Effects of the Use of Sulfitic Fly Ash in Mortars and Concretes


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Title: Effects of the Use of Sulfitic Fly Ash in Mortars and Concretes

Author(s): A. Carles-Gibergues and B. Husson

Publication: Special Publication

Volume: 132


Appears on pages(s): 671-692

Keywords: carbonation; concretes; corrosion; durability; fly ash; mineralogical analysis; mortars (material); quick lime; workability; x-ray diffraction; Materials Research

Date: 5/1/1992

Within the context of atmospheric pollution prevention, fly ash producers are brought to better desulfurize combustion gases. As a result, there are important modifications in the composition of the residues that are enriched with sulfur, especially in the case of calcium sulfite fly ash. The sulfitic fly ashes studied result from desulfurization by quick lime addition in dust removers of a thermal plant. Paper presents the physical, chemical, and mineralogical characteristics of this type of fly ash. Their examination by x-ray diffraction shows the presence of crystallized minerals: lime, calcite, and calcium sulfite, and the existence of a glass, the composition of which is given by electron microprobe. A special emphasis is given to the sulfite stability. In a second part of the paper, the behavior of these fly ashes in paste with water and slaked lime has been studied. It is shown that they are a very weak hydraulic binder but they present, on the other hand, pozzolanic activity. At last, the study has allowed determination of the influence on workability and mechanical properties of hydraulic mortars and concretes in which they have been introduced as partial replacement of cement. Corrosion and carbonation aspects have also been studied in mortars.