Reinforced concrete is a widely used construction material in the building industry. With the increasing age of structures and higher loads there is an immense demand for structural health monitoring of built infrastructure. Coda wave interferometry is a possible candidate for damage detection in concrete whose applicability is demonstrated in this study. The technology is based on a correlation evaluation of two ultrasonic signals. In this study, two ways of processing the correlation data for damage detection are compared. The coda wave measurement data are obtained from a four-point bending test at a reinforced concrete specimen that is also instrumented with fibre optic strain measurements. The used ultrasonic signals have a central frequency of 60 kHz which is a significant difference to previous studies. The experiment shows that the coda wave interferometry has a high sensitivity for developing cracks and by solving an inverse problem even multiple cracks can be distinguished. A further specialty of this study is the use of finite elements for solving a diffusion problem which is needed to state the previously mentioned inverse problem for damage localization. Concrete is a material commonly used in the construction industry. Especially the combination of concrete and steel reinforcement results in many advantages. During the lifespan of a concrete structure, the appearance of cracks in the structure is very typical. Those cracks are either intentional or due to environmental influences, increased loads, aging or local failure. Regular inspections and assessments are therefore very important to ensure the functionality of concrete structures. In addition to regular visual inspections, permanent structural health monitoring techniques are increasingly used. Established techniques use, for example, strain gauges on concrete and steel.Coda wave interferometry (CWI) is a rather novel monitoring and damage detection technique applicable to concrete. It is based on elastic waves and originates from geophysics, more precisely, seismology. Larose and Hall  were oneFor concrete structures, the used signals have a central frequency in the ultrasonic spectrum. Planès and Larose  differ tIn Coda wave interferometry uses diffuse ultrasound to measure relative changes of a signal compared to a reference state. Those changes are typically created by a change of the concrete’s temperature , moisturT in the signal t as following [The central measurement parameter in CWI is a cross-correlation coefficient (CC) that quantifies the similarity of two compared signals. It is computed for a time frame of length ollowing ,20:(1)CCCC is translated into a decorrelation coefficient (DC) that uses a magnitude from zero to one to describe how large the changes are in a signal. The relation of CC and DC is as follows:Very often, the The decorrelation of two signals is used for imaging the cause of the signals’ changes. Depending on the used method, the signal is either evaluated in one long time frame or multiple successive shorter time frames. Multiple evaluation windows can evaluate a DC development that tends to increase in later parts of the signal because more random wave paths cross the new scatterer and create different interferences with other wave fronts that all add up to an increased decorrelation. This described increasing development is very characteristic for the relative position of a cause to the source-receiver pair and is modeled by the sensitivity kernel introduced in With an ongoing monitoring, there are multiple measurements performed with each pair. For choosing a reference, there are typically two possibilities. One is a fixed reference measurement, e.g., the first one. The other one is a stepwise update of the reference signal such that the used reference is always the previous measurement. The CWI is based on small changes in the signal and a general reproducibility of the signals. This is usually fulfilled with the stepwise updated reference approach but not necessarily with a fixed reference. Thus, the stepwise approach is chosen for this study.The measured decorrelations are typically created by two slightly different phenomenons. One is a waveform distortion and the other one is a phase-shift of the signal. The phase-shift is created by a change of the signals’ wave speed that is inducted, e.g., by the acoustoelastic effect  that lind Wegler . After sIn this study, signals with a length of 2000 D. It can be determined with an envelope fitting of the signal as shown in 2/s.When thinking of a simulation that resembles the performed experiment, the model would need to contain a heterogeneous material with a very fine refinement in order to represent the used concrete. In addition, the time steps used would have to be very short to achieve numerical stability for an acoustic wave simulation. This causes great computational costs that limit the maximum size of the modeled geometry. Thus, a central simplification is used in the description of how the wave propagates through a heterogeneous medium. As Ryzhik et al.  have showww.cimne.com/kratos) for solving the FE problem.This study uses a novel finite element (FE) based formulation that solves the given problem. The use of FE is a significant difference to previous applications that are usually based on analytical solutions and opens the door to many improvements of the technology. FE and the accompanying use of unstructured meshes allow the problem to be solved for arbitrary, complex-shaped geometries, and the generic FE approach even allows the solution to be further improved by using a different partial differential equation that better approximates the given wave phenomenon. The present study uses the open-source project KRATOS Multiphysics  as well as staggered stirrup reinforcement (Ø12 mm / 300 mm / 2) are placed. With a field length of 3500 mm cf.  and a spTo detect cracks, an ultrasonic signal is intentionally to be guided into the concrete. For this purpose, ultrasonic transducers  embedded in the concrete are arranged in a net-like manner throughout the specimen cf. . The aimIn addition to ultrasonic measurement technology, FOS were used in particular. The FOS technology provides the possibility to measure strains and temperatures ,27 with From the very continuity of the fiber optic strain measurement , it becomes evident that a lot of strain data are acquired. The measured strains along the rebar for a load from 0 to 100 kN is shown in Due to the low tensile strength of concrete, it cracks even when subjected to a low tensile stress. The tensile strength The evaluation of the CWI data is performed in two different ways. Pair 1 and 6 are in a zone with comparable small stresses that is also the furthest away from developing cracks. The DC development with values around 0 up to load step 22 confirms this. Further load increases generate a slight increase of the DC that is relatively small compared to other measurement pairs. The reason are probably massive cracks in the middle third and a crack development further to the sides. This shows that measurement pairs have a limited extended sensitivity and the influence of ballistic waves passing through the specimen several times is very small.Pair 3 and 4 are in the zone with the highest tension stresses and an area where multiple cracks are expected to develop. The DC development shows a first significant increase in the DC around load step 8 and continues to increase until approximately load step 16. This indicates strong crack formation. The constant increase of the DC can be explained by the fact that the cracks open up more and more and thus, the transmission of the ultrasonic waves becomes increasingly worse. The time of crack formation coincides approximately with the average tensile strength of the concrete and is closer investigated in Pair 5 and 7 are closer investigated due to an observation that led to problems in the damage localization. The FOS indicates cracks close to transducers 6, 9 and 21 at load step 9. For transducer 21 at x = 2.85 the formed crack seems to have a large impact on the general reproducibility of the signals related to that transducer. It is possible that a crack into the mounting position of transducer 21 massively impacts the transmission of ultrasound into the concrete. This generates unusually large decorrelation. The fact that the decorrelation is unusually large also becomes apparent when comparing pair 2 and 7. Furthermore, the DC of pair 5 and 7 would be expected to be smaller than for pair 4. The unusual large decorrelation becomes a problem for the damage localization since the modeled approximation of measurements is not valid anymore. Affected measurements are therefore filtered from the used measurement set.For the damage localization, three states are distinguished. One is before cracks are detected by the FOS , one is In the early load stages, it is expected that the different monitoring systems detect no damage. An evaluation of load step 3 at 15 kN shown in An evaluation at the next load step with 20 kN applied confirms the first trends from the previous load step. Especially the first tendencies of the FOS data in Load step 4 shows that the first micro cracks already occur at stresses significantly below the average tensile strength of the concrete used The image from The crack pattern obtained with the inverse problem shows a good correlation with the more reliable FOS data. Remarkable is the distinction of multiple cracks which is strongly influenced by three factors. One is the superposed imaging. Each of the four individual damage images has a tendency to certain cracks or areas. Superimposing multiple states smoothes out this observation that possibly is related to a non-uniform crack development between each load step. The second factor is the use of an upper boundary on the variables of The third evaluation state is chosen relativity late in the loading progress. The aim is to investigate the extent to which a crack pattern still changes and what effect this has on the coda measurement technique. As in The FOS data and also the inverse problem imaging show that the crack development in the middle third is completed and changes in the specimen now appear in the previously unaffected areas further to the sides. This underlines the fact that existing cracks can only be detected to a limited extent with CWI. Once a crack development is completed, the CWI with a stepwise updated reference will not detect that crack since no more changes appear in the medium. The FOS data shows one clearly visible peak on the left and also the inverse problem localizes that area. Additionally, there are a few other areas detected that can not be seen in the FOS data. This can have two possible causes. First one is that the crack development at the height of the FOS is completed and a crack only develops above the FOS mounting height. The second one is that the filtering of unusually large decorrelated measurement pairs by engineering instinct was not sufficient. A further filtering would, however, affect an equally balanced measurement net. Thus, the conclusion is that in such a highly cracked condition, the application of CWI in concrete is very difficult.The material behavior in the four-point bending test is as expected. The FOS data appear to be very reliable and detect multiple cracks at a very early load state. Its crack detection, however, is limited to one reinforcement bar only and the installation on a large structural scale shows problems since the careful application of the fibre on the reinforcement is labour intensive and thus expensive. Here are advantages of the CWI that shows the potential to detect multiple cracks and covers a larger area with a simpler installation. Despite a longer wavelength compared to previous experiments by Larose et al.  and ZhanThe exact definition of one load step at which cracking happens is rather difficult. Thus, several load steps around the load level at which the concretes tensile strength is reached are evaluated and superimposed. With comparably large changes in the structure, the CWI is susceptible to bad measurements in the dataset. Those bad measurements can be caused by cracks into the mounting position of transducers. For the given specimen, this is not unusual because the ultrasound transducers weaken the cross section and thus attract cracks. Related measurements need to be filtered from the used dataset since the DC are unusually large and do not match used assumptions, e.g., a general good reproducibility of the signals. To date, this is done with engineering instinct, but will be parametrized and automated in future studies. A statement about the size of the cracks is not yet possible. The goal of future research will be to find structure-related damage limits for the coda technology. The analysis in the cracked state revealed a weakness of the CWI that existing damage is difficult to detect with a stepwise updated reference.Comparing the two CWI imaging approaches, the solution for an inverse problem can locate damage locations better than what is possible with influence areas. The computational effort however is significantly larger since an ill-posed problem needs to be solved whereas with influence areas only a matrix vector product is computed. Nevertheless, the influence areas have proven to be a useful tool for transferring the measured decorrelation to a spatial representation on the geometry. Especially with a lot of overlapping of measurement pairs, the technique is advantageous to simpler interpolations as, e.g., used by Niederleithinger et al. . The extThe FE formulation for the given problem is a major difference compared to previous studies ,5,6,7 thOverall the present study shows the high potential of CWI as a monitoring and damage detection technique for large structures. The used set-up with a central frequency of 60 kHz that belongs to the single scattering regime is a novelty in for inverse problem based damage detection with CWI in concrete. The high sensitivity to small changes in the concrete as well as a good localization and distinguishing of multiple appearing cracks underline the immense potential of CWI in concrete. The addressed problem of unusually large decorrelations that do not fit the model of the inverse problem (sensitivity kernel) in a suitable way and thus hinder a good localization is a challenging problem that was solved in a rather simple way by removing related measurements from the problem to be solved. The finite element based methodology is a significant difference and improvement over established approaches that use analytical solutions. The use of a new solving technique that contains boundary constraints for the inverse problem is another presented novelty that significantly improves the imaging results. The presented imaging using influence areas marks a new, simpler but less accurate way of imaging CWI results that is more independent of a good match between the model and measurement data and thus a more robust way of imaging. In summary, the frequency range used in combination with finite element based localization has proven to be suitable for damage localization in concrete with CWI and the experiment and used methods provide a reliable basis for upscaling the technology to large existing structures.


