COMT genotype, craving, and treatment outcomes. (2) Methods: To this end, we assessed craving, recent drinking history, and impulsivity in 70 individuals with AUD undergoing a standard course of treatment at a regional Veteran Affairs (VA) medical center. Saliva samples were collected to determine COMT genotype. In this prospective observational study, participants were followed for six months to determine who went on to relapse after treatment. (3) Results: Results revealed a significant interaction between craving and catechol-O-methyltransferse (COMT) genotype in predicting relapse. Post hoc exploratory analyses indicated that Met/Met homozygotes reported the highest levels of craving, and craving was associated with recent drinking history. Among Val/Val homozygotes, who had higher rates of relapse, craving was associated with impulsivity. (4) Conclusions: These associations highlight that specific profiles of psychological and biological factors may be important in understanding which individuals are at highest risk of relapse following treatment. Future studies that build on these findings are warranted.(1) Background: Alcohol use disorder (AUD) is associated with poor medical, psychological, and psychosocial outcomes and approximately 60% of individuals with AUD relapse six months after treatment. Craving is a core aspect of AUD and associated with high risk of relapse. One promising avenue to improve outcomes may be in understanding the relationship between  Alcohol is the third leading preventable cause of death in the United States ,2 and a Understanding the biological and psychological factors that contribute to relapse offers one promising avenue to improve clinical outcomes. Craving is a core aspect of AUD  and is aO-methyltransferse (COMT) gene may be particularly relevant to AUD, given its relationship to dopamine. The COMT gene, located on chromosome 22q11.22-23 [rs4680 is a guanine-to-adenine single-nucleotide polymorphism which changes the amino acid at position 158 from valine to methionine. This Val158Met substitution reduces the thermostability of the COMT enzyme and decreases its activity [COMT genotypes may be a key component in promoting relapse.Genetics may be relevant in understanding individual differences in the experience of craving . AUD dem11.22-23 ,39,40, pactivity ,39,40,41activity ,43. Indiactivity , therebyactivity , with thactivity ,51,52,53activity ,55. TherCOMT genotype, i.e., craving. To this end, there has been little research on the relationships between COMT genotype, craving, and treatment outcomes. Wojnar et al., 2009, found that individuals with AUD who are carriers of the COMT Met allele were more likely to relapse [COMT did not predict relapse rates, suggesting that the effect may be too subtle to detect, but critical in terms of physiology. Therefore, there is a need to extend this research further to understand the relationship between dimensions of craving, COMT genotype, and relapse prediction. Some studies have found an association between AUD and the Val158Met single nucleotide polymorphism, such that the lower activity Met allele was associated with higher odds for the presence of AUD ,57,58,59 relapse . HoweverCOMT genotype, and relapse risk in individuals with AUD following a standard course of residential treatment. We hypothesized that individuals with higher self-reported craving would be at higher risk of relapse. With the paucity of literature on the topic, we hypothesized that individuals with the Met allele variant would have higher craving and would be at increased risk of relapse, although directionality of this hypothesis was based on one study with weak findings. In addition, we tested if the relationship between craving and relapse, if any, was be mediated or moderated by COMT genotype. Specifically, individuals with higher craving and the Met allele were thought to be at greatest risk for relapse. Given that heterozygous individuals  have an intermediate level of COMT enzymatic activity in relation to the homozygotes [The aim of the current study was to understand the relationship between self-reported craving, ozygotes , we chosn = 70; 17 females) were recruited from residential treatment programs at the VA Palo Alto Health Care System (VAPAHCS) from a parent study aimed at understanding neural predictors of relapse in Veterans with AUD. All Veterans were actively seeking treatment for AUD at the time of their participation. These programs typically ranged in duration from 28 to 90 days. Participants were between 23 and 91 years old  and all met DSM-5 criteria for AUD. All participants provided written informed consent prior to the study. Study procedures were approved by the VAPAHCS and Stanford University Institutional Review Board and were in accordance with the ethical standards of the Declaration of Helsinki. Veterans with AUD  adults aged 18 and older; (ii) fluency and literacy in English; (iii) endorsement of at least two DSM-5 criteria for AUD; and (iv) seeking treatment for AUD. Exclusion criteria were: (i) presence of suicidal ideations representing imminent risk; (ii) general medical conditions, diseases, or neurological disorders that are known to affect the primary outcome measures of the study ; (iii) history of traumatic brain injury, resulting in loss of consciousness greater than ten minutes; (iv) severe impediment to visual and/or auditory acuity or motor skills, likely to interfere with ability to