The effect of organic halide atmospheres at calcination of limestone on the particle size and shape of a calcined product and the final product, hydrated lime, has been investigated. To prepare the organic halide atmospheres, tetrachloromethane or 1, 1, 1, 2-tetrafluoroethane (HFC134a) was introduced with air stream during the calcination of limestone at temperature range from 1000 to 1200°C. The degree of shrinkage of the calcined product and the fractional part of the dry-hydrated lime passed through 45 μm sieve were measured using four kinds of the limestones, and compared with the result obtained by the same procedure under an air atmosphere.
As the results, the influence of grain size of the limestones was found to be, on the whole, reduced under the organic halide atmospheres. In particular the tetrachloromethane atmosphere contributed to decrease the degree of shrinkage of the calcined product and to increase the fractional part of the fine hydrated lime, while the HFC134a atmosphere resulted to increase the degree of shrinkage, but not to influence for the fractional part of the fine hydrated lime. The change in the particle size and shape of the calcined product and hydrated lime was also observed using scanning electron microscopy. In addition, considerable amounts of the halogens in the organic halide atmospheres fixed in the calcined products depending on the calcination conditions. This calcination process can be expected as the process for improving the physical properties of the resulting quicklime and hydrated lime, simultaneously accompanying with the treatment of waste organic halide compounds.

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Al-containing low crystallized calcium silicate hydrate (C-S-H) was prepared by hydrothermal reaction at 95°C for 20 h, using water glass, calcium chloride and sodium aluminate as raw materials. The products were characterized by powder X-ray diffraction and NMR methods. and its ion exchange properties toward Ca²⁺, Mg²⁺, K⁺ and Li⁺ ions were studied.
C-S-H was predominantly formed and zeolites were hardly formed at the condition of H₂O/Na₂O =150. A type or X type zeolite was formed as by-products in the case of adding large amount of Al content at the condition of H₂O/Na₂O (molar ratio) = 50 and low Ca content. Cation exchange capacity (CEC) toward Ca²⁺ ion increased with increasing Al content of C-S-H. Ca²⁺ ion exchange was thought to correspond to the exchange reaction between Ca²⁺ and Na⁺ ion, some of which was introduced by Al substitution for Si and the other Na⁺ ion must be present connecting to broken bonds on C-S-H surface. Cation exchange reaction toward Mg²⁺ ion proceeded more slowly than that of Ca²⁺ ion. However its CEC was more than that of Ca²⁺ ion on many samples. CEC of Mg²⁺ increased with increasing Ca content of C-S-H. It was estimated that Mg²⁺ ion exchange reaction caused breaking of Ca-O bond in C-S-H structure. Amount of up-take of Mg²⁺ ion was roughly equal to the amount of release of Ca²⁺ and Na⁺ ions. Al containing C-S-H had CEC value more than 100 meq/100 g toward K⁺ ion but it was low value in the case of Li⁺ ion exchange.
It was suggested that Al containing C-S-H was composed of connecting and branching structure of silicate chain by NMR method.

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Hydroxyapatite (Ca₁₀ (PO₄) ₆ (OH) ₂; HAp) and β-tricalcium phosphate (β-Ca₃ (PO₄) ₂; β-TCP) are bio-compatible materials with bones and teeth. HAp is promising bone substitute materials for clinical applications because of chemical stability in vivo, while β-TCP has higher resorbability than HAp when the material is implanted in a bone defect. In the present study, HAp and β-TCP were soaked in the simulated body fluid, and then the reaction between the materials and the fluid was investigated in order to compare with the reaction in vivo. From the soaking test, carbonate hydroxyapatite was formed on the surface of HAp after 1 week, and then the amount of carbonate hydroxyapatite increased with increasing period of the soaking test. While β-TCP was not dissolved in the fluid, the carbonate hydroxyapatite was also formed on β-TCP after 12 weeks, and the amount of the precipitates on β-TCP was less than that on HAp. The reaction for HAp in vitro was similar to that in vivo, but the reaction for β-TCP in vitro was not similar to that in vivo.