Pervious concrete is an environmentally friendly paving material to reduce surface runoff in urban construction. However, due to low flexural strength and cracking susceptibility caused by the high porosity, pervious concrete is only used in low-volume traffic roadways and parking lots for current service. This study investigated the permeability, strength, and flexural performance of pervious concrete with different coarse aggregate size, geogrid position, and geogrid layer number. Test results indicate that the geogrid placed at an appropriate position in pervious concrete improved the permeability and compressive strength. Four-point bending tests were conducted in the laboratory to evaluate the flexural performance and toughness characteristics of pervious concrete beam. Meanwhile, this study also proposed a new evaluation method to distinguish the contribution of geogrids and concrete mixture to the flexural toughness of pervious concrete beam at the pre-peak and post-peak stages by two toughness indices. Test results indicate that geogrids improved the flexural strength, deformability, and energy absorption capability of pervious concrete beam. The geogrids placed at both one-third and two-thirds of the heights of pervious concrete beam resulted in the optimum flexural performance. Besides, the small size (5–10 mm) aggregates were conducive to providing high flexural strength for the geogrid-reinforced pervious concrete beam, while the large size (10–15 mm) aggregates played a significant role in obtaining noteworthy post-cracking performance. Pervious concrete has been used in urban construction due to its environmental and stormwater management benefits. Pervious concrete can allow rainfall to pass down through the ground to reduce urban flood hazards . At the Fiber is the main reinforcing material used to improve the flexural behavior of pervious concrete. Considerable efforts have been devoted to investigating the influence of fiber types ,6, sizesGeogrid has been playing an important role in solving geotechnical problems due to its high strength and elongation ratio ,12,13,14Flexural toughness is a major index to reflect the flexural behavior of geogrid-reinforced pervious concrete. However, the accepted flexural toughness evaluation methods are based on fiber-reinforced concrete ,24,25. BSo far, studies on the use of geogrid as reinforcement in pervious concrete to improve flexural performance are rare. Therefore, this study investigated the effect of aggregate size, geogrid position, and geogrid layer number on the flexural behavior of pervious concrete. In order to describe the flexural toughness characteristics of geogrid-reinforced pervious concrete, a new evaluation method was preliminarily introduced and used to evaluate the four-point bending test results. The outstanding advantage of this method is that it can distinguish the respective contributions of the geogrids and the concrete mixture to the flexural toughness of pervious concrete at the pre-peak and post-peak stages during the bending tests.3. Fly ash with specific surface area of 650 m2/kg was used as the active mineral to improve the strength of pervious concrete. There were no fine aggregates in the pervious concrete cast in this study. Two types of coarse aggregates were used to investigate the effect of coarse aggregates’ size on the flexural behavior of the geogrid-reinforced pervious concrete. The mix proportion of pervious concrete with single gradation coarse aggregates was calculated by volume method, as shown in Polypropylene biaxial geogrid with 40 mm × 40 mm apertures and a tensile strength of 21 kN/m was used as reinforcement in pervious concrete as shown in The satisfactory use of geogrid-reinforced pervious concrete as a composite structure depends mainly on the good interlock and bond between geogrids and concrete. To cast the geogrid-reinforced samples, a lower concrete layer was first poured to the marked location in the mold and compacted with a steel rod. Then, the flat geogrid layer was carefully placed at the marked position. Finally, an upper layer of concrete was poured above the geogrid with compaction. Most importantly, the aperture of the geogrid should be filled with aggregates as much as possible during the pouring process to ensure the proper bonding between the lower and upper layers of concrete. The cast specimens were maintained under a laboratory condition for 24 h. Then, the specimens were demolded and placed in a standard curing room for 28 days, with continuous wetting cycles at a temperature of 23 ± 2 °C and relative humidity of 95%.Similar to common pervious concrete pavement, the concrete formwork should be prepared first when building geogrid-reinforced pervious concrete pavement in the field. Then, the position of the geogrid is marked on the formwork. In the process of building the geogrid-reinforced pervious concrete pavement, the lower pervious concrete layer is first poured to the marked location with compaction. Thereafter, the geogrid is installed above the lower pervious concrete layer. In order to ensure the accurate installation position of the geogrid, the edges of the geogrid are fixed at the marked position on the formwork by steel wire. Then, the upper pervious concrete layer is poured above the geogrid with compacting to the design elevation. It should be mentioned that geogrids from different rolls should be overlapped and bound to ensure integrity when the length of single-roll geogrid is limited.k is the permeability coefficient (mm/s); Q is the permeating water in t seconds (mm3); L is the thickness of specimen (mm); A is the cross area of the specimen (mm2); H is the water head difference (mm); and t is the time (s).Based on Darcy’s law, the equipment for the permeability test was designed as shown in Unconfined compressive strength tests were performed on the pervious concrete cubes with different coarse aggregate sizes, geogrid positions, and geogrid layer numbers at a curing age of 28 days. The four-point bending tests were carried out using a hydraulic testing machine with a maximum load capacity of 1500 kN to evaluate the flexural behavior of the geogrid-reinforced beams. The permeability coefficient is the basic feature to reflect the permeability of pervious concrete. The placement of geogrid decreased the conjoint points between aggregates in geogrid-reinforced pervious concrete. As a result, Horizontal tensile stress occurred in pervious concrete under uniaxial loading. Then, the vertical micro cracks generated, propagated, and coalesced with other micro cracks until the specimen’s failure. When geogrid was placed in pervious concrete, the geogrid brought additional tensile strength to the pervious concrete with the help of the geogrid’s aperture structure; it also reduced the conjoint points between aggregates. While the geogrid redistributed the stress to restrain the generation and propagation of cracks, the gain of compressive strength provided by geogrids could offset the loss of strength caused by the decreased conjoint points. As a result, the geogrid-reinforced pervious concrete has improved compressive strength as compared with the unreinforced pervious concrete. Moreover, the geogrid position and layer number could influence the compressive strength of pervious concrete. The load-vertical displacement curves of the pervious concrete beams with small-size aggregates and large-size aggregates are shown in As compared with the unreinforced beams, the flexural strength and the post-cracking performance of the geogrid-reinforced pervious concrete beams were improved significantly. For instance, The aggregate size is an important factor to influence the flexural behavior of pervious concrete beam. Different aggregate sizes had different influences on the flexural behavior of the geogrid-reinforced pervious concrete beam at pre-peak and post-peak stages during the bending tests. The small-size aggregates played an important role at the pre-peak stage of the geogrid-reinforced pervious concrete beam. The small-size aggregates were interlocked well with the geogrids in the pervious concrete beam to resist brittle failure and improve the flexural strength. While the good interlock between small-size aggregates and geogrid absorbed a lot of energy at the pre-peak stage, the energy absorption capacity of geogrid was diminished after the first peak load, which caused a lower second peak load compared to the first peak load. As mentioned earlier, the pre-peak flexural performance of beams with large-size aggregates was not as good as that with small-size aggregates. As compared with the small-size aggregates, the large-size aggregates played a smaller role in improving the flexural strength of the geogrid-reinforced beam due to the poor interlock between geogrids and large-size aggregates. Since there was little energy absorption during the elastic stage of the geogrid-reinforced beam with large-size aggregates, the geogrid provided more tensile stress to absorb energy with the generation of cracks at the post-peak stage. As a result, the post-cracking performance of the reinforced beam with large-size aggregates was particularly outstanding, with a higher second peak load than first peak load. In a nutshell, while the geogrid-reinforced pervious concrete beam with small-size aggregates obtained high flexural strength, the reinforced beam with large-size aggregates had remarkable post-cracking performance.Pervious concrete is a porous structure formed by the bonding of coarse aggregates wrapped in cement paste. When geogrid was placed in pervious concrete, the aggregates filled into the apertures of the geogrid and bonded with the ribs of the geogrid to form a composite structure. Therefore, the interaction between geogrids and pervious concrete could directly affect the performance of geogrid-reinforced pervious concrete. There were friction, bonding, and interlocking interactions between the geogrid and pervious concrete. The polypropylene geogrid had a smooth surface, which led to a relatively low bonding strength and friction between the ribs of the geogrid and the pervious concrete. The geogrid being placed tightly in the porous structure of pervious concrete mainly relied on the interlocking effect between geogrid and aggregates. The use of geogrid at an appropriate position could provide additional tension stress to improve the strength and restrain the cracking of pervious concrete.The load-vertical displacement curves show that the unreinforced pervious concrete beam was brittle and had no post-cracking performance. As compared with the unreinforced pervious concrete beams, the geogrid-reinforced pervious concrete beams had improved flexural strength and remarkable post-cracking performance. This illustrates that the geogrids worked during both the pre-peak and post-peak stages of the reinforced pervious concrete beam in bending tests. During the pre-peak stage, geogrids and pervious concrete worked together to improve the stiffness, delay the cracking, and improve the flexural strength of the reinforced beam. After cracking, the geogrids outside the crack were fixed and clamped tightly by the interlock between geogrids and concrete. At the same time, the ribs and junctions of geogrid inside the crack withstood the tension and bending moment under loading. The ribs of geogrids were stretched and deformed gradually until failure. Toughness indices have been commonly used to evaluate the flexural performance of fiber-reinforced concrete beams. Toughness is referred to as the area under the load-vertical displacement curve during the bending test, which represents the amount of energy that a specimen is able to absorb during loading up to a certain vertical displacement . Moreovem was set to 150 in the JSCE SF-4 [m as 50 instead of 150 to guarantee sufficient consideration of the post-peak stage in the flexural toughness evaluation of the geogrid-reinforced beam.SCE SF-4 , PCS [28SCE SF-4  methods.The pre-peak equivalent flexural strength of plain pervious concrete , the geogrid could still enhance the compressive strength of pervious concrete.The unreinforced pervious concrete beam was brittle and had no post-cracking performance. As compared with the unreinforced beams LU and SU, the flexural strengths of geogrid-reinforced pervious concrete beams with large- and small-size aggregates increased by 6% to 14% and 14% to 52%, respectively. Meanwhile, the geogrid-reinforced pervious concrete beams had