スメクタイトを含む安山岩のアルカリ骨材反応性

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In several regions in Japan, damage to concrete due to alkali-aggregate reaction has recently been discovered. The rock type of aggregates used in the damaged concrete structures was glassy orthopyroxene andesite in many cases. The alkali reactivity of the andesite depends on the amount of cristobalite, tridymite and volcanic glass contained. The volcanic glass is often altered to smectite and zeolites by the weathering. In this paper, alkali reactivity of andesite samples collected from the Setouchi volcanic rock area is studied by the ASTM standard C289 test method for potential alkali reactivity (chemical method) and C227 test method for potential alkali reactivity of cement aggregate combination (mortar bar method). The behavior of reactive minerals and smectite was investigated by X-ray diffraction and polarizing microscopic observation. Special attention was paid to interpretation of the test results with regards to smectite in andesite. The results obtained were summarized as follows : (1) The measured value of Rc (alkalinity reduction) increased with the content of smectite in the samples. (2) It was shown by X-ray diffraction that the 001 spacing of smectite contained in andesite shifted from 1.5 nm to 1.26 nm, and the diffraction intensity became lower after ASTM C289 chemical test. This fact is an evidence for that smectite takes part in the reduction in alkalinity. (3) The pessimum phenomenon was observed in the expansion test of mortar-bars made of the andesite aggregates. The magnitude of the expansion of mortar-bar made at a pessimum ratio was inversely correlated to the amount of smectite in andesite.
日本粘土学会の論文
1987-09-05

スメクタイトを含む安山岩のアルカリ骨材反応性

スポンサーリンク

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