The hydration mechanism of 3Ca0·Al₂O₃ (C₃A) -CaSO₄·2H₂O-CaCO₃ system and the effects of the amount of CaSO₄·2H₂O were discussed based on the XRD quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed.
In the case of C₃A-CaSO₄·2H₂O system, the initial hydration of C₃A was delayed by the formation of gel containing of SO₄^2-. The early hydration of C₃A was delayed also furthermore by addition of CaSO₄·2H₂0 and CaCO₃. Because the gel containing SO₄^2- and CO₃^2-was produced on the surface of C₃A. When the reaction of CaSO₄·2H₂0 was finished, the reaction of CaCO₃ was started in the case of C₃A-CaSO₄·2H₂O-CaCO₃ system. Delayed ettringite formation would take place because monosulfoaluminate is not stable in the presence of CaCO₃. In the presence of CaCO₃, the SO₄^2- groups in the interlayer region of monosulfoaluminate are replaced by CO₃^2-. This reaction leads to the formation of monocarboaluminate, and to increasing the sulfate concentration in the solution, and hence to the recrystallization of ettringite. In order to prevent the delayed ettringite formation, the reduction of monosulfoaluminate formation is important. The delayed ettringite formation occurred in the C₃A-2/3CaSO₄·2H₂0-15 mass% CaCO₃ system. When mole ratio of CaSO₄.2H₂0/C₃A is 1/3, the delayed ettringite formation is not occurred until 28 day. But a large amount of monosulfoaluminate are produced and unreacted 3CaO·Al₂03 and CaCO₃ are remained. Therefore, the delayed ettringite formation will be occurred at long term. In the C₃A-CaSO₄·2H₂0-15 mass% CaCO₃ system, the delayed ettringite formation is not observed. Therefore, by the increasing of the amount of CaSO₄·2H₂O addition, the delayed ettringite formation can be prevented.

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Incineration ash of urban waste has been disposed in reclamation project but a shortage of reclamation sites is causing problems. Under these circumstances, we have completed a study on a method of recycling incineration ash by using the ash as a raw material of Portland cement.
Incineration ash consists of fly ash and main ash. Chloride has a bad influence on cement quality, and because main ash has lower chloride content than fly ash, a number of main ash can be recycled directly as a cement raw material. Fly ash cannot be used without prior treatment due to its high chloride content of 5 to 20%. Thus we attempted to remove chloride from fly ash by washing with water and filtering. The following summarizes the results.
1) We succeeded in using fly ash from municipal refuse as a cement raw material after removing chloride from the fly ash by washing with water.
2) We were able to precipitate and remove a small amount of heavy metals melted into the filtrate by adjusting the pH values 7-10 using carbon dioxide.
3) Due to hydration, Friedel's salt of low solubility was generated in some fly ash that was sprinkled water to prevent dust generate. Under wet conditions, the amount of Friedel's salt increased with age, resulting in a decline in the rate of chloride removed from fly ash.
4) Blowing carbon dioxide into the slurry during washing was found to be an effectual method of removing chloride when washing fly ash containing Friedel's salt.
5) Dioxines contained in fly ash did not dissolve in waste water by washing with water.

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A calcium silicate hydrate, Ca_1.5 SiO_3.5·xH₂O, was synthesized either by a hydrothermal or mechanochemical method using rice husk ash (RHA) and calcium hydroxide as raw materials. The particle diameters of the products prepared by the hydrothermal synthesis were mostly less than 10 μm with an average between 4.8 μm and 7.9 μm and were varied according to the synthetic method and conditions. Finer calcium silicate hydrate could be prepared by the mechanochemical synthesis. Similar to C-S-H gel in Portland cement paste the product appeared to be flocs with a porous structure and large specific surface area. When the product was heated it gradually lost the water that existed in its structure and pores but kept amorphous state up to 750°C. Above 780°C it was changed to wollastonite.

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The characteristics of cinker in the C₃S-C₂S-C₁₁A₇ ·CaF₂-C₄AF system vary depending on the cooling rate and change the early hydraulic properties of the cement. The size of alite becomes small with cooling rate and the fine crystals of alite which precipitated at cooling process coexist with the crystals of alite which precipitated at burning process in case of rapid cooling. The above changes in fine textures have a close relationship to the content of SiO₂ in the solid solution of C₁₁ A₇·CaF₂. The amount of SiO₂ and other impurities in C₁₁A₇·CaF₂ give a considerable influence on the early hydraulic activity of the phase; with the decrease in impurities, that is, with the decrease in cooling rate, the activity becomes high.

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Some glasses containing large amounts of TiO₂ were prepared in the Na₂O-TiO₂-P₂O₅ system. The composition region for obtaining the homogeneous glasses was 0-3 mol% of Na₂O, 66-74 mol% of TiO₂ and 25-34 mol% of P₂O₅. The incorporation of TiO₂ into phosphate glasses was very effective for the improvement of the properties. In particular, the thermal expansion coefficients of the glasses were 2.4-2.9 × 10^-6°C^-1 in the range from room temperature to 550°C. These values are smaller than those for any other known glasses containing P₂O₅ as the main component. From the glasses without Na₂O, (Tie) ₂P₂O₇ and TiP₂O₇ were produced, whereas from those with 2 mol% of Na₂O, NaTi₂ (PO₄) ₃, TiO₂ and (Tie) ₂P₂O₇ were produced by the crystallization.

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In order to investigate the influence of flame characteristics on the surface area of spherical silica powders, their preparation was carried out in the propane-oxygen flame using ground natural quartz powder with a mean diameter of 11.4 μm as a starting powder. The flow rates of propane and oxygen carrier gas were 5 and 7.5 Nm³/h, and the powder feed rate was 18 kg/h, respectively. Two kinds of oxygen gas, primary and secondary oxygen, were ejected from separate nozzles into the combustion room of burner. Being kept the total amount of oxygen constant, their flow rate ratio was varied. With an increase of the portion of primary oxygen from 16 to 50%, specific surface area of the products, collected between cyclone and bagfilter, decreased from 15 to 7m²/g. Distribution of temperature and particle velocity in the flame were found to depend greatly on the ratio of primary and secondary oxygen. Short residence time of particle in the temperature region >2300 K, where gaseous SiO is generated vigorously, resulted in the formation of smaller particles and increase of specific surface area

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The removal of heavy metal ions from waste water containing heavy metal ions by the ferrite process were examined.
For the waste water containing heavy metal ions, it has been found that the structure of the sludge was ferrite and that the heavy metal ions existed in a ferrite lattice as a stable solid solution, from the analysis of the sludge by X-ray diffraction patterns of the ferrite.
The lattice constant measurement revealed that it was possible to remove heavy metal ions from model waste water up to a Co, Cu and Ni ions concentration of 2000 mg/l. And it was possible to remove Cr ions from model waste water up to a Cr ions concentration of 500 mg/l.
The saturation magnetization of the Co-, Cu-, Ni-ferrite sludge was higher than the value of 60 emu/g required for application to magnetic materials. But the saturation magnetization of the Cr-ferrite sludge for magnetic materials.

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