Freeze–thaw damage is one of the most severe threats to the long-term performance of concrete pavement in cold regions. Currently, the freeze–thaw deterioration mechanism of concrete pavement has not been fully understood. This study summarizes the significant findings of concrete pavement freeze–thaw durability performance, identifies existing knowledge gaps, and proposes future research needs. The concrete material deterioration mechanism under freeze–thaw cycles is first critically reviewed. Current deterioration theories mainly include the hydrostatic pressure hypothesis, osmolarity, and salt crystallization pressure hypothesis. The critical saturation degree has been proposed to depict the influence of internal saturation on freeze–thaw damage development. Meanwhile, the influence of pore solution salinity on freeze–thaw damage level has not been widely investigated. Additionally, the deterioration mechanism of the typical D-cracking that occurs in concrete pavement has not been fully understood. Following this, we investigate the coupling effect between freeze–thaw and other loading or environmental factors. It is found that external loading can accelerate the development of freeze–thaw damage, and the acceleration becomes more evident under higher stress levels. Further, deicing salts can interact with concrete during freeze–thaw cycles, generating internal pores or leading to crystalline expansion pressure. Specifically, freeze–thaw development can be mitigated under relatively low ion concentration due to increased frozen points. The interactive mechanism between external loading, environmental ions, and freeze–thaw cycles has not been fully understood. Finally, the mitigation protocols to enhance frost resistance of concrete pavement are reviewed. Besides the widely used air-entraining process, the freeze–thaw durability of concrete can also be enhanced by using fiber reinforcement, pozzolanic materials, surface strengthening, Super Absorbent Polymers (SAPs), and Phase Change Materials. This study serves as a solid base of information to understand how to enhance the freeze–thaw durability of concrete pavement. Currently, the infrastructure construction in China is under heavy development. Pavement construction is essential for building a highly efficient transportation system. Concrete is currently the most widely used manufactured material, and its wide application has reshaped modern urban construction. Concrete has also been widely applied in pavement construction, and the Continuously Reinforced Concrete Pavement (CRCP) has the longest service life among all types of pavement structures . The totCompared to asphalt pavement, concrete pavement has the advantages of resistance to water damage due to its hydraulic nature  and supeSince its invention in 1824, Portland cement concrete has been used for almost 300 years. In addition to the mechanical performance, the durability performance of Portland cement concrete is essential in the long-term performance of concrete infrastructure. However, the freeze–thaw damage mechanism for concrete has not been fully understood. Currently, the most recognized freeze–thaw damage theories are the hydrostatic pressure hypothesis proposed by Powers in 1945  and 1949Currently, 19 review papers can be found on the “webofscience” database related to the freeze–thaw damage of concrete pavement. These papers mainly focus on the deicing agent in concrete, the coupling damage by both freeze–thaw and external loading , the freFocusing on the issues of freeze–thaw durability of concrete pavement, this study seeks to summarize the current understanding of the freeze–thaw mechanism of concrete materials. Recent investigations on the freeze–thaw damage of concrete pavement are summarized in Researchers started to identify the existence of freeze–thaw damage in the 1930s, and numerous investigations have been conducted since. This section mainly aims to summarize the current understanding of freeze–thaw damage and to identify the existence of knowledge gaps on freeze–thaw damage to concrete pavement. As summarized in reference , the masIn 1946, Powers proposed the classical hydrostatic pressure hypothesis based on observed phenomena occurring in concrete during freezing and swelling. The theory suggests  that wheBased on Powers’ hydrostatic pressure hypothesis, Fagerlund  further d/2 at the place. Its calculation formula is:k is the coefficient of the permeability of the material, the f/dθdw is the freezing rate, i.e., the increment of frozen water for every 1 °C decrease in temperature. The dθ/dt is the cooling rate.The d is the distance between the two air bubbles. Assuming the distance from the left air bubble to the freezing point A is x, then the maximum hydrostatic pressure occurs x = Although the hydrostatic pressure hypothesis can explain many phenomena in the freeze–thaw process of concrete , several critical experimental phenomena cannot be well explained, including the fact that organic liquids which do not expand in volume after freezing can also cause damage to concrete. Therefore, Powers and Helmuth et al. further developed the osmotic pressure hypothesis. The osmotic pressure hypothesis indicates ,63 that It has been widely confirmed that freeze–thaw damage development depends on the saturation rate of the concrete. Fagerlund first proposed the critical satiation theory in 1977, which describes a substantial satiation value for porous materials. Once this threshold is exceeded, the material can only withstand one freeze–thaw cycle before cracking or becoming damaged ,65. ThisThe crystallization pressure originates from the growth of ice from large pores to small pores. A hemispherical interface is formed between ice and water due to a capillary effect. The pressure is generated due to the difference in the ice–water interface curvature and the cylindrical pore curvature. The crystallization pressure is then needed to balance the pressure caused by the curvature difference . AccordiIn addition to the four hypotheses introduced above, the pore structure, temperature stress, ice prism, micro-ice-lens , salt frCurrently, the investigation of the cracking mechanism of these aggregates is not sufficient. For example, the deicing salt used for snow removal on the surface of concrete pavement can increase the concrete pore solution’s salinity, and thus change its freezing temperature. The expansion pressure during freezing and the deterioration mechanism of concrete material may then also be altered. Further investigation is needed to understand the deterioration mechanism of concrete material in the pavement.Concrete pavement in actual service conditions is usually subjected to various complex environmental factors. Hence, concrete pavement can deteriorate under a coupled action effect and co-create durability issues ,77.Concrete pavement bears continuous transportation loading during its service life. Current research shows that the coupling effect of external loading and freeze–thaw cycles can lead to more severe deterioration of the relative dynamic modulus concrete materials and accelerate the deterioration process . The micAccording to the freeze-swelling mechanism and related experiments, it is found that the mass-loss rate and decreasing rate of dynamic modulus can be increased by freeze–thaw cycles of concrete in a salt solution . At the 2 + 5% Na2SO4) complex solution < 5% MgSO4 solution < 10% NaCl solution. The salt for snow removal on concrete pavement mainly includes NaCl, KCl, CH₃COONa, and CH₃COOK. The investigation of the coupling effect between freeze–thaw and attack by acetates is still limited. The former studies indicate that acetates can lead to an alkali–silica reaction in concrete. Further research is needed to unveil the correlation between acetate exposure and freeze–thaw cycles.At the same time, experiments have shown that during the freeze–thaw cycle , differeIn the cold winter temperature of the marine environment or in cold areas where deicing agents are used, concrete pavement often suffers from the standard coupling of freeze–thaw cycles, external loads, and salt solution erosion. At present, relatively little research has been carried out on the deterioration laws of concrete under the combined effect of these three factors.Studies have shown ,85,86 thConcrete pavement has a superior load-bearing capacity and durability, enabling it to be used worldwide. As mentioned earlier, concrete pavement load-bearing power and durability can be significantly reduced when subjected to a combination of complex factors in the environment. Hence the investigation of concrete pavement is necessary.At the meso-level, concrete is a three-phase composite material, often considered a mixture of aggregate, cement mortar, and pore combinations. The evolution and spatial distribution of internal random pore and crack structures under the action of freeze–thaw cycles is a critical factor in the study of damage mechanisms and macroscopic mechanical properties of concrete materials . The preFor pavement and bridge decks, freeze–thaw damage often acts in coupling with fatigue loading. For this reason, a fine-scale method based on the rigid body spring method (RBSM) has been conducted , which dTo protect the safety of vehicles traveling on the road and to guarantee the normal transportation efficiency of the road during winter, deicing agents are often used to treat the road surface for snow removal. However, deicing agents often aggravate the freeze–thaw damage of concrete pavement. The cracks and scaling caused by freeze–thaw damage can also lead to the penetration of chloride ions, which can cause rusting of the reinforcement properties ,95,96,972 are commonly used in deicing agents and will be used as examples below [2 in the concrete. Therefore, the location where the Ca(OH)2 content initially exists becomes a pore within the concrete. The interaction between the salts and the Ca(OH)2 content increases the porosity and permeability of the concrete pavement. It leads to an increase in the amount of ice formation during the freeze–thaw process. The specific chemical reaction equation is shown below.On the chemical level, many deicing agents contain chlorine salts as the main component, which can react with concrete materials and cause the products to dissolve and create pores, or generate new salt crystals and increase crystallization pressure within the concrete. NaCl and CaCles below ,100. Whe2, it will react with tricalcium aluminate (C3A) to form calcium chloroaluminate . This reaction will lead to the scaling of the concrete over time. The specific chemical reaction equation is shown below:If the deicing agent contains CaCl2) with an initial ice thickness of 1 mm and reached 103 g (1.8 kg/m2) with an ice thickness of 10 mm.A physical process primarily causes the scaling of concrete surfaces caused by deicing agents. Due to the complexity of the concrete freeze–thaw damage mechanism, the actual tool has not yet been fully unveiled. The proposed hypotheses have mainly guided the research on concrete durability . Current2) as examples, the surface temperature of concrete drops rapidly due to the dissolution of sodium chloride in water and the heat absorption. However, calcium chloride produces an exothermic reaction, which rapidly increases the temperature of the concrete surface. The stresses generated by the rapid change in surface temperature may exceed the tensile strength of the concrete, leading to the development of minor cracks [The thermal shock hypothesis explains this phenomenon from another macroscopic perspective. It suggests that the dispersed deicing agents cause a sudden drop in the temperature of the concrete