2Al₂O₃, because a large amount of hydrocalumite formed in hardened cement by the reaction of CaO・2Al₂O₃ and Portlandite. When hydrated CaO・2Al₂O₃ and NaCl was mixed to various portland cements respectively, amount of fixed chloride ion has increased and ratio of soluble chloride ion in total chloride ion has decreased in hardened cement with increased additive amount of CaO・2Al₂O₃. When the various cement mortars made to mix CaO・2Al₂O₃ were immersed in salt water, the chloride ion penetration depth decreased and the chloride ion concentration of the surface part became high. This reason was chemical effect of fixation of chloride ion by formation of Friedel’s salt（3CaO・Al₂O₃・CaCl₂・12H₂O）for the reaction of hydrocalumite and chloride ion. The effect was remarkable in particularly Low heat portland cement.

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Accelerated tests were performed to evaluate the rebar corrosion resistance of ultra high-strength concrete with silica fume blended cement. It was proven that the ultra high-strength concrete exhibited high corrosion resistance even at chloride content of 10.0kg/m³. This was attributed to its dense pore structure and fixation of chloride ions as the Friedel's salt that control the transport of harmful mass.

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This study describes results on immersion tests of cement concrete specimens incorporating a ground granulated blast-furnace slag of which weight ratio to cement was 60 to 80%. The specimens were soaked into sulfuric acid hot spring and hydrochloric acid river at Hachimantai area in Akita prefecture. Parameter of specimen was water-binder ratio, incorporating ratio of the ground granulated blast-furnace slag, sand percentage, type of fine aggregate and type of coarse aggregate. Furthermore, unsaturated polyester polymer concrete was also examined. Although the immerse tests environment was very strict for the specimens because of a high temperature and a low pH, incorporation of the blast furnace slag powder could be repressible mass loss of the specimens. The polymer concrete had no deterioration due to the tests.

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Crushed stone powder is produced at the time of manufacturing of crushed stone and crushed sand. It is very important to make efficient use of this crushed stone powder. The purpose of this study is to investigate the properties（fluidity, filling, compressive strength, freeze-thaw resistance, etc.）of high fluidity and high strength regulated set cement concrete mixed two kind of crushed stone powder with different particle size together. As the results, it was recognized that fluidity and filling of concrete are affected by blend ratio of two kind of crushed stone powder and additional quantity of crushed stone powder. Furthermore, it became clear that the properties of high fluidity and high strength regulated set cement concrete mixed two kind of crushed stone powder are similar to the properties of that concrete mixed fly ash.

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The water-binder ratio of ultra high strength concrete is extremely low；therefore the addition of low-heat portoland cement（LC）, moderate-heat portland cement（MC）and silica fume is indispensable at mixing. This research was conducted to elucidate how was different in water-binder ratio, would affect the compressive strength and hydrate of low-heat portland cement if added to the cement along with silica fume. The influences were discussed from the perspectives of cement hydration required by the Rietveld method using powder X-ray diffraction（XRD）, silica fume hydration by the selective dissolution method and silicate-chain polymerization of hydrate calcium silicate（C-S-H）by the trimethylsilyl（TMS）derivatization method. As for the water-binder ratio of 15％ mixing used with the ultra high strength concrete, a reactive rate of SF was low and the amount of the C-S-H generation was a little though compressive strength had risen compared with water-binder ratios of 30％ and 22％ mixing. The extent of polymerization of the silicate anion has decreased to the influence of W/B on the silicate anion polymerization level as W/B lowers. The addition of silica fume promoted polymerization.

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Recently, ultra high strength concrete（UHSC）over compressive strength of 150N/mm² was developed. Ultra high strength concrete property is determined by its composition such as cement type, fine aggregate, coarse aggregate. Especially coarse aggregate was critical for making UHSC, because stress concentration is occurred at contact zone of aggregate and cement matrix. In this study, we applied to nonlinear voxel finite element method with three dimensional image of concrete. As a result, static elastic modulus and compressive strength was able to predict by this method within 10％ in error. Moreover, it was shown that the fracture strength of coarse aggregate, and the difference between the elastic modulus of mortar matrix and coarse aggregate is very important to achieve the ultra high strength of concrete.

