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Volume 1981 (1981)
- Issue 175 Pages 239-
- Issue 174 Pages 188-
- Issue 173 Pages 139-
- Issue 172 Pages 92-
- Issue 171 Pages 47-
- Issue 170 Pages 3-
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Volume 1981, Issue 174
Displaying 1-7 of 7 articles from this issue
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Shigeki MATSUYA, Masaji YAMANE1981 Volume 1981 Issue 174 Pages 188-193
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSThe mixture of CaSO4 and quartz (1 : 1 in molar ratio) was isothermally heated in a static air and dry N2 flow between 900 and 1300°C. The reaction products were investigated by means of X-ray diffraction. At the early stage of the reaction, both α-and β-CaSiO3 were formed in a static air and a-CaSiO3 was mainly formed in N2 flow. As the reaction proceeded further, Ca2SiO4 began to be formed. The amount of Ca2SiO4 formed was larger in N2 flow than that in a static air. It was considered that the Ca2SiO4 was mainly formed by the reaction between CaSO4 and CaSiO3. The rate of the initial reaction which corresponded to the formation of CaSiO3 was given by Serin and Elickson's equation, 1-α = (6/π2) ∞Σn=1 (1/n2) exp (-n2π2Dt/R2).The apparent activation energies were 97kcal/mol (in N2 flow) and 94 kcal/mol (in a static air), respectively. Diffusion coefficients calculated from the above equation, assuming that the radius of quartz particle was 5pm, well agreed wish those for Ca2+ ion in a-andβ-CaSiO3 reported by Lindner. Consequently the rate-determining step at the early stage seemed to be the Ca2+ ion diffusion in the CaSiO3 layer formed between CaSO4 and quartz.View full abstractDownload PDF (1127K) -
Koichi KISHITANI, Takayuki HIRAI1981 Volume 1981 Issue 174 Pages 194-198
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSSome glass roving reinforced gypsum planks were experimentally manufactured and flexural properties of the plank were improved by adopting an adhesive.
The strength of the adhesive-added glass roving planks corresponded to that of plywood in comparison with samples of the same thickness. Moreover, some properties facilitated forming process. The hardened adhesive covering the glass roving prevented the injury of the glass roving during the manufacturing process and made it possible to set the glass roving at the designed position in the cross section of the plank.View full abstractDownload PDF (649K) -
Tamotsu YAMADA1981 Volume 1981 Issue 174 Pages 199-204
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSThe hydration speed of gypsum hemihydrate (plaster of Paris) can be enormously accelarated by adding the ground gypsum dihydrate (Ground). This speed was measured as the viscosity change of the slurry after water was mixed by a specially prepared viscometer.
The speed increases as addition amount of the Ground increases and is satisfied by about 1 % adding. The hydration speed changes with the degree of grinding, 1-5 minutes grinding satisfies the speed. The effect of the Ground decreases with reserving time after grinding as much as half by a day and one third by 20 days, by reason of losing the activity of the ground crystals.
The accelarating effect of the Ground is presumed that the crystal structure is deformed or dislocated by grinding and this activated specks of the crystals proceed the nucleation, and the crystal growth of the dihydrate accelarated. The application experiments of the present accelarated gypsum hemihydrate to the fire extinguishing and to the prevention of sand sweeping under heavy rainfall are reported.View full abstractDownload PDF (1069K) -
Kazutaka SUZUKI, Kimio KATO1981 Volume 1981 Issue 174 Pages 205-210
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSHardened gypsum (CaSO4.2H20) was made as a cylindrical test piece of 30mm-diameter x 30mm-height with the low water/gypsum ratio up to 0.2 for β-CaSO4·1/2H20 by the following technique. The powder of β-CaSO4.1/2H2O was charged gradually into the cylindrical cell with alternate spraying of water and pressed under high pressure between 70-210 kg/cm2.
The compressive strength and porosity were investigated and the combined water was measured. The hardened sample prepared with water/gypsum ratio of 0.4 and pressed under 210 kg/cm2 showed the high strength up to 1050 kg/cm2 with a minimum porosity of 12.1%, and the water·gypsum ratio of this sample after press moulding was lowered to 0.26 nearing to the stoichemical amount of water for CaSO42H2O formation.
The water absorption rate and the strength drop by water curing were diminished with the reduction of porosity.
About 90% of hydration was proceeded by one day's curing in the moisture and the electron microscopic photographs showed that the press moulded sample that has high compressive strength has the quite different crystal appearance from CaSO42H2O crystal hardened from slurry as shown in Fig. 10.View full abstractDownload PDF (1169K) -
Osao SAKAEDA, Masamichi FUJIHARA, Toshikazu SEKIDA1981 Volume 1981 Issue 174 Pages 211-214
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
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Yasuo ARAI, Tamotsu YASUE1981 Volume 1981 Issue 174 Pages 215-222
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
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Kenichi TOKORO1981 Volume 1981 Issue 174 Pages 223-227
Published: September 01, 1981
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSDownload PDF (709K)
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