硫酸イオンの浸入と機械的特性の変化からみたセメント硬化体の変質

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It is well known that cementitious materials are deteriorated by sulfate attack. Submerging tests of hardened cement paste and mortars were employed with sodium sulfate solution. The samples were prepared from ordinary portland cement and blast furnace slag cement. The test results showed that the sulfate ion migration was not governed by Fick's law. In the region of sulfate ion migrated, ettringite precipitated as a secondary product and the volume of capillary pores, in diameter of 18.3-212.5 nm, decreased. It was also observed that pores in diameter of 18.3-212.5 nm developed at areas where sulfate ion did not migrate. This should be considered as an important feature. In addition, secondary formation of gypsum was identified in the case of blast furnace slag cement. Compressive strength test and 3-point bending test were carried out to diagnose the mechanical performance against the sulfate ion ingress. Two types of alteration model were considered to evaluate the alteration depth and degree. Each model is working for the compressive test and the bending test, individually. We have proposed new indexes with these models. These indexes describe the alteration depth and degree, and closely relate to other indexes, such as sulfate ion migration depth and so on. According to these indexes, it seems that sulfate ion migration might cause filling of pore and generating of micro defect, alternatively, and progress the deterioration. This mechanism showed good agreement with apparent phenomena such as changes in profiles of sulfate ion and in strength.
社団法人日本セラミックス協会の論文
2001-12-01

硫酸イオンの浸入と機械的特性の変化からみたセメント硬化体の変質

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