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Effect of TIPA on chloride immobilization in cement fly ash slurry

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Document pages: 11 pages

Abstract: The application of sea sand and coral aggregate in marine engineering concrete has attracted more and more attention all over the world. However, the potential risk of steel corrosion caused by chlorides in these raw materials is one of the most concerned problems. In view of this risk, the transport of chlorides to the steel surface should be prevented. The formation of Friedel salt during hydration is widely considered to be an effective way to eliminate this obstacle. In this study, an attempt was made to accelerate the formation of Friedel salt by adding triisopropanolamine (TIPA) to the cement fly ash system in order to chemically bind chloride and maintain chloride binding capacity at 60 ° C   d age check. The results show that TIPA can enhance the binding ability of chloride ionsy of cement-fly ash paste at 60 d age, and the reason is that the formation of Friedel’s salt can be accelerated with addition of TIPA. The mechanism behind is revealed as follows: on the one hand, the accelerated cement hydration provides more amount of calcium hydroxide to induce the pozzolanic reaction of fly ash, which can hasten the dissolution of aluminum into liquid phase; on the other hand, TIPA can directly hasten the dissolution of aluminum in fly ash, offering more amounts of aluminum in liquid phase. In this case, the aluminum sulfate (Al S) ratio was obviously increased, benefiting the formation of Friedel’s salt in hydration products. Such results would expect to provide useful experience to promote the chloride-binding capacity of cement-fly ash system.

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