remarkable post-cracking performance, with good deformability and energy absorption capability.The interlocking effect between geogrids and aggregates is the main mechanism for the improved flexural performance of the geogrid-reinforced pervious concrete beam. The geogrid position and geogrid layer number are important factors to affect the flexural performance of pervious concrete. The optimum position for the geogrid was at one-third the height of the pervious concrete beam to improve flexural performance when one layer of geogrid was placed. The placement of the geogrids at both the one-third and two-thirds heights could obtain the optimum post-cracking performance of pervious concrete beam.The coarse aggregate size could determine the interlocking effect between geogrids and aggregates to influence the flexural strength and load-vertical displacement curves shape of pervious concrete beam. While the small-size (5–10 mm) aggregates delayed the cracking and improved the flexural strength of geogrid-reinforced pervious concrete, the large-size (10–15 mm) aggregates played a significant role in obtaining noteworthy post-cracking performance.The proposed flexural toughness indices distinguished the respective contributions of the geogrids and the aggregates to the flexural toughness of pervious concrete at the pre-peak and post-peak stages. Test results verify the excellent effectiveness and reliability of this proposed method. In addition, this method is not constrained by the first crack vertical displacement, loading condition, or specimen size. Therefore, it can be used to evaluate the flexural performance of pervious concrete with different geometrical dimensions and reinforcements.This study focused on investigating the flexural performance and toughness characteristics of pervious concrete beam with different aggregate sizes, geogrid positions, and geogrid layer numbers. Four-point bending tests were conducted to evaluate the flexural strength, toughness, deformability, and energy absorption capability of the geogrid-reinforced pervious concrete beams. Based on the flexural toughness evaluation methods of the fiber-reinforced concrete, two dimensionless indices were proposed to evaluate the flexural toughness of the geogrid-reinforced pervious concrete. The following conclusions can be drawn:


Patients with COVID-19 receive high rates of antibiotic therapy, despite viral origin of infection. Reports of bacterial coinfection range from 3.5 to 8% in the early phase of infection. This study aimed to evaluate the relationship between diagnostic tests and antibiotic utilization in patients admitted with COVID-19 at the University of Maryland Medical Center to better inform future prescribing practices.Retrospective cohort study of adult patients with a positive SARS-CoV-2 PCR on admission from March 2020 through June 2020. Associations between diagnostic tests employed and antibiotic initiation and duration were explored using bivariate analysis (SPSS®). P=0.025), any degree of oxygen requirement on admission , and performance of blood cultures  were associated with antibiotic initiation. Positive bacterial diagnostic respiratory culture  and positive blood culture  were associated with longer antibiotic duration. Patients who did not have respiratory cultures performed had similar antibiotic durations as those with negative respiratory cultures.Baseline characteristics of 224 included patients are reported in Table 1. Excluding SARS-CoV-2 PCRs, most frequently performed diagnostic tests included blood cultures (65.6%), MRSA nasal surveillance (45.1%), respiratory cultures (36.2%), respiratory viral panel (RVP) (33.0%), and Legionella (28.6%) and pneumococcal (26.3%) urine antigens. Positivity of RVP, Legionella, pneumococcus, blood, and respiratory tests were low . A total of 62% of patients were initiated on antibacterial therapy with a median cumulative antibiotic duration of 77.9 hours . History of chronic respiratory disease


Monitoring antibiotic consumption is crucial to tackling antimicrobial resistance. However, currently there is no system in Sierra Leone for recording and reporting on antibiotic consumption. We therefore conducted a cross-sectional study to assess national antibiotic consumption expressed as defined daily dose (DDD) per 1000 inhabitants per day using all registered and imported antibiotics  system) as a proxy. Between 2017–2019, total cumulative consumption of antibiotics was 19 DDD per 1000 inhabitants per day. The vast majority consisted of oral antibiotics (98.4%), while parenteral antibiotics made up 1.6%. According to therapeutic/pharmacological subgroups (ATC level 3), beta-lactam/penicillins, quinolones, and other antibacterials  comprised 65% of total consumption. According to WHO Access, Watch, and Reserve (AWaRe), 65% of antibiotics consumed were Access, 31% were Watch, and no Reserve antibiotics were reported. The top ten oral antibiotics represented 97% of total oral antibiotics consumed, with metronidazole (35%) and ciprofloxacin (15%) together constituting half of the total. Of parenteral antibiotics consumed, procaine penicillin (32%) and ceftriaxone (19%) together comprised half of the total. Policy recommendations at global and national levels have been made to improve monitoring of antibiotic consumption and antibiotic stewardship. Antimicrobial resistance (AMR)—the ability of microbes to evolve and withstand the effects of antimicrobials—is a significant cause of morbidity and mortality globally ,2,3. So The main driver of the insurgence and spread of AMR is the inappropriate use and consumption of antibiotics. This includes irrational prescribing  and over-the-counter sales of antibiotics ,9. The aTo preserve the effectiveness of antibiotics and to continue to reap their benefits for health, achieving a balance between prudent use and improved access is key. To this end, the World Health Organization (WHO) has launched a global action plan (GAP) on AMR. One of the main objectives of the GAP is to optimize the use of antimicrobials, including antibiotics . To guidWHO has urged all member states to adapt the GAP to national contexts, and establish a stewardship program that monitors and promotes optimization of antibiotic use . In respIn 2016, WHO recommended a methodology for antimicrobial consumption surveillance using a standardized population-based metric of defined daily dose (DDD) per 1000 inhabitants . The metWe therefore carried out this study to assess national antibiotic consumption in Sierra Leone between 2017–2019. Specific objectives of the study were, for the period of 2017–2019, to report on, per route of administration, (i) consumption of antibiotics in defined daily dose (DDD) standardized by population size (DDD per 1000 inhabitants per day) alone and stratified by pharmacological subgroup and AWaRe categorization; and (ii) the top antibiotics consumed at the substance level.This was cross-sectional analysis of routinely collected data on antibiotics imported for human consumption and registered by the Pharmacy Board of Sierra Leone (PBSL).Sierra Leone is a country on the southwest coast of West Africa bordered by Liberia to the southeast and Guinea to the northeast. The country has a tropical climate, with a diverse environment ranging from savanna to rainforests. Sierra Leone occupies an area of about 71,740 square kilometers with a total population size of 7,075,641 . AdminisThe country frequently suffers from disease outbreaks such as Lassa fever, measles, malaria, cholera, yellow fever, meningitis and, more recently, the largest outbreak of Ebola virus disease in 2014–2016 [Sierra Leone has a three-tier health care system of primary, secondary, and tertiary health care. The overall responsibility of managing and organizing health care services is under the Ministry of Health and Sanitation (MoHS). Sierra Leone is divided into 16 health districts that correspond to the administrative districts. Each health district is supported by a health management team which is responsible for planning, organizing and monitoring health provision, training personnel, working with communities and supplying equipment and drugs . Each diExcept for the Free Health Care Initiative for children under five years, pregnant and lactating mothers, drugs are mainly acquired through out-of-pocket purchase. The public sector has a weak cost recovery of drug sales; patients are required to purchase from private pharmacies if prescribed drugs are out-of-stock or not included in the list of drugs procured by the hospital. There is a National Essential Medicines List and Standard Treatment Guidelines for some infectious diseases, but strict adherence to these guidelines is still a big challenge . MicrobiFor the public sector, drugs are procured through contracted suppliers and distributed by the Directorate of Pharmaceutical Services through the Central Medical Stores. Drugs are distributed to government health facilities by both the “pull” and “push” systems . Frequent drug stock-outs are common in the public sector , meaningThe PBSL, which is directly under the MoHS, was established by The Pharmacy and Drugs Act, 2001  and reguThe study population included all registered and imported antibiotics categorized under the subgroup J01  of the Anatomical Therapeutic Chemical (ATC) Classification System, including parenteral and oral formulations , route of administration, and quantity imported. Specific year of import was not available in the electronic database, and consumption for the entire study period was therefore aggregated.The data sources were the 2015 Sierra Leone Housing Census Population Projections ; PBSL DrThe Drug Clearance and Importation Permits Database is a Microsoft Access database maintained by the Factory Inspectorate & Import Control Department of the PBSL. Data from the Drug Clearance and Importation Permits Database were exported into Microsoft Excel. The route of administration variable was sourced by cross-referencing batch ID from the paper-based Drug Registration Record, also located at the Factory Inspectorate & Import Control Department of the PBSL. Data collection was done by two research assistants. Ten percent (10%) of the records entered were validated by the principal investigator as a quality assurance process.All import data collected were transferred by two data clerks into a formatted Microsoft excel template with embedded macros to calculate consumption provided by the WHO. The Principal Investigator reviewed all data in the WHO Excel template for quality control. Review of the data resulted in removal of three import values as they were deemed to have data entry errors in the database. These included two entries of imports for ciprofloxacin and one entry for import of metronidazole. There were some assumptions in interpreting the size, quantities, and strengths of some of the products in the database. These included: bottles of suspension, syrup or solutions were assumed to be 100 milliliters in size; and quantities for ‘strips’ of oral tablets were assumed to reflect quantities of tablets.Substances were categorized based on the ATC classification system , versionConsumption was estimated according to the WHO methodology for surveillance of antimicrobial consumption , which uTo adjust for population size, antibiotic consumption was presented as number of DDDs per 1000 inhabitants per day . This meAccess, Watch, and Reserve (AWaRe) categories based on the WHO Model List of Essential Medicines were assigned to each antibiotic substance (ATC5) using the latest version . AntibioTotal consumption of antibiotics for systemic use for the period 2017–2019 was 19 DDDs per 1000 inhabitants per day. The vast majority consisted of oral antibiotics , while parenteral antibiotics made up only 1.6% of all antibiotics consumed (0.3 DDDs per 1000 inhabitants per day). This is the first study to report on antibiotic consumption in Sierra Leone at the national level. The findings of this study are important as they serve as a baseline for future monitoring of antibiotic consumption in the country.Consumption over a period of three years (2017–2019) was 19 DDD per 1000 inhabitants per day. The most frequently consumed antibiotics according to therapeutic/pharmacological subgroup were beta-lactam/penicillins, quinolones, and other antibiotics, consisting mainly of oral metronidazole. Antibiotics were consumed orally and parenterally at different rates, with parenteral antibiotic consumption