“Portland-cement” should possess distnctive properties according to the purpose, so that it's function as cement will be in full play.
High durability should be the distinctive property of cement for asbestos-cement product, although it is required for cement for general contractions.
Then, serious consideration must be carefully paid towards the following elements that makes portland-cement possess high durability.
(1) Strength, especially strength against tension is required to be large.
(2) Free from crack due to contraction of cement, as well as from change of temperature and humidity.
(3) High resistance against solubility in water, as well as against abrasion.
After the result of a long-standing research and experiment on strength, contraction, modulus of elasticity, and etc. in many kinds of portland-cement, it will be understood that the chemical compostion of cement that is very suitable for asbestos-cement product will be as follow.
Chemical composition
H. M. Act. I. S. M. I. M. C3S. C2S. C3A. C4AF.
2.15 6.4 3.06 0.9 65 18 3 12
Fineness of cement
Residue 88μ 7.5%-8.5%.
Blaine specific surface value 2400-2700cm²/g.

View full abstract

Rockwool is popularly used as heat insulating material, which can usually be applied being filled in air space of walls as cotton type insulator. Especially the case which the rockwool is installed in walls of cold storage cars was considered and a vibration test was performed to the settling aspects thereof.
Rockwool was filled in a wooden box (Fig. 1) whose total inner height was divided in 10 layers each height 6.08cm, by sheets of thin paper to observe the settling condition. Observation was made from outside through the glass window. The vibration was given by an apparatus utilizing a flow tester of cement mortar (Figs. 2, 3). The last settled conditions were found by 100000-200000 vibrations (Figs. 10, 11, 12). The allowable heights of rockwool when filled in any density before vibration were found (Figs. 14, 15).
5 kinds of rockwool were examined, whose physical and chemical properties were referred, namely, thickness distributions of fibre (Fig. 4), thermal conductivities when filled with the density of about 0.2g/cm³ (Fig. 7), chemical analysis (Table 2), temperature gradients of thermal conductivities regarding void (Fig. 8), were comparatively referred. All the comparative results were shown in Tables 1, 3.

View full abstract

When Ube Fly=Ash are mixed with Cement by about 20%, the properties of Concrete are improved in many aspects as following,
1. much Reduction of Expansion due to Alkali=aggregate Reaction,
2. lower Heat of Hydration by about 20%,
3. increase the Resistance to chemical attacks,
4. increase the Workability of concrete, and decrease the amount of Water required to give normal Consistency,
5. the strengths of mortar and Concrete cured more than 3 monthes are superior to the one without Fly=Ash.
These improvements in property of concrete by mixing Fly=Ash are due to the fact that the Shape of grain of Fly=Ash is spherical, acting as Ball Bearing in Concrete mixture.

View full abstract

The properties of dicalciumsilicate being the chief component of portland Cement were investigated in comparison with several Commercial portland Cements. From the results of testing on the properties of Belit's low-heat Cements trially prepared from synthesized dicalciumsilicate, it was revealed that those Cements were effective as a low-heat Cements.

View full abstract

Electrical measurement of humidity has hitherto been done by several methods, but we have hardly been satisfied with the results brought about by them for many purposes.
A moisture-sensitive element of a hygrometer should have the following characters: it should have no timd-lag in humidity indication, no hysteresis phenomena and also no aging. For those characters, we are going to show a moisture-sensitve element of a hygrometer adopting the electric conduction of a thin film of selenium in humidity environment, and its application on some measurements of humidity.

View full abstract

The Authors measured the early volume changes of concretes which were placed under least friction in the moulds by own method and by devided rapid exact method, and obtained following results.
1) In the cases of Portland Cement of normal properties, the settling amount up to 10 minutes after placing of concrete indicates increased values from 40×10^-4 to 100×10⁴ (cowpared with initial unit length) as increasing W/C and slump values. Then the volume change stops for a short time and after 1-2 hours from initial placing, shrinkage due to cement paste in concrete of the order (3-1)×10^-4 reciprocal to W/C and to settling amount, appears.
2) Abnormal Portland Cements which showed the tendency of early craking at concrete building jobs, showed the abnormal settling in above described apparatus in laboratory continued till 60 minutes after placing of test concrete, and large shrinkage followed the rest period.

View full abstract

This paper presents the result of test conducted by means of Air-Meter for the purpose of measuring air content on the concrete produced at both the Ikebukuro and Narihirabashi Plants of our company.
(1) Air content per cubic meter in case the quality and quantity of AEA, cement, aggregates used are maintained constant:
The concrete tested was these manufactured at our plants during one year from Oct. 1952 to Sept. 1953. Vinsol. Resin used 0.75% of cement, and cement used more than 300kg for the concrete per cubic meter. Fine aggregates used are of same province and nearly 2.2 fineness modulus, while the maximum size of coarse aggregates which have nearly 9.8 of fineness modulus, is 25mm. Also distributing state of air was investigated for three different slumps ranging from 0-10, 10-20 and above 20 without considering of temperature.
(2) Variation of air content for every month when concrete was placed:
Of the results of air test made from Jan. to Sept. 1953 without reference to ratio of fine and coarse aggregates, taken into consideration was a concrete containing 250kg of cement per cubic meter. The results was that 47.9% of concrete contains 4+0.5% of air, 77.6% of concrete 4+1.5% of air and 92% of concrete, 4+1.5% of air as given in Table 6.
From the above, several problems such as variation of air content for different fineness of fine aggregates, selection of sample for air test and possibility of adding AEA into paste were investigated.

View full abstract

At high speed roller chain, rollers usually come into failure by repeated impact with sproket teeth. The authors have carried out many experiments on the fatigue strength of high speed roller chain, using the roller chain fatigue testing machine reported in the preceding paper in this journal. From the results of experiments, fatigue strength of rollers is obtained. Also many effects on the fatigue strength of rollers are cleared; that is, effect of thickness of cementation, effect of thickness of finishing, effect of pressure angle, effect of tensile load of chains, effect of tooth forms, effect of roller materials, etc.

View full abstract