Sludge treatment at a ready-mixed plant has significant high cost and high environmental impact. Although it has been studied to effectively use this sludge as a fine day sludge powder. In this research, it focuses on the treatment process and influences the time required for the treatment and the treatment temperature on the rehydration behavior and the characteristics of hardened mortar. As a result, it was found that when the treatment time is prolonged, the rehydration ability is inferior due to the progress of hydration. And the rehydration ability is improved by generating free lime at a treatment temperature of about 500 degrees Celsius. In addition, it was shown that the amount of calcium hydroxide contained in the hydrated powder is an indicator of the rehydration ability. Furthermore, although it confirmed that a mass transfer characteristic improved. However, it does not same behavior on the product fine dry sludge powder.

This study aims to establish the technology to produce recycled aggregate from waste concrete with acid solution. The determination of the optimum dissolution conditions （concentration, etc）, the evaluation of the physical property values of the regenerated coarse aggregate, and the possibility of multiple productions were considered. Physical properties （density in oven-dry condition, water absorption, fine particle amount, abrasion loss） of the regenerated coarse aggregate obtained by dissolution using a formic acid aqueous solution having a concentration of 20％ satisfy the Japanese Industrial Standards （JIS A 5021）.

Japan produces oysters in each district, and Hiroshima Prefecture is especially famous as being a high producing district. The production of oysters has created oyster shells as a by-product. Oyster shell porous concrete （OyPoC） is the porous concrete using crushed oyster shells as aggregates for the effective utilization of resources. In this study, the test method for void ratio and the long-term plant-growing performance of OyPoC were investigated. The particle size of the oyster shell aggregate ranged from 0.3 to 5mm. From the test results, voids in OyPoC were saturated with water by vacuum deaeration more than 10minutes with wet specimens for calculation on the void ratio of OyPoC. It was found that OyPoC with high absorption aggregate became oven-dry condition by drying in the oven more than 3days. The long-term planting test results showed that OyPoC compacted with the jigging method had higher plant-growing performance than the vibrator method, which had the high compaction energy. However, the grass on OyPoC compacted with the jigging method withered if it was not supplied with sufficient water during hot and dry summer. The grass cover level suggested in this study could estimate the grass growing condition more correctly than the grass length.

To show the applicability of the proposed waste indicator to other recycling industries than cement industry, the waste indicator values for cement, steel and paper industries were calculated and compared with the values obtained from the life-cycle impact assessment method based on endpoint modeling （LIME2）. In addition, the effects of the differences in the definitions of the recycling rate, which shows the difficulty of wastes recycling, on the waste indicator value were investigated. As a result, when the recycling rate was defined as a ratio of the recycling amount to the sum of the recycling amount and final disposal amount, the waste indicator value was consistent with the evaluation result by using LIME2. This definition of the recycling rate was suggested to most appropriately show the difficulty of wastes recycling. Besides, the evaluation results indicated that the cement industry contributes most to the wastes utilization.

A new environmental impact assessment method, LIME3, was applied to understand important impact categories of cement produced in each country. Environmental impacts of natural resource consumption and air pollution were different depending on the country. The effect of landfill avoidance by using wastes in clinker production was also different. Therefore, reducing the environmental impact by using mineral admixture was significantly different depending on the country. Some countries could get co-benefits between reduction of CO₂ and natural resource consumption or air pollution by using mineral admixtures. In Japan, however, the trade-off effect between CO₂ reduction and waste use in clinker production was significant by using mineral admixture.

Cr（Ⅵ） elution in improved volcanic coarse-grained soil with cement-based solidifying material, is often higher than the permissible limit under soil environmental standards of JAPAN. This is because the soil contains allophane in soil clay fraction, which inhibits the hydration of cement-based solidifying material. It is necessary to select a better ground improvement material according to the content of allophane in the soils. A method is presented to rapidly measure the content of allophane on site. Allophane test （active aluminum test） was performed using simulated soils with adjusted allophane content. Color analysis was performed on the image data of allophane test. The contents of allophane was accurately estimated from RGB values by color analysis. This method was verified using scoria in eastern Shizuoka prefecture and kuroboku soil （andosols） in Kumamoto prefecture. The soils evaluated were well estimated.

