Characterization and Evaluation of Sudanese Fly Ash as Partial Substitute for Cement in Concrete Mixtures

Selma.A.M. Ali, Bashir.M. Elhassan, Osama.M.A. Daoud


The main objective of this paper was to characterize the physical and chemical properties of the locally produced fly ash, to study its suitability to be utilized in concrete mixtures and to determine the degree of its pozzolanity .Physical and chemical properties of fly ash were tested according to the standards of the American Society of Testing and Materials (ASTM C311-02). Fly ash was tested for density, fineness, moisture, Loss on Ignition (LOI), chemical composition, X-ray Fluorescence test (XRF), X-ray Diffraction test (XRD) and strength test. The results were then compared with the (ASTM C618-03). It was found that the locally produced fly ash contains high level of silicon dioxide, hence it can be classified, based on its chemical composition, as class F fly ash; this may be probably due to the addition of sand applied in the combustion chamber. The XRD showed that it contained crystalline form of silicon dioxide which is not good for the use in concrete. The content and form of silicate should be modified through further research. On the other hand, the strength test proved that there was a degree of strength and pozzolanity obtained. The strength activity index of 28-day was found 70%.This may be due to presence of amorphous silica within the crystalline one.


fly ash; ASTM C311-02; ASTM C618-03; concrete mixture; silicon dioxide.

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