On The Relationship Between Interfacial Transition Zone And Alkali-silica Reaction

Alkali-silica reaction is an important factor affecting the durability of concrete, while the interfacial transition zone (ITZ) is the weakest in concrete. It is necessary to investigate the alkali-silica reaction of concrete from the viewpoint of ITZ.In this thesis, concrete specimen, with high activity of zeolite-base perlite as aggregate, mixed with different alkali and salt, were molded. The performance of pore solution and mortar bar were tested by atomic absorption spectrometry and Comparator. The mechanisms of admixtures for inhibiting ASR were analyzed by observing the characteristics of ITZ.The results showed that ITZ in ASR potential concrete characterized in more pores,micro-cracks,CH crystals and ettringites and little C-S-H gel. The ettringites net-like distribute in the ITZ. Alkali crystalled in the ITZ of the specimen mixed with high content of alkali. The more the alkali and salt mixed in concrete, the more R+,OH- and SO42- existed in pore solution. With the increase of incorporated alkali or salt, the expansion of ASR were more apparent. As the ASR potential concrete mixed with active mineral materials, new gel (such as CASH), generally wrapped in CH surface.,formed in the ITZ. In ITZ with lithium salt addition, large amounts of gel occurred, and the CH significantly reduced.The results revealed ASR are closely related with pore size and the concentration of alkali ions in solution. And the characteristics of ITZ in composition and structure play a decisive role in the changes of ions in pore solution.