complete the assessments; (v) magnetic resonance imaging (MRI) contraindications ; and (vi) exclusionary psychiatric history included diagnosed bipolar disorder, schizophrenia spectrum and other psychotic disorders, and/or other current substance use disorders, except tobacco and cannabis use disorders. Participants were breathalyzed and urine tested for illicit substances prior to the assessments. The MINI , a shortThe Alcohol Timeline Followback (TLFB)  is a staGiven that craving is not uniformly experienced among individuals with alcohol misuse, the OCDS was used to assess the multifactorial nature of alcohol craving. This scale  is a 14-The BIS  is a 30-In this longitudinal study design, participants were monitored one, three, and six months post-study assessment to evaluate alcohol consumption following treatment. Participants were interviewed via telephone and asked about relapse status and date of their initial relapse and administered the TLFB (if applicable). When participants could not be reached by telephone, relapse status was acquired via contact with a close family member or friend, or review of their medical records to determine relapse status. Participants were designated as relapsers if any alcohol was consumed after their participation in the study at any follow-up assessment per self-report via telephone interview, a close family member or friend contact, or if alcohol consumption or relapse was explicitly indicated in the medical records. If the participant was designated as a relapser at any follow-up assessment, relapser classification applied for all additional follow-up assessments, even if they remained abstinent in between. Participants were designated as abstainers if they either self-reported no alcohol consumption between the baseline and 6-month follow-up assessment or if there was an explicit report confirming abstinence in the available medical records. A lack of confirmation of alcohol consumption in the medical records post-treatment was not considered an indicator of abstinence. Saliva samples were collected using the saliva genetic collection kit (DNA Genotek #OGR-500) from participants who opted into this portion of the study. The cellular contents of the sample, in general, contain a higher ratio of leukocytes to epithelial cells. Genomic DNA was extracted in accordance with the manufacturer’s (prepIT∙L2P) instructions. Briefly, the samples were incubated in a lysis buffer and the DNA was precipitated from the supernatant via ethanol. DNA quantification and purity were checked by nanodrop and reisolated if the sample had low purity or low yield, in accordance with procedures and recommendations from Desjardins & Conklin . COMT Val158Met single nucleotide polymorphism (SNP) rs4680 was assayed using a polymerase chain reaction (PCR) method previously established [p = 0.30), and remained in equilibrium even when ethnicity was taken into account . t-tests. One-way ANOVA analyses were used to test the hypothesis that COMT genotype will influence self-reported craving. Examinations of whether COMT genotype mediated or moderated the relationship between craving and relapse were tested with moderation and mediation analyses using the PROCESS v3.4 (Hayes) macro in SPSS, specifically using models 1 and 4. Bootstrapping was used to determine confidence intervals, and therefore significance, of our results. Lastly, exploratory post hoc analyses were conducted to examine which, if any, additional psychological constructs were related to COMT genotype, craving, and/or relapse using Fisher’s exact t-tests and Pearson or Spearman’s bivariate correlation.All analyses were conducted using SPSS. To test our hypothesis that higher craving would be related to higher rates of relapse, we conducted Fisher exact n = 51) of the sample were classified as relapser by six months post-treatment. Detailed descriptive statistics related to demographics, psychiatric comorbidities and symptom severities are displayed in p’s > 0.25). Histograms and skewness of all variables demonstrated normal distribution. Overall, 72.9% .In the overall sample, craving, as measured by the OCDS total score, was not significantly different between relapsers and abstainers (t(68) = 1.43, COMT genotype groups. We found a trend toward significance between the three groups on OCDS total score  = 2.87, p = 0.06), and significant differences between groups on the obsessions subscale  = 3.22, p = 0.046). Pairwise comparisons revealed that observed differences were driven by Met/Met homozygotes, who reported the highest levels of craving ; however, it is worth noting the frequency of relapse by COMT genotype: Val/Val homozygotes had a relapse rate of 88.2%, Val/Met heterozygotes had a relapse rate of 66.7%, and Met/Met homozygotes had a relapse rate of 73.1% . However, the moderation model was significant such that OCDS total score  and COMT genotype  independently predicted relapse, as well as their interaction . This overall moderation model  to understand some of the psychological factors that may be driving these results. Given the surprising result that higher craving was associated with abstinence, we first examined recent drinking history and impulsivity as potential factors that may be associated with craving by COMT subgroups. Recent drinking history was significantly correlated with craving only in the Met/Met group in the expected directions: Days since last drink at the time of participation  was