Vojtěch Václavík

A Proposal for Simplifying the Method of Evaluation of Uncertainties in Measurement Results

Abstract The paper deals with the innovative ways of nonstandard, simplifying applications of the valid method for evaluating uncertainties in measurement results and with the definition of conditions of their usability. The evaluation of a substitute criterion for measurement accuracy by means of a relative difference between the measurand and its reference value is proposed. This nonstandard relative uncertainty is comparable with the overall relative standard uncertainty in the measurement result, and thus the evaluation of it enables other simplifications in the calculations of measurement result uncertainties. The use of the simplified evaluation of measurement results is illustrated in two experiments in measurement of the coefficient of thermal conductivity of an insulating material newly developed for the needs of building practice, namely measurement using commercial instruments, and measurement using a newly developed original measuring instrument.

Leachate from Municipal Waste Landfill and Its Natural Degradation—A Case Study of Zubří, Zlín Region

This work deals with the natural degradation of leachate from an old reclaimed landfill by means of a biological pond. Hamra is a municipal waste landfill with a limited formation of leachate, which has already been reclaimed. Leachate in this location is disposed of using natural biogeochemical method, and it is subsequently discharged into a surface stream. The main issue dealt with here is the long-term effectiveness of natural degradation of leachate and the limits of its use. The solutions of these fundamental questions took advantage of a database of analytical assessments collected during a long-term monitoring of the landfill site. The primary degradation trends and the long-term development have been revealed and described on the basis of these assessments. The main benefit of the biological pond is the dilution of the dominant contaminants, especially of inorganic character. In the case of ammonium ions, they show nitrification caused by their transition from the reduction into oxidizing environment. From a long term point of view, the disadvantage of natural degradation of leachate can be seen in the gradual reduction in efficiency due to the concentration of the substances or an undesired growth of water plants, which can be successfully eliminated, for example, by means of targeted aeration and by maintaining vegetation in the pond and its surroundings. The biological potential of the locality is very favorable and, despite its anthropogenic load, it creates a location with suitable living conditions for many water animals and plants. That is why it can be concluded that the efficiency of the natural biochemical cleaning elements can be considered as sufficient, taking into account the nature of the deposited waste, the quantity and quality of leachate, as well as the climate character of the locality.

Drainage Concrete Based on Cement Composite and Industrial Waste

The ongoing development of urbanization of our landscape has resulted in continuous demand for building materials, which are even nowadays produced mainly from primary natural resources. The continuous reconstructions and modernizations of already built-up areas are the cause of the production of construction waste which, for example, in Europe represents ¼ of the volume of all waste materials. Such a trend is inconsistent with sustainable development and considerate impact on the environment. The contemporary society is aware of these adverse impacts and it actively participates in the integration of construction waste back into production. Thanks to the systems of recycling, construction waste can return to the building industry as a fully valuable building material. The production of shaped pieces from grey cellular concrete after the autoclave process results in the creation of residual material in the form of waste blocks (rubble). This waste material is stored in dumps. The presence of these dumps has an adverse effect on the surrounding environment. This article presents the first results of a basic research dealing with the treatment process of waste cellular concrete rubble by means of a crushing process and its subsequent use as filler in the production of new porous concretes. The article presents 3 basic recipes of porous concrete, where 100 % of the filler was replaced with crushed porous concrete rubble with the fraction of 0/6 mm. The proposed recipes have been tested in regards to: density of fresh concrete mixture, concrete mixture consistency, strength, and thermal conductivity coefficient.

Capillary Active Insulations Based on Waste Calcium Silicates

The issue of capillary active calcium silicate insulation used in the systems of energy redevelopment of historic buildings is a very up-to-date topic. This article describes the properties of the developed material structures built on cement composites with a defined inner surface using industrial waste materials containing aluminosilicates. The article presents the structures containing fly ashes from heating plants improving the rheological properties of the mixture and the latent hydraulic properties allowing a reduction of the necessary amount of the binding matrix, represented by cement in this case, which has a direct impact on the economy of the final material. The aim of the developed material is to extend the segment of capillary thermal insulation board materials used for the purpose of energy redevelopment of historic buildings. The article will present the parameters evaluating the capillary activity of the material, the coefficient of diffusion resistance, the thermal conductivity coefficient and the physical and mechanical properties. The acquired values are then implemented into the simulation software Delphin, taking into account the moisture transport in porous materials under non-stationary conditions. The output of the software is a simulation describing the developed material in time, after the incorporation into a moisture-defined building structure showing a disruption of the waterproofing layers of the lower structure.

