Evaluation of the properties of cementitious mortars with the addition of thermoelectric generation residues

ABSTRACT

The partial cement replacement by solid wastes of thermoelectric generation in mortar formulations can contribute to environmental preservation and in a more durable materials building development. This study aimed to evaluate the influence of Portland cement partial replacement by coal fly ash and flue gas desulphurization by-product on the cementitious mortars properties. The experimental methodology consisted of the residues characterization by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and particle size analysis. Cylindrical blocks of mortar with a 50 x 100 mm dimensions and a 1: 3: 0.48 trace (cement: sand: water/cement) were prepared according with NBR 7215 standard. Cement was replaced, by mass, in the proportions of 6%, 16% and 26%. Comprehensive strengths (NBR 7215) were measured at 7, 14 and 28 days of wet cure. In addition, water absorption by capillarity test was performed (NBR 9722). The results were compared with a reference sample, that is, without residues. It has been shown that, mineralogically, the ashes contain mulita, quartz (mainly) and hematite and have 42.19 μm average diameter. Particle morphology is predominantly spherical containing some porosities. The by-product is a material rich in calcium sulfate and quartz traces with 17.8 μm average diameter and consists of agglomerated particles with varied morphology. The results showed that the replacement of 6% Portland cement by ashes improves the performance of mortars in terms of axial comprehensive strength and capillarity water absorption. For the mortars containing the by-product, the improvement in mechanical properties was not evinced.

Keywords
Coal fly ash; Gas desulfurization; Recycling; Thermoelectric generation; Cement mortars