surface, which causes a difference in internal and external stresses. The change in the concrete volume caused by the temperature stress results in tensile stresses inside the concrete. If the induced tensile stress is higher than the tensile capacity of the concrete, the concrete will crack . As illur cracks .Concrete pavement needs to resist the impact of wheel loading during its service life; fatigue resistance is essential for long term-durability performance. It is expected the generated internal defects during freeze–thaw cycles can promote crack initiation and propagation under fatigue loading. The development of fatigue cracks can increase water entrance due to enhanced percolation and can accelerate freeze–thaw deterioration. A study by Yang et al.  found thFreeze–thaw cycles are extremely damaging to concrete pavements, and the annual pavement rehabilitation work is also a considerable burden on national finances ,105. ResSurface treatment of concrete to improve its frost resistance is relatively efficient and inexpensive . One stuChemical air-entraining agents (AEAs) have long been used as a common and popular measure to mitigate damage to concrete from freeze–thaw cycles. Air-entraining agents stabilize the air bubbles generated during concrete mixing and prevent tiny bubbles from collecting and escaping . These sIt has been widely considered fiber reinforcement can enhance the toughness of fragile concrete. It is expected that the introduced fiber can prevent the development of internal cracking and mitigate freeze–thaw damage. A study by Cui et al.  indicateIn addition to fiber reinforcement, the addition of nanomaterials can densify the internal structure of concrete and improve freeze–thaw resistance by decreasing permeability. A study by Gonzalez et al.  enhancedAdding metakaolin and zeolite can effectively reduce the mass loss of concrete caused by surface scaling during freeze–thaw cycles . A studyPhase change materials (PCM) are latent heat substances that can repeatedly store and release large amounts of thermal energy as they melt and solidify ,116,117.Phase change materials can be divided into three main categories: organic, inorganic, and eutectic materials. Most organic phase change materials do not rely on subcooling for nucleation during freezing and are usually non-corrosive. Inorganic phase change materials can be divided into salt hydrates and metallic phase change materials, each which have their disadvantages. The metallic phase change materials are not in the temperature range required for construction applications, while the salt phase change materials may react with cementitious materials and be highly hazardous to concrete, or worse, may corrode metals ,120.Both(1)Currently, the freeze–thaw damage law of concrete pavement has not been fully understood, including the development of the mechanism of D-cracking caused by the specific coarse aggregate, and the coupling effect between freeze–thaw damage and fatigue loading and/or deicing salts. In addition, most investigation is conducted using Portland cement concrete; the deterioration mechanism of concrete pavement prepared with other cementitious materials is quite limited .(2)It is still difficult to reveal the differences between indoor test results and field durability performances ,99,127 d(3)Besides the widely used air-entraining methods, the application of recently proposed freeze–thaw damage mitigation protocols have not been widely used in field application. For example, it has been found that the added phase change materials in concrete can reduce its mechanical strength due to relative weak ITZ performance.Based on a critical review, the identified knowledge gaps are shown below:(1)The development of the mechanism of D-cracking should be investigated by unveiling the correlation between aggregate composition and D-cracking sensitivity. Furthermore, the freeze–thaw deterioration mechanism of low carbon concrete  should be investigated.(2)The testing methods related to the material and loading-level differences between field exposure and lab tests should be considered. At the material level, the physical (permeability and suction) and mechanical properties of the lab specimen should be consistent with that of the field concrete. At the loading level, the coupling effect of the external loading (fatigue loading) and environmental factors  should be considered in the test design. Furthermore, the correlation between the physical and mechanical performance of concrete and the durability of pavement under coupled fatigue loading and freeze–thaw cycles should be investigated.(3)The field application of the recently proposed freeze–thaw damage mitigation protocols should be conducted, including surface strengthening, the incorporation of phase change materials, and changing absorbency levels of the concrete. Furthermore, the content of the added phased materials and the absorbency should be optimized, while surface treatment is needed to enhance the ITZ performance.Based on the summarized research knowledge gaps, the further research needs are shown below:(1)The current deterioration theories are based mainly on the hydrostatic pressure hypothesis, the osmolarity hypothesis, and the salt crystallization pressure hypothesis. The critical saturation degree has also been proposed to depict the influence of the internal saturation on freeze–thaw damage development. Meanwhile, the influence of pore solution salinity on the freeze–thaw damage level has not been widely investigated. In addition, the deterioration of the typical D-cracking in concrete pavement has not been fully understood.(2)External loading can accelerate the freeze–thaw damage development, and the acceleration can be more obvious under higher stress levels. Further, the salt ions can also interact with the concrete during the freeze–thaw cycles, generating internal pores or leading to crystalline expansion pressure. Freeze–thaw development can be slowed down under relatively low ion concentration due to increased frozen points. The interaction between external loading, environmental ions, and freeze–thaw cycles has not been fully understood.(3)Besides the widely used air-entraining process, the freeze–thaw durability of concrete can be enhanced through Fiber Reinforcement, Surface-Strengthening, and incorporation of Pozzolanic Materials, Super Absorbent Polymers (SAPs), and Phase Change Materials.This study aims first to summarize the current understanding of the freeze–thaw mechanism of concrete materials. The coupling correlation between freeze–thaw damage and related durability issues is analyzed. Finally, the influence of freeze–thaw damage on the long-term mechanical performance of concrete pavement is investigated. The related damage mitigation protocols are proposed. The major research findings are shown below:


To evaluate the performance of diffusion-relaxation correlation spectrum imaging (DR-CSI) with support vector machine (SVM) in detecting prostate cancer (PCa).In total, 114 patients  who received a prostate MRI and underwent biopsy were enrolled in three stages. Thirty-nine were assigned for the exploration stage to establish the model, 18 for the validation stage to choose the appropriate scale for mapping and 57 for the test stage to compare the diagnostic performance of the DR-CSI and PI-RADS.2 values (both P < 0.001). The validation result shows that at least 2 pixels were required for both the long-axis and short-axis in the mapping procedure. In the test stage, DR-CSI had higher accuracy than PI-RADS ≥ 3 as a positive finding based on patient  and lesion  as well as PI-RADS ≥ 4 on lesion , while there was no significant difference between DR-CSI and PI-RADS ≥ 4 based on patient (P = 0.508). For clinically significant PCa, DR-CSI had higher accuracy than PI-RADS ≥ 3 based on patients  and lesions . There was no significant difference between DR-CSI and PI-RADS ≥ 4 .In the exploration stage, the DR-CSI model was established and performed better than the ADC and TDR-CSI combined with the SVM model may improve the diagnostic accuracy of PCa.This study was approved by the Ethics Committee of our institute . Written informed consent was obtained from all participants. The accetection .2 and apparent diffusion coefficient (ADC) are widely accepted as the two most valuable biomarkers for tumour characterization [2 and ADC have been found to be related to the aggressiveness of PCa, which is indicated by the Gleason score [Among the metrics derived from MP-MRI, Trization , 5. Furton score , 7. Howeon score , 9. As son score –12.2 or ADC, add difficulty for MP-MRI in differentiation. In addition, various tissue structural features at a microscopic scale produce another obstacle for visualization owing to limited MRI spatial resolution. To resolve this issue, some attempts have been made in multidimensional MRI, a method that tries to disentangle intravoxel signals in terms of parametric spectra, such as T1, T2 and ADC, and hence to infer the intravoxel tissue composition [2–ADC spectrum with prior knowledge [Concerning PCa, multiple intravoxel components with different or similar MR properties, such as Tposition , 14. Forposition . Moreoveposition  and succnowledge . Owing tIn this study, the machine learning technique, the support vector machine (SVM) model, was introduced in combination with DR-CSI. SVM, as a supervised ML technique that tries to find the optimal hyperplane that maximizes the margin between two classes, has been widely used for the detection and classification of PCa due to its mature mathematical formulation, flexibility, high accuracy, robust theoretical support, direct geometric interpretation, and wide availability of software implementations –23. For This retrospective study was approved by the Ethics Committee of our institute . Written informed consent was obtained from all participants. Three hundred and twenty consecutive patients who were scheduled for prostate MRI were recruited for this study between August 2020 and December 2021. The inclusion criteria were as follows: (a) prostate-specific antigen (PSA) elevated to ≥ 4 ng/mL or digital rectal examination (DRE) positive; (b) complete MRI examination and clinical data; and (c) no surgery before MRI examination. The exclusion criteria were as follows: (a) images with poor quality or artefacts; (b) patients with a previous history of prostate biopsy, prostate surgery, or other treatment; and (c) time interval between MRI and biopsy ≥ 3 months. In this study, 12 patients with previous chemotherapy, 5 patients with previous operation or treatment for PCa, and 2 patients with poor quality or artefacts were excluded. Three hundred and one patients were included . In total, 114 patients who underwent biopsy were enrolled in three stages. Detailed participant characteristics are summarized in Table After prostate MRI, patients were enrolled in three stages – the exploration, validation, and test stages. In the exploration stage, patients with PI-RADS ≥ 3 lesions or DRE positivity underwent biopsy, and a PCa detection model utilizing an SVM model was established based on the DR-CSI and biopsy results. Then, in the validation stage, an optimal filter scale for the SVM model was chosen with the images used to detect PCa from biopsy, in which the biopsies were carried out on patients with PI-RADS ≥ 3 lesions or positive results according to the PCa detection model or DRE positivity. Finally, in the test stage, the PCa detection model was used to predict PCa, and the results were compared with PI-RADS scores as well as the gold standard. The biopsy results of patients had the same criteria as in the validation stage. The comparison was performed based on patient level as well as lesion level. At the lesion level, a single lesion was defined as a positive targeted lesion in DR-CSI or PI-RADS. PCa proven in 12 systemic biopsies with negative imaging results was also defined as a single lesion. For patients biopsied due to positive DRE results with negative imaging and pathology results, the whole prostate was defined as a single case. The flowchart of the study design is presented in Fig. 1-weighted imaging (T1WI) and DR-CSI. T1WI and T2WI were acquired. The detailed MR protocols are presented in Table 2). The SS SE-EPI sequence was performed 6 times for each patient. For each time, TE was set as a specific value in its range with a full set of b-values , i.e., diffusion sequence with different T2 weights. As TE was increased, diffusion time was increased in parallel.All MRI examinations were performed on a 3.0 T scanner  with a commercial body phased array coil. MR examination included T2WI, DWI, DCE-MRI, T2 and D:According to DR-CSI theory , the MR 2 and D represent the transverse relaxation time and the diffusivity, respectively. 