The Use of Industrial Waste as a Secondary Raw Material in Restoration Plaster with Thermal Insulating Effect

The article describes the results of an experimental research dealing with the use of industrial waste in the form of secondary raw material - polyurethane foam after the end of its life cycle, as a 100% substitute of filler in restoration plaster with thermal insulating effect. The article presents the formulas of restoration plaster and its properties. They are: mortar consistency, volume weight, strength characteristics, thermal conductivity coefficient, coefficient of capillary water absorption, porosity and resistance against salts.

The properties of waste water from a concrete plant

This paper presents the results of a research dealing with the testing of the properties of wastewater forming during the production of concrete mixture in a concrete plant. The test results are compared with the limit values of concrete mixing water according to CSN EN 1008 in order to use this waste water as a partial replacement of mixing water during the production of concrete.

Measuring the Thermal Characteristics of Concretes Exposed to Extreme Conditions

This article presents the results of an experimental research dealing with the measurement of the thermal characteristics of concretes based on natural and artificial aggregates (steel slag). The samples of concrete composites were prepared on the basis of natural aggregate fractions 0/4, 4/8 and 8/16 mm and on the basis of steel slag fr. 4/8 mm. The volume ratio of the individual aggregate fractions in all experimental mixtures used for the production of concrete composites was 40:30:30 (fr. 0/4: 4/8: 8/16). The prepared samples of concrete composites based on natural aggregate and natural aggregate combined with steel slag were subjected to the tests of strength characteristics, water-tightness, thermal characteristics using a commercial device ISOMET 2104 (measurement of the coefficient of thermal conductivity λ, specific heat capacity c, and the coefficient of thermal diffusivity a), and heating in a prototype calorimetric computer-controlled chamber. The main attention was focused on the testing of the value changes of the coefficients of thermal conductivity λ depending on the changes of temperatures within the range of -5 °C to + 40 °C. The measurements of these thermal characteristics have very high informative value, especially because these material parameters are not tabulated for the newly designed building materials, and that is why they are not examined at extreme temperatures. This is a reason why they cannot be used as important data during the thermal calculations of a non-insulated concrete structure (e.g. using polystyrene and / or glass wool).

Analysis of Physical-Mechanical and Surface Properties of Wood Plastic Composite Materials to Determine the Energy Balance

Wood plastic composite (WPC) materials represent modern materials that are attracting interest worldwide. WPC are composite materials and they have properties of both components – plastic and wood. WPC materials are formed by combining two substances – discontinuous reinforcements (wood particles or cellulose microfibers) and a continuous binder (plastic matrix), in a certain proportion. The authors describe WPC machined surfaces after turning. On the basis of a set of experimental data collected by surface and mechanical tests obtained from the WPC materials, the mechanical deformation work was evaluated, the value of which presents specific information about the material as a specific material coefficient.

Energy Remediation Combining Insulation Materials Based on Calcium Silicate and Expanded Polymers

Energy rehabilitation of buildings using airtight insulating materials based on expanded polystyrene is often accompanied by the formation of moisture problems in the enclosure wall footing. Moisture progress in the rehabilitated structure is simulated using modern moisture transient models in Delphin software. Combinations of the developed plate thermal insulating materials based on calcium silicate and the conventional thermal insulation panels based on expanded polymer have been designed to address the moisture problems. This article describes the function of this solution during the reconstruction of a house built from full clay bricks with malfunctioning waterproofing in the lower house construction.

Comparative Measurements of the Thermal Properties of Solid Materials on a New Device and Using a New Non-Stationary Method

The aim of the publication is the comparative measurements of changes in temperature of the significant material coefficient - thermal conductivity for newly developed construction materials (lightweight concrete). The aim is met by using a newly proposed method and a newly developed device by the approximation modelling of the temperature dependence of the thermal conductivity coefficient of the new composites and also the interpretation of measurement results in the context of optimally desired characteristics of thermal insulation concrete. Construction materials for residential buildings should have good thermal insulation properties, i.e. relatively low coefficients of thermal conductivity. With regard to the relatively most important property of concrete – strength, however, the reduction in thermal conductivity of concrete is limited. Thermal conductivity of concrete can be reduced very effectively by increasing its porosity; on the other hand, by increasing the porosity, the strength of concrete is significantly reduced. The publication, therefore, compares the results of temperature dependences of thermal conductivity for three newly designed concretes, namely in the context of their compressive strength.