negatively correlated with craving, while total drinks consumed in the prior 90 days , total drinking days , average drinks per day , days of excessive drinking , and maximum drinks per day  were positively correlated with craving. With respect to impulsivity, higher craving was positively associated with higher global impulsivity , but only in the Val/Val group. Exploratory post hoc analyses investigated subgroups , and positively correlated with total drinks , total drinking days , and days of excessive drinking . In addition, among the relapsers, craving was associated with global impulsivity , perseverations , and lack of self-control .When looking at treatment outcomes regardless of Overall, our results highlight the complex interactions between genetic, biological, and psychological processes that influence the course of AUD recovery. While neither craving nor genotype predicted relapse independently, the interaction of these factors was predictive of relapse. In this sample, the Met/Met group reported the highest level of craving, which correlated significantly with recent drinking history, whereas cravings in the Val/Val group were correlated with impulsivity but not recent drinking history. Although this was not directly quantitated, data from the heterozygote group was similar to the Val/Val group in some cases (OCDS score) and, in others, similar to the Met/Met group (percent relapse). The mixed results in the heterozygous group may reflect an intermediate level of dopaminergic tone but requires further investigation. These results highlight that individuals of differing genotypes experience diverse profiles of psychological factors that may affect the clinical course of AUD. COMT genotypes influence the clinical characteristics of AUD. Dopamine is associated with incentive salience and reward anticipation and evaluation such that individuals with higher dopaminergic tone might derive more pleasure from contemplating future drinking and feel more motivated to drink [We found that the Met/Met group reported increased craving, specifically obsessions about alcohol, compared to the Val/Val group. This evidence is consistent with our hypothesis that to drink ,73. Howeto drink ,49,50,51In the Met/Met group, cravings correlated positively with drinking history, but factors such as stress were not significantly correlated with cravings. There has been speculation that because Met/Met individuals have higher consummatory rewards , drinkinCOMT genotype on impulsivity have yielded mixed results [On the other hand, we surmise that cravings in the Val/Val group was associated with impulsivity. Val homozygotes are presumed to have lower dopaminergic tone in the frontal cortex, and therefore less capacity to exert inhibitory control over behavior . Our fin results ,82,83,84Within the context of AUD, changes in both dopaminergic tone and impulsive/compulsive behavior are common and associated with alcohol-related neurobiological adaptations ,44. The While management of alcohol cravings and moderation of impulsive behaviors are common targets of current clinical treatment for AUD, our study offers a strong basis for tailoring treatment based on genotype, particularly if these findings are replicated. Genetic testing and counseling are becoming increasingly accessible and applicable to addressing mental health concerns . In the COMT gene is one of several within the dopaminergic pathway that may be related to AUD and, more specifically, cravings. For example, the SNCA gene that codes for alpha-synuclein has been associated with alcohol cravings but not necessarily AUD [DRD3, another gene within the dopaminergic pathways, and ITGAD, which is not expressed within dopaminergic pathways, have additionally been found to modulate alcohol cravings [The rily AUD ,88. DRD3cravings . Future cravings ,90 can bCOMT genotype rates by ethnicity, race, and sex, so although this is an important question to explore in future research, this likely does not undermine our findings. We were also unable to determine genetic ancestry or genetic sex and lacked the sample size to stratify by such factors as recommended by Nievergelt et al. [COMT genotype and cortisol response. Recent publications [COMT and AUD. We were limited in our ability to investigate factors that may be protective or promote resilience following treatment due to the relatively small proportion of abstainers in our study. We chose the analyze the three COMT genotypes in separate groups rather than combining the heterozygotes with a homozygotes group, which has been frequently done in the past. This may have resulted in a loss of overall power but given that the heterozygotes did not consistently fall within one group or another, merging them may have clouded our overall findings and could explain why there has been conflicting results in the prior literature. Our results shed light on the complex interaction between genetic, psychological, and environmental factors that contribute to addiction. However, this study has a few limitations. Our assessment of relapse was based on self-report rather than biological confirmation . Consistent attainment and analysis of biological samples is not practical in those who have completed treatment or are in an outpatient setting. This method of assessment has been successfully used in the past , so altht et al. . This ist et al.  did inclications ,94,95 haCOMT genotype in predicting relapse six months after a standard course of treatment. In addition, Met/Met homozygotes with AUD reported the highest level of craving, which correlated significantly with recent drinking history. Val/Val homozygotes had a higher rate of relapse, and craving was associated with impulsivity. This research has provided a direction for future hypothesis development and research endeavors, which can be specifically designed to evaluate the complex relationship between COMT genotype, craving, and treatment outcomes in AUD. In addition, relating these findings to underlying neural structure and function may allow for a more comprehensive understanding of the factors that need to be targeted to improve treatment outcomes.The current study provides evidence for an interaction between craving and