2-D spectrum with each spatial location.where TIn practice, the signal needs to be expressed in a discretized form:2 and D, respectively. T2i and Dj represent the transverse relaxivity and diffusivity, respectively. where I and J are the numbers of TThe distribution function was obtained through spectrum estimation, i.e., finding the solution to the above equation with consistency, a nonnegativity and a spatial smoothness constraint following steps in a previous study .2-D spectra space was empirically segmented into six subregions . A previous study demonstrated that the epithelial structure was more likely to be present within the scale of T2 < 50 ms and D < 0.5 mm2/μs based on ex vivo imaging [2/μs was also adopted as the cut-off value because the diffusion velocity of water molecules beyond 3 mm2/μs may likely characterize particular physiological information . Thus, the ranges of the subregions were finally classified as follows: 1) T2 < 50 ms, D < 0.5 mm2/μs; 2) T2 > 50 ms, D < 0.5 mm2/μs; 3) T2 < 50 ms, 0.5 mm2/μs < D < 3 mm2/μs; 4) T2 > 50 ms, 0.5 mm2/μs < D < 3 mm2/μs; 5) T2 < 50 ms, D > 3 mm2/μs; and 6) T2 > 50 ms, D > 3 mm2/μs. The corresponding fraction of each subregion, , the T imaging . Conside imaging , 15, the2-D spectral space.where 2 with the lowest TE (57 ms) [Figure  (57 ms) –27. For 2 and ADC maps of all ROIs were estimated following a monoexponential signal decay model using part of the DR-CSI data points , respectively [Accordingly, the fraction maps corresponding to six subregions of each ROI were acquired through DR-CSI analysis. Meanwhile, conventional voxelwise T2, ADC and six component fractions) of all voxels from all patients in the exploration stage were used for the construction of the PCa detection model. Then, an SVM classifier with a linear kernel for PCa prediction was trained and established through tenfold cross validation, which evenly split the dataset into 10 subsets with 9 subsets for training and the last subset for evaluation. This process was repeated 10 times, leaving one different subset for evaluation each time. Second, different filter scales with different numbers of pixels  were used in the validation stage to choose an optimal scale, which could reduce the false-positive results resulting from the SVM-based PCa detection model. Then, the optimal filter scale with the highest Dice ratio between the modelling results and biopsy results was determined. Third, the SVM-based PCa detection model with the optimal filter scale was used in the test stage, and the voxelwise model-predicted mapping results were generated.The SVM-related procedures were as follows. First, the quantitative imaging features (TThe PI-RADS score was determined by an experienced radiologist (with more than 10 years of experience in prostate MR imaging) unaware of the biopsy results in the exploration and validation stage. In the test stage, the GS of the lesions was assigned according to the most common GS in the biopsy result.2 maps in differentiating cancer from non-PCa tissue at the largest Youden index point in receiver operating characteristic (ROC) analysis based on each voxel. In the test stage, the comparison of accuracy between DR-CSI and PI-RADS in terms of the diagnosis of PCa or cs-PCa was assessed by the McNemar test. Differences were considered significant when the P value was < 0.05.Statistical analysis was performed by SPSS 24.0 . Kappa values < 0.20 indicated slight agreement, values of 0.21–0.40 indicated fair agreement, values of 0.41–0.60 indicated moderate agreement, values of 0.61–0.80 indicated substantial agreement, and values > 0.81 indicated almost perfect agreement . In the 2 and ADC values and six subregions contributing to the SVM model. Figure 2 value. The DR-CSI model was more accurate than the traditional ADC  and T2 value  at the highest Youden index point. Interreader agreement analysis showed that almost perfect agreement was achieved in each subregion .In the exploration stage, a total of 39 patients underwent biopsy, among which 3 were PI-RADS 2 but DRE positive, 21 were PI-RADS 3, 10 were PI-RADS 4, and 5 were PI-RADS 5. There were 72 lesions . The maximal diameter of the index lesion ranged from 0.4–3.9 cm (median = 1.3 cm). Of these, 17 patients were confirmed to have benign disease , and 22 patients had PCa . There were 29 PCa lesions . A total of 10,434 tumour voxels  were included in the analysis to establish an SVM model. Figure In the validation stage, a total of 18 patients (17 patients with PI-RADS ≥ 3 or DR-CSI positivity and 1 patient with PI-RADS < 3 and DR-CSI negativity but DRE positivity) underwent biopsy. Of these, 6 patients were confirmed to have benign disease, and 12 had PCa. We chose those 12 images and compared the performance of different mapping methods to choose an appropriate scale for further testing. Among each scale, the largest Dice ratio was found in the scale, with the long axis and the short axis having at least 2 and 2 pixels, respectively  and lesions . Considering PI-RADS ≥ 4 as a positive finding, DR-CSI had higher accuracy than PI-RADS ≥ 4 based on lesions , while no significant difference was found based on patients . For the analysis of clinically significant PCa, considering PI-RADS ≥ 3 as a positive finding, DR-CSI had higher accuracy than PI-RADS ≥ 3 based on patients  and lesions . Considering PI-RADS ≥ 4 as a positive finding, there was no significant difference between DR-CSI and PI-RADS ≥ 4 based on patients  and lesions .In the test stage, a total of 57 patients underwent biopsy, among which 7 patients were PI-RADS < 3 and DR-CSI negative but DRE positive, 1 was PI-RADS 2 but DR-CSI positive, 28 were PI-RADS 3, 13 were PI-RADS 4, and 8 were PI-RADS 5. The maximal diameter of the index lesion ranged from 0.3–3.2 cm with a median of 1.1 cm. Of these, 25 patients were confirmed to have benign disease , and 32 had PCa . Eighty-five lesions were subsequently verified. Thirty-one were confirmed to be benign, and 54 were PCa. Two typical cases are represented in Fig. In this study, the feasibility of DR-CSI combined with an SVM model for detecting PCa in vivo was initially explored, and its diagnostic performance was evaluated and compared with the PI-RADS score based on MP-MRI. The optimal performance of the former method suggested additional clinical value and potential to improve the detection of PCa, especially based on lesion level. The results demonstrated that DR-CSI could provide additional information for PCa characterization in some clinical scenarios .2 and ADC derived from MP-MRI independently have been widely used for cancer detection and have proven to be of clinical significance [2 and varies depending on the tissue composition in PCa [2 and ADC maps alone, the diagnostic accuracy was improved by the DR-CSI with the SVM model. This could be attributed to the fact that DR-CSI could resolve the distribution of tissue components according to different spectral regions, providing additional information on tissue composition or structural features at a subvoxel level and hence improving the clinical diagnosis of PCa.Conventionally, Tificance , 30. Somn in PCa , 32. ConWith decades of efforts, multidimensional MRI has been used to infer intravoxel heterogeneity in tissue due to its outstanding power to resolve signals from distinct tissue components. In pioneering work, DR-CSI has shown the potential to discriminate spatially overlapping phantoms and separate white and grey matter in both normal and injured animal spinal cords . SpecifiHowever, the clinical diagnosis of PCa by DR-CSI still needs further study. Particularly, it is worth noting that there still exist other challenges to DR-CSI application for the clinical diagnosis of PCa . First, 2-D spectrum to a specific component, dividing the entire T2-D spectral space into six areas with different ranges of T2 and D could be a feasible way to reflect the diffusion-relaxation correlation information and avoid the need to identify specific components in the high intravoxel heterogeneous tissue structure. Thus, our DR-CSI was established based on segmented spectral areas to evaluate tissue composition in the diagnosis of PCa rather than to define a specific peak.Instead of assigning an individual spectral peak in the T2-D spectrum without defining and explaining the associations between segmented spectral areas with multiple components in PCa on the premise of no adequate prior knowledge about the microstructure compositions in vivo PCa. The results of the training model easily converged and could be quickly translated into practical applications. Moreover, the SVM model can explore the importance of a specific factor with the weight of each component in the model. ADC was still an important factor in PCa diagnosis, while different compartments derived from DR-CSI can simultaneously contribute to the classification model. Interestingly, components 5 and 6, which were considered to be associated with tissue perfusion in vivo with D > 3 mm2/μs, also accounted for significant proportions in the model. This finding verified the importance of perfusion emphasized by PI-RADS [As the SVM model is an efficient way to deal with classification problems , it was  PI-RADS , 12. MorIn the validation stage, we used 2*2 voxels as the filters to establish the mapping model. It is important to choose an appropriate filter scale for image mapping in SVM. Since the EPI sequence on the imaging level in vivo is easily disturbed by various artefacts, the direct mapping method without adding filters may not reach satisfactory results, such as increased false-positive results. Lesions with 2*2 voxels will obviously provide more reliable information than lesions with a single voxel. The scale with 2*2 voxels is smaller than most prostate tumours that can be found by MRI and will not lead to missed diagnosis due to the choice of boundary.In this study, we also evaluated the performance of the DR-CSI model in detecting cs-PCa. Although the performance of the DR-CSI model did not exceed that of PI-RADS, it still has some practical significance. As the result of the DR-CSI model can be automatically derived with SVM, the method also provides a potential idea to solve the problem of lacking reproducibility with PI-RADS in diagnosis . MeanwhiOur study had some limitations to be acknowledged. First, considering that the diagnostic performance of saturation biopsy was consistent with that of radical prostatectomy pathology in general , 34, satIn conclusion, the DR-CSI combined with the SVM model has the potential to improve the diagnostic accuracy of prostate cancer.


