The influence of the compressive strength of concrete on fatigue resistance has not been investigated thoroughly and contradictory results can be found in the literature. To date, the focus of concrete fatigue research has been on the determination of the numbers of cycles to failure. Concerning the fatigue behaviour of high-strength concrete (HPC) and, especially, ultra-high-strength concrete (UHPC), which is described by damage indicators such as strain and stiffness development, little knowledge is available, as well as with respect to the underlying damage mechanisms. This lack of knowledge has led to uncertainties concerning the treatment of high-strength and ultra-high-strength concretes in the fatigue design rules. This paper aims to decrease the lack of knowledge concerning the fatigue behaviour of concrete compositions characterised by a very high strength. Within the priority programme SPP 2020, one HPC and one UHPC subjected to monotonically increasing and cyclic loading were investigated comparatively in terms of their numbers of cycles to failure, as well as the damage indicators strain and stiffness. The results show that the UHPC reaches a higher stiffness and a higher ultimate strain and strength than the HPC. The fatigue investigations reveal that the UHPC can resist a higher number of cycles to failure than the HPC and the damage indicators show an improved fatigue behaviour of the UHPC compared to the HPC. Developments in concrete technology nowadays allow the application of concrete compositions with ever-higher compressive strengths, which enable the construction of more filigree and slender structures. These structures are exposed to a higher extent to fatigue-relevant loads compared to massive structures due to their lower ratio of deadweight to non-static loads. For those structures, the fatigue resistance of the concrete becomes decisive for the design. At the same time, there has been a great demand in recent decades for types of structures for which fatigue-related stresses are characteristic, such as wind turbines or slender bridges made of high-strength or ultra-high-strength concrete. Thus, the research in recent decades has been more focused on the fatigue behaviour of concretes, e.g., ,2,3,4.The compressive fatigue resistance of plain concrete is described by the number of cycles to failure that the concrete can bear at a specified stress level  and exprfN/N [However, comparatively little research has been focussed on the concrete’s fatigue behaviour, especially on that of ultra-high-strength concrete, described by damage indicators, such as, e.g., the development of strain and stiffness in order to obtain more knowledge concerning the underlying damage mechanisms ,15,16,17N/Nf ,20,21,22N/Nf ,11,13,23fN in a double-logarithmic scale was conducted in [The stiffness of concrete within the fatigue process is usually described by the secant modulus in the decreasing branch of the hysteresis loop ,19,22,24ucted in , based oucted in ,15,25 toOverall, there is still a lack of knowledge concerning possible differences of the fatigue resistance and fatigue behaviour of high-strength and ultra-high-strength concrete, which leads to uncertainties concerning their treatment in the fatigue design rules. As a result, the currently valid design rules for compressive fatigue loading in the standards and guidelines, such as Eurocode 2  or ModelWithin the Priority Programme SPP 2020 ‘Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab’, the fatigue behaviour and damage mechanisms of high-performance concretes under fatigue loading are investigated in the framework of 14 participating projects at different universities, each with a special focus in this research field. In order to ensure a certain level of comparability, one high-strength and one ultra-high-strength concrete composition are used as reference compositions in the investigations conducted by the different participating projects. Furthermore, the compressive fatigue behaviour of the reference high-strength and ultra-high-strength concrete are investigated comparatively by the so-called ‘central project’ for the purpose of a basic characterisation to be used as a reference in the different research projects. In this paper, the results of investigations in the compressive fatigue behaviour of the reference high-strength and ultra-high-strength concretes are presented comparatively. The numbers of cycles to failure and the damage indicators strain and stiffness are analysed with respect to the influence of the compressive strength. The fatigue investigations were carried out at two test laboratories in the framework of the SPP 2020 in order to superiorly evaluate the validity of the concrete-related differences identified in the number of cycles to failure and damage indicators.However, since the fatigue behaviour of concrete cannot be considered detached from its behaviour under monotonically increasing loading, it is also presented and the fatigue behaviour is discussed considering the ’static’ material’s behaviour. The overall objective of the investigations presented here is to contribute to the decrease in the lack of knowledge and the previously described discussion in the literature concerning the influence of the compressive strength of concretes on their fatigue resistance.The investigations were conducted on one high-strength concrete and one ultra-high-strength concrete, which are the reference concretes within the SPP 2020. The UHPC composition was developed based on the M3Q composition previously used in the SPP 1182 . The comThe grain size distributions of the quartz sand, sand and basalt aggregate are shown in As a complimentary investigation, the 28-day compressive strengths for the different batches produced were determined continuously by seven laboratories participating in the SPP 2020 since the start of the SPP 2020 in 2017. The tests of the cubic specimens were carried out in accordance with the guidelines given in DIN EN 12390-3:2019 . The resckf is the characteristic compressive strength, cmf is the mean compressive strength, nk is the 5%-fractile factor according to [xσ is the standard deviation. The mean compressive strength with its standard deviation and the characteristic compressive strength calculated are shown in The frequency distribution and cumulative distribution of the compressive strength are shown in rding to  and σx iBased on this analysis, the HPC was classified as C80/95 according to DIN EN 206:2021  and the h = 180 mm and a diameter of d = 60 mm. The HPC specimens were produced at the Institute of Building Materials Science, Leibniz University Hannover (IfB) and those of the UHPC were produced at the Institute of Concrete Structures, Technical University of Dresden (IMB). Two batches  were produced for each concrete. The production at those two laboratories was scheduled considering the expertise in the production of the respective concretes and the availability of the components of the concrete composition. For the fatigue investigations, cylindrical specimens were prepared with a final height of h = 180 mm. The test specimens were sent in shockproof boxes [All specimens were cast in cylindrical formworks with a height of about 250 mm, compacted using a vibrating table. The formwork was removed after 48 h and the specimens were stored under standard climate conditions (20 °C/65% R.H.) until testing. The specimens were prepared by sawing a few centimetres off the top and bottom to remove areas where the concrete may have been disturbed due to the production process. Additionally, the test surfaces of the specimens were ground parallel and polished to achieve a uniform stress distribution. The final height of the specimens ready to be tested was of boxes  to the tminS = 0.05 for all fatigue tests. The maximum stress levels were maxS = 0.85 and maxS = 0.75. The load frequency applied was tf = 1.0 Hz in all tests. The fatigue tests at maxS = 0.75 were conducted at the IfB, while the fatigue tests at maxS = 0.85 were conducted at the Materials Testing Institute, University Stuttgart (MPA). This procedure was chosen to achieve a comparability of the results between HPC and UHPC for each stress level (no influence of laboratory). Investigations at maxS = 0.75 were additionally carried out at the MPA to investigate the stress level effect without laboratory influence. The number of fatigue tests conducted at each laboratory is summarised in The fatigue tests on both concretes were conducted under uniaxial compressive cyclic loading with constant maximum and minimum stress levels for each test. The minimum stress level was cm,reff of the concrete specimens were tested just before conducting the fatigue investigations, using at least five specimens from the same batch and having the same geometry of the specimens used in the fatigue investigations (cylinder d/h = 60/180 mm). The tests were conducted force-controlled with a stress velocity of 0.5 MPa/s, using the same testing machine as for the fatigue tests. The resulting mean compressive strength of each concrete and batch was used as fatigue reference compressive strength cm,reff for the fatigue tests to determine the compressive fatigue stresses required based on the stress level investigated .The fatigue reference compressive strengths The fatigue tests were carried out using servo-hydraulic testing machines with 1 MN actuators, exemplarily shown in The fatigue resistance of the plain HPC and UHPC was analysed by evaluating the numbers of cycles to failure obtained from the tests. Statistical analyses were applied regarding the influence of the two batches of each concrete and the influence of the two concrete compositions on the numbers of cycles to failure. T = 1.0 × 10−5 K−1. This approach is considered sufficient due to the low temperature increase observed during the tests (max. 9 K for the HPC and 13 K for the UHPC). In addition, the maximum and minimum strains at peak stresses of the sinusoidal load curve and the stiffness were analysed as damage indicators. The maximum and minimum strains were obtained from the three laser distance sensors and averaged per specimen. In the analyses of the strains, the temperature increase due to cyclic loading was considered using a thermal expansion coefficient of αmax∆ε0.0–1.0min, ∆ε0.0–1.0) up to failure and the gradients of strain development in phase II  were analysed as parameters  during the cyclic loading was calculated for each cycle as the secant modulus in the decreasing branch of the hysteresis loop. The gradient of the stiffness development in phase II (sgrad E0.2–0.8) was determined corresponding to the approach for the gradient of strain. The reduction of stiffness up to failure was analysed as percentile value with respect to the initial stiffness at the beginning of the fatigue loading (s∆E0.0–1.0). The stiffness , but not the absolute relationships between the curves for the varying types of concretes investigated. Therefore, the mean values of the parameters, which were calculated based on the individual developments, are additionally given in The strain and stiffness developments were determined for each fatigue test, leading to a large number of individual curves. Therefore, averaged curves of the damage indicators were determined for each concrete