Search Results (27)

Experimental studies have shown that osmosis could be one of the mechanisms of water transport in porous materials that act, to a certain extent, as semipermeable membranes. In this paper, an experimental apparatus and the corresponding model to measure and determine the osmotic efficiency, σ, of bulk porous materials are described. Both the apparatus and model to interpret water transport in samples are modifications of those of Sherwood and Craster. In addition to σ, the transport parameters of the model include Darcy permeability and water and salt diffusivity. These parameters are used to calculate the ratio of the individual components of the total molar flow. We used the apparatus to measure cylindrical samples made from an illitic clay with a diameter of 45 mm and thickness of 5 mm. The measured transport coefficients were then used to estimate the relative importance of the individual contributions to the total flow of water through the samples. Our results show that the contribution of the osmosis is 82–88%, while the diffusion contributes only 11–13% and the Darcy flow caused by the pressure difference contributes only 1–5%. Even after considering the uncertainties in the measurement of the transport coefficients, which are estimated to be up to 22%, the results show that osmosis makes an important contribution to the total water flow and should not be neglected in general. Full article

This study explores the application of materials used in 3D printing to manufacture the housings of non-invasive sensors employed in measurements using a TDR (Time Domain Reflectometry) meter. The research investigates whether sensors designed with 3D printing technology can serve as viable alternatives to conventional invasive and non-invasive sensors. This study focuses on innovative approaches to designing humidity sensors, utilizing Fused Deposition Modeling (FDM) technology to create housings for non-invasive sensors compatible with TDR devices. The paper discusses the use of 3D modeling technology in sensor design, with particular emphasis on materials used in 3D printing, notably polylactic acid (PLA). Environmental factors, such as moisture in building materials, are characterized, and the need for dedicated sensor designs is highlighted. The software utilized in the 3D modeling and printing processes is also described. The Materials and Methods Section provides a detailed account of the construction process for the non-invasive sensor housing and the preparation for moisture measurement in silicate materials using the designed sensor. A prototype sensor was successfully fabricated through 3D printing. Using the designed sensor, measurements were conducted on silicate samples soaked in aqueous solutions with water absorption levels ranging from 0% to 10%. Experimental validation involved testing silicate samples with the prototype sensor to evaluate its effectiveness. The electrical permittivity of the material was calculated, and the root-mean-square error (RMSE) was determined using classical computational methods and machine learning techniques. The RMSE obtained using the classical method was 0.70. The results obtained were further analyzed using machine learning models, including Gaussian Process Regression (GPR) and Support Vector Machine (SVM). The GPR model achieved an RMSE of 0.15, while the SVM model yielded an RMSE of 0.25. These findings confirm the sensor’s effectiveness and its potential for further research and practical applications. Full article

This article presents problems related to the storage of building material samples and discusses the related requirements and standards. Solutions for containers to store material samples were proposed and tests were performed in accordance with the EN ISO 12570 standard to demonstrate that all the water that may have condensed during the samples’ transport in the self-designed, closed container evaporates from the lid when unscrewed and placed under the container during the drying process. The aim of this study was to test the tightness of self-designed containers for transporting bulk samples. The drying efficiency at elevated temperatures in moisture tests for bulk material containers was determined and, finally, the influence of ambient conditions on a sample placed in a container for bulk material transport was estimated. The results confirmed that the designed container is vapour-tight and allows the collected material to be protected against evaporation during transport from the sampling site to the laboratory. Under extreme transport conditions, the water contained in the sample in a closed container partially evaporates from the material and condenses on the lid but this is taken into account when balancing the moisture of samples in the laboratory and does not falsify the readouts. Full article

In this article, the results of studies testing the anisotropy of autoclaved aerated concrete in terms of water and heat transport are presented. Using image analysis techniques, a study was conducted on four different samples of concrete produced in the same process. To ensure the comparability of results, the pictures were taken from a fixed distance with the same lens settings trimmed to a set size. Cross-sectional profiles of the material were examined and were arranged in two directions: perpendicular and parallel to the growth direction occurring in the autoclave. For each block, approximately 4750 objects were obtained, with an average of 2700 objects along the wall and 2050 across it. As a result of the comparative analysis, metrics concerning pores, significantly distinguishing the profile direction, were identified. These included the pore area (area), the maximum and minimum distance between points on the perimeter (Feret, MinFeret), lengths of the major and minor axes of the fitted ellipse (major, minor), and the ratio of the area of selection to its convex hull (solidity). As a reference, standard investigations were conducted for moisture transport using the time domain reflectometry setup and for thermal conductivity values using the steady-state heat flow plate apparatus. Full article

Paper is in the scope of moisture-related problems which are connected with mold threat in buildings, sick building syndrome (SBS) as well as application of electronic nose for evaluation of different building envelopes and building materials. The machine learning methods used to analyze multidimensional signals are important components of the e-nose system. These multidimensional signals are derived from a gas sensor array, which, together with instrumentation, constitute the hardware of this system. The accuracy of the classification and the correctness of the classification of mold threat in buildings largely depend on the appropriate selection of the data analysis methods used. This paper proposes a method of data analysis using Principal Component Analysis, metric multidimensional scaling and Kohonen self-organizing map, which are unsupervised machine learning methods, to visualize and reduce the dimensionality of the data. For the final classification of observations and the identification of datasets from gas sensor arrays analyzing air from buildings threatened by mold, as well as from other reference materials, supervised learning methods such as hierarchical cluster analysis, MLP neural network and the random forest method were used. Full article