Disposal of radioactive waste is a problem for the decommissioning of the Fukushima No.1 nuclear power plant. Cesium adsorbed zeolite is a secondary waste generated in the process of treatment of radioactively contaminated water. A disposal method of cesium adsorbed zeolite has not been established and is urgent. The cement solidification technology is superior to other solidifying methods in terms of the manufacturability and economic efficiency of the solidified product. These advantages are very important because a large amount of cesium adsorbed zeolite to be solidified is generated. In addition, cement solidification technology is referred to as a option for the disposal method of the cesium-adsorbed zeolite, as it has a proven method of low-level radioactive waste disposal in the past. The purpose of this study is to contribute to the feasibility evaluation of cement solidification technology of cesium adsorbed zeolite. Some studies have been conducted on the evaluation of the physical properties of cement-based materials using zeolite as a mixed material. However, there have been few studies aimed at solidifying zeolite. Therefore, in this study, the volume reduction efficiency and strength property of cement solidified product mixed with zeolite were examined by the compressive strength test and the flow test. As a result, it was confirmed that the cement solidified product can secure 1.5N/mm² or more, which is an indicator of stability against falling and stacking of cement solidified product. Moreover, it was confirmed that the mix proportion in which the zeolite occupies half volume of the cement solidified product has sufficient required fresh property and strength property even in an environment simulating heat generation due to decay heat.

This paper describes the investigations of the possibility of the recycled cement. Amorphous C-S-H with a high Ca/Si ratio was synthesized by the double-decomposition method using CaCl₂ and Na₄SiO₄ mainly. We analyzed the hydration reaction mechanisms and hydrated products for the highly reactive β-C₂S. Also, hydrated products were heated again to generate β-C₂S in the second cycle. As a result, when β-C₂S with high NaCl contents was hydrated, C-S-H with a high Ca/Si that CH did not coexist was confirmed even at room temperature 20℃. Also, the generated C-S-H had the same properties as the starting synthetic C-S-H. Furthermore, the highly reactive β-C₂S is generated again by reheating the hydrated products.

Increasing minor additional constituents in ordinary Portland cement （OPC） is one of the approaches for reducing the CO₂ emissions of the cement industry. However, it reduces the amount of waste use as a result of reducing the clinker ratio of cement. Therefore, it is important to maintain quality of cement concrete and the amount of waste use even after the increase of minor additional constituents. The purpose of this study is to achieve both CO₂ emissions reduction and waste use levels conservation. In this study, we widely investigated the influence of increasing minor additional constituents and aluminate phase on the quality of cement. As a result, it is possible to reduce CO₂ emissions and maintain the amount of waste use while conserving the quality of the cement by increasing the amount of aluminate in the base cement by 1 to 2％ compared to the current OPC and increasing minor additional constituents to 10％.

In this study, the basic physical properties of concretes were confirmed by using cement in which the C₃A content of base cement was increased with respect to the increase of small amount of mixed components, in order to achieve both reduction of CO₂ emission and maintenance of waste intensity. As a result, by using a base cement with an amount of C₃A increased by 12.9mass％ with respect to concrete using conventional cement, the strength of age of 7 days due to increase in the amount of mixture of limestone fine powder or fly ash The expression was confirmed to be equivalent. Moreover, as a result of estimating adiabatic temperature rise from inverse analysis when limestone fine powder and blast furnace slag fine powder are mixed at 10mass％ each, the final temperature rise amount is lower than that of concrete with a small amount of mixed component amount of 5mass％ It was suggested that the coefficient would be large. However, it shows a tendency different from the maximum temperature obtained from the simple adiabatic temperature rise test, and it is considered that there is still room for verification of the estimation of adiabatic temperature rise by back analysis.

