Consideration of Critical Parameters for Improving the Efficiency of Concrete Structures Reinforced with FRP

Funding Information: This research was supported by the Polish National Agency for Academic Exchange no.: PPN/IWA/2019/1/00155/U/00001 (Iwanowska programme). Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Fibre-reinforced polymer materials (FRP) are increasingly used to reinforce structural elements. Due to this, it is possible to increase the load-bearing capacity of polymer, wooden, concrete, and metal structures. In this article, the authors collected all the crucial aspects that influence the behaviour of concrete elements reinforced with FRP. The main types of FRP, their characterization, and their impact on the load-carrying capacity of a composite structure are discussed. The most significant aspects, such as type, number of FRP layers including fibre orientation, type of matrix, reinforcement of concrete columns, preparation of a concrete surface, fire-resistance aspects, recommended conditions for the lamination process, FRP laying methods, and design aspects were considered. Attention and special emphasis were focused on the description of the current research results related to various types of concrete reinforced with FRP composites. To understand which aspects should be taken into account when designing concrete reinforcement with composite materials, the main guidelines are presented in tabular form.publishersversionpublishe

Digitizing Historical Aerial Images: Evaluation of the Effects of Scanning Quality on Aerial Triangulation and Dense Image Matching

In the last decade, many aerial photographic archives have started to be digitized for multiple purposes, including digital preservation and geoprocessing. This paper analyzes the effects of professional photogrammetric versus consumer-grade scanners on the processing of analog historical aerial photographs. An image block over Warsaw is considered, featuring 38 photographs acquired in 1986 (Wild RC10, Normal Aviogon II lens, 23 × 23 cm format) with a ground sampling distance (GSD) of 4 cm. Aerial triangulation (AT) and dense image matching (DIM) procedures are considered, analyzing how scanning modalities are important in the massive digitization of analog images for georeferencing and 3D product generation. The achieved results show how consumer-grade scanners, unlike more expensive photogrammetric scanners, do not possess adequate recording quality to ensure high accuracy and geometric precision for geoprocessing purposes. However, consumer-grade scanners can be used for time and cost-efficient applications where a partial loss of data quality is not critical

Prevalence of electrocardiographic left ventricular hypertrophy among patients with coronary artery disease and diabetes mellitus

Introduction. Electrocardiography (ECG) is a widely used non-invasive diagnostic method for assessment of patients with cardiovascular diseases. Numerous different electrocardiographic criteria exist for detection of left ventricular hypertrophy (LVH). LVH is an important risk factor in patients with coronary artery disease (CAD) or diabetes mellitus and its presence is associated with increased cardiovascular morbidity and mortality. The aim of this study was to evaluate the prevalence of the most frequently used electrocardiographic left ventricular hypertrophy (ECG-LVH) criteria among patients with CAD and diabetes. Methods. A cross-sectional, multicenter study was conducted in outpatient clinics across Poland. Family physicians performed physical examinations and collected relevant information about: onset of CAD and diabetes, presence and onset of hypertension, dyslipidemia, heart failure, diabetic complications, history of acute coronary syndrome and pharmacotherapy. In order to detect LVH, we used seven ECG criteria: 1) the Sokolow-Lyon voltage, 2) the Gubner voltage, 3) the criterion of the R wave amplitude on the leads V5–V6 and 4) aVL, 5) the gender specific Cornell voltage and 6) product, and 7) the Romhilt-Estes point score. Centralized manual assessment of the obtained ECG tracings were performed. Results. We enrolled 1001 patients (48.5% women, 51.5% men, mean age 65 ± 11 years) into the study. At least one ECG-LVH criterion was met in 20.0% (n = 200) of the study participants. The ECG-LVH diagnosis was the most common when using the Romhilt-Estes point score (n = 138; 13.8%). The corresponding prevalence rates for the Cornell voltage, the Cornell product, the R wave amplitude on the lead aVL, the Sokolow-Lyon voltage, the Gubner voltage and the R wave amplitude on the leads V5-V6 criteria were 5.5% (n = 55), 5.2% (n = 52), 3.2% (n = 32), 2.2% (n = 22), 1.9% (n = 19) and 1.3% (n = 13) respectively. Subsequently, the prevalence of the three most frequently used in clinical practice electrocardiographic criteria for LVH (the Sokolow-Lyon voltage, the Cornell voltage and the Romhilt-Estes point score) was analyzed. At least one of them was fulfilled in 185 ECGs. All three criteria at the same time were met only in 5 ECGs (2.7% of 185). Two and only one out of three criteria were fulfilled in 20 (10.8%) and 160 (86.5%) ECGs respectively. Conclusions. The co-occurrence of all assessed ECG-LVH criteria, including the three most frequently applied in clinical practice, is very low in diabetic CAD patients. The Romhilt-Estes point score identifies the highest number of ECG-LVH cases in this setting. However, it seems reasonable to use routinely several ECG criteria for detection of LVH. Further studies are needed to compare diagnostic values of ECG-LVH criteria with imaging methods and to assess prognostic values of various ECG-LVH criteria

