Abstract: Deterioration of asphalt pavements by water immersion and increased moisture content, presents one of the principal issues for pavement technologists. Especially if concentrating on initial phases of the life-cycle of a pavement. Water in the form of rain precipitation and natural air moisture can be harmful to the bonds between bitumen and aggregate particles, which occurs through the medium deteriorated adhesion on the interface of those phases, or the overall deterioration of the adhesion. Even if it might look at the first glance that bituminous binder creates perfectly impermeable layer of particular aggregate particles, in reality the bitumen film makes unstable coating of aggregates in unequal thicknesses and frequencies. Those weakened areas are far more susceptible to water and moisture affects, which enter the asphalt layer on the boundary of aggregates and bituminous binder. To improve the adhesion between bitumen and aggregates and to get in general better functional characteristics of asphalt mixtures large number of available additives exists in civil engineering. First group can be defined as additives which are added directly to the bituminous binder and provides a kind of bitumen modification. Second group includes mineral additives, which may partially or completely replaced fine-grained particles, normally in the form of filler. In this article the objective was set to qualify effect of mechanically activated microfiller originating from limestone by-products or from recycled concrete as a substitute to fine-grained active filler in asphalt mixtures. The research targeted to utilize waste materials and to contribute to the reduction of overall negative impacts to the environment.
Abstract: 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.
Abstract: The evaluation of heterogeneous materials used in civil engineering on the microscopic level has become important aspect in proper understanding of the macroscopic behavior of the material. This contribution aims at advantages and problems related to the technique of grid indentation and at the evaluation of mechanical properties.
Abstract: The nanofiber textile was made by electrospinning on device Nanospider LB 500 (Elmarco, CR). The original basic polymer solution contains polyvinyl alcohol and additional supplement: a glyoxal and phosphoric acid for thermal stabilization and copper sulphate as a biotic agent. The concentration of copper sulphate pentahydrate (CuSO4·5H2O) in original basic polymer solution was 0.5 and 1% and it follows that the theoretical concentration of copper ions in nanofibers was 0.95 and 1.89%. Subsequently the nanofibers had stabilized by thermal heat (140 °C, 10 min), and by chemical cross linking methods with using of soaking in solution with glutaraldehyde, methanol. The stabilized nanofibers were characterized by scanning electron microscope (SEM) and atomic absorption spectrum (AAS). The results showed that the thermal stabilization did not change nanostructures too much, but subsequent soaking showed, that their structure has changed after 24 hour leaching, the crosslinked points has not sharp line. This measurement leads to conclusion, that the stabilization by heat is not fully absolute. Chemical stabilization nanofibers by glutaraldehyde changed the nanoproperties only in range a few percent and the solubility in water was absolutely completed. The stabilization by methanol has destroyed nanostructures of the fabrics, and the nanofiber textile looks like thin layer or thick membrane. The nanostructures didn't change their character nor after water soaking. The content of copper in nanofiber had measured by (AAS) and thus proved that the copper concentration in nanofiber is independent on original concentration in solution. The next results from this measurement confirm the assumption that the concentrations of copper are dependent on kind stabilization. The next results from this measurement confirm the assumption that the concentrations of copper are dependent on kind stabilization. The stabilization by soaking in stabilization solution leads to decrease of concentration of copper in nanofiber. The thermal stabilization didn't change final content of copper in nanofiber, the stabilization by glutaraldehyde changed the concentration, it was lower by 2 mg/g and the stabilization by methanol made nanofiber with one quarter original value of copper.
