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Volume 19 (1979)
- Issue 4 Pages 103-
- Issue 3 Pages 73-
- Issue 2 Pages 41-
- Issue 1 Pages 1-
Volume 19, Issue 2
Displaying 1-3 of 3 articles from this issue
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Akira ARIIZUMI1979 Volume 19 Issue 2 Pages 41-55
Published: May 25, 1979
Released on J-STAGE: September 20, 2011
JOURNAL FREE ACCESSConcrete is the most important material for construction industries. Performance of concrete depend on the kind of the components and on the environmental conditions involved. The neccesity of conservation of materials and energy plays a great role on the durability of concrete. As the result of the new tendency for cement production, to which suspension pre-heaters are widely installed, alkali content in cement is higher than it was used to be. On the other hand, because of the shortage of riverbed materials, aggregates with proven quality are becoming limitted. More over, the recent design of mixing proportion in concrete industries makes more cement and less water in unit volume of concrete. These three factors are unfavorable in the view of notorious reaction in future concrete.
It was already 40 years ago that the alkali-silica reaction was found to be one of harmful phenomena for concrete structures. In the first 20 years, the cause and the mechanism were investigated in order to prevent the reaction. During the next 20 years, a world-wide spread of the phenomena was reported in spite of the preventive efforts, and the further study continued.
This paper introduces the examples of damaged concrete structures, and points out the need to counter-attack the phenomena. As only few petrographers are engaged with the investigation into the deleterious aggregates, the author expects that the members of the clay society should pay attention to the problem. The summary of 20 years study is given in this report. The next report deals with alkali-silica reaction, alkali-carbonate rock reaction, aggregates with sulfides and sulfates, aggregates with clay minerals and laumontite and shrinkage-causing aggregates.View full abstractDownload PDF (19263K) -
Effect of Exchangeable CationsHidenobu TATEMATSU, Shigeru SUZUKI, Ryohei OTSUKA1979 Volume 19 Issue 2 Pages 55-60
Published: May 25, 1979
Released on J-STAGE: September 20, 2011
JOURNAL FREE ACCESSSurface morphology of bentonites and their Ca2+ and Na+ modifications were observed with scanning electron microscope (SEM).
Our observation indicated that the Ca-montmorillonite surface is rugged, whereas the Na-montmorillonite surface is relatively smooth and curly.
The above difference in surface morphology is considered to be due to the difference in kind and amount of the exchangeable cation.
The DTA-TG curves of these specimens are also presented.View full abstractDownload PDF (6034K) -
Effect of Sodium Hydrate Solution TreatmentMasami HOTTA, Kazuo TORII, Makoto ASAKA1979 Volume 19 Issue 2 Pages 61-68
Published: May 25, 1979
Released on J-STAGE: September 20, 2011
JOURNAL FREE ACCESSThe effect of alkali treatment on some physico-chemical properties of mordenite tuff was investigated with powder X-ray diffraction, chemical analyses, measurement of CO2 adsorption and gaschromatography. Mordenite tuff from Shirasawa, Miyagi-cho, Miyagi Pref., was used as a starting material and treated with 0.01-5 N NaOH aqueous solution at 97-98° in the water bath for 2hrs.
At the concentration of NaOH below 0.5 N, all chemical compositions in the tuff were virtually insoluble and the mordenite structure did not change.
At the concentration above 1 N, the chemical compositions such as silica, alumina, etc., were dissolved. The dissolution ratio of silica was larger than that of alumina, and the ratio of silica to alumina in the tuff decreased sharply in the concentration range of 2-3 N. Intensity of X-ray diffraction peak of mordenite (202) and the amount of CO2 adsorbed also decreased with the increasing concentration of NaOH above 1 N. These decreases corresponded to the degree of mordenite structure collapsed.
By alkali treatment, only H+ was exchanged by Na+, and K+ and Ca++ in mordenite were not exchanged, hence Na-rich mordenite was obtained.
Gaschromatographic separation of O2, N2 and CO was not affected by the alkali treatment, but elution peaks of CH4 and Kr tended to be broadened and their retention time was shortened. The elution peaks of both CH4 and Kr tended to be overlapped with those of N2 and O2.View full abstractDownload PDF (710K)
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