[in Japanese]

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Calcium chloride is now regarded as an excellent accelerator to the hydration of portland cement, however, its corrosive character to the steel in reinforced concrete is hardly ignored. Therefore, the accelerators without corrosive character are especially indispensable for concrete practice.
In this paper, the accelerating action of calcium thiosulfate discovered or by the authors is investigated, in comparison with other inorganic soluble salts, by means of various methods.
The accelerating ability of calcium thiosulfate on the setting of portland cement is very identical to that of calcium chloride. The early development of strength of portland cement increases in proportion to the amount of calcium thiosulfate added to portland cement. The early strength of mortar of portland blastfurnace slag cement (granulated blastfurnace slag 65%, portland cement 35%) is developed near that of ordinary portland cement, when calcium thiosulfate was used at the concentration of 3%. However, the accelerating action of calcium thiosulfate on the development of early strength of portland cement is slightly poorer than that of calcium chloride.
The most characteristic of calcium thiosulfate as an accelerator will be that calcium thiosulfate does not give any corrosive action to the steel in concrete. The results of corrosion test showed that the test pieces of mild steel buried in mortar containing respectively 2% and 5% of calcium thiosulfate were scarcely corroded after the mortars were exposed under the atmosphere of outdoors for 6 months. Under a same condition, the test pieces of steel buried in the mortar containing 2% of calcium chloride was markedly corroded after only one month. Calcium nitrate did not show corrosive action. However, calcium nitrate can not be regarded as an accelerator.
The heat liberation curves of the hydration of portland cement obtained by the use of a devised adiabatic calorimeter indicated that the accelerating action of inorganic salts on the hydration of portland cement is focused on the hydration of alite phase. The orders of effectiveness of anions and cations as accelerators of the hydration of portland cement are Cl^->S₂O₃^-->SO₄^-->NO₃^-, Cl^->Br^->I^- and Ca⁺⁺>Mg⁺⁺>Na⁺.
The hydration products of tricalcium silicate is CSH (II) when calcium chloride was present, is CSH (I) when gypsum was present and is not evidently identified when calcium thiosulfate was present. DTA curve of the 24 hours hydration product of C₃S paste (H₂O/C₃S:50%) with 3% of calcium chloride showed a sharp exothermic peak at 640°C. The peak showed that the produced CSH (II) in hydration products was converted into β-C₂S by heating. In the case of calcium thiosulfate, the continuous two exothermic peaks were obseved in DTA curve. The first peak could not be exactly assigned, however, the second was assigned as the oxidation of calcium sulfite which produced by the decomposition of calcium thiosulfate.

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[in Japanese]

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Self-diffusion of sodium ions in the system of Na₂O-RO-SiO₂ glasses containing oxides of divalent ion (RO) such as MgO, CaO, SrO, BaO, ZnO, CdO, PbO were measured in the temperature range 200°-450°C by means of a radio-isotope tracer technique employing ²²Na. The electrical conductivity of the glasses has also been measured.
Self-diffusion coefficients of sodium ions and electrical conductivity of the glasses decreased smoothly as the effective radius of the substituted divalent cationn increased. This indicates that the braking effects of divalent cations on the migration of sodium ion are largely determined by the polarising powers, i.e., field strengths, of the divalent cations.
So-called correlation factor (f) was calculated by the corrected Nernst-Einstein equation, yielding factors about 0.2-0.3 for each glass. The resultant factor indicates that transport mechanism of sodium ions in the glasses is either of a vacancy type or of an indirect interstitial type and is essentially the same to the binary Na₂O-SiO₂ glasses, and that also is not influenced by the kind of the divalent cation.

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In the previous report (Jiro Matsuda and Ryoichi Tanaka, this journal, 76, 94 (1968)), photochemistry of NaI doped sodiumsilicate glasses has been discussed and it's reaction mechanism, cage effects of the glass matrix and the influence of iodine ion upon the growth of color centers in the glasses have been illustrated.
In the present report, the writers made comparative studies on the alkalisilicate glasses (Li₂O-3SiO₂, Na₂O-3SiO₂, and K₂O-3SiO₂).
The results are as follows,
1) excepting F^-, halogen ions in the alkalisilicate glasses are photo-oxidized to X₂^- type (dihalogen ion) with the irradiation of U. V. or X-ray and the photo-oxidation tendency for each halogen ion is great as following order, Cl^-<Br^-<I^-.
2) dihalogen ions produced in the glasses are stable at room temperature in a dark room and their absorption bands are 380, 715mμ (I₂^-), 360mμ (Br₂^-) and nearly 350mμ (Cl₂^-), that is, the wave-lengths of their absorption bands are independent of the kind of alkali components in the glasses.
3) the more acidic is the glass, the halogen ion doped in the glass is the more easily photo-oxidized, and such produced dihalogen ion is the more stable.
4) it is difficult for iodine to dissolve in Li₂O-3SiO₂ glass as I^-, consequently, in this glass, the yield of I₂^- by photochemistry is small though lithia glass is the most acidic compared with other alkalisilicate glasses.
5) excepting F^-, halogen ions have suppression effects on the growth of glass color centers induced by U. V. or X-ray irradiation, but the 310mμ band of the color centers in alkalisilicate glasses is comparatively difficult to be suppressed, and rather strengthend in the case of KBr doped K₂O-3SiO₂ glass.

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