batch and stress level for the graphical presentation. These curves were determined for identical test conditions by averaging the development of the individual damage indicator as a function of the relative number of load cycles, cm,reff, the ultimate strain cmε (strain at maximum stress) and the stiffness E0.15–0.80 are summarised in Both concrete compositions were tested under monotonically increasing loading in order to obtain the fatigue reference compressive strength for the fatigue tests cf. . The resIt is noticeable from cm,ref =f 116.2 MPa for batch HPC-a and cm,ref =f 89.8 MPa for batch HPC-b, despite being of the higher concrete age. However, the 28-day cubic compressive strength of HPC-b was also significantly lower than that of HPC-a. Thus, this difference was batch-related and related to the scattering of the HPC  determined in a previous round robin test [cm,ref =f 174.0 MPa for batch UHPC-a and cm,ref =f 200.6 MPa for batch UHPC-b. The fatigue reference compressive strength of batch UHPC-a correlates with the results presented in [From  the HPC . Moreovebin test . The fatented in . Here, tmaxS = 0.85, while specimens of both batches were investigated at maxS = 0.75 , which means a better fatigue resistance of the UHPC. The scattering of the single values of both concretes is higher at the stress level maxS = 0.85 than that at the lower stress level maxS = 0.75. In statistical terms, the influence of the concrete type is not significant  for the higher stress level max =S 0.85. In detail, it is visible that most of the single values of the UHPC concrete at the lower stress level maxS = 0.85 are shown in maxS = 0.75 in maxS = 0.75 determined on specimens of different batches differed from each other, which is not surprising. When comparing the strain developments of the HPC and UHPC specimens at both stress levels, it can be seen that the initial maximum strains (maxε) and the following values of the UHPC were significantly higher than those of the HPC. Despite the same fatigue stress levels, the absolute stresses applied were higher for the UHPC specimens than for the HPC specimens due to their higher fatigue reference compressive strength  of the HPC were higher than those of the UHPC  and fatigue reference compressive strengths (cf. The averaged stiffness developments are shown in gths cf. . The ini∆Es0.0–1.0) of the HPC is higher on average than that of the UHPC. This material dependency corresponds to results from [The gradient of stiffness in phase II of the HPC is steeper than that of the UHPC at both stress levels and, thus, the same relationship exists as for the gradients of strain cf. . It can lts from . Furthercm,reff of both batches of each concrete were determined  are displayed with respect to the numbers of cycles to failure in double-logarithmic graphs.In addition to the numbers of cycles to failure, the damage indicators strain and stiffness were investigated comparatively for the HPC and UHPC. The analyses of the strain developments showed that the HPC exhibited a higher total growth of the maximum and minimum strain than the UHPC, although fewer numbers of cycles were suffered until failure. This correlates to the steeper gradient of strain in phase II of the HPC cf. . In FiguHPC: R² = 0.98(2)HPC: R² = 0.98(3)UHPC: R² = 0.88(4)UHPC: R² = 0.80(5)Linear relations between the logarithmic gradients of, respectively, the maximum and minimum strain and the logarithmic numbers of cycles to failure were found for both concretes. The regression lines can be expressed by the following equations (Equations (2)–(5)):The gradients of strain decrease with decreasing stress levels. Furthermore, the gradients of the minimum strain of both concretes are flatter than the gradients of the maximum strain. Both findings confirm the results of . Furthersgrad E0.2–0.8) of the HPC was steeper than that of the UHPC. In HPC: R² = 0.93(6)UHPC: R² = 0.69(7)The analyses of the stiffness developments showed a higher percentile reduction of stiffness of the HPC compared to the UHPC, although fewer numbers of cycles were suffered until failure cf. . SimilarmaxS = 0.75). Here, both regressions lines cross each other. In the range of lower flog N ≈ 4, the regression line of the UHPC is located below that of the HPC. Thus, flatter gradients of stiffness or, rather, a lower stiffness reduction per load cycle are observable for the UHPC compared to the HPC for the same number of cycles to failure, which correlates to the findings from [flog N > 4. The differences between the regression lines with respect to gradients of strain and stiffness in phase II  at the lower level. Thus, a negative influence of the higher compressive strength of the UHPC on the numbers of cycles to failure was not observed in the investigations presented.The UHPC reached higher mean numbers of cycles to failure than the HPC at both stress levels investigated. Furthermore, the difference in mean numbers of cycles to failure was statistically significant (ANOVA, The damage indicators showed a smaller total growth of strains and a smaller percentile reduction of stiffness of the UHPC compared to the HPC. Furthermore, the gradients of strain and stiffness in phase II, i.e., the increase in strain and decrease in stiffness per load cycle, respectively, of the UHPC were smaller than those of the HPC. In summary, the UHPC showed a less pronounced damage evolution compared to the HPC. Furthermore, the damage indicators reveal a different material-dependent fatigue behaviour.A batch influence on the results of the reference compressive strength for both concretes was identified. For each concrete, this batch influence was not found in the numbers of cycles to failure. Thus, the batch influence was equalised due to the determination of the tested fatigue stresses, based on the respective reference compressive strength of the batch.The compressive fatigue resistance of a high-strength concrete and an ultra-high-strength concrete, which are the reference concretes in the Priority Programme SPP 2020, were investigated comparatively considering the numbers of cycles to failure and the damage indicators strain and stiffness. The main objective of this study was to contribute to a decrease in the lack of knowledge concerning the influence of compressive strength on the fatigue resistance of concretes. The fatigue investigations were conducted at two stress levels, Overall, a higher fatigue sensitivity could not be found for the UHPC compared to the HPC investigated. Thus, this result contradicts the results from ,9 and co


In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. Hence, superfine cement is used innovatively in this study to modify coral aggregates; additionally, the effects of the water–cement ratio and curing time on the water absorption and strength of modified coral aggregates are investigated. Modified coral aggregate concrete is prepared, and the effect of using modified superfine cement on its workability and strength is investigated. Experimental results show that when the water-cement ratio exceeds 1.25, the slurry does not form a shell on the surface of the coral aggregates and the water absorption of the coral aggregates increases significantly. The strength of the modified coral aggregates cured for a short duration is slightly lower than that of unmodified coral aggregates, whereas that cured for 28 days is approximately 20% higher than that of unmodified coral aggregates. Using superfine cement to modify coral aggregate concrete can improve its workability, but not its compressive properties. Owing to the development and increased utilisation of the ocean, a significant amount of marine infrastructure is being constructed, which necessitates more building materials. Corrosion-resistant structural steels have been developed, such as fibre-reinforced polymer bars ,2,3, staTo effectively improve the workability and mechanical properties of coral aggregate concrete, the coral aggregates to be used must be pretreated. Coral aggregates are characterised by low density, high crushing index, high porosity, and high water absorption, which are typical of lightweight aggregates; therefore, coral aggregates can be regarded as a lightweight aggregate. To modify lightweight aggregate concrete, researchers typically use inorganic cementitious materials to treat the aggregates, reduce the aggregate porosity, and improve the aggregate strength and durability. He et al.  formed aConsidering the high porosity of coral aggregates and the typical methods used to modify porous lightweight aggregates, superfine cement is used innovatively in this study to modify coral aggregates. Changes in the water absorption and strength of coral aggregates before and after modification are investigated. Modified and unmodified coral aggregates are used to prepare coral aggregate concrete. Subsequently, the effects of using modified superfine cement on the workability, strength, and failure mode of coral aggregate concrete are revealed. The aim of this study is to provide a new method for modifying coral aggregates, which can promote the use of coral aggregate in the construction of islands and reefs. The experimental results are conducive to the design and construction of modified coral aggregate concrete structures.The coral aggregates used in this study were obtained from the South China Sea. As shown in Owing to the high porosity of coral aggregates, the coral aggregates were modified by soaking them in a high-activity micro-inorganic cementitious material. The internal pores and microcracks of the coral aggregates were filled with slurry to improve the internal structure of the aggregates as well as the workability and mechanical properties of the concrete. Ordinary Portland cement, which is typically used for modification, features a large particle size; thus, the particles do not permeate easily into microcracks. Generally, particles of ordinary Portland cement can only penetrate into pores larger than 0.2 mm; therefore, the modification effect on porous aggregates is unsatisfactory, and improvements to fine pores require cement with a smaller particle size. Superfine cement is a high-performance cement-based grouting material with a much higher fineness than ordinary cement . It has - in seawater affects the strengthening of concrete [42− may result in the expansion and cracking of concrete by affecting the formation time of gypsum and ettringite [Water is a basic component of concrete that also significantly affects its durability, strength, and workability ,36,37. Uconcrete  and thattringite . In the tringite . The comtringite ,42,43.The mineral composition of sea sand is similar to that of river sand; however, the content of shells and organic matter in sea sand deteriorates the strength and durability of concrete . In addiThe method of preparing aggregates reinforced by modified slurry is to soak aggregates in the slurry for a period of time, remove the aggregates before the initial setting of the slurry, and perform natural curing after the surface slurry has solidified. This process ensures a tight slurry shell on the aggregate surface. However, it is disadvantageous to the aggregates in two aspects: the smooth shell on the aggregate surface reduces the friction between the aggregates and cement gels as well as