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The mechanical properties of fiber－reinforced porous concrete may be improved by strengthening of binder. In general, the polymer modification of cement mortar improves the strength and adhesion properties of the mortar. The purpose of this study is to investigate the effect of the polymer modification of the cement mortar as a binder on the compressive and flexural behavior of the fiber－reinforced porous concrete. Polymer－modified mortars with various polymer－cement ratios are prepared as the binder for fiber－reinforced porous concretes using polymer for cement modifier. The fiber－reinforced porous concretes using polymer for cement modifier are prepared with various vinylon fiber contents, water－cement ratios and polymer－cement ratios, and subjected to compressive behavior, flexural behavior and voids tests. As a result, regardless of the polymer－cement ratio, the compressive and flexural strengths, modulus of elasticity and flexural toughness of the fiber－reinforced porous concretes using polymer for cement modifier increase with increasing fiber content up to 0.5%. The compressive strength and modulus of elasticity of the fiber－reinforced porous concretes using polymer for cement modifier are increased with an increase in polymer－cement ratio up to 4.0% regardless of the fiber content. The flexural strength and flexural toughness of the fiber－reinforced porous concretes using polymer for cement modifier are also increase with increasing polymer－cement ratio up to 6.0%. Brittleness of the fiber－reinforced porous concretes using polymer for cement modifier is improved by increasing the polymer－cement ratio. From the test results, the polymer modification of cement mortar as a binder for the fiber－reinforced porous concrete is effective technique for improving the mechanical properties of the fiber－reinforced porous concrete. The marked improvement of flexural behavior of the fiber－reinforced porous concretes using polymer for cement modifier is recognized with an increasing the polymer－cement ratio.

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In order to enhance the truck load capacity and fatigue property of RC slabs, the slab overlay method using steel fiber reinforced concrete（SFRC）has been proposed. In this study, the effects of adhesive coating on the load-carrying capacity and fatigue property of the slabs which were reinforced by SFRC overlay method was evaluated using wheel running fatigue test machine, especially when the rehabilitation applications are conducted under rainy condition. As results, the reinforcing effects of wet state slabs were as good as those of dry state ones, and the delamination between slab and the SFRC of wet state slab was not occurred until the deflection reached 1/400 of span L. The adhesion between slabs and SFRC was observed by using adhesive even when the application was conducted under surface water removed wet conditions.

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Fatigue tests under running wheel loading on RC slab test specimens with the top surface reinforced by overlaying the SFRC were conducted and evaluated fatigue resistance and predicted the timing of secondary repair about surface damage of RC slab. As result, that is derived which evaluated the number of equivalent cycles that is derived D-N curve with between the damage value associated with the increase in deflection and the number of equivalent cycles by running tests under running wheel loading, damage factor of moist condition concrete, and the number of equivalent cycles for reinforcement consider for revision factor of design quality. Therefore, this study is suggested S-N curve consider for design quality 1964, 1968 years enabled to predict of the timing of secondary repair.

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The CFS reinforcement method is planned to the fatigue damage of the RC slab in the repair and maintenance methods in the long life repair plan for road bridge. Then, it is fatigue tests under running wheel loading were conducted, to predict lifetime and the timing of re-repair of CFS using RC slab. As result, that is derived which evaluated the number of equivalent cycles by running tests under running wheel loading, D-N curve damage factor of moist condition concrete, and the number of equivalent cycles for reinforcement consider for revision factor of design quality. Therefore, this study S-N curve is suggested to predict destruction and re- repair time when design quality of 1964, 1968 designed RC slab with reinforced by the CFS enabled to predict of the timing of secondary repair. This study is contributory to the repair and maintenance methods in the long life repair plan for road bridge RC slabs with the bottom surface reinforced by bonding the CFS.

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Waste roof tile is expected as concrete aggregate of recycled resources. Moisture content of the waste roof tile is about five times the height of normal coarse aggregate. The moisture content influences making and quality of concrete, but that have an effect of water-retention of porous concrete. Using waste roof tile possessed excellent water absorption and retention as a coarse aggregate of porous concrete is expected to improve the water retention performance of porous concrete. The aim of this study is to comprehend for basic physical properties of a porous concrete using waste roof tiles. Study Items are determining propriety the production of the porous concrete with required performances, various performances by tests using specimens and water retention performance of porous concrete using waste roof tiles. As the result, the porous concrete using waste roof tiles was found out possible to secure predetermined porosity. And also, it is no problem as porous concrete pavement for the sidewalks judging from these strength. Furthermore, porous concrete using waste roof tiles as coarse aggregate is about twice water retention compared with porous concrete using normal coarse aggregate. In the future, mitigation of heat island effect by porous concrete improving water retention performance is required verification at examination of outdoor.

