As previously reported (J. Ceram. Assoc., Japan, 68 [3] 63 (1960)) the low temperature modifications of calcium hydrate silicates play an important roll in the bonding of cement at ordinary temperatures. And also the high temperature modifications formed hydrothermaly play a dominant part in the hardening of cement paste and relating secondary products cured at elevated temperature.
The present paper contains the results of the investigations on the reaction and solid reaction products in the system CaO-SiO₂ (gel)-water at 110°C by means of chemical analysis, electron microscope, X-ray and electron diffraction, differential thermal analysis, and differential thermo-balance.
The starting mixtures of the C/S(=CaO/SiO₂) mol. ratios 0.8-3.0 were kept at 110°C for 3 or 7 days in an autoclave with an electromagnetic stirrer.
The results obtained are summarized as follows:
(1) The C/S of the reaction products were in the range 0.76-1.69, increasing nearly proportional with the increase of C/S of the starting mixtures as long as C/S≤1.50, whereas C/S of the reaction products gave nearly the same values when the mol. ratios of the starting mixtures C/S≥1.50.
(2) Practically no difference was found in the amount of CaO remaining unreacted whether process was continued 3 or 7 days. This means that the reaction stops before 3 days, although the growth of crystals continues farther with time.
(3) The solid reaction products obtained were tobermorite phase in film, crumpled foil, fiber or plate, and afwillite in prismatic crystals.
Tobermorite phase appeared in fiborous form from the starting mixture of C/S=0.80, and in plate form from C/S=1.00 or 1.20. Prismatic afwillite was the main solid phase produced from lime rich starting mixtures (C/S>1.20). In the case of C/S=1.2 the mixed crystals of tobermorite phass and afwillite was observed, in which the former is developing from the surface of the latter.
(4) The filmy or fiborous tobermorite phase may be identical with CSH (B) or C₂SH₂, and the plate will be C₄S₅H₅. Both fibers and plates showed the habit of developing in the direction of b-axis.
The cementing properties of tobermorite phase and afwillite seems to be in the following order:
tobermorite phase (plate)>tobermorite phase (film and fiber)>afwillite
(5) The thermal curves showed an exothermic peak arising from a temperature between 782° and 823°C. The film or fiber crystal of tobermorite phase gave the higher peak than the plate crystal.
Dehydration of combined water up to around 600°C was measured by a thermo-balance. Afwillite showed an endothermic peak starting at a temperature between 282° and 331°C (dehydration of combined water) and also an exothermic peak arising between 816° and 893°C (structural change).

View full abstract

As a supplement of preceding papers on the effect of composition of pot material on The physical properties of optical glass pot the author re-investigated the effect of grain size distribution of chamotte, especially that of continuous and gap grading, on the gathering properties in combination with the effect of bonding clay.
The results obtained are as follows:
a) Packing density for three sizes with large diameter ratios varies with the degree of tapping, viz., the densest packing comes at three grading when tapping is full, whereas with poor tapping as in the case of flow packing the density runs parallel with the surface factor of chamotte, and the finer the chamotte the smaller will be the density.
b) Slip of good flow property may be obtained when the mixtures contains some amount of fine grain chamotte with additional bond clay. With increasing bond clay the mixture with no fine grain gives the best value, and the effect of grain size distribution becomes more and more smaller.
c) The effect of the packing of chamotte on the bulk density of dried body is seen clearly in the mixture with small amount of bonding clay, and the composition of chamotte with maximum bulk density shifts from the maximum packing density to the composition containing more medium particle.
d) The bulk density of fired body shows the effect of packing only in the coarse-medium series, the effect of fine chamotte being maximum, and the bulk density increase with the increase of fine particle. The effect of the packing, and of the grain size distribution of chamotte on the bulk density of material decreases more and more with the increase of bonding clay.
e) The influence of the packing effect of chamotte from the view point of the absorption property of fired body is quite the same as stated in item d).
f) The linear relation between the logarithm of particle diameter and the bulk volume of chamotte is seen, but the straight line bends at the point near 0.05mm, from where the finer particle the larger becomes the bulk volume.
g) The gap grading of three component system proves that the densest packing may be obtained at the composition near the side of fine-coarse particles as long as the diameter ratio is small. The compositions shift gradually toward the medium grain side with increasing diameter ratio.
h) The value of the densest packing of a three component system increases with increasing diameter ratio up to a certain maximum, and then decreases with further increasing ratio.
i) The packing of the continuous grading obtained by repeating the operation of adding the third particles to the mixture of densest packing of first and second particles to form again the densest packing of three component is practically the same as that obtained by ordinary method of mixing three separate components, and also the surface factors are the same in both cases.
j) The composition of the dense packing in gap grading is also the same as that in continuous grading.

