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Cement additives and resistance to chloride attack

D'Souza, Priyanka (2015). Cement additives and resistance to chloride attack. Bachelor of Engineering Co-op (4th Year Project) Thesis, Charles Darwin University.

Document type: Thesis
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Author D'Souza, Priyanka
Title Cement additives and resistance to chloride attack
Institution Charles Darwin University
Publication Date 2015
Thesis Type Bachelor of Engineering Co-op (4th Year Project)
Subjects ENGINEERING
Abstract Corrosion of reinforcing steel is the primary cause of deterioration of concrete exposed to seawater (Ash Development Association 2000). Chloride is the most aggressive of these ions when it penetrates the cement matrix (Barberona et al. 2005). The purpose of this thesis was to design a cement additive that would improve concrete’s resistance to chloride attack. The design additive was made from diatomaceous earth, gamma alumina and hydrated lime, which theoretically reduces the permeability of cement and increases chloride binding by producing additional C-S-H and Friedel’s salt. The properties of two mass ratio variations of the cement additive mix were compared to the properties of a mix with fly ash as an additive and portland cement with no cement additive replacement.

The results of this study indicate that gamma alumina and diatomaceous earth have opposing optimum chloride exposure times from the initial casting of concrete. Therefore, the combination of gamma alumina, diatomaceous earth and lime is not a viable cement additive for the prevention of chloride movement though concrete. However, the individual materials may be suitable for improving the chloride resistance of concrete for particular situations in marine environments, such as gamma alumina for in-situ reinforced concrete and diatomaceous earth for pre cast concrete. Further research is required to determine the success of the additive materials separately in their suggested ideal circumstances.
Keyword chloride attack
cement matrix
chloride binding capacity
hydration products
permeability
Friedel's salt
gamma alumina
diatomaceous earth
diffusion
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Created: Mon, 07 Sep 2015, 14:33:57 CST by Jessie Ng