reduces the bite force between the aggregates, which improves the mechanical properties of the concrete; additionally, the slurry shell forms additional pores, which increases the water absorption of the aggregates, thereby improving the water absorption of the modified aggregates to an extent greater than that before modification. The appropriate slurry water-cement ratio (W/C) and modification process must be identified. When the W/C of the slurry is relatively large, the slurry will be very thin, making it impossible to fill the aggregate pores when the slurry is solidified. On the contrary, the slurry will be very thick when the W/C is relatively small. The thick slurry will form a thick slurry shell outside the coral aggregate. The thick shell may affect the strength of the aggregate and lead to unexpected water absorption. Based on the results of pre-test, the values of W/C of slurry was determined as 1.0, 1.25, 1.5 and 2.0.The superfine cement was placed in a stirrer, and artificial seawater was added to the stirrer based on the W/C values specified. Both materials were mixed well. After the slurry was prepared, coral aggregates were soaked in it and stirred to ensure that the aggregates were in full contact with the slurry. When the aggregates were soaked, they were stirred once every hour to avoid bonding between the aggregates and ensure the uniformity of the modification. Before the initial set was formed, the aggregates were removed from the slurry. The aggregates were continuously sieved using a dense mesh to filter out the excess modified slurry and avoid the formation of an excessively thick slurry shell on the aggregate surface. Subsequently, the aggregates were arranged flat on a net and dried at room temperature for 24 h, during which the aggregates were flipped to prevent them from bonding with each other. In order to reduce the impact of the environment ,47, cora0m is the mass of the aggregates in the saturated surface condition, and m1 is the mass of the dry aggregates. Concrete is composed of water, cement and aggregate, constituting 70% to 80% of concrete volume. Aggregate strength greatly affects concrete strength. Therefore, it is necessary to clarify the strength of the aggregate. The strength of the coral aggregates was evaluated using the crushing index (rC). The mass of the coral aggregates (0G) was weighed, and then loaded using a pressure tester. Subsequently, the assembly was pressurised to 200 kN at a rate of 1 kN/s and then unloaded. A 2.5 mm sieve was used to remove crushed fine particles, and the mass remaining on the sieve (1G) was weighed. The rC of the coral aggregates was calculated using Equation (2) [To investigate the effect of superfine cement modification on the coral aggregate concrete, the properties of coral aggregate concrete and coral aggregates before and after the modification were evaluated. When mixing concrete, the dry aggregate will absorb the moisture of the concrete mixture, resulting in a change in the effective W/C of concrete, thus affecting the construction process and mechanical properties of concrete. Therefore, the water absorption of aggregate must be considered when designing the concrete mix proportion. Furthermore, coral aggregate has a high porosity, which may cause its water absorption to be different from that of ordinary aggregate. Therefore, it is necessary to clarify its water absorption. In accordance with the GB/T 17431.2-2010 standard , dry cortion (2) .The concrete shall meet the strength requirements to ensure the safety of the structure. In addition, it shall have good workability to facilitate transportation and construction. The physical and mechanical properties of the coral aggregates differed significantly from those of natural aggregates. Therefore, the workability and mechanical properties of seawater and sea sand concrete with coral aggregates differed significantly from those of seawater and sea sand concrete with natural aggregates. To investigate the effect of superfine cement modification on the coral aggregate concrete, modified coral aggregate concrete was prepared by replacing natural coarse aggregates with coral aggregates at replacement rates of 0%, 25%, 50%, 75%, and 100% by volume. There were three specimens in each aggregate replacement rate. The effects of the modification and replacement rate on the workability of coral aggregate seawater sea sand concrete were analysed. The mix ratio of the concrete is shown in When preparing concrete, the water content of the aggregate affects the water and aggregate consumption of concrete. To ensure the workability and strength of concrete, the water absorption of the aggregate should be considered when designing the mix proportion. The surface of the modified coral aggregates  formed ar) of the aggregates at each W/C was greater than that before modification for curing times of 3 and 7 d. This is owing to the insufficient strength enhancement of the cement slurry encapsulating the aggregates in a short duration. The cement slurry was susceptible to breakage under the pressure of the testing machine and fine particles were filtered using a 2.5 mm sieve, which resulted in an increase in Cr. r of the modified coral aggregates with different curing times. When the W/C of the slurry was 1.0 and 1.25, a dense slurry protective layer was formed on the surface of the aggregate; thus, the aggregate strength increased significantly after 14 and 28 d of curing. After 28 days of curing, the Cr of the aggregates with W/C of 1.0 was decreased by 21.98%. However, when the W/C was 1.5 and 2.0, the Cr of the coral aggregates decreased slightly with the increase of curing time. the Cr variation range of aggregate with W/C of 2.0 was within 4.43%. This may be due to the extremely high W/C of the superfine cement slurry and the inadequate slurry attached to and absorbed into the aggregate. In addition, a slurry with a high W/C cannot solidify for a long time, thus causing the slurry to be lost easily during the curing process; consequently, the formation of a compact slurry protective layer on the surface of the aggregate is hindered. Owing to these reasons, the Cr of the aggregates did not differ significantly from that before modification even at curing age of 14 and 28 d. The experimental results suggest that the slurry W/C should not be less than 1.25. Additionally, the modified aggregate must be maintained for 28 d, and until the strength of the slurry on the aggregate surface develops to a certain extent, it cannot be used for pouring concrete. The Cr of different types of aggregates was compared The water absorption of the modified coral aggregates increased with the slurry W/C. When the W/C was less than 1.25, the variation in the water absorption rate was not apparent; when the W/C exceeded 1.25, the slurry was overly thin, which prevented the formation of a slurry shell on the surface of the coral aggregate; consequently, the water absorption increased significantly with the W/C. After the coral aggregates were modified by superfine cement slurry, the water absorption of the aggregate reduced significantly, and the coral aggregate reached the saturated surface dry state after soaking for 1 h.(2)The Cr of the modified coral aggregate was higher than that of the unmodified coral aggregate when the curing time was shorter. When the W/C of the cement slurry exceeded 1.25, the Cr of the modified coral aggregate started to be lower than that of the unmodified coral aggregate after 7 d of curing and then decreased significantly as the curing time increased. A slurry with a W/C greater than 1.25 could not be solidified for a long time; hence, a compact slurry protective layer could not be formed on the aggregate surface. The Cr of the aggregates did not change significantly as curing progressed.(3)As the coral aggregate replacement rate increased, the slump and expansion of the concrete increased; meanwhile, at the same replacement rate, the slump and expansion of the modified coral concrete were significantly lower than those before modification. The slump and expansion of the modified concrete decreased by approximately 16.14% and 14.97% at 100% replacement rate, respectively. The dense slurry shell formed on the surface of the modified aggregate significantly reduced the water absorption and discharge effects of the coral aggregates, and the water secretion rate of the modified concrete was 47.4% lower compared with that before the modification.(4)After the axial compression failure, the gravel aggregate concrete, coral aggregate concrete, and modified coral aggregate concrete exhibited damage along the diagonal direction of the specimens. Compared with the gravel aggregate concrete, the coral aggregate concrete showed more vertical cracks. The axial compressive strength of the coral aggregate concrete was approximately 60% that of the gravel aggregate concrete. The effect of superfine cement modification on improving the compressive properties of the coral aggregate concrete was insignificant.(5)Based on the test results, it is suggested that the W/C of superfine cement shall be 1.25. The coral aggregate shall be cured for not less than 7 days after modification, and the soaking time of the modified coral aggregate shall not be less than 1 h.In this study, superfine cement was used to modify coral aggregates, and the physical and mechanical properties of modified coral aggregates were experimentally investigated. Subsequently, the effect of superfine cement modification on the workability and strength of coral aggregate concrete was investigated. The main results obtained were as follows:


Surgical site infection is a common complication after surgery. Periprocedural antibiotics are necessary to prescribe for preventing or treating infections. The present study aimed to explore the effect of intravenous antibiotics on gut microbiota and menaquinone biosynthesis in patients, especially in elderly patients undergoing cardiac surgery.A total of 388 fecal samples were collected from 154 cardiac surgery patients. The V3–V4 hypervariable region of the bacterial 16S rRNA gene was amplified and sequenced on a MiSeq PE300. The gut microbiota diversity of samples was analyzed in terms of α- and β-diversity at the OTU level. The different groups were classified according to antibiotics in combinations and single antibiotics. PICRUSt2 was used for preliminary prediction of the gut microbiota function for menaquinone biosynthesis.The intravenously administered antibiotics which are excreted via bile represents the main antibiotics that could disturb the gut microbiota’s composition in cardiac surgery patients, especially for elderly patients. The effect of antibiotics on gut microbiota is produced after antibiotics treatments over one week. The recovery of gut microbiota to the state of pre-antibiotics may require over two weeks of antibiotics withdrawal. Sex factor doesn’t represent as an influencer in gut microbiota composition. Long-term use of cefoperazone-sulbactam may affect coagulation function.The composition of the gut microbiota had a significant change post-intravenous antibiotics treatment in cardiac surgery patients. The richness and diversity of gut microbiota are increased in elderly patients. Infections are the most common noncardiac complications observed after cardiac surgery . Surgicavia the biliary tract and reaches the intestine to influence gut bacteria. Few studies have evaluated the effect of combined antibiotics on gut bacteria in clinical practice. It has been demonstrated that antibiotic use is associated with neurological disorders that range from anxiety and panic attacks to major depression, psychosis, and delirium in humans , imipenem cilastatin (tienam), meropenem, levofloxacin, moxifloxacin, ciprofloxacin, vancomycin, teicoplanin, tigecycline, ticarcillin-clavulanate, piperacillin-tazobactam, and penicillin. The regimen of combined antibiotics included: sulperazone combined with quinolones  or glycopeptides ; carbapenems  combined with quinolones, glycopeptides or tigecycline, etc.Fecal samples of patients were collected to analyze the composition of the gut microbiota. The time of fecal sample collection was set as: before antibiotics administration (pre-antibiotic group), antibiotics administration over 7 days (post-antibiotic group), and antibiotics withdrawal over 7 days  for cardiac patients.In order to evaluate the stability of fecal samples at room temperature, fecal samples by three healthy volunteers were kept at room temperature for 0, 2, 4, and 6 h after defecation.All fecal samples were collected into a sterile tube  and then stored at -80°C until further analysis.® 9700 thermocycler .Bacterial genomic DNA was extracted from fecal samples using a genomic DNA purification kit  following the manufacturer’s protocol. The V3–V4 hypervariable region of the bacterial 16S rRNA gene was amplified by polymerase chain reaction (PCR) using the primer pairs: 338F, 5’-ACTCCTACGGGAGGCAGCAG-3’, and 806R, 5’-GGACTACHVGGGTWTCTAAT-3’. PCR reaction system included: 4μL 5×fastpfu buffer, 2μL 2.5 mM deoxyribonucleotide triphosphates (dNTPs), 0.8μL 5μM primer, 0.4μL fastpfu polymerase, 0.2μL bovine serum albumin (BSA) and 10 ng template DNA. The remaining volume would be supplemented with purified water up to 20µL. The PCR cycling conditions were as follows: 3 min at 95°C; 27 cycles of the 30s at 95°C, 30s at 55°C, and 45s at 72°C; and a final extension step at 72°C for 10min. PCR was conducted in triplicate for each sample using an ABI GeneAmpThe PCR product was extracted from a 2% agarose gel and purified using the AxyPrep DNA gel extraction kit  according to the manufacturer’s protocol and quantified using a Quantus™ fluorometer . Purified PCR product amplicons were pooled in equimolar amounts and paired-end sequenced on MiSeq PE300  according to the standard protocols developed by Majorbio Bio-Pharm Technology Co. Ltd. .The raw 16S rRNA gene sequencing reads were demultiplexed, quality-filtered by FASTP (version 0.19.6) , and merFirstly, the data was divided into different groups before analysis. The different groups included the classification according to antibiotics (antibiotic treatment), single antibiotic (such as cefuroxime), and replacement antibiotic . The latter two groups were uniformly classified as a single antibiotic group because patients were also prescribed a single antibiotic for the replacement antibiotic group when fecal samples were collected. The difference in gut microbiota was also analyzed between the elderly and the non-elderly (younger) and between the sexes. Elderly was defined as age ≥60 years, and non-elderly was defined as age< 60 years in the present study.α- and β-diversity at the OTU level. The indexes of Sobs and Chao were used to reflect community richness for α-diversity. The indexes of Shannon and Simpson were used to reflect community diversity for α-diversity. The index of Coverage was used to reflect community coverage. PCoA  was used for β-diversity analysis, and Bray-Curtis and Anosim were chosen for the statistical test. The distribution proportion of dominant bacteria in each group of samples and the distribution proportion of each dominant bacteria in different groups were reflected at the genus level by a Circos graph.The gut microbiota diversity of samples was analyzed in terms of Mann–Whitney U test was used as a statistical test method for α-diversity indexes for the antibiotics group by GraphPad (version 8.0). Wilcoxon signed-rank test was used as a statistical test method for α-diversity indexes for single antibiotic and replacement antibiotic by GraphPad (version 8.0).Mann–Whitney U test at the genus level in the antibiotics group. The differences in gut microbiota for the top 20 bacterial species were compared between the pre-antibiotic and post-antibiotic groups by Wilcoxon signed-rank test in a single antibiotic group. Then, the present study further analyzed the effect of the days of antibiotics administration and withdrawal on gut microbiota at the genus level by the Wilcoxon signed-rank test, and this analysis also focused on the top 20 bacterial species in the antibiotics group.The differences in gut microbiota for the top 20 bacterial species which was the relative abundance of bacterial species ranked in the first 20 were compared between the pre-antibiotic and post-antibiotic groups, and between the pre-antibiotic and withdrawal-antibiotic groups by www.genome.jp/pathway/map00130+K05357) was the concern in the present study.PICRUSt2 (phylogenetic investigation of communities by reconstruction of unobserved states) was used to preliminarily predict the functioning of gut microbiota based on the KEGG (Kyoto encyclopedia of genes and genomes) database. Menaquinone biosynthesis by gut microbiota  for the diversity and functioning of gut microbiota.All data analyzing were performed on the free online platform of the Majorbio Cloud Platform . Sobs and Chao indexes indicated no significant difference between the post-antibiotic and withdrawal-antibiotic groups. However, Shannon and Simpson’s indexes revealed a significant difference between the post-antibiotic and withdrawal-antibiotic groups. These results indicate that the richness and diversity of gut microbiota are decreased post antibiotics administration which is quite predictable. When antibiotics are withdrawn, the same level of richness may not recover, but diversity has some recovery. However, the diversity could not recover to the same or similar level of pre-antibiotic. All coverage indexes of gut microbiota community coverage were over 0.99.The community richness and diversity are shown in β-diversity of gut microbiota, and β-diversity could recover when antibiotics are withdrawn over 7 days. The distribution of dominant bacteria in each group sample is shown in Bacteroides, Enterococcus, Blautia, Faecalibacterium, Lachnoclostridium, etc.PCoA showed that post-antibiotic group had a significant difference from pre-antibiotic and withdrawal-antibiotic groups at the OTU levels in the antibiotics group Figure 2Enterococcus and Lactobacillus increased  and over 7 days  according to the days of antibiotics use. Compared with the pre-antibiotic group, the relative abundance of 7 bacterial genera had significantly changed when antibiotics were administrated for 7 days  and more than 14 days  according to the days of withdrawal. Compared with the pre-antibiotic group, the relative abundance of 11 bacterial genera had also been significantly different when antibiotics were withdrawn for 7-14 days  and had no effect on diversity .The community richness and diversity are shown in β-diversity , and kept defecation samples for 2, 4, and 6 hours, respectively at room temperature. All fecal samples except 0-hour related samples were stored at room temperature before putting into a -80°C refrigerator. The result demonstrated that the broader composition of the gut microbiota had no significant change when the fecal sample was stored at room temperature even for 6 hours. It was previously reported that fecal samples should be transferred to the laboratory within 24 h after defecation when stored at room temperature or within 3 days when stored in a refrigerated condition . These rβ-lactam, quinolone, glycopeptide, and lincosamide drugs, were prescribed for patients in the present study. The present study explored the effect of intravenous antibiotics on gut microbiota. The results showed intravenous antibiotics could perturb the composition of the gut microbiota in cardiac surgery patients. The community richness and diversity were significantly decreased when antibiotics were administered over 7 days. This suggests that intravenous antibiotic treatments drastically changed the microbial community. The bacterial community in the intestinal tract is in an ideal equilibrium state, so the disappearance of one “keystone” species may have a great impact on other species. Hence, the effects of antibiotics on the gut microbiota may extend beyond the antibiotic-sensitive bacterial species  is removed xcretion . 4 patiexcretion , and appxcretion . These rα-diversity which included Chao, Sobs, and Shannon index was stable during adulthood and then increased in the elderly  and menaquinone . VK1 is found exclusively in plants, while VK2 (except MK-4) is mainly produced by a series of congeners synthesized by gram-positive bacteria in the human gastrointestinal tract (Bacteroides, Prevotella, Bifidobacterium, Eubacterium lentum, Enterobacter, Veillonella, Lactococcus lactis, Leuconostoc, Streptococcus, Staphylococcus aureus, Escherichia, Klebsiella, and Propionibacteria (Bacteroides and Prevotella have significantly reduced post-sulperazone treatment (The physiological function of gut microbiota was attempted to merely explore the sulperazone treatment in the present study because other single antibiotics did not affect both al tract . The humbacteria . Changesreatment .There were also some limitations of the present study. The composition of the gut microbiota is different in different gastrointestinal tract sites. Fecal samples were detected to learn about the gut microbiota in clinical practice, which merely reflected the composition of gut microbiota in the sigmoid colon lumen for patients . Patientvia bile could disturb the composition of the gut microbiota. The effect of antibiotics on gut microbiota is produced by antibiotics treatments over one week. The recovery of gut microbiota to the state of pre-antibiotics may require over two weeks of antibiotics withdrawal. The richness and diversity of gut microbiota are more in the elderly when compared with other age groups. There is no difference in gut microbiota composition between the sexes. Long-term use of sulperazone may affect coagulation function.In conclusion, the intravenously administered antibiotics which are excreted The partial data presented in the study are deposited in the Sequence Read Archive repository, BioProject ID: PRJNA923595. Further inquiries can be directed to the corresponding author/s.The studies involving human participants were reviewed and approved by the health authority ethics committee of the First Affiliated Hospital of Soochow University. The patients/participants provided their written informed consent to participate in this study.LX, ZS, BS, and LM designed the study. LX, YD, and QQ performed the study. LX analyzed the data and drafted the manuscript. YD, QQ, LL, XD, and YaZ interpreted the data. YiZ, KL, RS, KS, AD, BS, and LM reviewed the manuscript. All authors contributed to the article and approved the submitted version.