Antibiotic therapy is one of the most important strategies to treat bacterial infections. The overuse of antibiotics, especially in the perinatal period, is associated with long-lasting negative consequences such as the spread of antibiotic resistance and alterations in the composition and function of the gut microbiota, both of which negatively affect human health. In this review, we summarize recent evidence about the influence of antibiotic treatment on the neonatal gut microbiota and the subsequent negative effects on the health of the infant. We also analyze the possible microbiome-based approaches for the re-establishment of healthy microbiota in neonates. Antibiotic therapy is fundamental to the treatment of infectious diseases in humans and represents one of the greatest medical advances of the last century . However13 cells, with a number of genes exceeding 100–150-fold the number of human genes [The enteric microbiota is composed of a rich and dynamic population of microorganisms, including bacteria, viruses, archaea, fungi, and protozoa. The predominant microbial community is that of bacteria, consisting of approximately 3.8 × 10an genes ,10. The an genes . This rian genes . Such chan genes ,13. In tan genes ,11. In tan genes . Any facan genes ,13. SeveVarious studies have shown that the amniotic membrane, amniotic fluid, placenta, meconium, and umbilical cord blood harbor different microbial communities in healthy pregnancies, contravening the conventional concept that the fetus is sterile . InteresAn important issue to be considered is the possible in utero exposure to microbial metabolites produced by the mother’s gut microbiome, which may influence fetal growth and development, contributing to early signaling pathways at the fetal–maternal interface . NotablyThe colonization of an infant’s gut is fundamental for the development and maturation of the immune function and, consequently, of the health of the individual . During The infant microbiota is susceptible to a variety of environmental factors, including the mode of birth, prematurity, the birth location , diet , maternal gestational diet and weight, pet ownership, disease state and stress, and antibiotic treatment, with long-lasting consequences on the physical and mental health of the individual, at least for some of these effects ,23.Lactobacillus, Prevotella, and Sneathia spp. [Clostridium difficile, Streptococcus, Staphylococcus, and Propionibacterium spp., and a reduced concentration of Actinobacteria and Bacteroidetes [The mode of delivery represents one of the first factors influencing the neonatal gut microbiota, although the effects of the mode of birth on microbiota composition are no longer apparent by 6–8 weeks of age  or, accohia spp. ,25. Cesaroidetes ,25. Howeroidetes .Staphylococcus epidermidis, Klebsiella pneumoniae, Escherichia coli, Enterobacteria, and Streptococci; subsequently, these are replaced by other anaerobic bacteria  during the end of the first week of life [Bifidobacteria are predominant in the healthy term infants’ microbiota and are much less represented in preterm neonates and not detected before a post-menstrual age of 30 weeks [Another important factor influencing postnatal microbiota composition is the gestational age at birth. The microbiota of preterm infants’  is characterized by low diversity and increased levels of potentially pathogenic bacteria , even if of life . Bifidob30 weeks ,28.Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumoniae were found, and these microorganisms were present in the environment after and often before their detection in the preterm gut. A later study from the same research group suggested that hospitalized preterm infants and their caregivers shaped the microbiomes of NICU rooms [In preterm infants, a significant amount of the premature microbial gut population is environmentally acquired via the microbial exchange between the room and the occupant. Brooks and colleagues carried out a metagenomic study of the microbes present in 50 preterm newborns and in the environment of the neonatal intensive care unit (NICU) . In bothCU rooms . SimilarCU rooms . GeneticCU rooms .Bacteroides, Streptococcus, and Lactobacillus are present in breastfed infants’ microbiota, the microbiota of formula-fed infants is composed of a higher abundance of E. coli, C. difficile, and Bacteroides fragilis [Soon after birth, the microbial composition is greatly influenced by feeding. Breastfeeding favors the development of a simple community of obligate anaerobes, characterized by higher levels of Bifidobacteria compared to those of formula-fed neonates, which remain elevated after weaning. The low gut bacterial diversity in breastfeeding infants is suggested to depend on the presence of oligosaccharides in human milk, which represent important nutritional substrates for Bifidobacteria . Althougfragilis ,33. Matufragilis ,35. Suchfragilis ,36,37.The timing, duration, and type of antibiotic exposure are of particular importance when considering the main factors influencing the composition and function of the neonatal gut microbiota. The impact of antibiotic treatment on the developing neonate’s microbiota may derive both from maternal antibiotic uptake during pregnancy and lactation and from direct exposure to infants, owing to their health status. In the following paragraphs, we consider both conditions, distinguishing between the consequences of direct and indirect antibiotic exposure in term and preterm neonates.Streptococcus agalactiae) [-Via the umbilical cord—antibiotics reach the fetus’s blood and they persist up to at least ten hours after administration ,40.-Antibiotics can modify the maternal vaginal and intestinal microbiome, causing an alteration in vertical microbial transmission and post-natal immunity ,41.Maternal antibiotic treatment may influence the infant microbiota composition through prenatal exposure to the fetus or changes in the mother’s microbiota or breastfeeding . Intrapalactiae) . MaternaAntibiotic treatment during labor modifies the development of the gut microbiota in preterm neonates, reduces intestinal host defenses, causes some alterations in the vaginal microbiota before delivery, and influences the composition of the neonatal oral microbiota . PerinatLactobacilli in the vaginal microbiota, which may be associated with a high risk of preterm delivery and may cause an increased risk of vaginal GBS infection [Actinobacteria, especially Bifidobacteriaceae, and a more relative abundance of Proteobacteria compared with non-exposed infants [Bifidobacteria may stimulate genes which promote mucosal integrity and reduce the expression of inflammatory genes, whereas Proteobacteria are associated with metabolic and inflammatory diseases [IAP may also lead to decreased diversity and a lower concentration of nfection ,45,46. I infants ,39,47. Idiseases ,48.Bifidobacterium spp. in their milk [Finally, there are few data available regarding the effects of IAP on breast milk composition. It has been reported that mothers with IAP have a lower concentration or absence of eir milk ,49,50.Enterobacter in term infants during the first month [The neonatal gut microbiota is influenced by the timing, the duration, and the type of antibiotic exposure. Empiric antibiotic therapy is associated with lower intestinal bacterial diversity and a major concentration of st month .Bifidobacterium in the days immediately after birth and subsequently increased the levels of Enterobacteriaceae [In full-term infants, antibiotic administration during the first hours of life reduced the level of eriaceae  , as shown by Zhou et al., because patients with EOS have a different microbiota composition, such as a high concentration of cus spp. .Bifidobacteria, Lactobacilli, Bacteroides and butyrate-producers such as Bifidobacteriaceae, Bacteroidaceae, Eubacteriaceae, Fusobacteriaceae at the end of therapy [A retrospective, cross-sectional study led by Rooney et al. disclosed that in all infants within one week of discontinuation of the therapy, each additional day of antibiotics was associated with a lower concentration of obligate anaerobes such as  therapy ,53  and long-lasting (≥5 days) intravenous antibiotic treatment (amoxicillin/ceftazidime) during the first postnatal week in 15 late preterm infants (35 ± 1 weeks of gestation) severely affected their normal intestinal colonization. Both treatments had negative effects on the  infants  , late-onset sepsis, and the mortality of preterm neonates .Enterobacteriaceae, which are especially resistant to beta-lactam antibiotics [Early-life antibiotic therapy could increase the presence of pathogenic, antibiotic-resistant ibiotics . Additioibiotics . There aibiotics ,68,69,70ibiotics .yt+ and Foxp-3 positive Tregs. This change may lead to compromised immune tolerance, with the development of immunologic and metabolic disease [Trasand et al. demonstrated that antibiotic exposure during the first six months of life was associated with increases in body mass from 10 to 38 months, whereas later exposure  was not consistently associated with an increased body mass . Subther disease .Enterobacteriaceae other than E. coli . Amoxicillin, cephalosporins, macrolides, clindamycin, quinolones, and sulphonamides decreased the concentration of E. coli, whereas amoxicillin/clavulanate, in contrast to other penicillins, increased the abundance of E. coli. Piperacillin and ticarcillin, carbapenems, macrolides, clindamycin, and quinolones strongly decreased the abundance of anaerobic bacteria [Finally, in a systematic review that identified 129 studies, alterations of human intestinal microbiota due to antibiotics exposure were reported. In particular, amoxicillin, amoxicillin/clavulanate, cephalosporins, macrolides, clindamycin, tigecycline, quinolones, and fosfomycin increased the abundance of bacteria .In the literature, different pieces of evidence are emerging related to microbiome-based approaches for the restoration of a healthy microbiota in neonates.Bifidobacterium and Lactobacillus. These bacterial species may promote gut health and may prevent pathogen colonization [Bifidobacterium longum, Lactobacillus acidophilus, and Enterococcus faecalis seems not to restore the composition and diversity of the neonatal gut microbiota, the simultaneous use of probiotics and antibiotics might have a more beneficial effect by promoting an increase in the presence of Bifidobacterium [Antibiotic treatment in neonatal infections has important negative effects on gut microbiota due to the reduction of the populations of nization . Althougacterium .Saccharomyces bourlardii, Lactobacillus reuteri, Lactobacillus acidophilus and Bifidobacterium lactis, have shown modest improvements in gut health, whereas the greatest success has been observed in probiotic mixes [Lactobacillus rhamnosus GG, S. boulardii, L. reuteri, Lactobacillus sporogenes, or B. breve have shown limited effects in reducing LOS in formula-fed preterm neonates [Single probiotic strains, such as ic mixes . The useic mixes ,77. Howeneonates . These dBifidobacterium bifidum plus L. acidophilus and the second one with B. bifidum, B. longum subsp. infantis and L. acidophilus—was associated with a faster transition into two different Bifidobacterium spp. and to positive health outcomes [Bifidobacterium