打重ね条件とコールドジョイントの形成に関する基礎的研究(<特集>建設材料)

概要

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It is well known that alkali-aggregate reaction and chloride attack could cause rapid deterioration and serious damage to concrete structures, initial defects of concrete structures cause a trouble. There happened an accident that the lining-concrete-block of tunnel hit the Shinkansen super express at Fukuoka-tunnel of the Sanyo Shinkansen Line in June 1999. One of their causes was guessed the initial defect, this is called the cold joint. There are few reports on the unity of the concrete with the cold joint. In this paper, the effects of cold joint on bending strength ratio for that of concrete without cold joint was considered experimentally. Production factors of specimens were rodding method, water-cement ratio, casting temperature and construction time from lower layer to upper one. As a result, when even lower layer concrete is not rodded by a tamping rod, the bending strength was decreased. And it was found that bending strength ratio closely was related to bleeding, Proctor penetration resistance needle, mixture proportion and casting temperature. Moreover, bleeding water of lower layer concrete was removed in order to reduce a decrease in bending strength ratio by occurrence of cold joint. As a result, bending strength ratio was improved, in comparison with non-disposal specimen.
社団法人日本材料学会の論文
2001-08-15