representing less than 2% of total DDD per 1000 inhabitants per day. According to the WHO AWaRe categories, the highest consumption was found among Access antibiotics, followed by Watch antibiotics, with no consumption at all of Reserve antibiotics. According to chemical substance group, metronidazole and ciprofloxacin were the most frequently consumed oral antibiotics, while procaine benzylpenicillin and ceftriaxone were the most commonly used parenteral antibiotics.The total antibiotic consumption observed for Sierra Leone was slightly higher than, but comparable to, the median antibiotic consumption across 76 countries in 2015: 17.2 DDD per 1000 inhabitants per day . Of noteIn terms of frequently consumed antibiotics per therapeutic/pharmacological subgroup, our findings were similar to those found in Tanzania. In 2015, quinolones comprised the same proportion (14%) of total consumption by ATC3 in Tanzania . SimilarWe found that oral antibiotic consumption was 60 times higher than parenteral consumption. The higher proportion of oral antibiotics consumed is comparable to findings from Tanzania, Burkina Faso, and Côte d’Ivoire in 2015 were oral antibiotics represented between 96–98% of consumption of total antibiotics . This isIn Sierra Leone, Access antibiotics accounted for 65% of total consumption, comparable to 61% in the 76-country analysis , but lesWe found no consumption in the Reserve category of antibiotics in Sierra Leone. This is not an unexpected finding. According to surveillance data from 2015, none of the four sub-Saharan African countries reported any consumption of Reserve antibiotics . While iThis study has several strengths. The first is that we used import data to estimate national-level consumption as recommended by WHO . The secHowever, there were limitations. First, using import data as a proxy for consumption required certain assumptions. We only included antibiotics that came through the recognized legal channels . This does not include illegal or unofficial imports which are not registered with PBSL. In addition, the use of import data does not account for products which may be destroyed after the expiry date or which are otherwise not consumed. Antibiotics intended for human consumption may be used in the animal sector; our data did not include information about human or animal consumption, but assumed human consumption based on strength, type and route of administration. Finally, some antibiotics imported for use in Sierra Leone may be smuggled out to neighboring countries, which is not accounted for in this study.Second, the standardized methodology came with limitations. We could not assign ATC codes and DDD values to certain antibiotics in the database, as they are yet to be coded by the ATC system, and, thus, were not included in the generation of the DDDs reported. In addition, under the AWaRe classification, some antibiotics yet to be assigned to the three categories had to be coded as ‘other’. While the methodology for DDD per 1000 inhabitants per day accounts for population size, its interpretation should be contextualized to the burden of disease, health care system and financing, and informal market share in the country, which may limit conclusions drawn from cross-country comparisons.Third, the study relied on the completeness of information in the Drug Clearance and Importation Permits Database and the Drug Registration Records. The study data quality assurance processes revealed weaknesses in the design and use of paper-based forms and the electronic database. For example, for some products, validating the strengths and route of administration was based on information obtained from the product available in the market. Furthermore, we were unable to look at antibiotic consumption year-by-year because of challenges with the import date variable in the Drug Clearance and Importation Permits Database.Despite the limitations, our study points to some important recommendations for policy and practice at the global and national levels. At the global level, the WHO should ensure that the ATC/DDD system accounts for antibiotic substances that are commonly utilized in LMICs, so that these products can be included in the standard calculation of DDDs. Similarly, the WHO should ensure that all commonly utilized antibiotic substances are included in the AWaRe classification system.At the national level, this study identifies the need to improve information systems at PBSL, in terms of completeness and accuracy of data currently collected. This can be achieved through more comprehensive inclusion of key variables and also staff capacity building. The Sierra Leone AMR Technical Coordination Committee, which includes representation from the MoHS, PBSL, and WHO Country Office, amongst others, is well placed to support improvements in the PBSL information system, including the data capture and storage approach and staff capacity. Finally, Reserve antibiotics should be included in the National Standard Treatment Guidelines and be considered for the Essential Medicines List (EML) . It is eBetween 2017 and 2019, national antibiotic consumption for Sierra Leone was estimated at 19 DDD per 1000 inhabitants per day. Most antibiotic consumption was oral with parenteral use being less than 2%. Almost two-thirds of antibiotics consumed were in the Access AWaRe category, and there were no antibiotics consumed in the Reserve category. Finally, half of all the oral antibiotics consumed in Sierra Leone were metronidazole and ciprofloxacin, while half of all parenteral antibiotics were procaine benzylpenicillin and ceftriaxone. Policy recommendations at the global and national level have been made to help improve the monitoring of antibiotic consumption and antibiotic stewardship.


Geopolymer concrete is produced from the geopolymerization process, in which molecules known as oligomers integrate to form geopolymer networks with covalent bonding. Its production expends less thermal energy and results in a smaller carbon footprint compared to Ordinary Portland Cement (OPC) concrete. It requires only an alkaline activator to catalyze its aluminosilicate sources such as metakaolin and fly ash, to yield geopolymer binder for the geopolymerization to take place. Because of its eco-friendly technology and practical application, current research interest is mainly concentrated on the endurance of geopolymer concrete to resist heat and chemical aggressions. As such, it is pertinent for this review article to provide critical insight into the recent progress in research on the durability of geopolymer concrete. One significant outcome of the review is that the admixture of geopolymer concrete could be blended with additives such as micro-silica and fibers such as polypropylene fibers, to enhance its durability. The review on the durability aspects of geopolymer concrete showed that it had high compressive strength at an optimal elevated temperature, low to medium chloride ion penetrability, and high resistance to acid attack and abrasion. This makes geopolymer concrete a viable candidate to replace OPC concrete in the construction industry. Until now, cement has been widely used as a binding agent in the construction industry because of its capability to bind aggregate in the presence of water to form cement-based materials of various sizes and shapes [Approximately 5 to 7% of global carbon dioxide  gel. Lodeiro et al.  providedIt has been shown that geopolymerization can transform a wide range of waste aluminosilicate materials into building and mining materials with excellent chemical and physical properties, such as fire and acid resistance . Self-coAlthough Chen et al.  have revResidual compressive strength of a material is referred to as the maximum compressive stress that the damaged material can sustain under a loading application. The resistance of geopolymer concrete to crack propagation influences its residual compressive strength. The fracture toughness and residual compression resistance of geopolymer concrete tend to decrease when it is exposed to a very high temperature. High temperature, i.e., heat exposure, is one of the most important parameters that affects the surface characteristics, surface outlook, shape, and color of concrete . Therefo−1. The four types of concrete are ambient-cured normal-strength geopolymer concrete (GPN-A), heat-cured normal strength geopolymer concrete (GPN-H), ambient-cured high-strength geopolymer concrete (GPH-A), and heat-cured high-strength geopolymer concrete (GPH-H). The ambient and heat curing temperatures are 25 and 80 °C, respectively. The respective sodium-silicate-to-sodium-hydroxide ratios for the normal and high-strength geopolymer concrete are 2.5 and 3.0. Zhang et al.  evaluate−1 until an elevated temperature was achieved, and after that the elevated temperature was maintained for a duration of 2 h. The trend of the compressive strength development of the geopolymer concrete specimens is depicted in In another development, Luhar et al.  investigKantarci et al.  studied Based on three literature studies, the impact of geopolymerization methods on the compressive strength of geopolymer specimens at elevated temperatures can be further examined from In summary, it can be deduced from Rapid chloride ion permeability test (RCPT) is often used as a standard test to assess the chloride resistance of concrete in severe exposure conditions . In an RGanesan et al.  comparedThe effect of sodium-silicate-to-sodium-hydroxide ratio and the type of coarse aggregate on the chloride ion penetrability of metakaolin-based geopolymer concrete was studied by Koushkbaghi et al. . The twoThe chloride resistance of fiber-reinforced lightweight geopolymer concrete specimens based on rice husk ash and nano-alumina was examined by Mohseni et al. . Scoria −1. This was followed by the geopolymer concrete specimens of GEO and GEO2 with the average corrosion rates of 178.29 and 62.95 μm year−1, respectively. The decline in their corrosion rates may be associated with the greater capacity for fixing chlorides in this matrix [Amorim et al.  comparedIt can be epitomized from 4) [For geopolymer concrete, the acid attack may be associated with the depolymerization of aluminosilicate network structure and the liberation of silicic acid (Si(OH)4) . By compAriffin et al.  evaluateMehta and Siddique  studied Investigation into the sulfuric acid resistance of fly-ash-based geopolymer concrete was also carried out by Charkhtab Moghaddam et al. . The mixThe main discoveries on geopolymer concrete’s resistance to sulfuric acid for three published works are summarized in In summary of Abrasion wearing of concrete surface occurred due to mechanical scraping, wearing, or skidding of objects on the concrete surface, and it is one of the key considerations of concrete durability . The comWongsa et al.  comparedIn another study, Luhar et al.  comparedRamujee and Potharaju  exploredWongkvanklom et al.  evaluateBased on the overview of Dense structure is responsible for the increased strength characteristics of the concrete due to geopolymerization . In thisZhang et al.  assessedSontia Metekong et al.  performeThe long-term effect of sulfuric acid attack on the morphology and X-ray diffraction pattern of fly-ash-based geopolymer concrete was reported by Mehta and Siddique . Figure The chemical proofs of the fly-ash-based geopolymer concrete samples before and after sulfuric acid exposure could be traced from their X-ray diffraction patterns as illustrated in In Critical reviews on geopolymer concrete were published in several articles. Assi et al.  providedA comprehensive understanding on the durability behavior of geopolymer concrete could be achieved from this review. It can be concluded from this review that geopolymer concrete is durable and resistant to heat, chloride penetration, acid attack, and abrasion. An optimal addition of fibers and ultra-fine silica material such as nano-silica to geopolymer concrete could enhance its residual compressive strength. This could be achieved through the actions of reinforcing fibers and pore blocking of extremely-small-sized silica particles that prevented crack propagation in geopolymer concrete. In that regard, it is interesting for future research to explore the role of thermal insulating raw material such as fiberglass at enhancing the residual compressive strength of geopolymer concrete. A high degree of alkalinity in admixture; tough aggregate; and the optimal utilization of fibers and additives were the identified elements that could minimize the porosity and maximize the binding effect of geopolymer concrete, thereby protecting it from damage due to harsh environmental exposure. Additionally, it can be concluded from the review of the micrographs and X-ray diffraction analyses that geopolymer concrete deteriorated with time after exposure to an elevated temperature and a strong acid solution. However, its geopolymer binder was realized to be more stable than the cementation binder of OPC concrete to fend off heat and acid aggressions. As a recommendation, further research has to be carried out on the durability of geopolymer concrete, utilizing solid alkali activators such pentahydrate and anhydrous sodium metasilicate. The use of solid alkali activators in geopolymer mixes is less hazardous than the commonly used liquid activators and yields a “cement like” mix, where only water is added for its activation and hydration . More in