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On the preparing process of Mg-containing synthetic whitlockite using a wet chemical method, synthesis of phosphate compounds having whitlockite structure replaced with Sr²⁺ ion or Ba²⁺ ion at Ca site and with other divalent metal ions at Mg site in the crystal was investigated.
As a result, whitlockite solid solutions (Mg- (Ca, Sr) W) replaced with Sr²⁺ ion at Ca site were produced in the pH regions from a neutral pH to a weak alkaline pH with mixed solution of Ca²⁺ and Sr²⁺ ions. However, synthetic barium whitlockite (Mg-BaW) and the whitlockite solid solutions (Mg (Ca, Ba) W) replaced with Ba²⁺ ion at Ca site were not produced with mixed solution of Ca²⁺ and Ba²⁺ ions. On the other hands, strontium whitlockite solid solutions (Mg- (Sr Ba) W) replaced with Ba²⁺ ion up to 90 mole% at Sr site were produced in pH regions from a weak alkaline pH to a high alkaline pH with mixed solution of Sr²⁺ and Ba²⁺ ions. Further, strontium synthetic whitlockite (SrW) contained Ni²⁺ ion, Co²⁺ ion, Fe²⁺ ion, Mn²⁺ ion, Zn²⁺ion or Cd²⁺ ion at Mg site was produced. Synthetic whitlockite prepared in this works defected metal ion at Ca site, was a nonstoichiometric composition.

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In recent years, because of the shortage in land disposal site, the waste burning at cement plant has become very important. And so-called chlorine bypass process is supposed to be the key technology. The main composition of the extracted dust in chlorine bypass is KCl. And the utilization or disposal of this dust is necessary to burn waste in a cement kiln.
In the previous paper, authors reported the influence of KCl on the alite hydration and on the hydrated products. But the total amount of chlorine in ordinary portland cement is limited at 200 ppm. in Japan Industrial Standard, in order to prevent the corrosion of reinforcing bars in concretes.
This paper deals with the hydration reaction of slag-KCl system which can contain larger amount of extracted dust. As a basic study to utilize lager amount of extracted dust in cementitious material, experiments were performed to know the phase composition change during the hydration of slag-KCl system in comparison with that of slag-Ca (OH) ₂ system. The hydration products in slag-Ca (OH) ₂ system were aluminum hydroxide gel and calcium silicate hydrate gel. And in slag-KCl system, Fridel's salt is formed in addition to the products in slag-Ca (OH) ₂ system. The CaO/SiO₂ ratio of calcium silicate hydrate gel produced in slag-KCl system were smaller value than that in slag-Ca (OH) ₂ system, because of the CaO consumption to form Fridel's salt.

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The fundamental experiment for the purpose of recovery of vanadium from oil burning ash, which was the valuable resources in Japan, was carried out. The following summarized the results.
Sulfuric acid was superior to aqueous ammonia as extraction media in the process of leaching vanadium ion from oil burning ash.
Precipitation ratio of vanadium compounds at room temperature was low. For example, the yield of vanadium compounds for 259200 s was no more than 60%. On the contrary, the precipitation rate increased at the higher reaction temperature and the yield reached up to approximately 100% at 80°C.
Initial concentration of vanadium ion was the important factor besides pH and reaction temperature. The higher initial concentration of vanadium ion enlarged the appropriate pH range for the precipitation. In the case of 16000 ppm of the initial concentration, the pH range was 2.0 to 2.8. It was wider than that of 4000 ppm or 8000 ppm.
The above results suggested that the higher initial concentration of vanadium ion, proper pH and higher reaction temperature were necessary to recover vanadium from oil burning ash efficiently.

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CO₂ fixation as formation of MgCO₃ with Mg (OH) ₂ is of particular interest because of the abundance of magnesium. We have studied an effect of crystallinity of Mg (OH) ₂ powder on their carbonation reactivity using synthesized Mg (OH) ₂.
Three types of Mg (OH) ₂ specimens were prepared using autoclave at 60°C, 120°C and 180°C, respectively. These were analyzed using X-ray diffraction, scanning electron microscopy, thermal analysis method and BET method. Difference of synthetic temperature has yielded variation of crystalinity of Mg (OH) ₂ to affect thermal properties and specific surface areas.
These specimens were suspended in the thermogravimetric analysis apparatus to perform isothermal thermogravimetric analyses at 350°C, 375°Cand 400°Cin CO₂ as carbonation experiments, respectively. Each specimen acquired the greatest amount of carbonate in final product at 350°C, at which the specimens synthesized at lower temperature, having lower, crystallinity and higher specific surface area, acquired a greater amount of carbonate. The result shows that Mg (OH) ₂ with lower crystallinity favored the formation of carbonate due to its high chemical activity and specific surface area.

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