Pathological Q waves as an indicator of prior myocardial infarction in patients with coronary artery disease and diabetes mellitus: a comparison of the prevalence and diagnostic accuracy according to present and former criteria

Introduction. Electrocardiography (ECG) is a widely used diagnostic method for identification of patients with previous myocardial infarction (MI). The ECG manifestation of prior MI is the presence of the pathological Q waves. Patients with coronary artery disease (CAD) and diabetes are at high risk of MI. The aim of this study was to compare the prevalence and diagnostic accuracy of the pathological Q waves as an indicator of prior MI in patients with CAD and diabetes according to the present and former criteria. Methods. A cross-sectional, multi-centre study was conducted in outpatient clinics across Poland. Family physicians performed physical examinations, registered ECGs, and collected relevant information about onset of CAD and diabetes, presence and onset of hypertension, dyslipidaemia, heart failure, diabetic complications, history of MI, and pharmacotherapy. Centralised manual assessment of the obtained ECG tracings was performed. Two definitions of the pathological Q-waves were used — a present one according to the Universal Definition of MI and a former one based on the definition of MI developed by the World Health Organization. Results. We enrolled 796 patients (48.1% women, mean age 67.5 ± 10.2 years, and 51.9% men, mean age 64.3 ± 10.3 years) into the study. There were 158 patients (19.8%) — 102 men (24.7%) and 56 women (14.6%), who met the present definition of the pathological Q waves and 106 patients (13.3%) — 74 men (17.9%) and 32 women (8.4%), who met the former definition of the pathological Q waves. The prevalence of the pathological Q waves varied due to the certain group of leads. It was highest in the inferior leads — 104 and 75 according to the present and former definitions, respectively. Of note, the rate of the pathological Q waves increased up to 2.6 times in the lateral leads after the introduction of the less restrictive present definition. Sensitivity of prior MI detection by means of the present and former criteria was 26.8% and 19.8%, and specificity was 87.0% and 92.8%, respectively. The application of the present and former definitions detected prior MI with 65.6% and 71.6% positive predictive value, and with 56.3% and 55.6% negative predictive value, respectively. Conclusions. In the era of reperfusion therapy, ECG appears to be a poor diagnostic tool for detection of previous MI due to its low sensitivity. However, it may identify individuals without previous MI with rather high specificity. In diabetics with CAD, the present definition of the pathological Q waves increases sensitivity of prior MI detection by 7%, with a decrease in specificity by 6% as compared with the former definition

The Impact of Surface Preparation for Self-Compacting, High-Performance, Fiber-Reinforced Concrete Confined with CFRP Using a Cement Matrix

