Advanced Materials Research Vol. 1126

Abstract: Excess moisture in a building is a serious problem that affects the quality of life and the durability of construction. The usage of electro osmosis in historic buildings has longer data as it is the least destructive method for removing noxious moisture from masonries. Beneficial effects of electro osmosis on the moisture elimination have been documented in various scholarly articles and works. Wireless electro osmosis, based on the influence of magnetic or electromagnetic field on the water cumulated in masonries is often questioned because of the lack of scholarly works focused on the physical principles of the method. Results from our own tests were confronted with the theoretical background.

Abstract: The in-situ examination of the historical enclosure wall of the Star Game Preserve located in the capital of the Czech Republic, Prague, is presented in the paper, in order to obtain necessary information for a qualified design of renovation and reconstruction treatments. At the visual inspection of the researched structure, the previous reconstruction methods are identified and evaluated, together with possible moisture sources. Moreover, the damage extent and propagation are assessed. Most of the oldest as well as newly constructed parts of the enclosure wall are found in bad condition and dilapidating. On this account, the building stone (arenaceous marl) forming the original historical masonry is examined to find compatible materials for the reconstruction works. Its chemical composition is accessed by X-Ray Fluorescence analysis. For the researched stone, basic physical, mechanical, hygric and thermal properties are measured. Using the obtained data, the proper material for reconstruction purposes will be identified.

Abstract: Several thermal insulation systems were developed for improvement of thermal performance of buildings. Exterior thermal insulation systems represent usually natural solution of the problem of low thermal resistance of building envelopes. However, in some cases, there is necessary to realize interior thermal insulation systems, what brings number of possible problems. Their common disadvantage is a limitation of interior space due to the thickness of thermal insulation layer and a possible condensation of water vapor which permeates the thermal insulation system. On this account, new sandwich composite with silica aerogel originally designed for application in interior thermal insulation systems is studied in the paper. Thermal properties are measured by two transient methods using devices ISOMET 2114 and RTB. The water vapor transport parameters are determined on the basis of dry cup and wet cup methods. The obtained data gives information on thermal and water vapor transport properties of the particular layers of sandwich composite and predetermines its behavior at real climatic exposure of building.

Abstract: Studies of the heat capacity temperature characteristics for microalloyed high strength steel S960QL is reported. The investigations were concentrated in the region of the second order phase transition. Experiments were carried out using the Differential Scanning Calorimeter DSC 404F1 Pegasus (Netzsch). As a tested material a sample from the high strength steel S960QL was used within temperature range of 50-1100 °C. In addition to this dilatometric investigations with the same temperature range as DSC ones were carried out using Netzsch dilatometer DIL 402C. Measurements of thermal characteristic, i.e. the heat capacity c_p(T) and thermal expansion α*(T) were performed several times in order to observe thermal processes taking place in microalloyed high strength steel. Previous investigations have revealed the thermal hysteresis of the linear expansion in the region of the second order magnetic phase transition in the S960QL steel.

Abstract: The paper presents the validation of physical properties of refractory concrete with heavy filling, using the measurements under high temperature, assumed for the construction of a thermal storage. The whole system, consisting of the storage core and of the insulation container, is characterized by non-stationary thermal transfer, supplied from solar radiation into the core. The validation of behaviour of the system (including its sleeping state and the dynamics of charging and discharging) is needed for the optimization of its size parameters.

Abstract: Mould risk is an increasing problem in current housing branch. Mould is considered to be one of the most important features of Sick Building Syndrome. In most cases it is caused by the increased moisture of building barriers and improper humidity of indoor air. In old buildings it is caused by improper raising techniques, lack of isolation against moisture and insufficient building materials applied for construction. Modern housing also suffers problem of mould risk which is connected to introducing of the new materials and technologies for external envelopes of the buildings. These often increase the tightness of the buildings and cause improper performance of natural ventilation systems, which makes suitable conditions for mould to grow.In the paper there is proposed an attempt to evaluate mould risk in the buildings using e-nose, being a gas sensors array which consists of eight metal oxide semiconductor (MOS) gas sensors. This device is commonly applied for air quality assessment in environmental research. First part of the article is a description of e-nose technology and its possible applications in constructions. The second part shows the exemplary e-nose readouts of indoor air sampled in clean reference rooms and threatened with mould development. Obtained multivariate data are processed and visualized using a Principal Component Analysis (PCA).

Abstract: We study the hydration and pozzolanic reactions of cement pastes made from Argentinian and Czech Portland cements as a function of age, using thermogravimetry. The measurements are done for 2, 7, 28, and 90 days cured samples in order to monitor the rate of hydration. The investigation is performed in the temperature range from 25 °C to 1000 °C with a heating rate 5 °C/min in an argon atmosphere. The mass change during the decomposition of calcium silicate hydrate gels, portlandite, and calcite are determined, and the changes in the portlandite amount are estimated in dependence on the time of hydration.

Abstract: Utilization of advanced materials in civil engineering motivates research in both experimental and computational methods of reliable identification of their material characteristics, as e.g. the thermal conductivity and diffusivity in semilinear evolutionary equations of heat conduction, coming from the energy balance in classical thermodynamics, or the capillary transfer coefficient in similar equations, coming from the mass balance. The paper presents mathematical preliminaries of such inverse analysis and an overview of computational approaches with references to practical applications.

Abstract: Mannitol is an alcoholic sugar that is commonly used in the food industry. It is a white, odorless crystalline powder. Its melting temperature is about 168 °C. It is possible to be used also for the accumulation of energy in the heat exchangers based on oils. On its basis is sold a product PlusICE A164 of company PCM Products Ltd. (T = 164 °C, c_p = 2.42 kJ.K^-1 kg^-1). Thermal properties of the material in both, solid and liquid phase were investigated for this purpose in terms of potential applications. Temperature dependence of thermal parameters (thermal diffusivity, thermal conductivity, and specific heat) were determined using a transient (step-wise) method. Fractal model of heat transport was used for the determination of thermal parameters. This model is independent on the geometry and on the type of the sample heating, and includes heat losses too. The experiment confirms the phase change temperature about 168 °C.

Abstract: In this paper the results of storage modulus (E’), loss modulus (E’’) and damping parameter tan (δ)=E''/E' of epoxy resins Epidian 57 and L285 with curing agents Z1 and LH285, respectively are presented. In addition to this the stress-strain and thermal expansion characteristics of Epidian 53, 57 and L285 were obtained experimentally in order to compare Dynamic Mechanical Analysis (DMA) results. Temperature range of DMA investigations using Netzsch (Germany) DMA 242C analyzer was from-120 °C to +110 °C at the heating rate of 1 K/min with frequency of {0.1, 1, 10} Hz, respectively. Netzsch DIL 402C dilatometer was used to study the thermal expansion of the tested samples within temperature range from 30 °C to 80 °C at 1 K/min of heating and cooling rates, respectively and Huang TA computer servo control material testing machine HT-2402 was applied to determine the stress-strain characteristics. Measurements of sample elongation ΔL and physical α* were performed twice in heating and cooling cycles. The glass transition temperature T_g determined from maximum of tan (δ) curve at f = 1Hz was equal to 76.7 °C for E57 and 87.2 °C for L285. It has been observed durable deformed shape of L285 sample with deflection in the middle about 5 mm just after finishing the DMA first run of heating which significantly affected DMA results during the second run of heating