Ozturk, Akif Berke; Turan, Ahmet İhsan; Kumbasaroglu, Atila; Yalciner, Hakan; Ayaz, Yaşar

Deterioration caused by elevated temperatures in the micro- and macrostructure of concrete can lead to significant reductions in its mechanical performance, making it crucial to assess the residual behavior of concrete elements after thermal exposure. This study experimentally investigates the effects of elevated temperatures (25 °C, 200 °C, 400 °C, and 600 °C) on cubic and prismatic specimens produced with two different aggregate types (raw perlite aggregate and conventional coarse aggregate) across four mixtures (C25, C40, P25, and P40). Destructive (compressive and flexural strength) and non-destructive (ultrasonic pulse velocity, scanning electron microscopy) tests were conducted before and after thermal loading. Increasing the temperature to 600 °C reduced the compressive strength of conventional mixtures by 34.91 % (C25) and 41.79 % (C40), whereas perlite-based concretes exhibited significantly lower reductions of 9.91 % (P25) and 12.80 % (P40). Mass loss remained negligible (<2 %) up to 200 °C, increased to 4–6 % for conventional mixtures and 6–11 % for perlite-based mixtures at 400 °C, and reached 25–40 % and nearly 47 %, respectively, at 600 °C. UPV results revealed a substantial degradation in internal integrity at high temperatures, with decreases of 49–60 % in conventional concretes and only 16–17 % in perlite-based mixtures at 600 °C. Although the flexural strength of P25 and P40 was initially lower at 25 °C, their post-heating performance became comparable to conventional mixtures, showing similar residual flexural behavior at elevated temperatures. SEM observations further confirmed that perlite-based concretes exhibited fewer microcracks and reduced matrix deterioration compared to conventional mixtures. Overall, the findings clearly demonstrate that raw perlite aggregate significantly enhances the thermal resistance, internal stability, and residual durability of concrete, making it a promising sustainable alternative for structures exposed to elevated temperature environments.

Yildirim, Feride Secil; Karsli, Fevzi; Bahadir, Murat; Yildirim, Merve

The building layer, one of the fundamental elements of mapping, features various layouts and architectures and is used in many mapping activities, such as urban planning, property management, illegal building detection, and disaster investigation. Therefore, accessing building information from remotely sensed images in a fast and automated manner is a popular topic. This paper aims to design a new Convolutional Neural Network (CNN) architecture called FwSVM-Net (Fast with Support Vector Machine Network) for building extraction. The FwSVM-Net, with 16 convolutional layers, employs a fusion mechanism to reduce the semantic gap between the encoder and decoder sections. In the architecture's classification layer, a Support Vector Machine (SVM) is used to increase segmentation accuracy while reducing parameter density. The Massachusetts Building Dataset was used for the automatic building extraction from aerial images. The performance of the FwSVM-Net on the test data was calculated at 97 %, 91 %, 87 %, 89 %, and 86 % for Overall Accuracy (OA), Precision (Pr), Recall (Rc), F1-Score (F1), and Intersection over Union (IoU), respectively. FwSVM-Net shows approximately ±2 % similarity in accuracy with the U-Net architecture, which is trained and evaluated with the same dataset. Despite this, the fact that the FwSVM-Net completed the training process approximately twice as fast as the U-Net architecture provides a significant time advantage. As a result, it is predicted that the FwSVM-Net will offer speed and convenience in terms of usability because of its performance, which is equivalent to the performance of the U-Net architecture for segmentation, and its time advantage.

Bulut, H. Alperen; Şahin, Remzi

This article presents the results of a comprehensive study investigating the hypothesis that higher concentrations of natural radionuclides, that are harmful to human health, may be present in Self-Compacting Concretes (SCCs) due to its higher powder material content compared to conventional concretes. The fresh (slump-flow, T500 time, V-funnel) concrete and compressive strength of SCCs prepared by replacing Portland cement with fly ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBFS) in the respective range of 5%, 12.5%, and 20% were determined. The radionuclide activity concentration of all solid concrete components and SCCs were determined using the gamma spectrometry method. Radioactivity analyses including the calculation of the activity concentration index and annual effective dose equivalents were also performed. The findings showed that the specimens with the highest average compressive strength at the end of 120th day were, respectively, SF (54.2 MPa), FA (52.2 MPa) and GGBFS (46.1 MPa) added to the SCC. The obtained concentration of the Radium-226 value (41.1) of 20% UK with added SCC was 1.8 times higher than the control concrete (22.7) and 2 times higher than 20% SF added SCC (19.7). The highest Radium equivalent activity (Raeq) values were FA20 (89.52), GGBFS20 (72.05), control concrete (70.86) and SF20 (68.01). It was determined that the FA selected for the study exceeded the limit specified for structural material (3.38 > 1) and fell in the radiologically hazardous class. It has been proven that SF can be used as a radioactivity reducing material of concretes. The results revealed that the research hypothesis was confirmed in terms of FA.

Congedo, Paolo Maria; Baglivo, Cristina; Seyhan, Aslıhan Kurnuc; Marchetti, Raffaele

Around the world, expected climate changes can affect indoor comfort conditions in buildings. Analysing the climate in which buildings are located is the first step towards high-efficiency design, and today it is no longer possible to ignore impending climate change. This study has provided a worldwide picture of how comfort conditions inside a building can change as external climatic conditions change. For the first time, a building is tested worldwide over a long-term period, and not just in a specific climate or a small group of climates. Several cities homogeneously distributed around the world were selected, covering all climates of the Köppen-Geiger classification. A hypothetical building was implemented with the Termolog Epix 11 software in order to monitor the operative temperature (TOP) in free-floating mode on an hourly basis and test its temperature variations in the short, medium and long term. The percentage values of the hours when the TOP is in a comfort or discomfort conditions were compared for all configurations. The results showed that the comfort conditions vary with the climate. Climate zone A displayed for most subclimates high TOP values. Climate zone B showed an irregular trend, from 2020 to 2080 the hours when TOPs fall below 20 °C decreased in most locations. Climate zone C included areas where TOPs are mostly in the comfort range. Some sub-climates in zone D show very cold climates, with an average of about 15–20% of the annual hours in the comfort zone in 2020, then increasing slightly by a few percentage points in 2080.