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Before a new type of railway sleeper can be used in track, standardised laboratory tests must be carried out to determine its suitability. In addition to static load tests, assessments usually include cyclic load tests consisting of millions of load cycles, representing passing trains during the sleeper’s service life. In these laboratory tests, the loading cycles are applied continuously without resting periods to condense the test time. Traditional sleeper materials (timber, concrete) possess elastic properties for which such testing is appropriate. However, polymer sleepers exhibit viscoelastic properties, such as creep, a loading rate-dependent stiffness and heating due to non-linearity of the stress-strain curve. Subjecting polymer sleepers to continuous cyclic load tests with a load frequency reflecting permissible track speed can cause the sleeper to heat up. Intermittent testing with pauses between numbers of load cycles is proposed in this paper as a possible solution. The aim is to propose a laboratory loading procedure that adopts a traffic-resembling load of a railway line, considering an effective compromise between polymer visco-elastic behaviour and time consumption of the laboratory tests. The loading frequency is kept at the desired strain rate for track evaluation, giving a representative sleeper stiffness and strength assessment. Exemplary tests with varying test arrangements and loading procedures were performed to quantify the effects of intermittent loading in comparison with continuous loading. The proposed method eliminated most of the test-induced creep and heat accumulation, resulting in a more representative stiffness and strength assessment, which justifies the proposed intermittent testing for polymer sleepers. The proposed intermittent procedure is an optional test regime in ISO 12856-2 for polymer sleeper testing.

In a railway track structure system, trackbed layers are designed to compensate for insufficient bearing capacity and/or water orfrost resistance of natural soil. These, so called, ‘capping layers’ can be constructed from raw materials like sand or gravel or fromindustrial materials like asphalt or concrete. However, more environmentally and cost friendly alternatives have been studied in recentyears. Fly-ash represents one such promising material and a trial section of a main line track with the capping layer made froma fly-ash-based mixture was constructed in Czech Republic in 2005. The performance of the capping layer in the section has beenmeasured since. In this paper, results of the laboratory estimation of the elastic modulus under cyclic traffic-like induced loading arepresented for the most recent group of samples. The results show that the elastic limit of the fly-ash-based material lies well abovethe stresses induced by railway traffic and that its behaviour is stable under the cyclic loading. This suggests that the mechanicalproperties of the material may not be determinative for the design of the layer and that the feasibility factors may take precedent.This in turn suggests that either the design strength of the material or the designed thickness of the layer may be possibly reduced.

In transportation engineering, earthwork is the main structural material which geotechnical properties can be positively modified withadmixtures. This article focuses on the application of energy by-products in earthwork of transportation line structures and summarizes their advantages and define the scope of their utilization. Earthwork construction demands the considerable volume of qualitymaterial and therefore, the effort to optimize traditional material substitution is made. One possibility is to apply solid by-productsemerging when combusting coal, which is referred to as secondary energy products. These include various types of fly-ash, slag, bottomash or gypsum. Requisite for their further widespread utilization is the application in the construction and modernization of transportinfrastructure, including road and rail construction, or in the case of flood control dams within the framework of water managementmeasures against flooding. They can be utilized also as municipal waste dumps covering. However, the application of fly ashes inearthwork constructions delivers certain limits. When contacting with rain ingress or groundwater, the leaching containing heavy andtoxic metals depending on energy by-product type may occur. Alternatively, the limitation of their application can be relatively lowmechanical resistance to cyclic saturation and frost effect and consequent volume changes. This article deals with long-term observation results of the energy by-products saturation and additivity influence on volume changes. For the investigation purpose of failurecauses, the phase composition using X-ray crystallography and Raman spectroscopy was determined.

This article is related to the unique application of fly ash-based stabilizer in the track bed of a railway line. In detail, it is focused on following analysis methods of samples structure and properties. The long-term observation of the stabilizer layer is based on the periodical sampling which is done once per year for the following compression strength test. Results collected over one decade showed the increasing tendency of the compression strength which is attributed to formatting the C-A-S-H gel. It is assumed it is done within structural conversion caused by the alkali activation of aluminosilicate components. This phenomenon was proved using electron microscopy. The statistical analysis of the compression strength resulted significant deviations the presence of which may be based on grains, poor stirring the mixture during placing, predisposed surfaces or micro cracks created during sampling in the railway track bed. The main outcomes of the paper are findings from non-destructive methods of Micro-CT and of electron microscopy, which were performed on specimens for the purpose of displaying their microstructure and identifying non-homogeneities of the specimens.

In ballasted track, the wheel load is transmitted to the subgrade via sleepers commonly made of impregnated wood, prestressed concrete, steel or recently developed polymer sleepers. Mentioned material types of sleepers are characterized by different elastic moduli being a key parameter in any numerical model. Hence, this paper aims to determine the elastic modulus of sleepers subjected to a laboratory four-point bending test. Traffic resembling load level of 60 kN adopted from a typical axle load distributed by the rails to the sleeper was applied in a quasistatic and cyclic loading. The samples included sleepers made of polymers complemented with wood and pre-stressed concrete. The results of this paper are based on the elastic modulus investigation. Main conclusions are focused on the sleeper’s elastic modulus under changing loading frequencies. Wood and prestressed concrete sleepers indicated mainly elastic behaviour resulting in a constant elastic modulus. However, polymer sleepers showed a loading frequency dependent elastic modulus as a result of their viscous elastic behaviour. Moreover, the conclusions of this paper involve E-modulus measurements of impregnated beech sleepers in order to describe their piece by piece elasticity variation due to their natural origin.

The extent of the use of asphalt concrete in track bed layers is minimal in contrast to the application of granular materials mostly represented by coarse/fine crushed stone mixture. This article summarizes advantages and disadvantages of the use of asphalt concrete in the track bed construction and provides relevant literature research. The main part of this article focuses on the application of recycled asphalt concrete (so called R-material) in the track bed layer and its following non-destructive X-ray Micro Computed Tomography Method (Micro-CT) for the description of its structural parameters. The contribution of this research is based on the evaluation of the air void and soluble binder content of chosen recycled asphalt concrete. First, it was obtained from laboratory geotechnical models of a railway track, and then from the following implementation in a trial section of an operating railway track. The conclusion contains results of the R-material practical application and findings from Micro-CT.

This paper describes a unique application of a fly ash-based stabilizer in the trackbed of a railway main line. The key goals of the stabilizer application are to protect the subgrade against the ingress of rain water, to increase the frost resistance and to remediate the natural ground constituted of weathered rock. The stabilizer was designed as a mixture of fly ash, generated as a waste material from coal plants, gypsum, calcium oxide and water. The mixture recipe was developed in a laboratory over several years. In 2005, a trial section of a railway line with subgrade consisting of clay limestone (weathered marlite) was built in the municipality of Smiřice. Since then, periodical measurements including collection of samples for laboratory evaluation of the fly ash-based stabilizer have taken place. Over the time span of the measurements, changes in mineral composition and development of fly ash transforming structures leading to the formation of C-A-S-H gel were detected. This paper describes the experimental laboratory investigation of the influence of dynamic loading on the elastic modulus of fly ash stabilizer samples and the development of permanent deformation of the samples with increasing number of loading cycles.