Zuzana Rácová

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.

Mechanical Properties of Single and Double-Layered PVA Nanofibers

Multi-layered nanofiber textiles can be utilized in many applications. In such case the individual layers are laid in more stages and the question arises whether the connection is perfect. Two kinds of samples of PVA nanotextiles having the weight of 1.3 g/m2 (single-layered, AI) and 2.8 g/m2 (double-layered, AII), respectively. It was shown that mechanical properties, in particular the average tensile strength (24 N/mm for AI and 51 N/mm for AII) and stiffness (950 N/mm for AI and 1600 N/mm for AII), are independent of the number of layers, only their weight per unit area matters. This indicates that the bond between the individual layers is perfect.

Influence of Copper Ions on Mechanical Properties of PVA-Based Nanofiber Textiles

The nanofiber textiles are utilized in the textile industry, as a treatment of exposed surfaces, they find their use in medicine and in future they might be used in civil engineering as vapor barriers. For some applications it is advantageous to use the textiles with special, e.g. antibacterial, treatment by means of silver or copper ions. This paper is focused on the determination of mechanical properties of PVA-based nanofiber textiles produced by electro-spinning. The polymer solution used for electrospinning contained copper in the form of ions. The results of the tensile testing were compared with the results for the reference sample without any additives. The results indicate that the addition copper ions cause an increase of the strength and stiffness.

The Efficiency of PVA Based Nanofiber Textile PVA Doped Silver Particles against Mold

Mold and algae are primitive organisms that cause biological degradation of many type of construction materials. Subsequent remediation of damaged structures is very demanding and it is therefore necessary to take into consideration the high preventive protection against these microorganisms. In practice, as the prevention it is often use chemical products as a classical biocidal compounds. One of the modern methods of protection investigate the use of nanotechnology with biocidal ingredients, which is the main topic of this article. Silver ions and silver nanoparticles were selected as a biocide for the experiment. Research revealed that the silver in the form of nanoparticles and ions have biocidal effect against fungi and algae and it is conform to use theoretically possible them as a preventive protection against mold and algae.

The Dependence of Mold on the Relative Humidity in Different Types of Materials

Building materials commonly used in Central Europe across the material base tend to have problems with the occurrence of mold. This is not only an aesthetic issue, but attacked material loses its properties as strength and durability and there is also a deteriorationening in other properties. This paper is focused on the susceptibility of wood and gypsum based materials to the development of mold at different humidity. There were also studied mold species occurred in samples naturally. Significantly increased the growth of mold on the surface was observed with samples placed into 98 % relative humidity than samples at 80 % relative humidity. Predominant mold was found on the surface of samples of solid wood. The most observed species was Trichoderma viride on wood based materials.

The Occurrence of Mold in Construction Materials before Inbuilt into New Building and Protection against this Type of Biodegradation

Mold together with other microorganisms are belonging to the group of biodeteriogens which is common occurred on both the inner and outer surfaces of building structures. Mentioned study is comparing the generic composition of mold on the surface of board materials (wood and plaster based) with the generic composition of mold trapped air in Central Bohemia. In the air they were identified following species of mold: Cladosporium, Aspergillus, Penicillium, Aureobasidium, Epiccocum, Alternaria, Mucor. The almost identical species of mold was found on board materials. It also investigated the minimal inhibitory concentrations of silver nanoparticles against selected mold (Cladosporium, Aspergillus, Penicillium, Aureobasidium, Epiccocum, Alternaria). The results show that the minimum inhibitory concentration for most of mold is 1.5 g / m2 except Apergillus species, where the minimum inhibitory concentrations have a double value.

Performance of Stabilized and Non-Stabilized PVA Nanofiber Textiles Subjected to Tension

Nanofiber textiles became indispensible in medicine and many other industries because of their unique properties. Recently, the pioneering works suggested their use also in a building industry in the form of moisture barriers. For a better chemical stability and resistance to air humidity it is suitable to stabilize the spun textiles. Our study is focused on the influence of the physical-chemical stabilization, also called crosslinking, on the mechanical properties of nanofiber textiles in tension, namely stiffness, strength and ductility. During the process of crosslinking the individual fibers bond in nodes, ensuring a better spatial integrity. However, the presented results indicate that the stabilized nanofiber textiles exhibit significantly lower ductility while their ultimate strength is lower only by about 10 %.

Microscopic Filamentous Fungi in Buildings, Preventing their Occurrence and their Remediation Using Nanofibers

The article is focused on prevention and remediation of the occurrence of microscopic filamentous fungi in buildings. The remediation of these fungi can be performed using classical methods (spray, paint, etc.) or use new methods - which include use of nanotechnology, e.g. nanofibers. The nanofibers have specific functional characteristics (e.g. large surface area, etc) according to their production and it can be used for remediation and prevention of occurrence of microscopic filamentous fungi. The effect of nanofibers can be increase by adding nanoparticles or another antimicrobial substance into electrospinning polymer. The article presents the first experimental results with the nanofibers, which could be applied on place with the occurrence of microscopic filamentous fungi, or on place where is expectation their occurrence in future.