Patients with pneumonia and upper respiratory tract infection were 15.9  and 2  times more likely to be prescribed antibiotics, respectively. Conclusions: We, therefore, report high rates of antibiotic prescriptions, poor adherence to standard treatment guidelines and high levels of antibiotic prescribing practices among prescribers with a diploma in clinical medicine.Background: Accelerated by the misuse or overuse of antibiotics, antibiotic resistance remains a global public health threat. We report the prevalence and predictors of antibiotic prescriptions in primary healthcare facilities in Dodoma, Tanzania. Methods: This retrospective cross-sectional study by medical records review was conducted in the Dodoma region, Central Tanzania. Results: In this study, children < 5 years accounted for over 45% (474/1021) of the patients consulted. The majority, 76.3% (779/1021), of consultations had an antibiotic prescribed; amoxicillin and cotrimoxazole were the most prescribed. Over 98% (766/779) of the antibiotics prescribed were on the National Essential Medicines List, but only 45% (429/779) of the antibiotic prescriptions adhered to the Standard Treatment Guidelines. The prescribing of antibiotics by clinical officers was almost 2.55 times higher than that among medical doctors (Odds Ratio (OR) = 2.546; 95% Confidence Interval (CI): 1.359, 4.769;  Antibiotic resistance is one of the greatest public health issues threatening the prognosis of bacterial infections globally . It deveIn low-income countries, problems such as poor sanitation and waste disposal control programs, lack of clean and safe water, unregulated community prescribing and sale of antibiotics and an ever-increasing human population are among the key factors fueling the spread of antibiotic-resistant pathogens . In 2019The use of antibiotics in clinical practice is mainly manifested by both the transactions of these agents in community drug shops and the antibiotic prescribing practices by healthcare workers across the entire healthcare spectrum ,7,8. In Antibiotic-prescribing practices in primary healthcare facilities in Tanzania largely rely on clinical examination and patients’ medical history rather than microbiological evaluation ; this inThe Tanzanian National Action Plan on AMR (NAP–AMR) was launched in 2017 with the aim of reducing the burden of AMR in the country and contributing to the AMR global data . Among tThe prescribing of antibiotics by healthcare practitioners across the entire healthcare referral hierarchy has to abide by the Standard Treatment Guidelines (STG) and the National Essential Medicines List (NEMLIT), prepared and updated every three years by the Ministry of Health . While mThis was a retrospective cross-sectional study by medical records review conducted in two districts of the Dodoma region in Tanzania. The two districts were randomly selected from a group of rural districts and urban districts of the Dodoma region to represent the rural and urban settings, respectively. Dodoma City Council houses the central business district of Dodoma City and is an urban setting. Chemba District Council represents the rural setting. Dodoma City Council (urban) has a population size of approximately 460,000, and Chemba District Council  has a population size of approximately 250,000 . Dodoma The sampling frame of this study was primary healthcare facilities in the two districts. Data collection was based on the WHO indicators of antibiotic prescribing  and the p) of 50% with 95% confidence, and the degree of precision employed was 5%, with a design effect of 1 and a response rate of 90% [The sample size calculation was calculated based on the unknown prevalence  digital questionnaire. The questionnaire was adopted from a similar study  and modiAll records from prescription books in primary healthcare facilities recorded from January 2020 to December 2020 were deemed relevant; however, records from maternity clinics were excluded.Antibiotic prescription was an outcome variable in this study, and other independent variables included diagnosis as well as social and demographic characteristics. SAS version 9.4 was used for data analysis, and the significance of all statistical tests was set at the 5% level of significance. Basic descriptive statistics, such as frequency and percentages, were evaluated and used to describe baseline characteristics. A chi-square test of association was also employed to test the association of diseases diagnosed and the status of antibiotic prescription.The outcome variable had two responses (Yes/No); thus, a binary logistic regression model was used to determine factors associated with prescribing antibiotics.The results of the model are presented in the form of regression parameter estimates and estimated odds ratios (ORs). The estimated ORs, determined by taking the exponent of the regression parameter estimates, show the increase or decrease in the likelihood of the outcome at a given level of the independent variable compared to those in the reference category. The estimate of OR > 1 indicates that the likelihood of receiving antibiotics at a given level of the independent variable is greater than that of the reference category. Similarly, the estimate of OR < 1 specifies that the chance of receiving antibiotics at a given level of the independent variable is less than that for the reference category.Of the 1021 retrospective prescribing consultations in this study, 61.8% (631/1021) were from Dodoma City Council. The majority  of the consultations were those recorded from public primary healthcare facilities, and 5.88% accounted for consultations recorded in private and other faith-based primary healthcare facilities. Children under the age of five accounted for over 45% (474/1021) of all the consultations. There were more consultations involving females  than those involving males. Medical doctors , Clinical officers , and medical assistants  were the prescribers recorded in this current study. The majority  of the antibiotic prescriptions were made by prescribers with a diploma in clinical medicine .The most common empirical diagnoses were upper respiratory tract infections (URTIs), urinary tract infections (UTIs) and diarrhoea, which accounted for 30.3%, 12.1% and 7.7%, respectively .Of the 1021 prescribing consultations recorded in this study, 76.3% (779/1021) had an antibiotic prescribed, with amoxicillin and cotrimoxazole accounting for over 60% of all the prescribed antibiotics .access’ category as per the WHO AWaRe  antibiotic classification system as classified in the Tanzanian Standard Treatment Guidelines (STG) [The majority  of the antibiotics prescribed were listed on the National Essential Medicines List (NEMLIT)  and werees (STG) . About 4p value = 0.0382) than that among female patients (73.3%). The most common diagnoses for which antibiotics were prescribed included urinary tract infection (UTI) , upper respiratory infection , pneumonia , diarrhea , skin diseases  and pelvic inflammatory diseases (PIDs)   of patients diagnosed with malaria were prescribed antibiotics.The proportions of antibiotic prescriptions among male patients (78.8%) were significantly higher (= 0.101) . Neverthp = 0.0386). Compared to medical doctors (degree in medicine), there was an almost twofold increase  in the odds of antibiotic prescriptions among clinical officers . Patients diagnosed with upper respiratory tract infection and pneumonia were 1.913 times  and 16.678 times  more likely to be prescribed antibiotics, respectively, than patients who did not have these conditions. Patients with malaria, skin diseases and other disease conditions were 66% , 65.9%  and 31.4%  less likely to be prescribed antibiotics, respectively . Patients with pneumonia and upper respiratory tract infection were 16  and 1.709  times more likely to be prescribed antibiotics, respectively. Patients with malaria and skin diseases were 70.7%  and 67.9%  less likely to be prescribed antibiotics compared those with other diseases  and urban  districts had an antibiotic prescribed. The observation in our current study is higher than that reported in Cameroon, where 36.7% of the consultations recorded in primary healthcare were prescribed antibiotics . AdditioThis study reports low adherence 55%; 429/779) to standard treatment guidelines (STG) among primary healthcare prescribers. More than half  of the malaria cases in this study were prescribed antibiotics (cotrimoxazole and amoxicillin) against STG. Additionally, even though the Tanzanian STG recommends that PID be treated with a combination of antibiotics, 60% of the PID cases in this study were not prescribed antibiotics. This is supported by the previous study in primary healthcare facilities in Dodoma, Tanzania, where 25% of malaria cases were also prescribed antibiotics against STG . Adminis9/779 to In this current study, the odds of antibiotic prescriptions by the clinical officers  were almost three times higher than those of medical doctors . In a study on the use of antibiotics for cough and/or diarrhoea in northern Tanzania, clinical officers were also among the prescribers associated with excessive and inappropriate antibiotic prescriptions for nausea, vomiting and diarrheal conditions . ClinicaAmong the medical conditions recorded, symptomatic pneumonia was an important predictor for antibiotic prescriptions in this study. Similar findings have been reported in Uganda , where tOver half  of patients with dermatological conditions in this study were prescribed systemic antibiotics, being a 66.9% decrease in the odds of systemic antibiotic prescriptions as compared to patients with other disease conditions. The observation in this current study is lower than that reported in a study elsewhere on the prescription of antibiotics among dermatology patients, where the odds of empiric antibiotic prescriptions were almost five times higher compared to all others . In anotUpper respiratory infection (URTI) was another empirically diagnosed condition in the current study, and antibiotic prescriptions among patients with URTI were almost double those with other disease conditions. This is comparatively higher than that in another study in Indonesia on the use of antibiotics in URTI, where 44% of the cases attended were prescribed antibiotics ; in anotThe limitation of this study is that the observations do not account for the accuracy of the written diagnosis and how patients’ history and physical examinations were recorded. However, the study gives a clue on the general practices of prescribers in low-level healthcare facility settings and provides information on which interventions can be made to improve their antibiotic prescribing skills in a more concerted effort against both the urgency and spread of antibiotic resistance.In this study, we report high rates of antibiotic prescriptions and poor adherence to Standard Treatment Guidelines (STG) among prescribers in primary healthcare facilities. Prescribers with a diploma in clinical medicine were much more likely to prescribe antibiotics. There was an increase in the odds of antibiotic prescriptions among patients empirically diagnosed with urinary tract infections (UTIs), upper respiratory illness (URTI) and pneumonia.


