Fly ash and slag utilization for the Serbian railway substructure

Abstract

Approximately 7 million tons of fly ash and slag are produced in thermal power plants in Serbia every year, only 3% of which is used in the cement industry. About 300 million tons of the ash-slag mixture are disposed in landfills, occupying an area of approximately 1600 hectares and generating environmental issues. Fly ash from Serbian power plants has pozzolanic properties and due to low concentration of calcium compounds (less than 10% CaO), they do not have self-cementing properties. According to the ASTM C618-15, this ash is from class F. According to the European Standard EN 197-1:2011, this ash is siliceous (type V) ash. From April 2014 to May 2015, an investigation of engineering properties of fly ash and mixtures of fly ash and slag from landfill (without or with binders of cement/lime) was conducted at the Laboratory of Soil Mechanics at the Faculty of Civil Engineering of the University of Belgrade (Serbia) and at the Institute for Testing of Materials – IMS Institute in Belgrade. The laboratory test results were showed in the study ‘Utilization of fly ash and slag produced in the TPP JP EPS thermal power plants for construction of railways’. Four kinds of waste materials from Serbian power plants were laboratory tested: (a) an ash-slag mixture from landfills at the ‘Nikola Tesla A’ thermal power plant; (b) fly ash from silos in the ‘Nikola Tesla B’ thermal power plant; (c) an ash-slag mixture from landfills at the ‘Kostolac A’ and ‘Kostolac B’ thermal power plants and ‘Srednje kostolačko ostrvo’ landfill; (d) fly ash from the ‘Kostolac’ thermal power plant. The following physical and mechanical properties of ash and mixtures were investigated: grain size distribution, Atterberg limits, specific gravity, moisture-density relationship, shear strength parameters in terms of effective stresses, California Bearing Ratio (CBR), and deformation parameters. The paper presents the results of laboratory tests of the materials with and without binders, and based on the laboratory results and previous research, the paper presents possibilities of using fly ash and slag for the construction of railway substructure in the planned construction and reconstruction of railway network in Serbia. The obtained results indicate that tested fly ash and ash-slag mixture have met the technical requirements and that they have the potential to be used in railway substructure.

Sustainable Railway Infrastructure and Specific Environmental Issues in the Republic of Serbia

“…In addition, the electrification of 254 km of Serbian tracks is planned. The characteristics of the railway network, the planned railway projects and the position of TPPs were shown in detail in [24]. Unfortunately, railway electrification does not necessarily contribute to the environmental protection.…”

“…The results of geotechnical laboratory testing [30] showed that investigated fly ash (produced in TPPs in Serbia) could be suitable for utilisation in the railway infrastructure for [24]: -stabilization of soft subsoil, -construction of embankment (using fly ash, with the core of ash ( Fig. 3, type 1), or using soil stabilized with ash), -construction of prepared formation layer using fly ash with cement or lime activators ( Fig.…”

“…In addition, the paper points out ecological problems which follow production of electricity in Thermal Power Plants (TPPs) in Serbia. Results of the previous geotechnical laboratory testing [24] showed that investigated fly ash and slag produced in TPPs in Serbia could be suitable for utilisation in the railway infrastructure. For the purpose of research presented in this paper, chemical laboratory testing was performed in order to assess the ecological suitability of fly ash as a material for the railway substructure.…”

Evaluation of the benefits of utilization of fly ash as a material for road subgrade

“…In the last four years, at the Faculty of Civil Engineering of the University of Belgrade, two studies were conducted [1,2] on the possibility of the use of ash from the Nikola Tesla thermal power plants (TENT A and TENT), Kostolac and Kolubara, in the construction of roads and railways. The studies have shown that fly ash from thermal power plants is a suitable material for construction of embankments and soil stabilization from the perspective of physical and mechanical characteristics [3,4,5]. The main goal of this paper is to present possible savings in the costs of construction of road structure if only the fly ash were used in the subgrade or a stabilizer.…”

Utilization of ash from power plants for high embankments on soft soil

“…The objective of this research was to investigate of engineering properties of fly ash from the power plant "Nikola Tesla B" (TENT B) in Serbia and to investigate benefits of utilization of ash in the case of the construction of a high embankment on soft soil. The investigation was conducted at the Laboratory of Soil Mechanics at the Faculty of Civil Engineering in Belgrade, as the part of the research project funded by Electric Power Industry of Serbia [10,11].…”