Abstract: This paper presents an experimental verification of the alternative options for using by-products or mineral waste materials applied to cold recycled mixtures with low level of stabilisation intended for low-volume road structures. To achieve the necessary refinement and a certain level of reactivity potential, the by-products were activated mechanically, i.e. pulverized in a high-speed disintegrator with respect to the lowest possible energy demands of the process and to the level of wear-and-tear of the working components in the milling machine. Such refined material, with average particle size of 10-15 μm, is applies as an active filler component allowing to partly substitute hydraulic binder in cold recycled mixtures. The application of such materials in structural pavement layers should increase the environmental benefits and result in added economic value. The experimental measurements taken focused on cold recycled mixtures with low level of stabilisation, modified by a combination of binders, or namely cement, mechanically activated concrete from reclaimed concrete pavement slabs originating from the Czech backbone D1 highway modernisation, mechanical-chemically activated fluid ashes from the Pilsen heat plant and foamed bitumen. Both basic volumetric properties and strength and deformation parameters were set for the purposes of evaluation of the characteristic measured in the experimental mixes.
Abstract: The paper deals with the influence of level of grinding of the recycled concrete. Level of grinding mostly influence the hydration heat evolution of cement paste. Measurement of hydration heat evolution is one of the ways to detect reactive properties of recycled concrete powder modified by high speed mill device. Basic characteristics that most influence the hydraulic properties of recycled concrete powder are grin size diagram and chemical composition of the original concrete. Non-hydrated inner part of cement grains could further react if it is exposed to water. In this experiment the recycled concrete from recycled railroad sleepers and structural layers of the D2 highway was used. Recycled concrete powder from highway was divided into 4 more variants which differ by grinding process during production. To detect difference in hydration process four mixtures of cement paste with different types of recycled concrete powder were made and further subjected to calorimetric measurement. The results were after compared with the hydration heat rate of reference cement paste. According to results the type of milling process had minor influence on hydraulic properties of recycled concrete powder compared with influence of origin of recycled concrete.
Abstract: Presented work is focused on the time depend wettability deterioration of plasma treated polymeric macro-fibers. The commercial fibers designed especially for reinforcement of concrete composites – Concrix ES (made from polyolefin) and BeneSteel (polyethylene and polypropylene mixture) were surface modified by oxygen cool low-pressure coupled plasma to attain their water wettability enhancement. The wettability development of thus treated fibers was observed through contact angle sizes between fiber surfaces and distilled water using a direct horizontal optical static method. Contac angle measurements were realized (i) immediately, after (ii) 1 day, (iii) 7 days and (iv) 30 days over the treatment execution, while fibers were stored on the air on standard laboratory condition in the meantime (temperature ~22 °C, moisture ~50 %). Both, the treated Concrix ES and BeneSteel fibers exhibited significant wettability increase. The enhanced wettability of modified fibers stayed approximately constant even after 30 days over the treatment execution in the case of BeneSteel, while in the case of Concrix ES the wettability decreased almost to the reference (no treated) samples, respectively.
Abstract: While the matters of the moisture of external walls of historical buildings it turned out that apart from classical sources of moisture (such as capillary attraction, condensation etc.) there is another source which is often left behind – rainfall humidity which leaks to perimeter walls from the exterior. Whilst the Czech approach of standard assessment works with condensed moisture only, some foreign authors (especially those from Germany) point out a notable influence of rainfall humidity on the moisture regime of the mentioned constructions. Its amount exceeds the amount of rainfall that leaks into the construction due to diffusion by several times. The issue deserves to be examined in more detail, but the use of nanotechnology could help to solve or improve the problem. In some cases it would be possible to apply the suspension with added nanoparticles into the insulated masonry and improve the properties of masonry, which is facing to rainwater
Abstract: This work deals with the determination of basic waterproofing properties of nanofiber textiles with basis weights of up to 30 g/m2. Samples used in this experiment were made from nanofiber textiles based on two polymers – PVDF and PUR. Each polymer was prepared in three basis weights. All samples were not treated prior to testing. One of the key properties was the contact angle of water and the resistance to penetration of liquid water. Water-resistance of nanofiber textiles was tested according to the harmonized European standard EN 13859-1., Underlays for discontinuous roofing in pitched roof constructions are tested according to this standard. In the position of underlays there has to be some layer with low diffusion resistance of water vapor and relatively high waterproofing. We suppose such properties of nanofiber textiles. Testing of the two groups of material basis shows correlation between the contact angle and water-resistance of the nanofiber textile.