The issue of brittleness and low post-peak load energy associated with the plain HSC led to the development of fiber-reinforced concrete (FRC) by using discrete fiber filaments in the plain matrix. Due to the high environmental impact of industrial fibers and plasticizers, FRC development is ecologically challenged. Sustainability issues demand the application of eco-friendly development of FRC. This study is aimed at the evaluation of coir as a fiber-reinforcement material in HSC, with the incorporation of silica fume as a partial replacement of cement. For this purpose, a total of 12 concrete mixes were produced by using three different doses of coir  with silica fume . The examined parameters include compressive strength, shear strength, splitting tensile strength, ultrasonic pulse velocity, water absorption, and chloride ion permeability. The scanning electron microscopy (SEM) technique was adopted to observe the microstructure of the CF-reinforced concrete. The results revealed that due to the CF addition, the compressive strength of HSC reduces notably; however, the splitting tensile strength and shear strength experienced notable improvements. At the combined incorporation of 1.5% CF with 5% silica fume, the splitting tensile strength and shear strength of the concrete experienced improvements of 47% and 70%, respectively, compared to that of the control mix. The CF incorporation is detrimental to the imperviousness of concrete. The combined incorporation of CF and silica fume is recommended to minimize the negative effects of CF on the permeability resistance of concrete. The SEM results revealed that CF underwent a minor shrinkage with the age. In recent years, applications of HSC have risen in the construction sector due to several customized advantages as compared to conventional plain concrete, such as improved workability, higher compressive strength, and excellent durability characteristics. These properties are attained by utilizing appropriate amounts of supplementary cementitious materials (SCMs) and water-reducing admixtures at a low water to binder ratio. The use of waste SCMs has significantly increased in HSC development in recent years as a consequence of increased awareness about environmental issues. Incorporating waste SCMs, e.g., silica fume, ground steel slag, waste glass powder, and fly ash, can substantially reduce the cement content of concrete ,2,3,4, aSilica fume is a by-product of ferro–silicon alloys owing to its extremely fine particle size, and it contributes to the strength and durability of concrete due to its high pozzolanic potential . The porTo supplement the tensile strength and toughness of HSC and to control the cracks, fibers have proven to be very encouraging ,10. FibeGenerally, industrial fibers, such as steel fibers, glass fibers, polypropylene fibers, polyvinyl alcohol fibers, basalt fibers, and carbon fibers, have been used for the development of FRC ,19,20,21There are several inexpensive and eco-friendly alternatives for industrial fibers. These include recycled waste fibers and natural fibers. FRC can be developed with waste fibers derived from the tire and polymer scrapes. The carbon footprint of processing recycled steel fibers from scrap tires is 20 times smaller than that of industrial steel fiber . RecycleCompared to most natural fibers, coir is generated as a waste product of coconut fruits. The global annual production of coconut is around 60 million tons . GeneralUntil now, the feasibility of coir as a fiber reinforcement for cementitious materials has been examined by several researchers ,42,43,44Khan and Ali  reportedStudies relevant to the durability properties are still very few. Hwang  studied An overview of the existing literature demonstrated that fewer investigations ,52 have 2/kg. Owing to its extremely small particle size compared to that of the cement, silica fume offers a filling effect and a high pozzolanic potential with OPC. Granulometry of silica fume and OPC is shown in Ordinary Portland cement (OPC) was used as the main binder for the preparation of all mixtures. This general-purpose cement complies with ASTM C150 , having For fine aggregate, siliceous sand was used. This sand was picked from the Lawrancepur quarry in the Northern Punjab region  of Pakistan . Owing to well-gradation, this sand is recommended for high-performance concrete development. Dolomitic sandstone was used as coarse aggregates. This high-quality aggregate was obtained from the Kirana Hills quarry situated in the central Punjab region of Pakistan  was used as coarse aggregate. For the development of high-performance concrete, the maximum aggregate size of the coarse aggregate was kept smaller than 12.5 mm. The characteristics of both aggregates are provided in Tap water of concrete laboratory, free from organic matters, was used for the mixing and curing of all batches. The water has a pH of 7.9. Whereas, to control the workability of CF-reinforced mixtures, Sika Viscocrete 3110 was used. This belongs to the polycarboxylate-based 3rd generation of water-reducers. It complies with the ASTM C494  as a typCoir was extracted from waste coconut husks and chopped manually into lengths of 50 mm. This length of coir was selected based on its optimum effect on the mechanical performance reported in the literature ,45. The A total of twelve concrete mixes were designed in this study to examine the singular and combined effects of silica fume and coir on the properties of HSC, as shown in All mixtures were prepared in a rapid-speed mechanical mixer equipped with a speed regulator. Firstly, the binding materials and aggregates were mixed together for 2 min at a rotary speed of 30 rpm. Then, the required amount of water and plasticizer was added to the dry mixture, and mixing was done at the speed of 60 rpm for 3 min. In the case of plain concrete mixtures, the freshly mixed concrete was tested for a slump and proceeded for casting. Whereas, in the case of fiber-reinforced mixes, the coir was gradually added to the fresh concrete in the running mixer to ensure uniform dispersion of fibers. The mixing speed during the addition of coir was increased to 80 rpm and this stage lasted for about 2 min. The high-speed mixing ensured a thorough mixing of coir filaments without accumulation. After completion of mixing, the samples were tested for slump testing and subsequently for casting. The schematic representation of the mixing procedure is illustrated in Bs) test was conducted on the specimens of 150 mm × 150 mm × 150 mm dimensions, as shown in the schematic setup in Bs is calculated using Equation (1). Where uP is the peak load (kN), As = area of shear plane. For the determination of the splitting tensile strength, 100 mm × 200 mm cylindrical samples were tested in a CONTROLS Universal Testing Machine as per ASTM C496 [A CONTROLS Universal Testing Machine of 3000 kN capacity was used to perform the compressive strength test on 100 mm × 100 mm × 100 mm cubical samples according to BS: EN 12390 . The comSTM C496 . The she3). When the nitrate solution reacted with the penetrated chlorides, it left silver-colored precipitates forming silver chloride (AgCl), also indicating the penetration depth of chloride ions, as shown in Ultrasonic pulse velocity test was performed on 100 mm cubical samples of all mixes following ASTM C597  to assesThe effect of the coir addition with and without silica fume on the compressive strength of HSC is shown in The incorporation of coir fibers led to notable reductions in the compressive strength of HSC. Compressive strength was reduced by about 4%, 15%, and 17%, respectively, due to the incorporation of 1%, 1.5%, and 2% coir. These reductions can be blamed on the two factors: (1) the density of coir is considerably smaller compared to the concrete and binder matrix; (2) fiber accumulation may increase the porosity of concrete. Fiber-reinforcement is not as effective in compression as it is in splitting tensile strength and flexural strength. Similar to coir, industrial polypropylene and polyvinyl fibers, due to their lower density, have also exhibited negative effects on the compressive strength ,75.3) is not sensitive to the incorporation of low-density coir content, thus the confinement effect of fibers demonstrated an increase in compressive strength. It is also postulated that the HSC family is highly sensitive to the strength reduction owing to the coir addition as compared to lower strength class families, i.e., MSC, NSC, lightweight concrete, etc. Silica fume controlled some of the negative effects of coir addition on the compressive strength of HSC. This could be credited to the strengthening of the concrete matrix owing to the pozzolanic reactions. Silica fume may also solidify the bond between the fibers and concrete matrix.Low-density fibers may also act as the voids in concrete, such that increasing the coir content is anticipated to increase the porosity of concrete. Previous studies have confirmed both positive and negative effects of coir on the compressive strength ,76. The The effect of varying contents of coir and silica fume on the bi-surface shear strength of HSC is illustrated in The incorporation of coir proved to be extremely useful in enhancing the shear strength of HSC. The shear strength of SF0/CF0 or control mix was increased by 39.3%, 59%, and 45.5%, respectively, at 1%, 1.5%, and 2% contents of coir. As coir filaments possess high tensile strength, these can effectively supplement the shear resistance of the plain HSC matrix. Similar to industrial fibers, i.e., glass, polypropylene, and steel fibers ,80, coirThe shear strength of HSC was improved by more than 70% (w.r.t SF0/CF0), due to the incorporation of 5% silica fume and 1.5% coir. The results of the mixes made with the combined incorporation of silica fume and coir demonstrated that the benefits of coir and silica fume can be combined to obtain a higher shear strength. However, synergistic behavior was not observed due to the combined incorporation of coir and silica fume.c) and bi-surface shear strength (Bs) is shown in Bs with fc0.5 was derived as the function of coir percentage (CP). As the ratio between fc and Bs  for plain and coir-reinforced mixes are significantly different, the relationship between these two parameters was derived as the function of CP. The value of Bs/fc0.5 also indicates the ductility of concrete. The increase in the Bs/fc0.5 value with the rising CP implies an increase in ductility. A strong linear correlation is found between CP and Bs/fc0.5, as the coefficient of the determination value is 0.827. Thus, using fc, the value of Bs can be predicted with good accuracy at a required CP.The relationship between the compressive strength  within a concrete mass is also found to negatively influence the UPV value . The UPV2 > 0.85).The incorporation of low-density synthetic fibers has also demonstrated a minor decline in the UPV of concrete . Das et The durability of concrete structures is directly affected by the transport of water into the microstructure of concrete. The water absorption capacity indicates the permeable porosity of concrete. The permeable pore volume in concrete is affected by the connectivity and tortuosity of pores inside the concrete media. A water absorption test was conducted on the samples cured for 28 days. The effect of the different contents of silica fume and coir on the water absorption capacity of concrete is shown in It was observed that the increase in silica fume content from 0% to 10% reduced the water absorption capacity of HSC by 32%. The decrease in the water absorption is due to the decline in the connectivity of pores. Silica fume refines the size of pores and increases the tortuosity between pore connections. This ultimately reduces and slows the absorption of water into the microstructure of concrete. Furthermore, the reaction between free portlandite and silica generates dense CSH gel to enhance the impenetrability of concrete. The water absorption capacity of concrete was increased by 5%, 11%, and 33% due to the incorporation of 1%, 1.5%, and 2% coir by wt. of binder, respectively. Fiber reinforcement is known to increase the permeability and absorption of concrete due to the increased interaction between pores ,90. AlthOwing to the positive effect of silica fume, the water absorption of coir-reinforced mixes is significantly controlled. All mixes containing silica fume with or without coir fibers exhibited water absorption capacity more than that of the plain HSC. The growth of more CSH gel due to a pozzolanic reaction can reduce the gap between the fiber filaments and matrix, consequently leading to the restriction of water transport.The permeability of chloride ions in concrete causes the corrosion of steel rebars in reinforced concrete structures. Thus, it is convenient to study the chloride ion permeability of concrete families for the assessment of durability. The permeability of chloride ions into concrete is highly influenced by similar factors that influence water permeability, i.e., pore size, pore connectivity, etc. The effect of varying coir and silica fume contents on the chloride ion penetration depth (CPD) of HSC concrete is shown in It was noticed that the incorporation of coir increased the CPD value. An increase of 66% in the CPD was observed when 2% coir reinforcement was incorporated into the plain HSC. As coir reinforcement makes the HSC more permeable, it allows a deeper penetration of the chloride-bearing solution into the concrete. Unlike coir reinforcement, silica fume incorporation drastically reduced the CPD. The incorporation of 5% and 10% silica fume by mass of cement reduced the CPD by 50% and 63%, respectively. The CPD value reduces, as the porosity and