The overall decrease in antibacterial drug prescriptions over time was larger in less deprived areas (p = 0.03). Higher prescribing rates were linked to GP practices located in areas with a higher percentage of the population aged ≥65 (p < 0.001) and <15 years (p < 0.001). There were also significant regional differences in antibiotic prescribing. We advocate that any future antibiotic prescribing targets should account for local factors.Antimicrobial resistance has become one of the greatest threats to global health. Over 80% of antibiotics are prescribed in primary care, with many prescriptions considered to be issued inappropriately. The aim of this study was to examine the association between prescribing rates and demographic, practice, geographic, and socioeconomic characteristics using a multilevel modelling approach. Antibiotic prescribing data by 320 GP surgeries in Northern Ireland were obtained from Business Services Organisation for the years 2014–2020. A linear mixed-effects model was used to identify factors influencing antibiotic prescribing rates. Overall, the number of antibacterial prescriptions decreased by 26.2%, from 1,564,707 items in 2014 to 1,155,323 items in 2020. Lower levels of antibiotic prescribing were associated with urban practices ( Antimicrobial resistance (AMR), identified by the World Health Organisation as one of the top global public health threats, is largely driven by excessive and inappropriate prescribing . IncreasTo address the threat posed by AMR in the UK, the first fully integrated five-year strategy for tackling AMR was published in 2013 to address the actions needed in key AMR areas including infection prevention and control, prescribing practice, education and public engagement, development of treatment and technologies, surveillance, and research . One of Concerns about AMR resulted in increased monitoring and evaluation of antibiotic prescribing, mainly in primary care. It is estimated that over 80% of all antibiotics are prescribed by general practitioners (GPs)  and inapThis is the first study to provide a comprehensive longitudinal analysis of antibiotics prescribing in Northern Ireland primary care using a multilevel modelling approach. Specifically, we aim to (1) evaluate temporal changes in antibiotic prescription; (2) identify the extent of between-GP variations in antibiotic prescribing; and (3) examine the impact of demographic, geographic, socioeconomic, and practice characteristics on antibiotic prescribing.This was a retrospective cohort study of antibiotic prescribing using routinely collected primary care prescribing data.n = 320) that were operational throughout the study period, with antibiotic prescriptions dispensed from January 2014 to December 2020. Accordingly, 31 practices that closed and 1 practice that opened during the period under review were excluded from the analysis.NHS primary care in Northern Ireland was the setting, including general practices  prescribing and dispensing information systems . The datA number of factors, previously shown to be associated with variation in prescribing, were selected from publicly available data. These variables were: deprivation, GP practice size (the number of registered patients), Local Commissioning Group (LCG), setting , patient demographics, and household income. Given that deprivation and patient demographics were not available at the GP practice level, we used the aggregate data collated at the super output area (SOA) level for the practice postcode. SOAs are geographical areas designed for the publication of the Census outputs. As such, area-level deprivation was assigned to each GP practice by linking the SOA code of a GP practice’s postal address and the NI Multiple Deprivation Measure (MDM) rank . The MDMTo allow temporal and between-GP practice analysis of changes in antibiotic prescribing, the standardised antibiotic prescribing rate (per 1000 patients) was calculated by dividing the total number of antibacterial drugs (‘items’) prescribed in each year by the total number of registered patients. The descriptive statistics, including median (interquartile range [IQR]) were provided for each time point. The Shapiro–Wilk test was used to determine if the data deviate from a normal distribution.p-values. The use of multilevel modelling, specifically a linear mixed-effects model, in our study allowed us not only to accommodate nonindependence of repeated measurements but also draw subject-specific conclusions.Given that our research design was based on the repeated-measures data for individual GP practices that were organised in nested levels (clusters), the descriptive analyses were complemented by performing the multilevel modelling analysis. The implementation of a multilevel modelling approach is a suitable choice for studies with the same outcome variable, which is repeatedly measured over time in the same study subjects . Note that such repeatedly measured data are not independent. Many statistical techniques for analysing longitudinal data assume independence of the measurements. However, repeated measurements taken from the same individual  are often correlated, and hence, not independent. By not taking into account this correlation, we can obtain biased estimates and invalid p < 0.05), hence supporting the case for multilevel modelling [p-value-based stepwise deletion [p < 0.001). Maximum likelihood estimates were obtained using the Nelder–Mead method. Data management was performed using Python, version 3.6.9, with analysis carried out using R, version 3.6.3.We first evaluated the appropriateness of using our multilevel modelling approach by testing an “unconditional model” including only the dependent variable  and the grouping variable . Note that no predictor variables were entered at this stage. The unconditional model revealed significant between-GP practice variation , i.e., for every one-year increase, the standardised number of prescribed drugs decreased by 40.3 items/1000 patients. On average, urban practices prescribed antibiotics less than rural practices . Practices located in areas with a lower level of deprivation (indicated by a higher score on the MDM Rank) were associated with a lower level of prescribing . A higher percentage of the population aged ≥65 years was associated with higher rates of prescribing , i.e., for one percentage increase in the proportion of the population aged ≥65, we observed the 9.9 items/1000 patients increase in the standardised number of antibacterial drugs. A higher percentage of the population aged <15 years was also associated with higher rates of prescribing . The GP practices located in Northern LCG , Western LCG , and Belfast LCG  prescribed, on average, more antibacterial drugs than GP practices in Southern LCG. The practice size  had no effect on prescribing rates.Changes in standardised antibiotic prescribing rates were further evaluated using a linear mixed-effects model with a random intercept for each GP practice. We observed a substantial decrease in prescribing rates over time , meaning that the overall decrease in antibacterial drug prescriptions over time was larger in less deprived areas. Although higher percentage of the population aged ≥65 years was, on average, associated with higher rates of prescribing, this trend was becoming less significant over time . The effect of time on prescribing was also higher by 5.3 items/1000 patients (p = 0.003) for urban practices compared to rural practices. Finally, the change in the level of prescribing in GP practices located in Northern LCG, Western LCG, and South Eastern LCG was higher every year by 6.7 items/1000 patients (p = 0.003), 8.9 items/1000 patients (p < 0.001), and 9.7 items/1000 patients (p < 0.001), respectively, than prescribing in Southern LCG.Given the interaction terms in our model, we observed that the effect of time on antibiotic prescribing rates decreased by 0.007 items/1000 patients for every one-unit increase in MDM rank , and this difference was becoming more significant over time . Furthermore, lower levels of antibiotic prescribing were associated with GP practices in less deprived areas  as well as those in areas with higher percentages of the population aged ≥65  and <15 years . Although higher percentage of the population aged ≥65 years was, on average, associated with higher antibiotic prescribing, this trend was becoming less significant over time . The GP practices located in Northern LCG , Western LCG , and Belfast LCG  prescribed, on average, more antibacterial drugs than GP practices in Southern LCG. Moreover, the change in the level of prescribing in GP practices located in Northern LCG, Western LCG, and South Eastern LCG was higher every year by 6.3 items/1000 patients (p = 0.009), 7.2 items/1000 patients (p = 0.007), and 7.5 items/1000 patients (p = 0.006), respectively, than prescribing in Southern LCG. The practice size  had no effect on antibiotic prescribing. Finally, for every one-year increase, the standardised number of prescribed antibiotics decreased by 28.4 items/1000 patients (p < 0.001). The annual rate of change in prescribing over the period 2014–2019 was therefore substantially lower than the 40.3 items/1000 patients decrease for every one-year increase in the period 2014–2020, highlighting the potential impact of the COVID-19 pandemic on the overall reduction in antibacterial prescribing.To further validate the robustness of the main findings, we implemented a sensitivity analysis to measure the potential impact of the COVID-19 pandemic on the association between different demographic, geographic, socioeconomic factors and antibiotic prescribing rates. Accordingly, a multilevel modelling analysis was conducted using only antibiotic prescription data from the period 2014–2019 , and the results compared with the findings of the main analysis based on the antibiotic prescription data from the period 2014–2020. The results of sensitivity analyses were consistent with those from the primary analysis. On average, urban practices prescribed antibiotics less than rural practices  and GP characteristics . The inclusion of GP characteristics could potentially further improve the fit of our model given the fact that significant between-GP practice variation in prescribing was previously related to intra-physician variability . It is aThe observed decrease in antibiotic prescribing in Northern Ireland has likely been influenced by the implementation of antimicrobial guidance for primary care that complements the work of HSC Trusts in reducing antimicrobial resistance . FurtherOur findings contribute to the debate on determinants of antibiotic prescribing in primary care and provide actionable insights to policy makers responsible for antimicrobial stewardship and public health campaigns. Indicators of antibiotic prescribing used in NI primary care do not incorporate the provider or population characteristics. The currently used STAR-PU measure only adjusts for the age and gender composition of the NI population. Our results indicate the need for further adjustment for other factors to ensure unbiased comparison between GP practices, and to target interventions appropriately. Future research will focus on conducting an individual-level analysis by linking individual clinical, microbiology, and prescribing records to assess the extent to which prescribing conformed to local guidelines. Specifically, we will assess how the rates of antibiotic prescription deviate from the prescribing guidelines, based on the type of recorded infection.


