Calcium silicate hydrates were synthesized using fly ash as a silica raw material by hydrothermal reaction, and its filter aid property was studied.
The results were summarized as follows.
(1) Formation of hydrogernet was inhibited by adding alkali raw material, and aluminum content with raw material was introduced into tobermorite to form Al substituted structure. The sample synthesized with adding KOH was suitable for filter aid material. The sample synthesized with adding NaOH had stiff surface of secondary particles.
(2) Blain specific surface area increased with increasing of KOH content and its value drastically increased with increasing of NaOH content. The average filtration resistance of cake was more largely influenced by its Blain specific surface area than porosity.
(3) When large amounts the fine particle slurry were added to calcium silicate hydrates filter aid slurry system, the filtrate passage was preserved since it had large void volume.
(4) In the case of using the sample synthesized with adding KOH, filtrate became clear immediately. In the case of using the sample synthesized with adding NaOH, filtrate did not become clear since the fine particle slurry passed through filter material.

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This paper discuss the synthesis of standard hydrates and the drying method for XRD quantitive analysis of C₃A-CaSO₄·2H₂O-CaCO₃-Na₂SO₄-H₂O system. Monocarboaluminate was synthesized by using of mixture of C₃A and CaCO₃ (mole ratio 1 : 1). Combined water of monocarboaluminate (mole ratio) was 10.4 by aspirator drying after 3 h. Hemicarboaluminate was formed by the mixture of C₃A : CaCO₃ : Ca (OH) ₂ = 1 : 1/2 : 1/2 at 28 day. Combined water of hemicarboaluminate was 11.2 by aspirator drying after 3 h. Chemical compositions of ettringite and monosulfoaluminate were C₃A·3CaSO₄·31.4H₂O and C₃A·CaSO₄·11.5H₂O respectively by the same drying method. Single phase of U was formed by the mixture of C₃A : CaSO₄·2H₂O : Na₂SO₄ = 1 : 0.9 : 0.5. The chemical composition of U phase may be C₃A·0.9CaSO₄·0.5Na₂SO₄·13H₂O.

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The reaction between CaSiO₃ in water and CO₂ was carried out in the temperature range of 30 to 70°C. The experimental data clearly indicated that the reaction of CaSiO₃ with CO₂ produced SiO₂ and Ca (HCO₃) ₂ in the following equation, CaSiO₃+2CO₂+H₂O→SiO₂+Ca (HCO₃) ₂. The SiO₂ obtained was amorphous and on the other hand calcium carbonate particles with crystal habits were obtained from the decomposition of Ca (HCO₃) ₂.
It was kinetically shown that the reaction was controlled at the initial stage by calcium dissolution from CaSiO₃ into water and at the intermediate to the final stage by the surface reaction of calcium on CaSiO₃ with HCO₃-. The activation energy of the reaction obtained was 5.4 kcal/mol, which was suggested to be the energy for the surface reaction.
The reaction is considered to be very useful for fixing carbon dioxide as calcium carbonate as well as for producing SiO₂.

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To study the organism adherance properties of porous concrete and the cleansing effectiveness of organic substances and nutrient salts such as nitrogen and phosphorus, a porous concrete specimen was placed in a semiclosed water area called Katagami, in Oomura Bay.
The results obtained were as follows;
1) One month after placement of the porous concrete specimen in the field sea area, large sized adhering organisms were seen. Comparing the organism adherance properties of the porous concrete specimen and that of ordinary concrete in the field sea area, porous concrete is a more suitable adhering substrate.
2) Extreme lowering of compressive strength was exhibited in the specimen in the field sea area.
3) There seems to be good circulation of organic substances and nutrient salts such as nitrogen and phosphorus inside and around the specimen. Though further investigation and study are necessary, it seems there is a good possibility to improve water cleansing.

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The initial stage polymerization of silicic acid in aqueous solution was investigated by using a monosilicic acid solution prepared from hydrolysis of TMOS (Tetra-methyle-silicate).
Results obtained were as follows.
1) The silicic acid concentration in aqueous solution by ion resin method of sodium silicates decreased rapidly.
2) The silicic acid solution prepared from the hydrolysis of TMOS was stable on standing at 25°C. The rate of initial stage polymerization can be applied of the second-order reaction equation. Its initial stage polymerization were distinguished for three step in acid solution, and for two step in alkaline solution. The rate of polymerizationin alkaline solution proceeded greatly than this of in acid solution.
3) The activation energies for polymerization were 26.4 kcal/mol in water, 9.5 kcal/mol in acid solution.
From these results, it was found that the polymerization took place in a different mechanism by acid solution and alkaline solution, and formed ⁺H₂OSi (OH) ₃ in acid solution, (HO) ₃SiO^- in alkaline solution.

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The removal of beryllium ions from complex component waste water containing beryllium and other heavy metal ions by the ferrite process were examined.
For the complex component waste water containing beryllium and heavy metal ions, it has been found that the structure of the sludge was ferrite and that the beryllium 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 beryllium ions from model waste water up to a beryllium ion concentration of 100 mg/l.
The saturation magnetization of the sludge was higher than the value of 60 emu/g required for application to magnetic materials.

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Crystallization of CaCO₃ from Ca (NO₃) ₂ aqueous solution by mixing Na₂CO₃ aqueous solution and homogeneous precipitation methods were investigated in the presence of Ni²⁺, Co²⁺, Mn²⁺ and Fe³⁺ ions on the morphology and color of deposit. The results are follows :
(1) In solution mixing method at 35°C, Ni²⁺ ions accelerated transformation from vaterite to aragonite and Mn²⁺ ions did that to calcite, whereas Fe³⁺ ions stabilized vaterite.
(2) In homogeneous precipitation method at 90°C, all additives stabilized aragonite, and the stabilizing effect decreased in order of Mn²⁺, Co²⁺>Ni²⁺>Fe³⁺ ions. The larger the effect was, the smaller the aragonite particle size was.
(3) Lattice constants, ao, of pure calcite by homogeneous precipitation method at 90°C was smaller than that by solution mixing method at 35°C. The addition of Ni²⁺ and Mn²⁺ ions decreased both ao and co, suggesting their substitution of Ca²⁺ ions in calcite. The lattice constants changed little by addition of Fe³⁺ ions.
(4) On lattice constants of aragonite, the addition of Mn²⁺ ions decreased ao and co, but increased bo in solution mixing method at 90°C. In homogeneous precipitation method at 90°C, lattice constants changed little in the presence of Mn²⁺, Ni²⁺ and Co²⁺ ions.

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