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The goal of this research is to establish the concrete mix design containing both low quality recycled coarse aggregate and CfFA（Carbon-free Fly Ash）. CfFA is high quality fly ash which has unburnt carbon of less than 1%, and the use of CfFA is very effective for the improvement of flowability of concrete and the prevention of alkali-silica reaction of recycled aggregate. In this paper, the fundamental data on drying shrinkage strain of recycled coarse aggregate concrete were discussed in detail. As a result, the factors influencing drying shrinkage strain of concrete were cement content, water content, coarse aggregate content and the dosage of CfFA. In particular, for recycled coarse aggregate concrete, the effects of high absorption of recycled coarse aggregate and the amount of mortar adhering to coarse aggregate should be concerned. Then, the effects of these factors on the values of the final drying shrinkage strain at the age of 6 months were discussed, by introducing the apparent water content defined as the sum of water content and the absorption of aggregate（W´＝W＋W_G）and the apparent coarse aggregate content subtracted the adhered mortar content from coarse aggregate content（G´＝G－M）, instead of water content and coarse aggregate content in the mix proportion of concrete. In this paper, the multiple regression analysis was applied to calculate the final drying shrinkage strain as well as the prediction equation proposed by AIJ. It was found that the proposed equation for drying shrinkage strain of recycled coarse aggregate concrete can express the experimental data.

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In this study, we perform a flesh property examination and a strength examination for application of Clinker Free Concrete（CFC）which doesn’t include any cement, to roller compacted concrete pavement（RCCP）. CFC’s water-powder ratio is 20％（W/P＝20％）and powder content is 500（kg/m³）. 5 types of mixed ratio of ground granulated blast-furnace slag and fly ash, and two types of mortar-coarse aggregate volume ratio were used for CFC. Two types of curing time were changed at this study. As a result of this study, the flexural strength of clinker free concrete of 12 hours age showed over 3.5 N/mm². And that of 28-days age showed over 4.5N/mm². The flexural strength increased with the increase of BS’s mixed ratio. There is the best Curing temperature of clinker free concrete.

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This study aimed at proposing an idea for manufacturing porous concrete by aggregating remained concrete using flocculant. In experiment 1, influences of flocculant dosage on void ratio and compressive strength of the concrete were investigated. As a result, it was shown that the concrete including flocculant met the requirement of total void ratio for permeable pavement at a flocculant dosage of 2.0kg/m³, however, its compressive strength was smaller than that of normal porous concrete with the same void ratio. In experiment 2, to investigate the applicability of the concrete including flocculant to the permeable pavement, fundamental properties（void ratio, compressive strength, flexural strength, and permeability coefficient）of the concrete with a flocculant dosage of 2.0kg/m³ were evaluated. Our results showed that the concrete satisfied the requirements of void ratio and permeability coefficient for permeable pavement. However, the flexural strength of the concrete with a flocculant dosage of 2.0kg/m³ was smaller than that required for permeable pavement, so that more investigations are needed to enhance the flexural strength of the concrete including flocculant.

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Fluidized bed Advanced cement Kiln System（FAKS）is an innovative cement manufacturing technology with higher reaction efficiency than any other kiln system. A FAKS plant with the capacity of 1,000 tons/day was constructed by Kawasaki Plant Systems in the International Coal Utilization Project by New Energy and Industrial Technology Development Organization（NEDO）in Shandong Province, China. And its performance tests were conducted. In this study, clinker samples from a FAKS plant were examined by Chemical Analysis, Rietveld Analysis and Optical Microscopy. Moreover, physical tests for cement and tests for slump, air content and compressive strength of concrete were performed to confirm their qualities. As a result, it is clear that clinker produced by FAKS was burned as well as by conventional rotary kiln system, though there are differences in the process of clinker minerals’ formation, burning conditions such as temperature and retention time in the kiln, etc. Compared among the clinker samples from a FAKS plant, there was a significant difference in especially the increase of compressive strength in the long term. It is obvious that the physical property of cement could have been affected by the difference of mineral composition in our tests. In addition, it is possible that it might have been affected by the difference of a melting state of minor constituents such as MgO in clinker minerals.