Rational surgical antibiotic prophylaxis is suggested for some selected surgical processes. However, inappropriate utilization of antimicrobial prophylaxis reduces benefits and increases costs and risks, such as antibiotic resistance. This study aimed to evaluate the current practice of antibiotics prescribed by surgeons in common otologic surgeries.This cross-sectional study was conducted among otolaryngologists with at least 5 years of experience in common otologic surgeries  surgeries). A total of 257 otolaryngologists filled a checklist about their selected regimen and timing of antibiotic(s) administration. The rates of antibiotic prophylaxis prescription in dry and wet ears in tympanoplasty were 7.4% and 87.1% (preoperative), 40.9% and 47% (intraoperative), 88.3% and 98% (postoperative); in tympanomastoidectomy with no cholesteatoma were 7.1% and 97.8% (preoperative), 39.6% and 50.9% (intraoperative), 93.7% and 99.6% (postoperative); in tympanomastoidectomy with cholesteatoma were 14% and 98.3% (preoperative), 45.4% and 51.9% (intraoperative), 98.3% and 99.6% (postoperative), respectively, and in stapes or MEE surgeries were 6.4% (preoperative), 41.7% (intraoperative) and 73.1% (postoperative), respectively. There were no significant differences in the rates of prescribing intraoperative prophylaxis between wet and dry ears, except in tympanomastoidectomy without cholesteatoma. Overall, the most prescribed antibiotics were cephazolin, cephlexin, and ciprofloxacin drop. The results of this study revealed the inappropriate administration and timing of antibiotic prophylaxis regarding current literature evidence. Despite the lack of evidence on the potential role of antibiotic prophylaxis in clean-contaminated and contaminated ears, a significant number of surgeons prescribed prophylactic antibiotics in tympanoplasty and tympanomastoidectomy without cholesteatoma. Surgical site infections (SSIs) are one of the main concerns in the field of medical surgery all around the world and account for 31% of all infections among hospitalized patients ,3. MarkeThere is evidence that the inappropriate utilization of SAP causes a reduction in its potential benefits and increases risks and costs . The resThis cross-sectional survey study was approved by the Research Ethics Committee of Shiraz University of Medical Sciences, Shiraz, Iran , and was conducted from December 2019 to January 2021. The primary inclusion criterion for otolaryngologists was having at least 5 years of experience in otologic surgery. Initially, a text message was sent to 650 otolaryngologists and asked them to participate in this voluntary survey. First, 488 specialists replied to our text message; however, 231 of them refused to cooperate, did not perform these surgeries, or did not have enough surgical experience, and consequently, were excluded from this study. Subsequently, invitations to complete the survey were sent to the otolaryngologists via text messages with no subsequent reminders. Finally, 257 otolaryngologists, who had at least 5 years of experience in these types of surgeries and met the inclusion criteria, were contacted either via phone or email to fill out the questionnaire anonymously and willingly.The collected demographic data included the surgeons’ age, gender, and years of work experience. The questionnaires also consisted of questions on prescribing prophylactic antibiotics for seven specific types of surgeries, including tympanoplasty in dry and wet ears, tympanomastoidectomy in dry and wet ears with and without cholesteatoma, and stapes or middle ear exploration (MEE) surgeries, in pre-, intra-, and post-operative phases. If the antibiotics were prescribed, the properties of their selected regimen, either single or mixed therapy, the name of the antibiotic(s), and the timing of antibiotic(s) administration were mentioned regarding the specific type of operation.The phone conversation duration was about 3-30 min (median=5 min). The sample size was 237 persons, with the possibility of 90% for using antibiotics, a confidence level of 0.95, an error of 5%, and a design effect of 1.7 (n=Z*2pq/D*2).Data were collected from 257 surgeons, including 216 (84%) males and 41 (16%) females. The mean scores of participants' age and work experience were 53.6±10.5 years (range 30-94) and 20.4±10.3 years (range 0.5-60). Concerning tympanoplasty in dry and otorrhea ears, 7.4% and 87.1% of the surgeons prescribed antibiotic prophylaxis 1-30 (median 2) and 1-42 (median 9.5) days before the operation, respectively. Moreover, 40.9% and 47% of the surgeons utilized antibiotics during the operation and 88.3% and 98% of them prescribed antibiotics 1-28 (median 7) and 1-20 (median 7) days postoperatively, respectively in dry and wet ears. The most prescribed antibiotic agents were cephazolin and Cipro drop  in the preoperative phase, cephazolin  in the intraoperative phase, and cephalexin  after the operation. Regarding tympanomastoidectomy in dry and wet ears without cholesteatoma 7.1% and 97.8% of the surgeons prescribed antibiotic prophylaxis 1-30 (median 7) and 1-42 (median 10) days before the operation, 39.6% and 50.9% of the subjects used antibiotics during the operation, and 93.7% and 99.6% of the cases prescribed antibiotics 1-47 (median 7) and 1-20 (median 7) days after the operation, respectively. The most prescribed antibiotics were cephazolin and Cipro drop  in the preoperative phase, cephazolin  during the surgery, and cephalexin  after the surgery. Considering tympanomastoidectomy among dry and wet ears with cholesteatoma, 14% and 98.3% of the surgeons prescribed antibiotic prophylaxis 1-30 (median 7) and 1-30 (median 8.5) days preoperatively, respectively. Also, 45.4% and 51.9% of the surgeons utilized antibiotics intraoperatively, and 98.3% and 99.6% of the surgeons prescribed antibiotics 1-47 (median 7) and 1-28 (median 7) days after surgery, respectively in dry and wet ears. The most prescribed agents in dry and otorrhea ear surgeries were Cipro drop  before the surgery, cephazolin  in the intraoperative phase, and cephalexin  in the postoperative stage.There were no significant differences in the rate of intraoperative antibiotics prescription between wet and dry ears in either tympanoplasty (P=0.185) or tympanomas- toidectomy with cholesteatoma (P=0.158) surgeries; however, in tympanomastoidectomy without cholesteatoma operations, this rate was significantly higher in wet ears than in dry ones (P=0.013). Moreover, no significant differences were observed in the rate of prescribing antibiotic prophylaxis between tympanomastoidectomy with and without cholesteatoma in dry ears (P=0.187). In stapes or MEE surgeries, 6.4%, 41.7%, and 73.1% of the surgeons prescribed antibiotic prophylaxis in pre, intra, and postoperative phases, respectively. Additionally, the duration of antibiotic usage varied from 1 to 7 days before the operation (median=1.5) and 1 to 30 days after the operation (median=7). Furthermore, the most pre-, intra-, and post-operatively prescribed antibiotics were cephazolin (40%), cephazolin (96.9%), and cephalexin (63.2%), respectively  Figure .The present study was designed to determine the otolaryngologists' tendency to prescribe antibiotics in common otologic surgeries. The results indicated that in wet ear operations, most of the surgeons prescribed preoperative antibiotics, and approximately half of them prescribed intraoperative antibiotics. Moreover, the majority of the surgeons administered postoperative antibiotics in both dry and wet ear surgeries. The findings of the current study showed that seemingly antibiotic prophylaxis needed to be more evidence-based. A review of the relevant literature has indicated that the use of SAP in clinical practices is inadequately highlighted in terms of administration time of the first dose, choice of antibiotic, lack of intraoperative dose administration, and prolonged use of antibiotics . AccordiRegarding the administration rate of postoperative antibiotics and the type of surgery, the results of the present study showed that the surgeons' antibiotic prescription rates in postoperative tympanoplasty were 88.3% and 98.02% in dry and wet ears, respectively. In comparison, Raine et al. reported this rate as 59% in their survey in the United Kingdom . The litAs  In terms of the type of antibiotic selected by surgeons, our findings showed that ciprofloxacin otic drop and cephazolin in pre-operative, cephazolin in intra-operative, and cephalexin in the postoperative stage were the most prescribed antibiotics. In addition, the results of an Iranian single-centered retrospective chart review study indicated that the main pre-operative prescribed antibiotics were cephalosporins in general otolaryngology surgeries . Since tSurprisingly, there was no significant difference in the rate of intra-operative prophylactic antibiotic prescription between wet and dry ears in both tympanoplasty and tympanomastoidectomy with cholesteatoma groups. In spite of surgical wounds in ears with cholesteatoma classified as dirty or infected and in other ears classified as clean-contaminated or contaminated , remarkaThe study findings revealed a considerable variation of antibiotic prophylaxis prescription, duration, and type in common otologic surgeries in comparison with literature evidence. One of the mainstays of appropriate prophylaxis antibiotics is to change the healthcare system from the push by cultural and institutional routines for adherence to a patient-centered base. Regarding current literature evidence, the results of this study showed inappropriate administration and timing of antibiotic prophylaxis. To provide a rationale based on the concepts of antibiotic prophylaxis efficiency in common otologic surgeries, it is recommended to develop local and international guidelines. Regarding the improved quality in surgical wards, surgeons should prevent the misuse of antibiotic prophylaxis by paying attention to the Hippocratic maxim of “do not harm patients.”


