Martin Lidmila

Utilization of Recycled Fine-Ground Concrete from Railway Sleepers for Production of Cement-Based Binder

The environmental awareness and potential cost reduction have promoted the recycling of materials in civil engineering. This paper is dealing with the recycling and secondary use of old concrete railway sleepers for reconstruction of old railway lines. In particular, it is focused on the investigation of material properties of a binder prepared from finely crushed old concrete sleepers. This material could be used for strengthening of subsoil and embankments supporting the railway structures. The study shows that the compressive and bending strength of the investigated material is sufficient for this purpose and that the strength can be further increased by suitable curing conditions. These findings could contribute to the utilization of old concrete sleepers during railway reconstructions and safe money spent for the purchase of new materials and disposal of old sleepers.

Application of Granulated Cable Plastic Waste for Soil Stabilization

Paper deals with the assessment of practical utilization of granulated cable plastic waste (GCPW) for the production of stabilized soil layers in transport engineering. The main goal of the experimental work was the evaluation of the influence of GCPW on mechanical properties of soil stabilization based on the fluidized fly ash. Mechanical properties were investigated using standard procedures in soil mechanics. GCPW was dosed as a partial replacement of fluidized fly ash up to 30 %. It was concluded, that the studied level of replacement performs critical level, additional increasing of GCPW would lead to a decline of required mechanical properties. Besides, replacement by studied waste material caused lower values of the bulk density.

Microstructural Analysis of Fly Ash-Based Stabilizer for Track Bed

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.

Determination of the elastic modulus of fly ash-based stabilizer applied in the trackbed

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.

Application of Non-Destructive Methods for the Determination of Microstructural Parameters of Recycled Asphalt Concrete in Track Bed

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.

Comparison of Compressive Strength and Young’s Modulus of Cement Samples with Different Types of Aggregate

Several different types of aggregates were used for production of tested samples, namely: the standard sand of a fraction 0-4 mm, quartz sand of a fraction 0-0.4 mm, finely ground recycled limestone powder of a fraction 0-0.07 mm, finely ground recycled concrete of a fraction 0-0.13 mm (ground by Lavaris Company), and finally crushed bricks of a fraction 2-5 mm. The Portland cement CEM I 42.5 R produced in Radotín was used as a binder. Testing was carried out on prismatic samples of dimensions 40 × 40 × 160 mm. Compressive strength and static Young ́s modulus were measured for individual samples and these differed by the type of a microfiller and its amount.

Testing of 3-Dimensional Stabilizing Elements for Protection of Slopes: Possibilities of In Situ Testing

The testing results obtained during investigation of 3D mat are presented in the article. The spatial mat is designed to provide a cheap, efficient and durable soil stabilization on slopes. The testing was focused on development of suitable methods to be used when assessing foil properties on-site. The tested samples were extracted from mats that were used for soil stabilization at the location of mine Nástup Tušimice (Company Severočeské doly, Czech Republic) and exposed to external environment and weathering for 2 years. The performance of the mats was compared with reference samples from unused mats stored for 2 years in laboratory conditions. The testing revealed that deterioration of the material is negligible over the period of 2 years.

Effect of Reinforcement on Flexural Strength and Ductility of Gypsum-Based Composites with Recycled Wires from Automobile Tires

Gypsum, as well as cementitious materials, attains after hardening relatively high compressive strength, however its tensile (or flexural) strength is low. Therefore, it is often necessary to improve the tensile properties, such as strength and ductility, via suitable modifications or by adding reinforcement. Dispersed reinforcement appears to be quite suitable for most of the application, allowing to utilize waste products such as recycled wires from automobile tires or metal textiles etc. The presented study was focused on the influence of such reinforcement on the behavior of gypsum specimens, in particular on the flexural strength and ductility of the reinforced material.

Compression Testing of Gypsum-Based Composite Reinforced by Recycled Wires from Automobile Tires

The use of recycled materials is nowadays greatly promoted and these are exploited in many industries, including construction and civil engineering. It is advantageous and efficient to exploit mainly those materials that cannot find their use in any other application. The steel wires from old automobile tires are a perfect example – they can be used as a dispersed reinforcement to stabilize subsoil in railway construction. In order to test the structural performance of the recycled wires as well as the composite behavior, gypsum was chosen a model matrix material. Such approach resulted in a relatively cheap gypsum-based composite material effectively combining gypsum as the material able to resist relatively high levels of compression and recycled wire reinforcement from old automobile tires, which is able to transfer tensile stress. The material can be removed from a formwork after less than 20 minutes of curing and immediately loaded. The study presents the results of a compression test carried out on three different materials – the reference sample was composed of a pure gypsum matrix, while the other two were reinforced by the dispersed wire reinforcement, which has been poorly and perfectly compacted. The results indicate the huge potential of the recycled material for the improvement of soils and brittle materials.