Geopolymerization of Industrial By-Products and Study of their Stability upon Firing Treatment

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Author(s) H.M.Khater | Sayieda.R.Zedane
Pages 308-316
Volume 2
Issue 2
Date February, 2012
Keywords cement dust, phosphogypsum, Fly ash, alkali, firing.

There is a growing interest in the development of new cementitious binders which enhance optimal utilization of industrial by-products such as phosphogypsum, fly as and cement dust. Among all the industrial by-products, fly ash predominates as an alternative building material for building construction activities. Cement kiln dust (CKD) with its high alkali content in the activation of geopolymer specimens to create nonconventional cementitious binders was investigated. Relatively high alkaline content of CKD is predominant factor preventing its recycling in cement manufacture. However, it was observed that depending on the water-soluble alkalis and sulfate compounds, CKD could provide the necessary environment to activate geopolymer materials. Phosphogypsum that is rich in sulfate will enhance geopolymerization process when added in a lower dose. Materials used in this investigation are fly ash (FA), phosphogypsum (PG) and cement kiln dust (CKD) calcined. Phosphogypsum was partially replaced fly ash in the ratio from 0 up to 50%, while the remaining ratio is for cement dust. Alkaline activation by 2 % NaOH along with the added cement dust was studied and the used water to binder ratio is 0.55. Curing was performed under 100 % relative humidity at 60oC. Results showed that 10% PG is the optimum ratio for geopolymer formation and results in best enhancement in mechanical as well as microstructural characteristics. Firing treatment for both 10 and 20% PG mixes possess a lower strength values up to 800oC, while strength exposed to strength gain up to 1200oC.

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