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In this study, a new concept of the fixation of carbon dioxide（CO₂）in the air to cementitious materials was proposed by using the function of the photosynthesis of microorganism, Euglena. The amount of CO₂ fixation was calculated from the measured change in CO₂ concentration in sealed containers with porous mortar, Euglena, or porous mortar with Euglena. As a result, it was observed that the amount of CO₂ fixation of porous mortar was increased by the photosynthesis of Euglena. The temperature dependency of the amount of CO₂ fixation was also investigated. Then, it was found that the amount of CO₂ fixation by photosynthesis of the Euglena in porous mortar smaller than the amount by Euglena in water because the supply of the sunlight was limited for the Euglena in porous mortar.

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In general, concentrated suspension shows non-Newtonian behavior under shearing due to flocculation of suspended powder particles. Thus it is of importance to predict the thixotropic behavior of concentrated suspension to transporting and handling of them. However, the thixotropic behavior is strongly influenced by the formation of particle aggregate due to the interparticle forces and the fragmentation of the aggregate due to shear stress. In this study, we propose the thixotropy model for concentrated and flocculated suspension based on fractal concept to predict the time-dependent shear viscosity. We adopt the viscosity model proposed by Mills based on the assumptions of mean-field theory. According to the model, the viscosity of flocculated suspension is expressed by an effective volume fraction of fractal aggregates instead of solid volume fraction. In order to determine the size distribution in fractal aggregates, a population balance model proposed by Barthelmes, et al. is introduced to account the coagulation and fragmentation of the aggregates under shear flow. From the evolution of the aggregate size distribution, the mean effective volume fraction can be calculated at arbitrary time and then it is applied to the viscosity model. Further the fractal dimension accounting for the aggregate structure is determined by the rheological approach proposed by Chougnet, et al. The model prediction is in good agreement with experimental data.

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Polycarboxylate-based superplasticizer（PC）is used to be dispersed the suspended colloidal particles, thereby improving the fluidity of such suspensions. The driving force for dispersing of PC might be contributed by the steric repulsion arising from overlap of polymer layers of PC adsorbed on surface of colloidal particles. According to enormous past studies, the repulsion force might be represented as a function of the thickness of the layer adsorbed on the colloidal particle surface. Therefore, it is of great importance to estimate the conformation of adsorbed PC and its thickness. However, for concentrated suspension, it is too difficult to directly measure the conformation and thickness of PC adsorbed on the surface of cement particles.
In this study, we estimated the thickness of adsorbed polymer layer of PC using the two different models：the rheological model for prediction of relative viscosity of concentrated suspension proposed by Chougnet et al. and the steric repulsion model to predict the relation between the thickness and steric repulsion, which is proposed by Alexander and de Gennes. Using the former model, one can estimate an effective volume fraction of aggregate of suspended particles. Since the effective volume fraction of aggregate can be expressed as a function of the interparticle force F_a and the shear stress τ, the interparticle force can be calculated. The interparticle force is a sum of electrostatic repulsion, van der Waals attraction and steric repulsion. As the electrostatic repulsion and van der Waals attraction can be calculated according to DLVO theory, the steric repulsion can be determined. Using Alexander and de Gennes’s model, the thickness of polymer dispersant adsorbed on the suspended particles can be predicted. We used fine CaCO₃ powder as the suspended particle, and two different PCs that consist of different graft polymer with different length. The results of rheological approach studies indicated that the viscosity of suspensions added two PCs almost the same and thus the thicknesses of adsorbed PCs were estimated to be the same despite length of graft polymer with different length. This implies that the conformation of adsorbed PC does not agree with the previous conformation model that the main chain is adsorbed on the surface and polyethylene oxide chain is stretched into the solution. In this manner, the thickness is proportion to the length of grafted polymer. Thus the main chain of adsorbed PC partially becomes detached on the surface of particles.

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