In this paper, some properties of cement made by trial manufactural method using a large amount of sewage sludge was discussed. The discussion included change of f-CaO contents in the cement, effect of HM and specific surface area on compressive strength of mortar, effect of P₂O₅ contents on the rate of heat liberation of hydration, effect of reacting P₂O₅ with alite, belite and interstitual phases and the relationship between P₂O₅ contents and stability of C₂S phase.
1) It was recognized that f-CaO increased in accordance with the increase of sewage sludge.
2) At the age of 28 days, the compressive strength of mortar using sewage sludge was lower than that of ordinary cement. But the strength was improved to a certain extent by the increase of HM and specific surface area by more than 3, 500 cm²·g^-1.
3) The rate of heat liberation on the secondary peak measured by using conduction calorimeter decreased with increase of P₂O₅ contents in cement.
4) It was found that P⁵⁺ion in P₂O₅ in sewage sludge did not react with interstitual phases but react with alite and belite substitutionally.
5) α-C₂S in clinker was stabilized by the reaction of P₂O₅ with C₂S phase.

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Magnesium silicon nitride (MgSiN₂) powder compacts with 0, 0.5, 1, 2 and 3 mass% of yttrium oxide (Y₂O₃) addition were hot-pressed between 1450°C and 1650°C for 90 min in a nitrogen atmosphere under a uniaxial load of 31 MPa. Densification of the MgSiN₂ compacts was promoted by the addition of Y₂O₃. The optimum hot-pressing temperature to fabricate dense MgSiN₂ compacts was first examined by fixing the amount of Y₂O₃ addition to be 3 mass%. The MgSiN₂ compact with 3 mass% of Y₂O₃ addition possessed a maximum relative density of 96.5% at 1550-1650°C whilst a maximum hardness of 19.2 GPa was achieved at 1550°C. On the basis of these results, the optimum amount of Y₂O₃ addition required to fabricate a dense MgSiN₂ compact was further investigated by fixing the hot-pressing temperature to be 1550°C. A maximum relative density of 99.9% was achieved for the case of 1 mass% Y₂O₃ addition whilst the fracture toughness (≈1 MPa·m^1/2) showed only a slight dependence on the amount of Y₂O₃ addition. The phases detected by X-ray diffraction were MgSiN₂ and Y₂Si₃O₃N₄ whilst a thermal conductivity of 20-21 W·m^-1-K^-1 was achieved for 0-3 mass% Y₂O₃ addition at 1550°C.

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Some calcium and magnesium phosphates were prepared by adding the solution ([Ca²⁺] + [Mg²⁺] = 0.5 mol·dm^-3) in presence of Ca²⁺ and Mg²⁺ ions into the mixed solution ([KOH] = 4.0-8.0 mol·dm^-3, [H₃PO₄] =4.0 mol·dm^-3) of KOH and H₃PO₄ at 25°C. The resulting products were HAp, CaHPO₄·2H₂O, Ca₈H₂ (PO₄) ₆·5H₂O, amorphous calcium phosphate, Mg-containing whitlockite (Mg-CaW), KMgPO₄. 6H₂0 and MgHPO₄ ·3H₂0, and depended on the pH of suspension and Mg/ (Ca+Mg) molar ratio of starting solutions. The synthetic Mg-containing whitlockite was produced by using the starting highly concentrated solutions at about neutral pH when Mg/ (Ca + Mg) molar ratio was 0.1-0.3, and was stably formed for 72 hours at Mg/ (Ca+Mg) =0.2 in particular. The pH region obtained the synthetic Mg-CaW became wider to a weak acidify by using NaOH solution instead of KOH solution.

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Adsorption and photocatalytic decomposition of dimethyl sulfide (DMS) by a new type silica bead coated with TiO₂ (TiO₂/SiO₂ bead) were investigated. It was found that titanium existed as TiO₂ (anatase form) on the surface of the silica bead. Specific surface area of the bead was 391 m²·g^-1 and adsorption efficiency of the bead was superier to commercial TiO₂ grain for gaseous DMS. Photocatalytic decomposition by the bead was 65% for 33.5 h^-1 of space velocity (SV).Reaction products detected after photocatalytic decomposition of DMS by the TiO₂/SiO₂ bead under ultraviolet light were dimethyl disulfide, SO₂, SO₄^2- ion and acetic acid. Thus, it is recognized that oxidative decomposition mainly proceed in the photocatalytic reaction.

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Many investigations on permeability of ultrafine cement grout have been carried out in a view of phenomenal consideration with various soil properties for injection, mix proportions of grout, methods of construction and so on. There is little investigation of properties of ultrafine cement itself.
In this paper, some effects on the permeability characteristics of two kinds of ultrafine cement grout, which have different permeability with similar physical characteristics, are investigated by observation with scanning electron microscopy, measuring viscosity, zeta potential, particlesize distribution and rate of heat evolution.
The results of above experiments were shown as follows;
(1) The permeability of ultrafine cement grout was influenced by the growth of particles.
(2) Increase of viscosity and aggregation of particles reduced the permeability of ultra fine cement grout.
(3) The permeability of ultrafine cement grout with high dispersibility tended to be better than that with low dispersibility.

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