With the development of concrete technology, the tendency to combine different materials with each other to achieve a greater efficiency and durability of structures can be observed. In the modern construction industry, various materials and techniques are increasingly being combined in order to achieve e.g., an increased resistance to dynamic impacts of a structure, or an increased scope of work of a selected constructional element, which translates into a significant increase in the energy of destruction. Thus, hybrid elements, known as composite ones, are created, which consist of concrete and reinforcements. This study examined the influence of the preparation of the concrete surface on the behavior of high-performance, self-compacting, fiber-reinforced concrete (HPSCFRC), reinforced with carbon fibers (CF) using a cement matrix. In the general lamination processes, this is preformed using epoxy resin. However, epoxy resin is sensitive to relatively low temperatures, and therefore the authors attempted to use a cement matrix in the lamination process. When connecting hardened concrete with a fresh concrete matrix or mixture, the type of the concrete surface is significant. In this research, three types of concrete surfaces e.g., unprepared, sanded and grinded were considered. All of the surfaces were examined using a 3D laser scanner, to determine the Abbott-Firestone profile material share curve. In this research, cylindrical concrete specimens were reinforced with one, two and three layers of laminates. They were then subjected to a uniaxial compressive test. The results of tests showed that the use of cement matrix in the lamination process, due to its low efficiency, should not be applied when reinforcing concrete elements with a high compressive strength. Moreover, the grinded surface of concrete showed the best cooperation with CF reinforcement

Large Panel System Technology in the Second Half of the Twentieth Century—Literature Review, Recycling Possibilities and Research Gaps

Large panel system (LPS) buildings, during the 1950s–1990s, were the most widespread among precast systems and are still a huge part of some national housing stocks. Disadvantages in characteristics, poor quality of all construction stages, sudden disasters and poor retrofit and repair techniques can result in demolishing some LPS buildings and thus the creation of huge amounts of waste. There is urgent need of evaluating the possibility of reusing the elements of LPS buildings. The novelty of the article is based on the formulation of research gaps in terms of recycling these buildings and the justification of such need. The authors reviewed the current state of knowledge regarding characteristics of LPS buildings, directions of retrofitting, durability and their locations within cities. The possibility of recycling elements of LPS buildings was analysed. The findings are that concrete load bearing panels, proved to be in satisfactory conditions in terms of strength and durability, have the possibility to be recycled into recycled coarse aggregate (RCA), so such waste could be beneficial for concrete. However, there are research gaps of such an application highlighted in the text. The authors suggest that conducting comprehensive basic research in this area could have significant benefits for the next generation of researchers and engineers

Large Panel System Technology in the Second Half of the Twentieth Century—Literature Review, Recycling Possibilities and Research Gaps

Large panel system (LPS) buildings, during the 1950s–1990s, were the most widespread among precast systems and are still a huge part of some national housing stocks. Disadvantages in characteristics, poor quality of all construction stages, sudden disasters and poor retrofit and repair techniques can result in demolishing some LPS buildings and thus the creation of huge amounts of waste. There is urgent need of evaluating the possibility of reusing the elements of LPS buildings. The novelty of the article is based on the formulation of research gaps in terms of recycling these buildings and the justification of such need. The authors reviewed the current state of knowledge regarding characteristics of LPS buildings, directions of retrofitting, durability and their locations within cities. The possibility of recycling elements of LPS buildings was analysed. The findings are that concrete load bearing panels, proved to be in satisfactory conditions in terms of strength and durability, have the possibility to be recycled into recycled coarse aggregate (RCA), so such waste could be beneficial for concrete. However, there are research gaps of such an application highlighted in the text. The authors suggest that conducting comprehensive basic research in this area could have significant benefits for the next generation of researchers and engineers

Low-Energy Clay–Cement Slurries Find Application as Waterproofing Membranes for Limiting the Migration of Contaminants—Case Studies in Poland

The purpose of this review was to present clay–cement suspensions that are mainly used in the construction and renovation of hydrotechnical facilities and flood protection. We present the characteristics of clay–cement slurries that are used in waterproofing barriers. One of their significant components are clays of different types and origins. Examples of kaolin-type and smectite-type clays, which are associated minerals, as balanced components of suspensions are presented. As mentioned, before the hydration process, barriers are suspended, and the main test methods are rheometric measurements. Their rheological parameters, extremely important from the point of view of injection mechanics, are shown. The higher the flow limit and faster the reconstruction of thixotropic structures, the higher the energy input of the injection processes. After the hydration process, it is important to form agglomerates and seal the barrier; therefore, we present a summary of the strength results, filtration coefficients and microscopic images of the resulting structures. Additional properties of such barriers in terms of limiting contaminant migration are indicated. One of the aspects affecting the use of liquid slurries is their application methods; thus, a summary of low-energy slurry injection methods is also presented