permeability of concrete are reduced by the silica fume incorporation. The literature ,91 has eSEM images of coir reinforcement in the binder paste were analyzed, see The coir reinforcement demonstrated a negative effect on the compressive strength of HSC. Silica fume helped in controlling the negative effect of coir on the compressive strength of concrete.The shear strength of HSC improved drastically with the addition of both silica fume and coir. The maximum increase of about 45.5% in shear strength of HSC was observed upon the addition of 2% coir without silica fume. With 5% silica fume and 1.5% coir, the shear strength of HSC was increased by 70% compared to that of the plain HSC.The splitting tensile strength demonstrated a nominal change with the varying contents of coir. A maximum splitting tensile strength, about 6% higher than that of the plain HSC, was observed at 1% coir content. Higher contents of coir negatively affected the splitting tensile strength.The addition of silica fume with coir exhibited synergistic behavior in the results of splitting tensile strength, as silica fume improves the bond strength of fiber filaments by strengthening the binder matrix.The incorporation of low-density coir in the plain concrete reduces the UPV. However, CF-reinforced mixes containing silica fume exhibited higher UPV values compared to those without silica fume.The incorporation of coir drastically increased the water absorption and CPD in plain HSC. Silica fume controlled the negative effects of coir incorporation on the permeability-resistance of HSC.SEM observations indicate a minor shrinkage in coir filaments, which might have increased pore connectivity. Furthermore, both pullout and breaking types of failures were observed for coir filaments.Based on the results of mechanical performance, 1% coir by wt. of binder can produce higher net gains in tensile and shear strength. For further enhancement of mechanical and durability performance of coir-reinforced HSC, the inclusion of 5% silica fume yields the best results.In this study, the effect of varying contents of coir and silica fume was investigated on the properties of HSC. The following are the main conclusions of this study:


Currently, there is a scientific and practical deficit in new methods of integrated technological and design solutions based on improving the properties of concrete as the primary material that perceives compressive loads, and its joint work with various types of reinforcing rods. A new system using an integrated engineering approach to the design of building structures is proposed, which involves minimizing their cost and weight through numerical simulations and an experimental verification of the operation of reinforcing bars made of various materials in concrete of various densities. The control of the bearing capacity of reinforced building structures on the example of compressed elements is proposed to be carried out using the developed recipe-technological methods at the manufacturing stage. The economic and environmental efficiency of nano modification with the help of production waste and the use of lightweight dispersion-reinforced concrete to obtain such structures was revealed. The most effective concrete formulations showed strength gains ranging from 10% to 34%. Ultimately, this led to an increase in the bearing capacity of the elements up to 30%. The application of such an integrated lean approach will allow saving up to 20% of resources during construction. Outdated technologies in the conditions of intensively growing volumes of buildings and structures being erected are a problem for modern construction, and they require improvement based on a scientific approach. For many decades, including the present, reinforced concrete has remained the main structural material for buildings and structures of various levels of responsibility. Many attempts by modern scientists and engineers to improve concrete technology have been successful; however, until now, the issues of transition to a qualitatively new level of structural composites remain open.-searching for new solutions regarding concrete, from which reinforced concrete structures are built, namely: recipe-technological solutions that meet the latest science and technology criteria;-constructive solutions comprising geometric shapes and reinforcing cages, which are the basis of reinforced concrete and an integral part for the perception of loads, including ultra-high ones;-finally, engineering solutions related to the specific replacement and transition from traditional types of materials and structures to modified components, which are based on fundamentally new approaches in terms of technology, design, and calculations.Some of the most relevant areas in terms of the construction of buildings and structures made of reinforced concrete are the following:In this regard, an analysis of the currently existing solutions in terms of concrete science and the reinforcement of concrete structures is required, as well as an analysis of the types of concrete and reinforcement used in various products, and structures made of heavy concrete, including the possibilities of their combinations, layout, and collaboration.An application of steel elements in concrete is considered in many works, among which ,10,11,12The behavior of Ultra High-Performance Concrete (UHPC) beams was studied using a finite element model that takes into account the response of UHPC and rebar to tensile and compressive stress-strain, the bond between concrete and reinforcing steel, and the effects of work hardening in bars and UHPC. The proposed model was claimed for application in the field of quantifying the contribution of stirrups and concrete to the shear strength of beams to study the possibility of removing transverse reinforcement in UHPC beams .Hybrid fiber reinforced concrete, reinforced with two types of fibers , was studied to create a stress-strain model to predict the strength of steel fiber concrete in the range from 40 to 120 MPa. It was shown that an increase in the content of steel fiber to a certain level, at a constant amount of fiber from polyvinyl alcohol, leads to an increase in stress resistance values .3. It is summarized that the shear capacity increased in concrete beams with steel or basalt fibers. In this case, the type of fracture changed from shear (brittle) to flexural shear (less brittle) [The effect of adding different types of fibers to concrete mixtures on the shear behavior of two-span fiber-reinforced concrete beams with or without shear reinforcement was studied by the authors in . Steel obrittle) . Increasbrittle) ,17. Resebrittle) ,19.The works ,21 contr3 of synthetic fibers of various geometries and shapes. An increase in bending strength up to 13.5%, depending on the type of mixture, and an increase in plasticity were noted. It is summarized that the proposed fiber-reinforced concrete mixtures cannot replace traditional reinforcement as steel rods [Fiber-reinforced concrete is widely used to increase the durability of reinforced structures. The redistribution behavior of bending and shear moments in fiberglass-reinforced and polymer-reinforced (GFRP) continuous concrete beams was studied in . The papeel rods .Modeling and calculation of hollow reinforced concrete elements were considered in ,25. The Textile mortar reinforcement (TRM) of reinforced concrete (RC) columns through the shell, under combined axial and cyclic loads, showed that increasing the length of the shell improves the lateral deformation capacity, and linearly increases the length of the plastic hinge up to a constraint factor of 0.2. Mortars with higher flexural strength resulted in somewhat greater deformation capacity; however, the difference in the compressive strength of the solution did not affect the ultimate capacity for lateral deformation .An increase in strength and deformation characteristics due to the use of polymer rods was considered in ,31,32,33The joint use of experimental and computational methods of high-strength concrete and mortar subjected to a compressive load was reflected in . At a loWorks that studied the modification of concretes with polymers in various dosages, with various sizes of large aggregates, at various sample testing temperatures , and calSummarizing the results of the review and its analysis, it should be noted that the scientific deficit and the practical gap based on it is associated with the applied development of new methods of complex technological and design solutions. They are based, firstly, on improving the properties of concrete as the main material that perceives compression loads and its joint work with various types of reinforcing rods. Focusing on the main principle of design improvement, maximum reduction of the weight and cost of the structure, and at the same time increasing its manufacturability, there is a need to check the compatibility of specific types of concrete of certain classes, and specific types of reinforcing bars made of certain materials with certain specified characteristics.The works studied during the literature review are relevant, but they need to develop the theoretical ideas and practical recommendations received by these authors. In the work of the considered authors, several scientific and applied problems are identified that should be solved. These problems stem from the poor adaptability of traditional building technologies for modern complicated construction conditions. In particular, these problems are concerned with the large weight of buildings, complex engineering geological conditions, and dense urban development. These problems can be effectively solved, and the data already obtained by the authors of the considered works should be developed in the direction of creating new lightweight types of structures with various types of reinforcement in various types of concrete. Such questions have not yet been investigated and are unresolved. Our study aims to address and answer these questions. After a theoretical review of experimental studies and analytical interpretation, the novelty of our work will be the developed integrated approach that will solve these problems.-the formulation of a working hypothesis, development of an experiment plan, and based on a selection of the most significant factors that are based on the analysis, results that affect the bearing capacity of compressed reinforced concrete elements;-conducting large-scale numerical experiments aimed at identifying bottlenecks and points to strengthen solutions in terms of technology and design;-the determination of directions and vectors that can be verified by laboratory-physical experiments;-setting up a physical experiment in a laboratory to confirm a hypothesis in terms of technology;-carrying out a design check of the proposed technological solution and, on that basis, developing a design proposal with justification from the point of view of efficiency on operational and economic grounds.The objectives of the study are:-from the point of view of theory, the study of compatibility and the development of existing ideas about such compatibility concerning various types of materials and their interaction from the point of view of the stress-strain state, and obtaining new knowledge about their joint work. Both stone materials (concretes), metals, and various kinds of composite materials are studied thusly, and the theory and empirical basis for the interactions of various materials in the body of a single composite under a load is developed;-various kinds of experimental data obtained with the help of special calculation programs and numerical experiments were investigated and applied, as well as physically verified and tested;-complex technological and design solutions are presented, combining simplified methods of technological design, applicable, first, for further scientific research in this direction, and second, for the engineering and construction industry in the construction of buildings and structures of a new type.The scientific novelty of the research is:One of the most important parts of the proposed integrated approach is the choice of research methodology. It should be understood that we are dealing with an even greater synergistic effect, which, in our opinion, arises from a simultaneous careful analysis of material science and the design components of the study. In this regard, our methodology is divided into the choice of initial components, recipes and technologies for laboratory physical experiments, as well as the appropriate material, software base, and verified calculation methods from the point of view of numerical experiments; therefore, in the section “Materials and Methods”, it is necessary to provide materials for conducting laboratory physical experiments, and the subsections detailing the methods should not only indicate the methods of testing and research in the conditions of the laboratory of the planned materials, but also the method of conducting numerical experiments using modern software. All this will allow us to obtain the necessary synergistic effect, which takes into account two components: materials science and design.Reinforced concrete columns with a cross section of 400 mm × 400 mm, and a length of 3000 mm, 6000 mm, and 9000 mm, made of class B30 concrete, were chosen as the basic object of study. The subject of the study was the characteristics of the columns depending on the changing technological and design factors.A previously developed composition with micro silica nano-modifier was used and adopted as heavy concrete for the experiments. It allows, using industrial waste, as an additive to heavy concrete, to achieve, first, a denser packing of particles, improving the quality of