Shrinkage and creep were tested on 150 × 250 × 1000 mm3 beams. Creep was tested under prestressing load for 539 days and concrete shrinkage for 900 days. The measurement results were compared with the calculations carried out according to the Eurocode 2 as well as with the results of other research. A very low creep coefficient and lower shrinkage in relation to the calculation results and the results of other research were found. It was also revealed that there is a clear correlation between shrinkage and creep, and the amount of water in the concrete. The value of the creep coefficient during the load holding period was 0.610 and 0.537, which is 56.0 and 49.3% of the value determined from the standard. The prestressing losses in the analyzed period amounted to an average of 13.0%. Based on the obtained test results, it was found that the tested lightweight aggregate concrete is well suited for prestressed concrete structures. Shrinkage was not greater than that calculated for normal weight concrete of a similar strength class, which will not result in increased loss of prestress. Low creep guarantees low deflection increments over time.The paper presents the experimental results of shrinkage, creep, and prestress loss in concrete with lightweight aggregate obtained by sintering of fly ash. Two concrete mixtures with different proportions of components were tested. Concrete with a density of 1810 and 1820 kg/m The first application of lightweight concrete as a construction material is known from ancient times when, due to its benefits derived from a lower density and simultaneously high strength parameters, lightweight concrete was used to erect buildings for which construction with the use of heavier materials was hampered. It was mainly used when large spaces had to be covered or when there was a need to reduce the load imposed on land.The use of lightweight concrete can be traced to as early as 3000 BC, when Mohenjo-Daro and Harappa were built during the Indus Valley civilization . However3 and a compressive strength of no less than 28 MPa would be an effective material.The new beginning of lightweight concrete in modern times dates to 1917, when S. J. Hyde developed a rotary kiln for drying slate and clay, thus obtaining a material lighter than traditional concrete. At around the same time, F. J. Straub pioneered in the use of coal ash in the production of concrete blocks employed in the construction of buildings . The matCurrently, due to a number of advantages, lightweight concrete is used both in prefabrication and in cast-in-situ concrete construction. The lower density paired with high strength allows for the reduction of cross-sections, increasing the span or service loads. Lightweight concrete has been used in monolithic construction in the world, primarily in high-rise buildings (reducing their weight), in long-span roofs , in mulExamples of the application of lightweight concrete in high-rise buildings are Water Tower Place in Chicago, Yokohama Landmark Tower in Japan, Commerzbank Tower in Germany, and the Shard in London, which was once the tallest building in the European Union.A different field of concrete construction is prestressed concrete structures. Here, too, lightweight concrete has been used for several dozen years, mainly in bridges, allowing for achievement of larger spans and smaller cross-sections. As has been shown by many studies ,7, lightLong-span structures made of lightweight concrete also include the Doncaster Racecourses Grandstand and Wellington Regional Stadium in New Zealand, the Oberstdorf ski flying hill, and the Bergsøysundet and Nordhordland pontoon bridges. It is also worth mentioning the highest structure in the world to have been transported, i.e., the Troll gas platform, which was made entirely of lightweight concrete .Unfortunately, lightweight concrete has not been used in the construction of posttensioned concrete long-span slabs so far. The authors of this paper took a few years to design several post-tensioned concrete slabs with unprecedented spans and span-to-depth ratio ,11,12. N3 were made of the mixtures. Some of the beams were post-tensioned 16 days after concreting. The remaining beams were unloaded as witness specimens. All specimens were placed in an air-conditioned chamber. The prestressing was released after 539 days. The strains were measured on all specimens for 900 days. Witness specimens were used to determine concrete shrinkage. The difference between the average strain of prestressed beams and witness beams allowed the researchers to determine the development of creep. The release of the prestressing made it possible to determine the immediate and delayed strain return of the concrete and the value of irreversible strain.The rheology of concrete is of great importance in thin post-tensioned concrete floor slabs with a span-to-depth ratio of more than 40. On the one hand, increased shrinkage and creep of concrete will lead to greater prestress losses, while on the other, they will cause excessive increases in long-time deflections. Because of the limited scope of the research carried out in this area so far and the lack of sufficiently precise standard procedures that describe these phenomena in lightweight concrete, the authors carried out long-term tests of concrete shrinkage and creep on the new Polish sintered fly ash aggregate Certyd. The aim of the research is an initial identification of the rheological characteristics of concrete before using it for long-span post-tensioned floor slabs. For this purpose, two concrete mixtures of different compositions were made. Nine beams with dimensions of 150 × 250 × 1500 mmLightweight aggregate concrete is a composite with a matrix and aggregate that, unlike normal weight concrete, have a similar modulus of elasticity. This results in a more even distribution of stresses in the concrete structure, and thus a lower likelihood of crack propagation and increased concrete durability. Another advantage of lightweight aggregate concrete structures is the tight construction of the matrix-aggregate contact zone and the regular shape of grains in artificial aggregates, which is reflected in the high strength–density ratios. The structure of the contact zone between the aggregate and cement matrix, different in relation to concrete with rock aggregates, causes a different behavior of lightweight concrete under load and exhibits a different collapse mechanism. Lightweight concrete is not associated with the occurrence of three stages of crack development, as is the case in normal weight concrete . For typical normal weight concretes with rock aggregate, stage I goes into II at compressive stresses amounting to 30–40% of concrete strength, while stage II goes into stage III at stresses of about 70–90% of strength. In lightweight aggregate concrete, the first load-induced cracking appears only at stresses of 85–90% of strength . It was The study  showed tAn important parameter of structural concrete is the modulus of elasticity. Due to the nature of concrete, which is a composite of aggregate and matrix, the modulus of elasticity depends on the modulus of both components, taking into account their volumetric contributions and mutual adhesion. Similarly to normal weight concrete, in lightweight concrete the modulus of elasticity largely depends on the aggregate; however, here, the aggregate is the weaker link, which causes a considerable reduction in the modulus of the entire composite. In paper , it was The different structure of concrete with lightweight aggregate, in addition to lower values of strength properties and increased shrinkage, causes a different creep range compared to normal weight concrete. Many publications have indicated that structurally lightweight aggregate concretes may show greater creep than those with rock aggregates of comparable strength classes. Report BE 96-3942/R2  stated tThermal treatment has a beneficial effect on the reduction of lightweight concrete creep. As a result of low-pressure machining, lightweight concrete creep can be reduced by 25–45% compared to concrete subject to wet treatment. Use of autoclaving turns out to be even more effective—it is possible to reduce creep even by 60 to 80% .Shrinkage of lightweight aggregate concrete has been the subject of many studies ,25,26,27Results of one of the first lightweight concrete creep tests were published by Best and Polivka in 1959 . The aut2, loaded for 730 days. It was shown that both shrinkage and creep decreased with increasing sand content. For lightweight concretes containing 0 to 100% sand, a creep coefficient of 1.26 to 1.00 was obtained. When the lightweight aggregate was completely replaced with sand, the creep coefficient was up to 30% lower compared to concretes with other proportions of sand and lightweight aggregate.The study  investig3, respectively. A total of 26 samples from two concretes were tested. The load was applied after 16 and 24 h from concreting to the level of 40 and 60% of the current compressive strength. Six hundred and twenty-day values of the shrinkage and creep coefficient were determined. Based on the conducted tests, it was found that, for the higher strength mixture, the creep after 620 days is lower and, in this case, the age at the moment of loading is of little importance. The shrinkage study showed that for both mixtures, 90% of the shrinkage measured after 620 days had occurred after 260 days. Research published in  studied 2, φ150 × 300 mm2, and beams 38 × 38 × 125 mm3. Samples were subjected to a constant load after 24 h and 28 days of maturing of the concrete; furthermore, measurements of strains caused by creep were taken for 120 days. It was observed that creep increased with decreasing specimen size. The authors also observed less creep for lightweight concrete compared to normal weight concrete. This effect was justified by the presence of absorbed water in lightweight concrete samples due to the use of pre-wetted aggregate. It should be emphasized, however, that in the presented research, shrinkage and creep strains were not separated. All conclusions for creep are based on the analysis performed by DIC .The paper  presents3. Seven cylindrical specimens with a diameter of 100 mm and a height of 1245 mm were tested. At the same time, the shrinkage was measured on four cylindrical test specimens of φ100 × 200 mm2. The first series (four cylinders) was loaded after one day with a stress of 14.8 MPa (which comprised 40 and 50% compressive strength after one day). The second series was loaded after 28 days with stresses of 19.3 MPa, which accounted for 40% of the compressive strength. The observations were carried out for a period of one year. Simultaneous tests were carried out on lightweight and normal weight concrete. It was noticed that the creep coefficient for lightweight concrete is slightly lower than for conventional concrete for a load time of one day; however, the intensity of its development in the first days of loading is higher for lightweight concrete. For a load applied after 28 days for lightweight concrete, a greater creep coefficient was obtained than for normal weight concrete.The results of more recent creep studies on self-compacting lightweight aggregate concrete were published in 2018 in . Concret3 was used. Two kinds of lightweight aggregate were used: expanded clay and sintered pulverized fuel ash. The beams had a span of 3.00 m, varied cross-section  with a height of 240 mm, varied ordinary and prestress reinforcement ratio, and varied compressive concrete strength (25.1–42.3 MPa). The presented results are difficult to compare with the creep results from other studies. The authors found that most of the creep