and Bacteroides, whereas formula-fed infants maintain Enterobacteriaceae for longer periods of time [Bifidobacteria and decreasing those of staphylococci [Bifidobacterium produces short-chain fatty acids (SCFAs) that reduce gut permeability and preserve the integrity of the intestinal barrier [Streptococcus (GBS), which is the main organism responsible for neonatal infections [In a 10-year observational study led by Beck and colleagues, it was demonstrated that supplementation with two different probiotics in preterm infants—one with outcomes . In thesoutcomes . Breastm of time . Human m of time , counterylococci  (Figure  barrier . In addifections  (Figure fections . Finallyfections . HMOs alfections .In this way, breastmilk components, such as HMOs, growth factors, immunological factors, and probiotic bacteria could establish a healthy gut microbiota and might promote more effective crosstalk among probiotics, gut microbiota, and the immune system .Bifidobaterium-containing probiotics during hospitalization after preterm birth might prevent the persistence of antibiotic resistance genes in the gut microbiome, such as aminoglycoside and beta-lactam resistance [Some evidence has revealed that supplementation with sistance ,85,86.Finally, probiotic, prebiotic, or synbiotic administration to cesarean-born neonates might be associated with improvements in some health outcomes through their immunomodulatory effects, such as decreasing atopic and infectious diseases or increasing the immune vaccination response .During prenatal and postnatal life, infants are colonized by different microorganisms. Gut colonization is a dynamic process, influenced by a wide range of factors such as the mode of delivery, diet, environment, feeding, and antibiotic treatment. Antibiotic-induced alterations of the gut microbiota might affect the maturation of the immune system and increase susceptibility to obesity, diabetes, inflammatory bowel disease, and immune-related diseases such as asthma and allergies. Additionally, dysbiosis causes an increased risk of early adverse outcomes such as NEC, sepsis, and fungal infections. However, the rapid interruption of antibiotic treatment and the use of probiotics may allow for the recovery of the composition of the gut microbiota and appear to have beneficial effects on human health.An important possible future strategy could involve the consideration of microbiota as a possible intervention target to promote infants’ health, because full-term delivery, a lack of perinatal antibiotic exposure, and the use of probiotics seem to be protective factors against gut dysbiosis and all its consequences.


Nonetheless, there are still technical aspects to be answered within a research framework before the influence of these variables on the mechanical response of FRC could be covered with sufficient reliability. In this regard, this research is aimed at shedding light on the influence of the mould geometry and concrete pouring/vibration procedures on the fibre orientation and distribution variables as well as on the post-cracking performance of the FRC. An extensive experimental programme aimed at characterising these variables using novel testing techniques  was carried out for this purpose. A relationship has been found between the shape of the formwork and the direction of pouring, along with the direction and distribution of the fibres, both of which proved to have an influence on the residual tensile strength of the concrete. However, it has been confirmed that the first crack resistance depends on the concrete matrix, with the addition of fibres having no relevant influence on that mechanical parameter. The results and conclusions derived from this experimental programme can be extended to FRCs and boundary conditions similar to those established herein.The use of fibre-reinforced concrete (FRC) in structural applications is increasing significantly as a result of (1) the acceptance of this composite into design guidelines and (2) the improvement in terms of sustainability performance that has been reported for cases where FRC has been used. In this context, fibre orientation and distribution are factors that govern the post-cracking response of the FRC. Researchers have already dealt with the analysis of both variables from an experimental and numerical perspective, and design-oriented recommendations were included in existing design guidelines (i.e.,  Fibre-reinforced concrete (FRC) is becoming increasingly important as research progresses, and its use in structural components is being accepted in national and international design guidelines and recommendations . StructuThe addition of fibres improves several mechanical properties  and non-mechanical properties  of the concrete depending on the type and amount of fibres used ,8,9,10. The modulus of elasticity of reinforced concrete depends to a large extent on the orientation of the fibres; the more the fibres are aligned with the direction of stresses, the lower the tensile elastic limit . The resIt has been shown that the change in fibre orientation and fibre distribution is highly dependent on the length and height of the formwork . StudiesRegarding the influence of the rheology of the fresh concrete on the fibre orientation, some authors affirm that the fluidity of the fresh concrete is the governing parameter . This flIn some studies, equations have been developed to help predict fibre orientation in concrete, as well as CFD-based methods to monitor fibre orientation and distribution ,24,31,32Knowledge of the variation in fibre orientation and distribution is of great importance for improving the mechanical properties of reinforced concrete. Some works, such as ,34,35, fIn this paper, a complete characterization of fibre distribution on concrete-reinforced specimens with commercial hooked-end fibres HE++90 or HE++60 is performed depending on the pouring method. The characterisation of this reinforced concrete is a continuation of other studies performed by some of the authors ,36.3, obtained according to UNE 80103:2013 [The concrete was manufactured using a CEM I 52.5N, according to EN 197-1:2011 , with a 103:2013 . A superHooked-end type steel fibres were selected to manufacture the reinforced concrete. These fibres were HE 90/60 made by ArcelorMittal, and their properties are shown in Limestone gravel and limestone sand were used to produce the concrete. Its physical properties can be seen in The concrete mix proportions were obtained by the Fuller method, adding a 0.44% by volume of steel fibres, and are shown in 3 were used to determine compressive strength at 28 days, according to EN 83507:2004 [Three different cubic specimens of 150 × 150 × 150 mm507:2004 . These s507:2004  and cure3 were used to determine the flexural tensile strength at 28 days, according to UNE-EN 14651:2007 [Three different prismatic specimens of 600 × 150 × 150 mm651:2007 . These sTo quantify the fibre distribution and its influence on the behaviour of the concrete depending on the direction of pouring, two blocks  of dimensions 1200 × 400 × 1200 mm were manufactured to simulate real dimensions. These blocks were arranged in two different ways, as shown in In the first one, called “BH”, the concrete was poured on the larger side of the cube (1200 × 1200 mm), while the one called “BV” was poured with concrete on one of the smaller sides (1200 × 400 mm).A letter and a number that indicate the position on the block ;A letter V or H, depending on the block from which they have been extracted;A letter I or S, in the case of the BH block, which indicates whether the tested specimen comes from the top (pouring side) or the bottom (base) of the block.From the previously described concrete blocks, cylindrical specimens with a diameter of 132 mm were extracted using a diamond drilling machine and cut to obtain 132 mm high specimens (L/d = 1). These specimens were coded as follows:The inductive test is an application of Faraday’s law of magnetism and takes advantage of the inductance variations produced by metallic elements when interacting with the magnetic field. For such a test, the specimens must be placed within a plastic container with an established cylindrical geometry. Copper or aluminium wire coils are placed around the container, constituting the sensor element of the system, which is shown in The inductance variation measured when conducting the inductive test is essentially produced by the interaction between the fibres present in SFRC and the magnetic field. In this line, the results of the inductive test mainly depend on the type of fibre (the content of steel in the fibres), as well as the amount and the orientation ,32,43,44Calibration must be done beforehand using samples with variable fibre content that need to be characterised by means of the inductive test and subsequently crushed and ground to weigh the fibres inside the sample. The calibration curve is calculated using a zero value of inductance for a sample with no fibre content and the relationship between inductance and the weight of fibres in the analysed and crushed samples. Once this calibration is done, no further calibration is required if the same type of fibre is used.The test can be conducted in both cubic and cylindrical specimens  since thThe Barcelona test (BCN) responds to a double punch test configuration applied to a cylindrical (300 × Ф150 mm) or cubic (150 mm) specimen. It is carried out by applying a vertical force above the specimen through cylindrical steel punches of 25 mm height, the diameter of ¼ of the cross-section minor dimension. The load is applied at 0.5 ± 0.05 mm/min through the upper punch. During the loading process, a triaxial compressive stress state occurs at both extreme faces, and internal cones are generated (one per face). As the cones penetrate inside the specimen, vertical cracks that open circumferentially appear, and fibres prevent these cracks from widening through a residual tensile concrete strength mechanism. A Load-Total Circumferential Opening Displacement (TCOD) curve or Load-Axial Displacement  can be derived from the test .The BCN was originally developed to control the TCOD through a circumferential extensometer, as described in the standard UNE 83515. The test procedure was simplified through the definition of a correlation between the TCOD and the vertical displacement ,45,46 toThe correlation between the circumferential opening and the vertical displacement allows replacing cylindrical specimens with cubic samples. Even though the use of cylindrical specimens for testing is an advantage in cases of extracting cores from existing structures, testing cubic specimens under the BCN and properly analysing the results could provide an evaluation of the fibres’ preferential orientation .Cracks should propagate in the direction corresponding to the preferential orientation of the fibres, meaning that the minimum orientation direction is perpendicular to the crack. For this, cubic specimens can be tested in different directions to take advantage of the relationship between post-cracking strength and fibre orientation. This provides an estimation of the orientation of fibres in % according to the contribution of the fibres in each direction to the residual strength .p-value of less than or equal to 0.05 is obtained, it