Abstract

This research focused on analyzing the physical, mechanical, and leaching properties of wallboards manufactured with gypsum (79-100% wt) derived from flue gas desulfurization (FGD-G) along with fly ash (0 and 20% wt). Two different heating temperatures of FGD-G, 120 °C and 130 °C, were used as well as two water-to-solid weight ratios, 0.4 and 0.6. Although fly ash is classified as hazardous waste (due to Se) and gypsum is considered inert waste, a leaching stabilization process was observed in a matrix consisting of 20% wt of fly ash and 80% wt of gypsum. However, the addition of fly ash, higher heating temperatures, and higher water-to-solid ratios resulted in worse mechanical properties, with compressive strength decreasing by up to 39% and 90%, respectively; a leaching stabilization process was observed in a matrix consisting of 20% wt of fly ash and 80% wt of gypsum. The effect of adding 0.5 or 1% wt of two types of carbon fibers with different mechanical properties was also explored. Flexural strength increased by up to 267%, but this improvement primarily depended on the dispersion of fibers within the matrix rather than on the tensile strength of the fibers, considering the same fiber content and aspect ratio. As part of the eco-design, a life cycle analysis of materials was conducted. A 10 °C increase in the heating temperature of desulfurization gypsum led to a worsening of over 34% due to increased natural resource consumption. Adding fly ash to the desulfurization gypsum increased all environmental impacts by up to 42% compared to using desulfurization gypsum alone. Lowering the solid-to-water ratio from 0.4 to 0.6 decreased environmental impacts compared to other materials, including traditional ones. The superior mechanical properties of these waste-derived materials compared to commercial gypsum led to an improvement in environmental aspects, confirming that the material developed in this study outperforms the commercial gypsum currently in use. At distances of less than 200km between the thermal power plant and the production plant, materials without fibers presented environmental advantages in most impacts.