The influence of adding gypsum on the chemical reactions and strength of lime-quartz based autoclaved board samples were investigated. The samples were prepared by adding 0, 5, 10, 20 mass% of gypsum (converted to CaSO₄) under saturated steam pressures at 180°C for various times from 0-160 h and 140°C for 0 h. The starting materials of Ca (OH) ₂ and quartz with Ca/Si = 0.8 were mixed with gypsum, cellulose fiber and water, followed by molding to a density of 1000 kg· m^-3. The demolded boards were then hardened by autoclaving. The specimens without gypsum reacted hydrothermally : Carich C-S-H+ quartz→C-S-H→tobermorite with 1.1 nm spacing. Adding gypsum to the starting mixtures, hemihydrate dehydrated form of the gypsum reacted with lime and quartz to form hexagonal prisms of hydroxyl ellestadite which grew radially, and inhibited the formation of C-S-H and tobermorite. This inhibition resulted in the delay of the elevation of the strength. As the hydrothermal reaction progressed, hydroxyl ellestadite reacted with quartz and decomposed into tobermorite crystals and anhydrite. A finer microstructure developed, resulting in a high strength. Further hydrothermal treatment increased the strength of specimens prepared with higher quantities of gypsum, indicating higher tobermorite crystallinity. Prolonged treatment of specimens prepared with 0, 5 or 10 mass% of gypsum caused tobermorite to decompose into gyrolite, and led to a coarser microstructure and reduction in strength. However, gypsum that was added to constitute 20% give tobermorite to remain stable and inhibited the decomposition into gyrolite.

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Phenol resin-alumina cement composite (PRAC composite) with flexural strength as high as 200 MPa has been developed by Hasegawa et al. from the composition of phenolic resin (resol resin), alcohol soluble polyamide, glycerol and alumina cement. In comparing with MDF (macro-defect-free) cement, this newly developed composite has higher flexural strength and resistivity to water and heat. From mechanism study, we indicated the existence of interaction in the interface area between hydroxyl group in phenol resin and alumina cement.
In this paper, the effect on flexural strength of diphenolic and triphenolic compounds with palafolm added in PRAC composite was studied. Addition of a slight amount of diphenolic compounds, such as resorcinol, or triphenolic compounds, such as pyrogallol or phloroglucinol, raised the flexural strength of the PRAC composite by approximately 33% in comparison with that without addition of di-and triphenolic compounds. From the results of model reaction of AC and pyrogallol or phloroglusinol, it was suggested that hydroxyl group and alumina cement play an important role to enhance the strength of the composite.

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Alumina cements were manufactured as experiments from aluminium dross ashes and oyster shells. Aluminium dross ashes were oxidized by burning treatment at 1100°C, and oyster shells dried at 110°C. The mixture of pretreatment aluminium dross ashes and oyster shells were crushed in a grinding mill. Alumina cements were obtained by burning ground mixtures. Mixing ratio of these wastes were designed to be 0.25-4.0 CaO/Al₂O₃ mass per cent, and the burning conditions were set to be 1100-1300°C. Alumina cements were characterized by means of XRD and XRF, and the refractoriness were examined in accordance with JIS R2204. Compressive strength of hardened mortar was examined in accordance with JIS R2521.
The results obtained from the present study are as follows.
1) Main components of alumina cements were CA, MA, and C₂AS. The formation of CA was confirmed by burning at 1100-1300°C and set to be 0.43-0.67 CaO/Al₂O₃ mass per cent.
2) Compressive strength of hardened mortar reached at 51.4 N·mm^-2 in 28 days. The refractoriness of alumina cement reached at roughly 1500°C. There seems to be a chance that alumina cement can be used for refractory brick, unreinforced concrete and so on.

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From the viewpoint of resource-and energy-saving, and for the purpose of global environmental safeguard, the authors are studying applications of ground granulated blast-furnace slag as a concrete aggregate by paying particular attention to the granulated blast-furnace slag, which is subsidiary produced as an industrial by-product in such a great quantity as 16 million tons a year in Japan.
In order to realize practical use of the ground granulated blast-furnace slag for high strength and durability concrete on the basis of the experimental results in the laboratory, including those which have been reported in the past, the authors compiled in this article experimental research results about applications of the ground granulated blast-furnace slag to the concrete mixed up in a ready-mixed concrete plant qualified by the JIS.
As a result, it was practically clarified that the ground granulated blast-furnace slag can be sufficiently utilized as the aggregate for the high strength and durability concrete.

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Permeability properties of incineration ashes suspension due to ceramic membrane in supersonic flow field were investigated.
The permeation flux of coloidal suspension in supersonic flow field decreased by prompt fouling. In filtration for one day, the flux decreased with increasing time because of the pore narrowing.
The membrane resistance increased with increasing time. However, backwashing to take off plugging by nitorogen gas was found to be effective for the recovery of flux.
The permeation flux of coloidal suspension under supersonic flow field decreased with increasing the concentration of slurry. The permeation flux, however, change very little with the concentration for not less than 4 mass%. The limitations of concentration to be fluidized slurry under this experimental conditions was found to be 3.5 mass%.

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In recent years, amount of urban waste is increasing and a shortage of land disposal site has been caused as a serious problem. The study was carried out to establish recycling process of fly ash included with chloride without generating any secondary waste. The following summarized the results.
Chloride in the fly ash was leached with water. We can downsize facilities for subsequent process, because volume of residue was reduced by 1/5 to 1/10.
Copper and zinc ions in the residue were leached with sulfuric acid solution. From this filtrate, copper metal was recovered by cementation and zinc hydroxide was recovered by adjustment pH, respectively.
Lead ion was leached with aqueous solution of sodium hydroxide and was recovered as lead sulfide. At the same time, calcium sulfate was converted to calcium hydroxide which was able to be utilized as a raw material for cement.
The waste water caused from this process could be content with effluent standard by water treatment attaching importance to de-selenium processing.

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