is assumed that there is evidence of significant differences between the means of the distributions;T-Test: It is an analysis that allows the comparison of the mean value of two data distributions. In general, if a p-value of less than or equal to 0.05 is obtained, it is assumed that there is evidence of significant differences between the standard deviation of the distributions;Levene’s Test: It is an analysis that allows the comparison of the standard deviation of two data distributions. In general, if a p-value is less than or equal to 0.05.Shapiro–Wilk: This is a test used to check the normality of a data set. In general, the test rejects the hypothesis of normality when the Several statistical analyses were carried out using the SciPy Python library:2), and values near -1 indicate a strong inversely proportional correlation. Values close to 1 indicate a high correlation in a directly proportional way, and those values close to 0 will imply a low correlation between the variables.The Python libraries Pandas and Matplotlib were used to generate the correlation matrix. The Pearson correlation coefficient (r) is visually represented in a correlation matrix. That is, the squared values will be the coefficient of determination (rfcm = 50 MPa (CoV = 7.4%). The mean residual flexural strength for the 0.5 mm crack opening  was 3.5 MPa (CoV = 7.1%), and for the 2.5 mm crack opening , it was 6.3 MPa (CoV = 8.3%). In The mean compressive strength resulting from three specimens was t-test and the Levene’s test, which allow a comparison of the two distributions, and gathers the mean value, standard deviation, and p-value of a t-test in the case of BH.3) and with a significantly lower dispersion than that obtained for BH. Longer concrete face travel results in better fibre distribution, which is consistent with other studies [It is concluded that the amount of fibre is equivalent in both types of pouring, but that the results of vertical pouring allow proving that the distribution of the amount of fibre is more homogeneous than in horizontal concreting (note the differences in CoVs). Thus, according to the results in  studies .t-test provides a Pvalue of 4.6 × 10−7, allowing the statement that, with high probability, the height has a significant influence on the amount of fibre distribution. In this regard, the average fibre amount at the top (24.2 kg/m3) and bottom (39.7 kg/m3) of the BH prism is 31% and 13% lower and greater, respectively, in comparison to the theoretical fibre amount (35 kg/m3). This is due to a slight segregation effect [Concerning the effect of the height of the cross-section poured (BH top and bottom), the n effect ,48, withp-value according to the row and column for which it is computed, from which it can be concluded that in all cases the available data conform to a normal distribution.Once it had been verified that in the case of BH there were significant differences depending on the position of the cores, it was then analysed to see if these variations were also observed in the case of BV. 3 of fibres).It can be seen from the results obtained that there is more dispersion where there are more fibres  reveal the differences of the means are not significant and, with high probability, these belong to the same sample population. Consequently, it can be stated that position is not an influencing variable for the fibre amount distribution.According to the results obtained and the statistical tests performed, it can be concluded that the fibre amount distribution tends to be more uniform in the case of pouring the slabs from the vertical direction. According to the results obtained, the most suitable pouring method to achieve better homogeneity according to the number of fibres distributed in the slab would be the BV.It can be observed that in all cases, the largest number of fibres (more than 36%) are oriented in the XY plane, which means that they are mostly aligned with the larger face of the formwork, both in the horizontal and vertical pouring directions.Focusing on the case of the horizontal concreting direction, it can be observed that in the upper part of the block this tendency is less clear, which may be due to the fact that the fibres have less time and space to align with the flow.ct) and residual strengths (Rs) as a function of the type of concreting (a) and of the height in BH (b). The residual strengths (Rs) are given for crack openings of 0.5, 1.5, 2.5, and 3.5 mm. Regarding the influence of the pouring procedure on the Barcelona test results , Based on the results obtained, the method of pouring does not influence the cracking load, but it does influence the residual properties of the concrete. This is due to the influence of the concreting method on the fibre orientation, an influence that other studies ,35 have Based on the results obtained in BH, it can be concluded that the position in height does have a certain influence on the post-cracking strength properties of the concrete, which makes sense considering that it has been found that there is a higher amount of fibres in the lower part of the concrete.From ct is not highly related to any other of the variables analysed. This is because it is a parameter depending on the concrete matrix, and throughout this study, the concrete (without fibres) has been the same in all cases.From 2.5 and Rs3.5. In particular, it can be seen that this correlation is higher as the circumferential deformation value increases. From Regarding the correlation between the results of the inductive test, a high linear correlation between all parameters is observed. Regarding the correlation between residual strength values and fibre quantity, it can be seen that the correlation is rather small, but that it correlates better with the projected fibre values in the XY plane than with total fibre values. This is because fibres oriented perpendicular to the direction of the force provide the most resistance.In The circumferential deformation depends on the amount of fibre in the XY plane , so that the smaller the crack opening, the more dependent it is. Furthermore, it can be seen from This means that the fibres are oriented parallel to the direction of flow, so that they flow from the centre (where the concrete is poured) to the sides. The fibres are oriented preferentially in the direction of the larger faces of the formwork.In There is a trend between the number of fibres in the XY plane and the circumferential deformation in the BH. However, in the BV, both parameters are not correlated.Referring to the different parts of the BH, As shown in 3, the main conclusion drawn from the analysis of the results is that the method of pouring has little influence on the cracking load and a great influence on the behaviour of the cracked concrete, with the following conclusions in particular:In horizontal pouring (BH), the preferential fibre direction is in the plane parallel to the bearing face on the ground (a mean of 38.18% of fibres are oriented in the XY plane), while in vertical concreting, the preferred orientation is the face perpendicular to the ground. There is an influence of the formwork walls on the orientation of the fibres in the concrete, so that the fibres tend to align with the larger faces;The pouring method does not influence the cracking load (Fct) but does influence the residual strengths, which are higher the more fibres are perpendicular to the load (XY plane);In a vertical pour, homogeneity according to the number of fibres distributed in the slab is achieved;There is a correlation between circumferential deformations, which is more accurate at high crack opening values;In the lower part of the BH, there are more fibres than in the upper part (approximately twice the density), which in turn influences the residual strength, which is higher in the lower part;According to the results of the experimental program, both the BCN and inductive tests are appropriate for quantifying the amount of fibres within the concrete, their orientation, and the post-cracking indirect strength.For the specific case study of reinforced and internally vibrated concrete with a fibre dosage of 35 kg/m


This paper presents a new bridge deck reinforcement alternative using hybrid reinforced concrete (Hybrid) consisting of Glass Fiber Reinforced Polymer (GFRP) rebar and alkali-resistant fiberglass composite macrofibers added to the concrete mixture. Fiberglass composite macrofibers are a miniaturized GFRP reinforcing bar that is a composite of resin and glass fibers. An experimental testing program and analytical modeling were conducted to evaluate the structural performance at the service and ultimate limit states. Thirteen full-scale bridge deck specimens were constructed and tested under static and fatigue loading. The fatigue loading was applied up to two million cycles at a frequency of 4 Hz. Post-fatigue, the specimens were tested to failure to compare pre-and post-fatigue behavior. Simplified and moment-curvature analytical models were used to predict the specimens’ flexural strength at the ultimate level, and both were found to be accurate for predicting pre- and post-fatigue strength. Deflection and crack width were monitored throughout the fatigue loading, and these values were compared to the recommended AASHTO LRFD serviceability limits. Testing and analytical results showed that the Hybrid deck is a viable alternative to steel-reinforced and GFRP-reinforced bridge decks for flexural behavior. The service and ultimate level behavior of each bridge deck type was adequate as compared to the AASHTO LRFD service limits. The exceptional post-peak energy absorption demonstrated by the Hybrid adds ductility to previously elastic GFRP reinforced sections. Since the 1990s, Fiber Reinforced Polymer (FRP) technologies have been implemented in infrastructure applications ,3,4. TheTwo of FRP rebar reinforcement’s primary drawbacks are its perfectly brittle behavior after the peak  and low modulus of elasticity compared to steel rebar reinforcement. The elastic response of FRP without significant plasticity or crushing of the concrete can result in sudden and catastrophic failure at the ultimate limit state . TypicalThere is limited research available on the behavior of hybrid concrete sections reinforced with both macrofibers and discrete GFRP rebar. Some researchers refer to the combination of rebar and FRC as Hybrid Reinforced Concrete (HRC) ,16, inclOther researchers have investigated the improved ductility exhibited by these HRC flexural elements has become a topic of both academic and practical interest. Wang et al.  showed tWith respect to investigating fatigue performance of HRC decks, in 1991, the National Research Council advised that there is an “urgent national need” to use composites in load-bearing scenarios. They cited improved fatigue resistance due to stress redistribution among the matrix and fibers after microcracking of the FRP, and there is an increase in residual strength . Porter Later, in 2006, the structural benefit of the FRC was researched by performing static and fatigue tests on full-scale bridge deck panels with a hybrid GFRP and FRC with polypropylene fibers with strain-softening behavior, and it was determined that the fiber addition improved ductility, bond, and crack widths in comparison with GFRP-reinforced