effects accumulate in the first year, strong creep effects last for the first 5 years, and a noticeable incremental creep displacement exists through 20 and 30 years of testing.The results of the unique creep studies were published in 2020 in the paper . The aut3 and 50 × 150 × 450 mm3 made of lightweight concrete with expanded clay, expanded perlite, and agloporite. Concrete compressive (cubic) strength was from 10 to 60 MPa. The authors reported concrete deformation after two years, however, they did not draw any significant conclusions. The results were presented in a way that made it difficult to analyze and compare with others.In 2020, other but much poorer and poorly documented studies were also published . The autAs mentioned earlier, the creep of concrete with lightweight aggregate has so far been the subject of few studies. Creep is an essential property of concrete for prestressed structures. The few studies conducted mainly included artificial aggregates obtained from natural resources . There is little research on concrete with aggregates produced from waste. Due to the high demand for natural aggregate at the beginning of the 21st century, the Polish Aggregates Producers Association predicts that in the next 10 years there will be no more sands and gravels, while the next 50 years will bring a shortage of crushed stone aggregates. Meanwhile, the presence in Poland of large amounts of waste in the form of ash from the production of electricity derived from the combustion of hard coal speaks for the production of artificial aggregate. The novelty of the presented research compared to the previous studies is the use of new Polish artificial aggregate with much better mechanical properties than the aggregates used previously, whence it could be assumed that the tested concrete is characterized by improved rheological properties. From here, it can be concluded that the use of artificial aggregates will have a positive impact on the rational management of natural resources.The few creep tests carried out so far, reported in This research was begun when the production of a new Certyd artificial aggregate was launched in Poland in 2015. It is produced with sintered fly ash. Certyd aggregate is produced from ash from heat and power plants deposited on heaps, which derive from the burning of hard coal. These are fly ashes from electrostatic precipitators and ash–slag mixtures from wet carrying of furnace waste. The aggregate is produced by sintering ash at a temperature of 1200 °C. The process occurs without the use of external fuel, using the heat from the combustion process of carbon residues in ash. Only a small amount of energy is needed at the beginning to the launch process. Lightweight aggregate in the form of regular spherical granules or crushed grains of various fractions is obtained from the remains after the combustion of hard coal . The bas3. Cement CEM I 42.5 N was used. The amounts of individual components for the C-1 and C-2 mixtures are given in Two concrete mixtures were made with a dry density of 1810 and 1820 kg/m2 for compressive strength testing, nine cylindrical specimens φ150 × 300 mm2 for modulus of elasticity testing, nine cylindrical specimens φ150 × 300 mm2 for axial tensile strength testing, nine beams 150 × 150 × 600 mm3 for modulus of rapture testing, and nine cubes 150 mm for splitting strength testing. The specimens were taken out from the mold and placed in water, then pulled from it just before testing.As part of this work, the strength properties of two types of concrete, C-1 and C-2, were tested. The average compressive strength, modulus of elasticity, modulus of rapture, axial tensile strength, and splitting strength were tested after 7, 14, and 28 days. Each of the strength properties was tested on three specimens. Finally, we prepared nine cylindrical specimens φ150 × 300 mm3  were placed on a steel frame in an air-conditioned chamber .2 cylinders. Despite the different water content and W/C ratio (0.41 and 0.51), similar values of the average compressive strength were obtained after 28 days  were used to examine the strength characteristics of concrete after 7, 14, and 28 days of concrete maturation. Each feature was determined on three specimens. The average compressive strength and modulus of elasticity of concrete were determined on φ150 × 300 mm 28 days a, i.e.,  28 days .3. However, when comparing with normal weight concrete of the corresponding strength class (C50/60), the obtained values are 40.3 and 39.5% lower, respectively (cmE = 37 GPa).In the case of the modulus of elasticity for both mixtures, similar but low values were obtained b, i.e., The axial tensile strength obtained in the tests d is 3.86The beams used for shrinkage and creep tests were placed in an air-conditioned chamber and kept there for 900 days. A constant temperature of 20 °C and a humidity of 50% were programmed. Excluding the first day after demolding, the recorded temperature values in the chamber ranged between 18 and 23.7 °C, and the humidity varied from 45 to 54% .3). Immediate strain under loading was: for concrete C-1: 473 − 126 = 347, for concrete C-2: 525 − 119 = 406 με, while the strain recovery upon removing the load was 865 − 610 = 265 and 1122 − 764 = 358 με. Thus, the immediate strain recovery was 76% for C-1 concrete and 88% for C-2 concrete. Therefore, less water content in the concrete means less strain recovery during unloading.Due to the fact that the loaded beams contained strains caused by both shrinkage and load, and the shrinkage of concrete is independent of the load, the difference in the average strains of the loaded and unloaded beams allowed for isolation of only the strains caused by the load. The development of these strains over time for both tested concretes is shown in In general, concrete deformation over time under the load is divided into: instantaneous and time-dependent, as well as recoverable and recoverable. There are four kinds of deformation: elastic (instantaneous and recoverable deformation), plastic (instantaneous irrecoverable deformation), delayed elastic (time-dependent recoverable deformation), and viscous (time-dependent irrecoverable deformation). Elastic deformation is usually associated with the energy stored in the crystal or molecules that is fully recoverable. Plastic deformation occurs when a slip in a plane of maximum shear stresses changes positions of crystals, molecules, or atoms. Slip in the plane of maximum stresses presents no change in volume and it is not time-dependent. Delayed elasticity is usually a consequence of a lack of order in the microstructure, upon loading the microstructure slowly reaccommodates. The energy is not dissipated but stored, and it is therefore fully recoverable. Finally, viscous deformation describes the behavior of fluids and appears only under sustained load. The strain rate is proportional to the applied stresses, and there is no recovery upon load removal. The last two forms of deformation are considered to cause creep in concrete.Based on the presented values of strains, four strain components discussed above were separated . The insIt can be seen that the higher the water content in the concrete (C-2), the more elastic and the less plastic the behavior in the concrete. Higher water content also causes a more viscous behavior in the concrete. It is fully justified because viscous deformation describes the behavior of fluids.The sum of plastic and viscous strains indicates residual strain. Residual strain values are 173 and 185 με adequate . It can The same figure compares the measured creep coefficient with the results of other presented tests of concrete with lightweight aggregates, in which the results were presented sufficiently for comparison. The measured creep coefficient for concrete with sintered fly ash is significantly lower compared to the results of all other presented tests.pkf = 1860 MPa and the strand cross-sectional area was 150 mm2. pk.f The wide dispersion in force results from the short length of the elements (1000 mm) and thus the major influence of anchoring on the change of force. Aalthough a special non-slip system of threaded anchorages was used, the short elements are sensitive to anchoring inaccuracies. The mean value of the force after 539 days of prestressing was 161.9 kN and the mean loss was 13.0%. The maximum force decrease (for the C-2/1 beam) was 16.2%. The difference in losses can be noticed between the beams made from C-1 and C-2 concrete. For beams made of the first mixture, losses of 11.5 and 10.9% were recorded, while for beams made of the second mixture—16.2 and 13.7%. This difference can be explained by higher shrinkage in the case of C-1 concrete caused by more water  does not discriminate against using concrete for prestressing and it can also be considered acceptable. It should be emphasized that these results were obtained on small-scale elements. In the case of elements on a larger scale, the prestress decrease may be smaller (creep increases as the element size decreases ).The authors of the presented research want to mark that the creep strain and the creep coefficient were determined with decreasing load (decrease in prestressing force). For this reason the authors estimate the error in designation strains and creep coefficient to about 10%. It is an error which allows comparison of the obtained results with others obtained in different test conditions.The obtained results of research on rheological properties of concrete with Certyd aggregate showed low shrinkage and creep in such concrete. The research showed a better quality of the aggregate compared to other artificial aggregates analyzed in other studies. The information obtained can be a supplement to the scarce global database of results in the field of creep in lightweight concrete with artificial aggregates. They can also be an opportunity to popularize this aggregate.Research confirmed the good quality of aggregate for concrete made with waste materials. It is of great local significance. This is important because of the dwindling supplies of natural aggregates and the large reserves of ash in Poland which remain after the production of energy from coal combustion.The authors see the most important benefits in the possibility of using this aggregate for prestressed concrete. The lower weight of the concrete can reduce the cross-section and increase the span of the elements ,13. In tThe concrete made exhibited a lower shrinkage than that obtained from the calculations in accordance with the Eurocode 2 , for theThe tested concrete exhibited a very low creep coefficient in the considered period. The creep coefficient value was 0.610 and 0.537, which is 56.0 and 49.3% of the value determined from the standard . It is aThe concrete showed clearly viscous behavior and high residual strain;The prestressing losses in the analyzed period amounted to an average of 13.0% (maximum 16.2%), which is an acceptable value and does not discriminate against concrete being used for prestressing.The paper presents the results of tests of shrinkage, creep, and prestress losses in lightweight aggregate concrete with artificial aggregate obtained by sintering fly ash. Creep was tested under load for 539 days and shrinkage for 900 days. Based on the obtained results, it was found that:To summarize the obtained test results, it was found that the tested lightweight aggregate concrete with sintered fly ash aggregate Certyd is well suited for prestressed concrete structures. Low creep guarantees low deflection increments over time. Although this concrete is characterized by a lower modulus of elasticity compared to normal weight concrete , several computational analyses ,13 and i