View full abstract

This paper concerns with the determination by quantitative chemical analysis, etc., of the minerals (2MgO⋅SiO₂, MgO⋅SiO₂, free MgO and free SiO₂) which may exist in the process of the synthesis of forsterite from magnesium hydroxide and crystobalite.
The mixtures prepared for the molar ratio of about 2MgO⋅1.1SiO₂ from magnesium hydroxide and silica gel or cristobalite were heated up to the temperatures, 700°-1550°C, at the interval of 40°C.
The samples so obtained using cristobalite as a siliceous starting material were subjected to quantitative analysis, whose method was based on the characteristics that cristobalite and enstatite are not affected, but magnesium and forsterite are soluble or decomposable by dilute hydrochloric acid.
It was confirmed that the quantities of each minerals existing in the specimen after various heat treatment could be measured successfully.
Such specimens were analysed by X-ray using internal standard, and by measuring the variation of the intensity of diffraction pattern.
From the results of chemical analysis and X-ray diffraction pattern the calibration curves were set up taking into consideration of the best condition of X-ray analysis.
The variation in the process of forsterite formation from other silicious starting materials, silica gel or quartz, were investigated quantitatively using above calibration curve.

View full abstract

Recrystallized titania, sphene (CaO⋅TiO₂⋅SiO₂) and zircon opaque glazes were compared in view of the scattering coefficient, reflectivity and covering power calculated by Clewell's and also by Kubelka's formula.
It became evident from the results of experiments and calculations that
(1) titania opaque glaze gave the highest opacity, which was followed by sphene, and then by zircon glaze, although the Clewell's formula gave the reverse ranking of the last two as may be interpreted by the refractive index of dispersed crystalls in glaze layer, and that
(2) the reflectivity of sphene glaze was the highest giving nearly pure white, zircon the next, and the titania glaze gave the lowest value as may be expected from the unstable firing tint of recrystallized titania glaze.
The reflectance of above three glazes was calculated by Kubelka's formula and plotted against the reflectance of bisque in order to estimate at a glance the covering power of the glazes.
From the graph it may be concluded that the bisque of low reflectance would be rather favourable for obtaining the glazed products of uniform colour when opaque glazes are applied on a discoloured bisque, although the reflectance itself might be low.

View full abstract

For the purpose of elucidating the phenomena of nucleation and thermal reduction process of developing color by the dispersion of fine metallic crystals a glass of the composition of Na₂O 15.0, CaO 10.0, SiO₂ 75.0, Cu₂O 0.225, SnO 1.125 (wt. ratio) was subjected to the heat treatment under various conditions, and the development of the absorption around 570mμ was observed.
The absorption of the specimens heated between 480° and 710°C was found to follow the Lambert-Beer's law.
It was confirmed that the amount of copper, B, dispersed in glass in an early stage of heating was represented by
B=const.×aIGt^5/2
which means that the reaction proceeded with the homogeneous nucleation of velocity I, and later with the thermal reduction controlled by the rate of the reaction
Cu⁺+Sn²⁺=Cu°+Sn⁴⁺,
and was represented by a saturation curve of the form
B=const.×C₀g(t)
Moreover, the value of (log I+log G) which includes the growth coefficient G reached to the maximum between 580°-647°C.

View full abstract