Dataset for article: Fly Ash and Bottom Ash from Biomass and Coal: Comparison of Properties in Grate and Fluidized Bed Combustion from the Perspective of Construction Applications

This dataset was created to systematically capture the variability in chemical, mineralogical, and selected physical properties of ashes generated from biomass and coal combustion under real operational conditions. The primary motivation was to support the assessment of these ashes as potential supplementary cementitious materials (SCMs) and minor constituents in cement, with a focus on sustainability and resource efficiency in the construction industry. The data originate from 23 ash samples collected between 2021 and 2024 from six locations in the Czech Republic, representing different fuel types (bark, hay and straw mixtures, wood chips, sawdust, and coal) and combustion technologies (grate combustion and fluidized bed combustion, including co-combustion with coal). Both fly ash and bottom ash, as well as their combinations, are included to reflect the diversity of by-products produced in practice. Each sample was characterized using a consistent analytical framework, covering chemical composition (XRF), phase composition and amorphous content (XRD), loss on ignition, density, specific surface area, particle size distribution, and microstructural features (SEM/EDS). The dataset is structured to allow comparison across combustion methods, fuel inputs, and ash types, and to benchmark the measured properties against existing standards (notably EN 450‑1, used as a reference).