The diffusion of calcium ions Ca²⁺ in aquatic solutions (10 g/l) was measured for two brick samples from a region in Bohemia (Vysoké Mýto, Holešov-Žopy). The experiment was performed under laboratory conditions at the ambient temperature of 20 ± 2 °C for a period of 240 h. The bricks were cut into three depth layers. The calcium concentrations were analyzed chelatometrically. The biodegradation potential of the individual layers was also studied. The results indicated that the depth and quality of firing are of importance regarding the transport of calcium, and they affect the success of bio-colonization. Full article

The measurement of the moisture content of building materials is of key importance both in the process of building structures and in their subsequent operation. In engineering practice, indirect techniques of moisture measurement, mainly, resistance and capacitive, are the most popular. The main objective of this research work was to compare the classic TDR measurement technique to the non-invasive, surface TDR sensors. Moisture measurements were carried out on samples made of cellular concrete with density class of 400 and 600. These samples were moist to various degrees, from 0 to 69% (400 c.c.) and from 0 to 55 (600 c.c.). For each sample, five measurements were carried out. Both the RMSE and the expanded uncertainty values were more favorable for the TDR FP/mts probe and were consistent with the literature data. Compared to them, the measurement result for the 400 c.c. samples with the S1 probe was 154.6%, and that with the S2 probe was 87.03% of the values obtained with the invasive probe. When measuring the 600 c.c. samples, we found values of 122.16% for S1 and of 120.1% for S2 of those obtained with the invasive probe. The use of surface TDR sensors provided an easy and quick measurement without damaging the surface and structure of the tested material, as there was no need to introduce the probe actuators inside the tested material. Full article

During the building design phase, a lot of attention is paid to the thermal properties of the external envelopes. New regulations are introduced to improve energy efficiency of a building and impose a reduction of the overall heat transfer coefficient; meanwhile, this efficiency is more influenced by the efficiency of the heating system and the type of fuels used. This article presents a complex analysis including the impact of: heat transfer coefficient of the envelope, efficiency of building service systems, the type of energy source, and the fuel. The analysis was based on the results of simulation tests obtained for an exemplary multi-family residential building located in Poland that is not equipped with a cooling system. The conducted calculations gave quantitative evaluation of the influence of particular parameters on building energy performance and showed that the decrease of heat transfer coefficient of building boundaries, in accordance to the Polish regulation for 2017 and 2021, gave only 11% of reduction on usable energy demand index. On the other hand, it was found that modification of the heating system and heat source can significantly influence the values of the final and primary energy consumption at the level of 70%. The application of heat pumps has a greater influence on the final and primary energy consumption for heating indices than other parameters, such as the building’s envelopes. Full article

The article concerns the issue of non-invasive moisture sensing in building materials. Two techniques that enable evaluating the value of the relative permittivity of the material, being the measure of porous material moisture, have been utilized for the research. The first is the microwave technique that utilizes the non-contact measurement of velocity of microwave radiation across the tested material and the second is the time domain reflectometry (TDR) technique based on the measurement of electromagnetic pulse propagation time along the waveguides, being the elements of sensor design. The tested building material involved samples of red ceramic brick that differed in moisture, ranging between 0% and 14% moisture by weight. The main goal of the research was to present the measuring potential of both techniques for moisture evaluation as well as emphasize the advantages and disadvantages of each method. Within the research, it was stated that both methods provide similar measuring potential, with a slight advantage in favor of a microwave non-contact sensor over surface TDR sensor designs. Full article

The article presents the results of studies concerning raw hemp shives obtained from the Polish crop of industrial hemp as a loose-fill thermal insulation material. The study focuses mainly on the measurements of the pore size distribution, thermal conductivity and air permeability of material. An increase in the value of the thermal conductivity coefficient (0.049–0.052 W/(m·K)) was demonstrated with an increase in the bulk density. The porosity of the individual pieces of shives is 78.7% and the predominant number of pores is in the diameter range of 0.9–3 μm. The paper also presents an example of the use of the tested material as thermal insulation of the wooden frame wall. The heat flow analysis was performed in various wall variants (insulation thickness: 100, 200 and 300 mm and pressure difference 0, 5, 10 and 15 Pa). A clear influence of the variables on the temperature distribution was observed. Full article