decks without fibers. The hybrid system’s fatigue performance was also comparable to steel-reinforced slabs during 1 million cycles . Klowak Sivagamasundari and Kumaran  investigIn the present study, 13 large-scale bridge deck specimens were tested under static and fatigue loading to evaluate the structural performance of the Hybrid Reinforced Concrete (Hybrid) at the service and ultimate limits. Three reinforcement strategies were used: steel-reinforced control panels, GFRP-reinforced panels, and Hybrid panels with discrete GFRP rebar and randomly distributed, alkali-resistant GFRP macrofibers capable of sustaining many post cracking load, suitable for use as structural reinforcement. Simplified and moment-curvature analytical models were used to predict the specimens’ flexural strength at the ultimate level. Pairing GFRP rebar reinforcement with load-carrying GFRP macrofibers reduces total discrete reinforcement and is not used currently in United States practice. This concept has the potential to provide exceptional corrosion mitigation while enhancing the GFRP-reinforced sectional ductility and crack behavior and remaining cost-effective. Testing results showed that the Hybrid bridge decks are a viable alternative to steel-reinforced and GFRP-reinforced bridge decks for flexural behavior.3, a tensile strength of 1000 MPa, and a modulus of elasticity of 45 GPa. These FRP macrofibers contained Alkali-Resistant (A.R.) Glass Fibers in a vinyl ester resin. The specimens were tested under static and cyclic loading. Four steel-reinforced, four GFRP-reinforced, and five Hybrid deck panels were constructed and tested to compare the structural performance at nominal strength and service levels. Seven specimens were tested under monotonically increasing load until failure, while six specimens were tested under cyclic load followed by flexural strength test until failure. American Association of State Highway and Transportation Officials does not require the design engineer to consider the fatigue of concrete bridge deck sections [Thirteen full-scale bridge deck specimens were tested in flexure to evaluate the performance of three different reinforcement alternatives: (1) steel rebar reinforcement, (2) GFRP rebar reinforcement, and (3) hybrid reinforcement that consisted of GFRP rebar along with alkali-resistant fiberglass composite macrofibers added to the concrete mixture, see sections   until a visual crack was apparent with an initial load to achieve a steady-state cracked condition, that is, to reach a cracking moment of 28 kN-m. During the cyclic loading, potentiometers monitored the peak and valley deflection of each load cycle at mid-span. The fatigue cycles were applied using a load-controlled actuator so as to observe changes in deflection over the fatigue process. Additionally, linear variable differential transformers (LVDTs) were placed at the maximum crack on each side of the deck with the plunger at the level of the bottom surface of the panel as shown in The specified concrete compressive strength at 28 days was 34.5 MPa. Concrete compressive strength, split tension strength, and elastic modulus were measured using ASTM C39/39M , ASTM C4Testing specimens focused on comparing load at mid-span, cracking pattern, and failure modes for the three reinforcement types under static and fatigue loads. Each of the thirteen specimens behaved similarly until the appearance of the first crack, at approximately the same load, regardless of the reinforcement type. This performance was expected because the cross-section and panel geometry were the same for each specimen. The key findings of this research are presented in the following sections.cf’), modulus of elasticity (E), and split tension strength (rf) for each concrete mixture on the day of testing. The difference in the strength and stiffness of each concrete mix can be attributed to the variability in the mixes received from the batch plant. The concrete was allowed to reach at least 100 days prior to fatigue testing to ensure that steady-state strength and stiffness were achieved. An Analysis of Variance (ANOVA) was run to determine if the values were statistically different. For a threshold value of 0.05 probability, cf’, E, and rf were calculated, indicating the difference was insignificant between the time of static and fatigue strengths. No splitting tensile strength test was performed for the Hybrid decks since the EN 14651 standard [Four different concrete batches of the same 35 MPa design strength concrete were used. For each batch, standard  was usedThe residual flexural tensile stress in the FRC was obtained following the European standard EN 14651  for concSpecimens reinforced with GFRP bars  showed a nearly identical bi-linear relationship with a uniform initial uncracked slope and a post-post-cracking slope on the load versus deformation plot in The three hybrid reinforced sections  experienced similar behavior with a bi-linear moment versus deflection plot similar to that of GFRP specimens through maximum flexural resistance. The maximum recorded flexural strength of Hybrid 1, Hybrid 2, and Hybrid 3 specimens were 164.3, 146, and 150.2 kN m with corresponding deflection values of 114, 116, and 117.6 mm, respectively. The three specimens experienced compression-controlled failure by crushing of the concrete before the rupture of the GFRP, as shown in After the fatigue cycles were completed, a post-fatigue static test was performed for each of the bridge deck specimens. Comparisons between moment-deflection responses for specimens tested in flexural strength before (static test only) and after fatigue for each bridge deck type are shown in Each of the six specimens tested for post-fatigue flexural strength showed similar load-deflection behavior to those tested under pre-fatigue static loading. The maximum static flexural strengths of the steel specimens were 131.4 and 139.4 kN m with corresponding deflection values of 66.5 and 45.5 mm, respectively, for the one and two million cycle cases. The maximum static flexural strengths of the GFRP specimens were 201.9 and 205.7 kN m with corresponding deflection values of 98.3 and 95.3 mm, for the one and two million cycle cases, respectively. The maximum static flexural strengths of the GFRP specimens were 182.4 and 134.2 kN m with corresponding deflection values of 122.9 and 126.0 mm, for the one and two million cycle cases, respectively. The average differences in the maximum moment attained by the fatigued decks ranged from 3% to 11% and may be attributed to the concrete compressive strength and modulus of elasticity increase with age, see It is well documented that bridge decks fail in punching shear at ultimate loading conditions ,53,54 dusimple). This approach is consistent with the level of complexity required and performed by design engineer practitioners and supplied as Two levels of analytical models were formulated to predict the ultimate flexural behavior of each deck type at the concrete crushing strain. The first approach was an equilibrium-based approach combining Whitney’s stress block for each section at a concrete crushing strain of 0.003, tensile force in the reinforcement, and a uniform tensile stress over the tensile region, set to Equation (1), per the fib Model Code  subclausThe second analytical model involved implementing an iterative moment-curvature solution by using the constitutive models of each element based on material testing. Refer to McRory  for detaThe second analytical model involved generating constitutive relationships for each material based on experimental data. The model used to describe the compressive behavior of the concrete was based on Hognestad’s relationship for unconfined plain concrete . By usinThe nonlinear reinforcing steel model adopted by the California Department of Transportation  Seismic Design Criteria was adjusted for the data in this experiment . As suggmeasured) for the tested specimens along with the predicted flexural strength using the simple (Msimple) and moment-curvature (MM-C) model. The simplified method, as mentioned above, relies on a simplified stress distribution and a single value for the FRC stress and is intended for design. The average measured-to-predicted ratio of 1.09 indicates it provides an adequate prediction that is slightly conservative for these decks. Based on this information the simplified method is suitable for design. The moment-curvature-based method is unlikely to be used for design but was more accurate with a measured-to-predicted ratio of 0.95 but it was slightly below unity. Both methods are accurate and likely acceptable for design.Once all of the constitutive relationships were established for each deck type, the sections were discretized into 1000 layers, and a neutral axis was assumed. For each iteration, the curvature in the section was incremented, and the strain, force, and stress were calculated for each layer. If the section achieved the equilibrium of forces, then the assumed neutral axis position was correct, and the moment at that increment of curvature could be calculated as long as no failure criteria had been met . If equilibrium was not satisfied, then the neutral axis location was varied by using the Newton-Raphson method until the equilibrium conditions were met, and as long as the failure conditions were not exceeded, the moment could be calculated. This process of incrementing curvature and balancing equilibrium in the section according to the constitutive relationships was repeated until the failure criteria were met, at which point the moment-curvature relationship until failure had been developed. A moment-curvature program was created to calculate the flexural strength of the tested bridge deck specimens, refer to  for the AASHTO LRFD Section 2.5.2.6.2  specifieThe live load crack opening was recorded and reported as the amount the crack varied from peak to valley; however, the peak crack opening is the value that the AASHTO LFRD code attempts to limit by the spacing of the reinforcement. For a class 1 exposure, the AASHTO LRFD Specification states that the crack width equation is based on a crack width equal to 0.43 mm (0.017 in.) . The AASFailure of the bridge deck panels was defined as the point at which the concrete crushes. This crushing occurred after the yielding of the steel in the steel-reinforced bridge decks but before the GFRP rupture for both the GFRP-reinforced and Hybrid members. Comparing the pre- and post-fatigue M-C strength prediction ratios for each deck type listed in In general, the fatigue cycles did not adversely affect the overall flexural strength of the different bridge deck types. Before fatigue, the M-C model over-predicted the moment capacity by an average of 7.6%. After fatigue, the model over-predicted the moment capacity by an average of 3%. This demonstrates that the post-fatigue decks performed adequately, if not better, when compared to the pre-fatigue decks, as mentioned before. The steel failure is the most desirable failure mechanism of the three deck types, but the added ductility at maximum load and enhanced bond from the Hybrid compared to the GFRP decks makes the Hybrid decks a viable alternative.All bridge deck specimens were acceptable for the live load deflection criteria established by AASHTO LRFD specification