A simple method to decrease CO₂ emission from cement industry is an increase in minor additional constituent in ordinary Portland cement（OPC）. The total amount of minor additional constituents in OPC is restricted to 5％ at most in Japan now, thus OPC containing 10％ additional constituents is a candidate. However, the qualities of cement （strength, reactivity, fluidity, etc.） have to be kept even if the amounts of minor additional constituents increase. The authors have reported that an increase in C₃S amount by 1. 03 times in OPC with an increased additional constituent brings the same quality as current OPC. However, for a more effective use of cement containing more additional constituent, not only C₃S amount but also C₃A amount in OPC should be increased when the amount of minor additional constituent increases. It is because cement industry utilizes wastes as the raw-material of cement and contributes to the recycling society. In this paper, the authors investigate the influences of mineral composition of base cement and an increase in the amounts of minor additional constituents on reactivity of cement paste. The authors used three OPCs containing different amounts of C₃S and C₃A as the base cements. C₃S and C₃A amounts in OPC（A） are 60.4 and 9.0 mass％, respectively. OPC（C） contains more C₃S than OPC（A）：the amount is 61.9 mass％. OPC（F） contains more C₃S and C₃A than OPC（A）：the amounts are 61.9 and 10.9 mass％, respectively. As the minor additional constituents, blast furnace slag（BFS）, fly ash（FA）, and limestone powder（LSP） were used. With regarding heat liberation of base cement without minor additional constituent as 100％, the ratio of heat liberation of blended cement was evaluated. Independent of base cement type, heat liberation ratio of blended cement with 10％ BFS to the base cement increased as the hydration progressed. The decrease in heat liberation of OPC（C）with 10％ BFS was larger than OPC（A）. Independent of base cement type and the hydration time, heat liberation ratio of blended cement with 10％ FA was almost constant. The decreases in heat liberations with 10％ FA were almost equal in all base cements. Heat liberation ratios of OPC（A） 90％＋LSP10％ and OPC（C） 90％＋LSP10％ decreased as the hydration progressed, but that of OPC（F）＋LSP10％ was independent of the hydration time. Independent of base cement type, the heat liberation of one blended cement containing two or three additional constituents can be estimated as the average of heat liberations of two or three blended cements containing one additional constituent.

The absorption capacity of superabsorbent polymers （SAP） in a real cement environment is a need-to-know property as a new admixture for concrete. In this study, fundamental stereology techniques were applied to cross sections of cement pastes in which solution-polymerized SAP particles were embedded. Its absorption capacity was estimated from the area fraction and particle size distribution of the SAP in the 2D planes. Further, a characteristic distance between the SAP particles was also evaluated using point process statistics. The absorption capacity estimated was greater than that obtained by the tea-bag method using a cement filtrate. The SAP seems to absorb mixing water quickly in the initial short time during mixing. The number density of the SAP particles in the cross sections was also greater than the estimation calculated from the absorption capacity and the particle size distribution of initial dry SAP. This fact suggests that the SAP particles broke away during mixing. The centroids of SAP particles were distributed as to form a regular pattern. A procedure to evaluate the median distance from a given location to the surface of the nearest SAP particle was proposed by combining the mean diameter of swollen SAP profiles and the point process G- and F-functions. The distances between SAP particles were found at most a few mm for the mass fraction of 0.58％ against cement.

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.

Volcanic glass powder （VGP） is manufactured from pyroclastic flow deposits. This paper reports the effect of BET surface area and replacement ratio of VGP as a supplementary cementitious material on compressive strength. The performance of VGP as a SCM was evaluated by conducting tests on mortar mixture, replacing 0％ to 30％ by weight of Portland cement by VGP with 0.3 water to binder ratio. VGP mortar with BET surface area of 15m²/g showed better results of 7-, 28-and 91-day compressive strength compared to control mortar in all replacement ratio. In particular, VGP demonstrated better strength development in mortar from 28-day to 91 day when replacing 25％ and 30％ by mass of Portland cement.

In this study, in order to verify the structural performance of a pre-cast RC slab by means of PC binding post-tensioning experimental and analytical investigations were conducted regarding the flexural behavior of a RC slab specimen with a crimp-style connecting joint using unbonded prestressing bars compared with one by the existing construction. As a result, it was confirmed that the unbonded prestressed pre-cast RC slab is superior in cracking resistance and damage control effects compared with the existing one because of a large increase in the flexural cracking load and a large decrease in the residual displacement, and a safety calculation of ultimate strength in flexure based on the flexural analysis substituting axial compressive force for effective prestress can be provided against the experimental result.