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Abstract

This article presents the results of the study of changes in mineral and chemical composition of artificial aggregates consisting of coal shale (a hard coal mining waste) and fluidized ashes. Such an aggregate was used for road construction. After completion of the construction works but before making the road available for public use, significant deformation of the surface in the form of irregular buckling of the asphalt layer occurred. It was excluded that this resulted from mining damage, design errors or performance mistakes, among others. A study of the materials that had been incorporated in the construction layers was undertaken in order to find the component and the mechanism responsible for the buckling of the road surface. A comparison of the mineral and chemical composition of aggregate samples collected from the embankment where the road buckled with the reference sample and samples from places without deformations showed that the bumps in the road embankment consisted of minerals that were not initially present in the aggregate. Wastes produced as a result of high temperatures (slag and power plants ashes, metallurgical wastes) are not as stable in terms of chemical and phase composition in the hypergenic environment. As a result of the processes occurring in the road embankment, anhydrite, which is the primary component of fluidized ashes, was transformed into gypsum and ettringite. As a result of contact with water CaO (present in fluidized ashes) easily changed into calcium hydroxide. As the crystallization of these minerals is expansive, it resulted in the filling of pores and, in extreme cases, in a substantial increase in the volume of the aggregate and, consequently, in the deformation of the road surface.
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Authors and Affiliations

Zdzisław Adamczyk
Marcin Grygierek
Marian Łupieżowiec
Jacek Nowak
Ewa Strzałkowska
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Abstract

The analysis of the costs and emissions of greenhouse gases for individual phases of construction investments allows for the implementation of solutions and the prevention of negative environmental impacts without significantly increasing construction costs. The share of individual investment phases in the amount of carbon dioxide (CO2) produced for the construction and use of buildings depends mainly on the materials used and the implemented design solutions. In accordance with the idea of sustainable construction, materials and design solutions with the lowest possible carbon footprint should be used. This can be achieved by using natural building materials, materials subjected to appropriate chemical composition modifications, or materials in which their production does not require large amounts of energy. The aim of the article is to determine the value of the purchase costs of selected road materials (concrete paving blocks, cement-sand bedding, concrete curbs, semi-dry concrete and concrete underlay, washed sand, and crushed aggregate with a fraction of 0–31.5 mm) for the implementation of a road investment. In addition, the authors focused on determining the size of the embodied carbon footprint due to GHG (greenhouse gas) emissions and GHG removals in a product system, expressed as CO2 equivalents for the same materials that were subjected to cost analyzes. The article presents the results of original analyzes, and indicates the optimal solutions in terms of minimizing the cost of purchasing road materials and minimizing the carbon footprint. The discussion also covers the issue of changing the chemical composition in the context of the potential impact on the reduction of material costs and CO2 equivalent emissions.
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Authors and Affiliations

Damian Wieczorek
1
ORCID: ORCID
Krzysztof Zima
1
ORCID: ORCID

  1. Cracow University of Technology, Faculty of Civil Engineering, Warszawska 24, 31-155 Kraków, Poland

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