the structure of concrete, and allowing this concrete to acquire improved mechanical structural characteristics with an increase in the bearing capacity of elements obtained from such a concrete ,44.Samples of heavy concrete with nano-modified micro silica for compression testing are shown in Information about the initial components used in the manufacturing of concrete using a nanomodifier is presented below.When conducting research, we used Portland cement of the CEM 0 52.5N brand , the physical and mechanical characteristics of which are presented in Granite crushed stone  was used as a large dense aggregate, and slag pumice  was used as a porous aggregate. The physical and mechanical characteristics of the aggregate are presented in Quartz sand  was used as a fine aggregate, the physical characteristics of which are presented in In numerical experiments, steel reinforcing bars , and polymer composite reinforcement (PCR) , were used as reinforcing elements. Characteristics of steel reinforcement are presented in Micro silica grade MK-85  was used as a nanomodifying additive in concrete. The granulometric composition of the applied nanomodifier is shown in The micro silica particle size distribution plot shows that most of the particles (more than 80%) have a size of 2 to 40 µm, with the main peak at 20 µm.X-ray phase analysis of micro silica particles is shown in Micro silica  is repreLightweight fiber-reinforced concrete was also studied in accordance with ,48,49,50The calculation was performed using SP 52-101-2003 , SP 63.1−4 m2.The column was designed for central compression according to the formulas  p.6.2.17The plan of the numerical experiment is shown in bR is the design resistance of concrete to axial compression for the limit states of the first group; According to , the limA is the area of all concrete in cross section;Rsc is the resistance of reinforcement to compression;As.tot is the area of all longitudinal reinforcement in the section of the element;φ is the coefficient taken for a long-term load according to Table 6.2 from [6.2 from  dependinThe plan of the physical experiment is shown in For particle size analysis of micro silica, a Microsizer 201C laser particle analyzer  was used in .An X-ray phase analysis (XPA) of micro silica was carried out on an X-ray diffractometer HZG-4C .The concrete mixture was made in a laboratory concrete mixer BL-10 . First, the dry components were mixed for 60 s, then the mixture was mixed with water and mixed until a homogeneous consistency was obtained. The fiber-reinforced concrete mixture was prepared according to the algorithm described in . In the To obtain a lightweight fiber-reinforced concrete, some large and small dense aggregates were replaced by a porous aggregate—slag pumice—the fractions and dosages of which were taken in accordance with Tables 8 and 9 (composition S4) from .The parameters of the composition of the concrete mix were applied similarly to Table 7 from .The composition of heavy concrete nanomodified with micro silica was chosen according to the recommendations .F is the breaking load, N;Compressive strength tests of specimens were carried out in accordance with GOST 10180 “Concretes. Methods for strength were determined using reference specimens”  on an IPA is the area of the working section of the sample, mm2;and α is a scale factor for converting the strength of concrete to the strength of concrete in samples of a basic size and shape .The strength of concrete in a series of samples was determined as the arithmetic mean of the strength of the tested samples in a series of six samples—four samples with the highest strength.3 using the formula:m is the mass of the sample, g;The average density of samples in a state of normal humidity was determined according to GOST 12730.1 “Concretes. Methods of determination of density” . The volV is the sample volume, cm3.The average density of concrete was calculated as the arithmetic mean of the test results for all samples of the series.In total, 2 series of sample cubes of each type of concrete were made and tested (in one series—6 sample cubes). That is, a total of 48 sample cubes of four types of concrete were tested (12 of each type).The microstructure of fiber-reinforced samples was studied using a ZEISS CrossBeam 340 microscope equipped with an Oxford Instruments X-Max 80 X-ray microanalyzer  ,55.The microstructure of micro silica-modified samples was studied using a VEGA II LMU microscope  ,44.The results of a numerical experiment—calculation of the bearing capacity  of reinforced concrete columns with a cross section of 400 mm × 400 mm with a reinforcing bar diameter of 6 mm—are presented in From the data of the numerical experiment, the results of which are presented in (1) the use of polymer composite reinforcement instead of steel, leads to an insignificant decrease (by 0.5–1.0%) in the bearing capacity of columns operating in compression;(2) the bearing capacity of elements in the form of columns working in compression does not depend on the type of polymer composite reinforcement used in the study;(3) the difference in bearing capacity between 3000 mm and 6000 mm columns is 9–10%, and between 6000 mm and 9000 mm columns it is 2% to 3%, regardless of other parameters considered;(4) increasing the concrete grade from B30 to B40 results in an increase in the bearing capacity of compressive columns by up to 30%.After analyzing the data obtained as a result of the numerical experiment in The results of the numerical experiment are presented in From the data of the physical experiment, the results of which are presented in (1) the difference between lightweight and heavy concrete is up to 10% (concrete grade reduction from B30 to B25);(2) glass fiber reinforcement brings the compressive strength of lightweight concrete up to that of heavy concrete (upgrading concrete from B25 to B30);(3) nano-modification of heavy concrete with micro silica resulted in an increase in the compressive strength of concrete up to 35%, whereas the concrete grade increased from B30 to B40. Photographs of the microstructure of the fiber-reinforced sample are shown in The results of microscopic studies with high-resolution photographs and high magnification made it possible to determine the physical nature and mechanism of the destruction of fiber-reinforced composites, which are the basis for building elements. The microphotographs a–d clearThe description and analysis of photographs of the microstructure of samples nanomodified with micro silica were carried out, among other things, in accordance with ,44.The compared criteria for determining the role and place of research in modern science included such parameters as the size of the section of products, the class of concrete, the length of the product, the types of reinforcement, the class of reinforcement, and the diameter of the rod, which ultimately influenced the limiting value of the longitudinal force for compressible elements.-in relation to nanomodified concrete;-in relation to lightweight fiber-reinforced concrete;-in relation to lightweight concrete;-in relation to control heavy concrete.Thus, according to the indicated criteria, we evaluated the effectiveness of each of the considered methods when comparing different types of materials:In terms of the result achieved, we note that the most effective compositions obtained showed strength gains from 10% to 34%. Ultimately, this led to an increase in bearing capacity of up to 30%.It is possible to explain the obtained quantitative increases in concrete indicators by the observed qualitative picture of these changes. Thus, we have obtained significant improvements, which, in an integrated approach, led to an improvement in the structure of concrete, a decrease in the weight of concrete and, thereby, loads on the base. At the same time, the bearing capacity due to a rationally selected recipe and technological factors continues to remain at a high level. Thus, we have achieved a significant improvement in the qualitative picture, which leads to a synergistic effect from the developed proposals. This ultimately leads to an improvement in the characteristics of materials, then to an increase in the bearing capacity, and ultimately, to greater economic efficiency of the created building structures.This is in agreement with the results of the authors who dealt with the previously mentioned issue ,16,23,28In the case of concrete being nanomodified with micro silica and a reinforced element, we obtain a cheaper element with improved characteristics due to the use of industrial waste . This leNumerical experiments have established that one of the most important criteria in the calculation of elements is the class of concrete. At the same time, this characteristic has an effect for all types of reinforcement and all types of reinforcing bar material, for various section sizes, and bar lengths. Due to this, the compressible elements are significantly dependent on the class of concrete used.Therefore, we applied such a numerical physical approach when conducting experiments to produce a direct correlation between these quantities and to prove the effectiveness and possibility of obtaining reinforced building elements based on concrete using various types of reinforcing bars with different densities and weights.It has been confirmed that by increasing the class of concrete, it is possible to increase the bearing capacity of the element, or by reducing the mass of the element, it is possible to maintain the bearing capacity at the same level. All of this became possible thanks to the use of various recipe-technological methods at the stage of manufacturing a concreted reinforced structure, which works as a compressed element.Thus, due to inexpensive recipe methods, namely, nanomodification with the help of production waste, or the use of lightweight dispersed-reinforced concrete to obtain such structures, we achieve significant technological, design, and installation effects. The design effect reduces the importance of the rod reinforcement and supplements the improved element with dispersed fiber reinforcement. The technological effect is achieved using concrete modification, a more rational selection of its formulation, and by improving the characteristics of the concrete, an increased bearing capacity of elements arises. The construction and installation effect lies in the fact that such lightweight universal structures are more applicable and have a wider area of operation at construction sites of various levels of responsibility and different directions.The proposed integrated system approach has a number of advantages over existing approaches. In particular, our developed approach makes it possible to take into account both the characteristics of the materials used and the quality of the technological process of concrete production, that is, technological and design advantages, expressed in design and design efficiency, using software, and taking into account the characteristics of materials, especially in relation to lightweight structures of new types. Such structures are designed for the difficult conditions of modern construction and certainly require an integrated systematic approach in their creation, calculation, and design.A new integrated system engineering approach to the design of building structures is proposed, which involves minimizing their cost and weight through numerical simulations and experimental verificationss of the operation of reinforcing bars made of various materials in concretes of various densities.It has been confirmed that by increasing the class of concrete, it is possible to increase the bearing capacity of the element, or by reducing the mass of the element, it is possible to maintain the bearing capacity at the same level.The control of the bearing capacity of reinforced building structures, using the example of compressed elements, is proposed to be carried out by the developed recipe-technological methods at the manufacturing stage.-design effect, which consists of reducing the importance of rod reinforcement and supplementing the improved element with dispersed fiber reinforcement;-technological effect, which is achieved through the use of concrete modification, a more rational selection of its formulation, and by improving the characteristics of a concrete by obtaining an increased bearing capacity of elements from it;-construction and installation effect, which consists of the fact that such lightweight universal structures are more applicable and have a wider area of operation at construction sites of various levels of responsibility and various directions.The economic and environmental efficiency of the proposed engineering methods, namely, nanomodification with the help of production waste or the use of lightweight dispersed–reinforced concrete to obtain such structures, has been revealed. This allows significant effects to be achieved, such as:The most effective concrete formulations have demonstrated strength gains ranging from 10% to 34%. Ultimately, this led to an increase in the bearing capacity of the elements up to 30%.The use of such an integrated lean approach will save up to 20% of resources during construction.Future prospects, and ways to develop the study further, are planned in terms of bending elements with various types of concrete and reinforcement. Moreover, taking into account the improvement of the technology for calculating and designing lightweight building structures, it is of interest to develop the results obtained in the direction of concrete with an improved structure. Thus, in further research, we will apply the developed integrated system approach for concretes obtained using technologies other than standard vibration.