Using Fly Ash Wastes for the Development of New Building Materials with Improved Compressive Strength
Maria Harja,
Carmen Teodosiu,
Dorina Nicolina Isopescu,
Osman Gencel,
Doina Lutic,
Gabriela Ciobanu,
Igor Cretescu
Affiliations
Maria Harja
Department of Chemical Engineering, Faculty of Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University of Iasi, 73 D. Mangeron Blvd., 700050 Iasi, Romania
Carmen Teodosiu
Department Environmental Engineering and Management, Faculty Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University of Iasi, 73 D. Mangeron Street, 700050 Iasi, Romania
Dorina Nicolina Isopescu
Department of Civil and Industrial Engineering, Faculty of Civil Engineering and Building Services, Gheorghe Asachi Technical University of Iasi, 65 D. Mangeron Street, 700050 Iasi, Romania
Department of Material Chemistry, Faculty of Chemistry, Alexandru Ioan Cuza University, 11 Carol I Bd., 700506 Iasi, Romania
Gabriela Ciobanu
Department of Chemical Engineering, Faculty of Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University of Iasi, 73 D. Mangeron Blvd., 700050 Iasi, Romania
Igor Cretescu
Department Environmental Engineering and Management, Faculty Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University of Iasi, 73 D. Mangeron Street, 700050 Iasi, Romania
Fly ash wastes (silica, aluminum and iron-rich materials) could be smartly valorized by their incorporation in concrete formulation, partly replacing the cement. The necessary binding properties can be accomplished by a simple procedure: an alkali activation process, involving partial hydrolysis, followed by gel formation and polycondensation. The correlations between the experimental fly ash processing conditions, particle characteristics (size and morphology) and the compressive strength values of the concrete prepared using this material were investigated by performing a parametric optimization study to deduce the optimal processing set of conditions. The alkali activation procedure included the variation of the NaOH solutions concentration (8–12 M), temperature values (25–65 °C) and the liquid/solid ratio (1–3). The activation led to important modifications of the crystallography of the samples (shown by powder XRD analysis), their morphologies (seen by SEM), particle size distribution and Blaine surface values. The values of the compressive strength of concrete prepared using fly ash derivatives were between 16.8–22.6 MPa. Thus, the processed fly ash qualifies as a proper potential building material, solving disposal-associated problems, as well as saving significant amounts of cement consumed in concrete formulation.
