Sustainable Blended Cements—Influences of Packing Density on Cement Paste Chemical Efficiency

This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their production. The reduced clicker content was based on improved particle packing density and surface area of the cement powder by using three different limestone particle diameters: smaller (7 µm, 3 µm) or larger (70 µm, 53 µm) than the clinker particles, or having a similar size (23 µm). The effects of the different limestone particle sizes on the chemical reactivity of the blended cement were studied by X-ray diffraction (XRD), thermogravimetry and differential thermogravimetry (TG/DTG), loss on ignition (LOI), isothermal calorimetry, and the water demand for reaching normal consistency. It was found that by blending the original cement with limestone, the hydration process and the reactivity of the limestone itself were increased by the increased surface area of the limestone particles. However, the carbonation reaction was decreased with the increased packing density of the blended cement with limestone, having various sizes

Production of environmentally friendly sand-like products from granitoid waste sludge and coal fly ash for civil engineering

Processing granitoid rock for civil engineering, countertops, and paving generates sub-economical (transportation costs exceed their retail value) granite powder sludge. This paper evaluates the possibility of mixing granite waste (GW) produced at the Spanish quarries of Galicia with a second sub-economical substance, Class F coal fly ash (FA <20 wt% CaO). The GW would reduce the leachability of toxic trace elements enriched in Colombian fly ashes and form a sand-like product that could serve as a substitute product and would reduce the costs in industrial concrete and civil engineering projects. To investigate both the capability of the GW to reduce FA leaching (by physical adsorption) and the potential use of the aggregate product as a partial substitute in industrial concrete, the physical (e.g. morphology, crystallographic patterns, and surface area), mineralogical, and chemical (including leachability and chemical composition) properties of the aggregate product were tested. Moreover, properties of the concrete (compressive strength, ion penetration, workability, and electron microscope scanning results (SEM)) were also analyzed. The use of the end scrubbed product in the concrete mixture was found to enhance the performance of the concrete mixture, reducing the leaching of the hazardous elements, and improving the concrete produced. © 2019 Elsevier LtdWe would like to thank the ICP-MS, ICP-AES technicians in the IDAEA/CSIC Institute. We would also like to thank the Centro Tecnologico del Granito (CTdG) for supplying granitoid byproducts from the Pontevedra quarries. Thanks to the Israeli Coal Ash Board for supplying the Israeli fly ash samples, and to ENDESA for supplying the Los Barrios fly ash. We would also like to acknowledge the Generalitat de Catalunya (AGAUR 2015 SGR33) for its support.Peer reviewe

Potential of Hazardous Waste Encapsulation in Concrete Compound Combination with Coal Ash and Quarry Fine Additives

Coal power plants are producing huge amounts of coal ash that may be applied to a variety of secondary uses. Class F fly ash may act as an excellent scrubber and fixation reagent for highly acidic wastes, which might also contain several toxic trace elements. This paper evaluates the potential of using Class F fly ashes (<20% CaO), in combination with excessive fines from the limestone quarry industry as a fixation reagent. The analysis included leaching experiments (EN12457–2) and several analytical techniques (ICP, SEM, XRD, etc.), which were used in order to investigate the fixation procedure. The fine sludge is used as a partial substitute in concrete that can be used in civil engineering projects, as it an environmentally safe product