with an average deflection adequacy ratio (i.e., The steel reinforced decks outperformed both the GFRP and Hybrid decks with respect to the live load deflection with an average deflection adequacy ratio of 0.46 for the two specimens tested for one and two million cycles. This is attributed to the comparatively high stiffness of the steel. The Hybrid and GFRP deflections were similar under service loading conditions with an average deflection adequacy ratio of 0.67 and 0.59, respectively.All of the bridge decks performed well concerning the peak crack width. The average ratio of actual crack width to allowable crack width for steel, GFRP, and Hybrid specimens were 0.41, 0.33, and 0.52, respectively.In static flexure, the Hybrid decks deflected an average of 29% more than the GFRP decks for pre- and post-fatigue and 119% more than the steel reinforced decks pre- and post-fatigue.Although the steel reinforced decks demonstrated much more energy absorption after failure, the Hybrid decks also showed post-peak residual strength and ductility. The post-peak behavior of the GFRP is minimal due to the linear elastic behavior of the GFRP.measured/MM-C ratio of 0.95 for all specimens.A moment-curvature model can be created to calculate the flexural strength using the constitutive relationships of each material that predicts the pre- and post-fatigue static behavior for hybrid reinforced and discretely reinforced decks. The model created in this study predicts behavior with an average MA lower-bound prediction can also be provided using Whitney’s stress block and neglecting contributions from the compression reinforcement. This simplified approach predicts behavior with an average Mmeasured/Msimple ratio of 1.09 for all specimens.The GFRP-reinforced deck sections experienced some bond loss as exhibited by the failure modes during fatigue loading. The same bond loss was not seen in the Hybrid or steel sections. This seems to indicate that the fibers in the Hybrid aided in the bond behavior of the GFRP bars during fatigue loading and may be a topic of future interest.The fatigue loading, while more severe than a deck with in-service boundary conditions, did not adversely affect the behavior of the deck sections in static flexure.The steel-reinforced decks experienced a tension-controlled failure, but the GFRP and Hybrid decks experienced a compression-controlled failure, which is consistent with the design approach of each deck type.By examining the decks in both static and cyclic behavior, it was determined that the Hybrid decks with discrete GFRP bars and alkali-resistant macrofibers are viable alternatives to steel-reinforced and GFRP-reinforced bridge decks for flexural behavior. Both the ultimate and service level behavior of each bridge deck type was adequate per the established AASHTO provisions, and the exceptional post-peak energy absorption demonstrated by the Hybrid adds ductility to previously elastic GFRP sections.An experimental testing program was conducted to evaluate the structural performance of steel-free bridge decks reinforced with GFRP rebar and alkali-resistant fiberglass composite macrofibers added to the concrete mixture. A total of 13 large-scale bridge deck specimens were constructed and tested under static loading as well as fatigue loading. The static load consisted of a monotonically increasing load until failure was reached. The fatigue loading was applied over one million cycles for the first set and two million cycles for the second set. Following the fatigue loading, the specimens underwent a static test until failure to compare pre- and post-fatigue behavior. Simplified and moment-curvature analytical models were used to predict the flexural strength of the specimens at the ultimate level. Deflection and crack widths were monitored throughout the fatigue loading, and these values were compared to recommended AASHTO LRFD serviceability limits. The following conclusions were drawn from the experimental and analytical investigation:


Antibiotics are used extensively throughout the world and their presence in the environment has caused serious pollution. This review summarizes natural methods and enhanced technologies that have been developed for antibiotic degradation. In the natural environment, antibiotics can be degraded by photolysis, hydrolysis, and biodegradation, but the rate and extent of degradation are limited. Recently, developed enhanced techniques utilize biological, chemical, or physicochemical principles for antibiotic removal. These techniques include traditional biological methods, adsorption methods, membrane treatment, advanced oxidation processes (AOPs), constructed wetlands (CWs), microalgae treatment, and microbial electrochemical systems . These techniques have both advantages and disadvantages and, to overcome disadvantages associated with individual techniques, hybrid techniques have been developed and have shown significant potential for antibiotic removal. Hybrids include combinations of the electrochemical method with AOPs, CWs with MFCs, microalgal treatment with activated sludge, and AOPs with MFCs. Considering the complexity of antibiotic pollution and the characteristics of currently used removal technologies, it is apparent that hybrid methods are better choices for dealing with antibiotic contaminants. Since the discovery of penicillin and its application on industrialization and commercialization, hundreds of antibiotics have been discovered and are utilized . CurrentFor the protection of public health, the European Commission has established maximum residue limits (MRLs) for antibiotics and other pharmacologically active substances in foods of animal origin ,13. In tAntibiotic pollution is widespread in the environment and can be detected in surface water, groundwater, sediments, soil, and even drinking water ,21. The Antibiotics are even found in groundwater. The three main sources of antibiotic contamination of groundwater are drainage from the soil, infiltration from sediment, and introduction through the exchange between surface water and groundwater . AntibioAlthough antibiotics in the environment are usually detected only at the trace concentration level, “false persistence” may occur due to poor degradation of antibiotics and persistent input resulting from continuous discharge into the environment .Residual antibiotics in the environment pose both toxicological effects and ecological risks . For exaAccordingly, the environmental problems caused by antibiotics have become a significant challenge that requires urgent solutions and have attracted attention from environmental scientists around the world . AlthougAntibiotics can degrade to varying degrees in different environments by non-biological and biodegradation processes. Non-biological degradation includes photolysis, hydrolysis, oxidative degradation, and ionizing radiation degradation, while biodegradation in the natural environment includes degradation through the action of microbes, algae, and plants . Table 2Photolysis in the natural environment can be divided into three pathways, namely, direct, indirect, and self-sensitized photolysis .Direct photolysis refers to the process by which the antibiotics absorb photons directly, causing the molecules to become excited through the transference of light energy and leading to the formation of products through bond breakage or structural rearrangement . The pro2− and ·OH) . B. B169]. Chlorella, Scenedesmus, Microcystis, and Chlamydomonas [Previous studies have demonstrated that MFCs can effectively remove organic substances, although nutrient removal is limited due to anaerobic conditions at the anodic pole ,200. To ydomonas ,203.3-N within 90 h at the biocathode, while the degradation of florfenicol was enhanced through the anodic bioelectrochemical reaction; in addition, florfenicol promoted the growth of Pseudomonas species, leading to a 3.2-fold increase in power output. Furthermore, MFC systems can eliminate ARB and ARGs [Based on the cooperative interactions between microalgae and bacteria, hybrid microalgae–bacteria–MFC systems have been developed to deal with antibiotic pollutants. In these systems, cooperation between microbial metabolism and electrochemical redox reactions promotes the removal of antibiotics ,204. A nand ARGs . Therefoand ARGs ,207. TheDespite high removal efficiencies and rapid removal rates , AOPs haAntibiotics in natural environment can undergo photolysis, hydrolysis, and biodegradation, all of which are affected by various environmental factors, including pH, temperature, and the environmental medium. However, antibiotic removal by these methods is low and requires extended times for degradation. Thus, there is an urgency to develop more effective methods of antibiotic removal to reduce the contamination problem.Biological methods have been traditionally used for the removal of pollutants. These have the advantages of low cost and large-scale operation. Unfortunately, antibiotics can inactivate the bacteria and increase the amounts of ARGs and ARBs, thus compounding the pollution problem. Adsorption technology and membrane separation technology have advantages of simplicity and convenience. In terms of adsorption technology, there is usually a significant gap between static adsorption effect under laboratory conditions and dynamic adsorption effect in practical engineering. In terms of membrane separation, the membrane is easily blocked and the application is also limited by the water quality conditions. AOPs can effectively remove most antibiotics with both high levels of efficiency and effective degradation. However, AOPs have different effects on different antibiotics and are susceptible to the complexity of antibiotic wastewater. The formation of intermediates during the reaction is highly likely. At present, we do not fully understand the toxicology and potential pathology of these intermediates. In addition, AOPs are also costly, with complex operational and maintenance issues.Compared with the traditional biotechnology biotechnological applications, CWs and microalgal treatment have the advantages of effective antibiotic removal but nevertheless have the disadvantage of ARG transfer. MESs is not only an effective and reliable technique for treating antibiotic-containing wastewater but also has great potential for the reduction in ARGs. The relatively low concentrations of antibiotics in the environment present difficulties for their removal by traditional treatment techniques. It is hard to achieve ideal removal by relying solely on one technique. This suggests that the advantages of different treatment techniques should be combined for the effective removal of antibiotics. Many studies on hybrid techniques, combining EAOPs, CW–MFC, microalgae-activated sludge, and AOPs–MFC, have demonstrated their effectiveness.Research into the different techniques for antibiotic removal has been fruitful, although most are currently at the laboratory stage. This indicates that there is a significant gap between the transitions from the laboratory environment to the practical application. It is important to apply these findings as soon as possible and, in particular, the application of hybrid technology to achieve effective removal in large-scale operations should be the focus of future research.