The article concerns the electric techniques of moisture detection that are based on the evaluation of the apparent permittivity of the tested medium. The main goal of the research was to evaluate the non-invasive Time Domain Reflectometry (TDR) sensors’ sensitivity by measuring the span of elements and material moisture. To that aim, two non-invasive sensor designs were investigated for their sensitivity in the evaluation of the apparent permittivity value of aerated concrete. Sensors A and B were characterized by the spacing between the measuring elements equal to 30 mm and 70 mm, respectively. The tested samples differed in moisture, ranging between 0 and 0.3 cm³/cm³ volumetric water content. Within the research, it was stated that in the case of the narrower sensor (A), the range of the sensor equals about 30 mm, and in the case of the wider design (B), it equals about 50 mm. Additionally, it was stated that material moisture influences the range of sensor influence. In the case of the dry and low-saturated material, it was not possible to evaluate the range of sensor sensitivity using the adopted method, whereas the range of sensor signal influence was visible for the moist material. Full article

Biopolymers based on proteins are applied in the building materials technology to modify and improve their selected properties. These polymers are designed as natural admixtures that improve the workability of materials. Casein is an example of a protein-based organic polymer. It is a protein obtained from cow’s milk. The paper aimed at investigating the prospects of enhancing the strength properties of a binder prepared on a basis of metakaolin and hydrated lime. The mix was modified with powdered technical casein at 0.5%, 1%, 3%, and 5% as a partial replacement for the binder mix by mass. The study involved investigating the effect of the applied natural admixture on the flexural and compressive strengths, as well as pore size distribution. The average pore diameter decreased in the recipes with casein in the amount of 0.5% and 1%, while it increased when the amount of casein equaled 3% and 5%. Only the 0.5% casein admixture caused a decrease in the total porosity. The results show a clear dependence of the strength parameters on porosity. The admixture of casein significantly increased the flexural strength of the pastes, and decreased the compressive strength. The highest increase in flexural strength (by 205.7%) was caused by the admixture of 0.5% casein, while the greatest decrease in compressive strength (by 28%) was caused by the 3% casein admixture. The flexural strength was enhanced, i.a., due to the improved adhesion and mutual bonding of lime particles, resulting from the application of a sticky admixture. No notable difference was indicated during carbonation by the phenolphthalein test. The lime binder is characterized by a slow setting process and low mechanical strength. The results of the research showed the possibility of improving the flexural strength using small amounts of natural admixture, which may broaden the scope of application of this binder. Full article

The aim of the research presented in the article was to check the differences in the hygro-thermal and mechanical properties of hemp-lime composites with different shives fractions, depending on the direction of mixture compaction. The research part of the paper presents the preparation method and investigation on the composites. Thermal conductivity, capillary uptake, as well as flexural and compressive strengths were examined. Additionally, an analysis of the temperature distribution in the external wall insulated with the tested composites was performed. The results confirm that the direction of compaction influences the individual properties of the composites in a similar way, depending on the size of the shives. The differences are more pronounced in the case of the composite containing longer fractions of shives. Both thermal conductivity of the material and the capillary uptake ability are lower in the parallel direction of the compaction process. Composites exhibit greater stiffness, but they fail faster with increasing loads when loaded in the direction perpendicular to compaction. Full article

The article assesses an impact of thermal retrofitting on an improvement of the energy quality of public buildings in terms of their heating. The analysis covered a group of 14 buildings, including schools, kindergartens or offices, while energy audits were carried out for 12 of them. The indications of individual gas meters were the source of actual data for the assessment of changes in energy consumption indexes in operating conditions. The analysis showed a clear improvement in the energy quality of buildings; however, the actual effects were much lower than forecasted. The average forecasted decrease in energy consumption was supposed to be 64.3%, but the measured data showed only 37.1%. The investigation confirmed that the most complex refurbishing provided the most satisfactory decrease in energy consumption (51.4% of real decrease in energy consumption), while objects with partial thermal refurbishing reached an efficiency of only 21.8%. It was stated that in operating conditions, special attention should be paid to the manner of energy use, since different indicators of energy consumption can be obtained with the same parameters of building’s balance cover. The results obtained can be further utilized in thermal-refurbishment implementation procedures. Follow-up investigations on the impact of selected parameters on energy consumption are planned. Full article

The paper presents the results of research concerning three fiber materials—mineral wool, hemp fiber and wood wool—as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in relation to bulk density. These materials exhibit open porosity; thus, convection is an essential phenomenon in the heat transfer process. The paper aimed at conducting thermal simulations of various frame wall variants which were filled with the above-mentioned insulation materials. The simulations were performed with the Control Volume Method using the Delphin 5.8 software. The studies accounted for the effect of wind pressure and the time of its influence on a wall insulated by means of fiber material with a thickness of 150 as well as 250 mm. The simulation enabled us to obtain such data as maximal R-value reduction and time to return to equilibrium after filtration for the analyzed materials. The study proved that heat transfer in these insulations strongly depends on the bulk density, thickness of the insulation and wind pressure. The decrease in R is reduced as the density increases. This results from the decreased air permeability characterizing the material. Wind washing causes lower R reduction than air filtration in all models. The greater the thickness, the longer it takes for the models to return to the equilibrium state following air filtration (and wind washing). This period is comparable for air filtration and wind washing. Hemp fibers were characterized with the strongest susceptibility to air filtration; in the case of wood wool, it was also high, but lower than for hemp fibers, while mineral wool was characterized with the lowest. Full article