When evaluating the energy efficiency of buildings and implementing the necessary measures to increase energy efficiency levels, thermal technical characteristics are determined. For this purpose, in situ measurements of the thermal resistance of external enclosing structures were carried out. One of the methods most often used by researchers is the non-destructive method—the heat flow meter (HFM) method regulated by ISO 9869. In the case of surveying a building with a high level of thermal resistance, researchers are faced with low-density heat flux measurements, which is always a difficult task due to significant fluctuations and the influence of external factors on the measurement results. This is due to the fact that it is difficult to determine what is a useful signal and what is a consequence of the effects of non-stationarity and heat transfer conditions. The article provides an example of low-density heat flux measurements when determining the thermal resistance of a building and proposes a data pre-processing procedure that allows for the reduction of heat flux fluctuations, which has a significant impact on the final result at low density. The proposed use of wavelet analysis in the pre-processing of low-density heat flux measurement data makes it possible to reconstruct them or reduce disturbances that occur during research. A comparison of the obtained results with the results of the calculation according to ISO 9869-1 showed a decrease in the standard deviation of the measurements from 5.74 to 2.81%. The results of this study can be used to reduce the noise of low-density heat flux and, as a result, reduce the standard deviation of the measurement when applying the HFM method of determining the thermal resistance of external enclosing structures.

The cement industry is responsible for 8% of global CO₂ production. Therefore, a clear trend has been observed recently to replace to some extent the main binder of cement composites with environmentally friendly or recycled materials with a lower carbon footprint. This paper presents the effect of brick powder (BP) on the physico-chemical and mechanical properties of cement mortars. The effect of a short-term thermal shock on morphology and strength properties of green mortars was investigated. BP addition caused increase in porosity and decrease in compressive and flexural strength of mortars. The best results were obtained for samples with 5% wt. BP addition. Above this addition the strength decreased. The mechanical performance of the samples subjected to thermal loading increased compared to the reference samples, which is the result of a process called as the “internal autoclaving”. The BP addition positively affects the linear shrinkage, leading to its reduction. The lowest linear shrinkage value was achieved by the mortar with the highest BP addition. An intelligent modeling approach for the prediction of strength characteristics, depending on the ultrasonic pulse velocity (UPV) is also presented. To solve the model problem, a supervised machine-learning algorithm in the form of an SVM (support vector machines) regression approach was implemented in this paper. The results indicate that BP can be used as a cement replacement in cement mortars in limited amounts. The amount of the additive should be moderate and tuned to the features that mortars should have.

The article discusses the impact of vertical partition, technology on thermal insulation of the building, and the resulting savings and residents thermal comfort. The study is carried out as an analysis of three selected design solutions including such materials as: aerated concrete elements,...

The present paper investigates the axial and shear buckling analysis of a carbon nanotube (CNT)-reinforced multiscale functionally graded material (FGM) plate. Modified third-order deformation theory (MTSDT) with transverse displacement variation is used. CNT materials are assumed to be uniformly distributed, and ceramic fibers are graded according to a power-law distribution of the volume fraction of the constituents. The effective material properties are obtained using the Halpin–Tsai equation and Voigt rule of the mixture approach. A MATLAB code is developed using nine noded iso-parametric elements containing 13 nodal unknowns at each node. The shear correction factor is eliminated in the present model, and top and bottom transverse shear stresses are imposed null to derive higher-order unknowns. Comparisons of the present results with those available in the literature confirm the accuracy of the existing model. The effects of material components, plate sizes, loading types, and boundary conditions on the critical buckling load are investigated. For the first time, the critical buckling loads of CNT-reinforced multiscale FGM rectangular plates with diverse boundary conditions are given, and they can be used as future references.

The study on the wetting properties and surface free energy (SFE) of mineral-asphalt mixtures was presented in the paper. The composition of the two mineral-asphalt mixtures was prepared: the mixtures with dolomite and the mixtures with dolomite and recycled ceramic aggregate. The use of different aggregates results in diversification of the wetting properties in porous bituminous mixtures. The microstructure was shown based on the SEM study. The wetting properties of mineral-asphalt mixtures were determined by measuring the contact angle of their surface using water as measuring liquid. Measurements were carried out immediately after the time of application of the drops. The total surface free energy (SFE) was determined using the Neumann method. While analysing the examination results it can be noticed that the values of contact angles depends on the type of aggregate used in mixtures and the smoothness of mineral-asphalt mixtures surface. The highest contact angle was noticed for the bituminous mixture with dolomite aggregate on flat surface. The smallest contact angle with water was obtained for the mineral-asphalt mixture with dolomite and recycled ceramic aggregate on rough surface. This is due to the physical characteristics of this aggregate. Ceramic aggregate is characterized by the high absorbability. This indicates an increased wettability and adhesion properties.