This paper presents an experimental program that includes 78 fiber reinforced polymer (FRP)-confined square concrete columns subjected to eccentric loading. The degradation of the axial strength of FRP-confined short concrete columns due to the load eccentricity is investigated in this work. A larger load eccentricity leads to a greater decrease in the axial strength. From the test results, it is found that FRP confinement can cause less strength degradation compared with that of unconfined concrete specimens. For FRP-confined square concrete specimens, the strength enhancement due to FRP confinement increases with increasing load eccentricity. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. The relationship between the strength of eccentrically loaded FRP-confined square columns and their corner radii is evaluated. Fiber reinforced polymer (FRP) jacketing or confinement has been widely adopted and used in rehabilitation work on concrete structures ,2,3,4. TMany experimental investigations on eccentrically loaded FRP confined columns have been carried out on circular columns ,39,40,41Overall, the available tests on eccentrically loaded FRP-confined concrete columns are limited in the open literature, especially for square cross-sections. As the confinement mechanism for square columns is different with that of circular columns, it is necessary to clearly understand the relationship between column section and confinement efficiency under eccentric loading. This work aims to investigate the degradation of the axial load capacity due to the load eccentricity on FRP-confined square and circular short concrete.The experimental program included 78 square confined columns with different FRP confinements , corner radius ratios , and a full range of load eccentricities . The details of the specimen design are given in b), a depth of 150 mm (d) and a height of 300 mm with different corner radii (r). To independently study the behaviors of the confined concrete, no internal reinforcement was used for the specimens. The corner radius ratio ρ is a key factor that affects the confining effect of FRP wrapping and is determined as [b is the length of the side for square cross-sections and the diameter for circular sections. The effect of the corner radius ratio ρ and the steel molds for concrete casting can be found in All the specimens were designed with a width of 150 mm  was used for the FRP wrapping, which had a nominal thickness of 0.167 mm. A two-part Sikadur-300 was used as the saturant resin. Flat coupon tensile tests were conducted following ASTM D3039  to deterFor the specimen IDs in All the specimens were tested after 28 days of curing. The test setup is shown in For unconfined concrete specimens with concentric loading, the concrete mainly split longitudinally on the side surface, and the cone appearance could also be found on the failure surface. For unconfined columns with relatively larger load eccentricities, the failure of the specimens was generally marked by concrete crushing at the compression side at or near the mid-height of the specimen, and a horizontal crack at approximately mid-height or at the top of the column was clearly observed on the tensile side. For the columns with the largest eccentricity of 60 mm, the specimens crushed at the top of the specimen on the compression side. The typical images of failure modes of the tested FRP-confined square short columns are shown in eN), of all the specimens are listed in The failure of all FRP-confined specimens was always caused by FRP rupture, and no delamination of the FRP at the overlapping zone was observed. Clicking sounds could be heard during the loading stage, and the failure occurred suddenly with an explosive sound. The fracture of the CFRP jacket was mainly near the corner of the compression side due to the stress concentration. On the tensile side, horizontal cracks along the fiber hoop direction were observed at mid-height or in adjacent areas. Furthermore, crushing of the concrete core occurred in the specimens with a relatively large load eccentricity. The test results for the axial strength, which refer to the peak load for a section in the tests , the cross-sectional strength reduction degree is limited and is occasionally close to 0. However, when the load eccentricity increases, the decrease in the axial strength is more significant. Additionally, a greater confinement (or number of FRP layers) results in a higher strength.A nondimensionalized term 2eN/cN is carried out by modifying the results in cN is the axial strength for concentrically loaded specimens with the same confinement level as that of eN. The results are shown in To better understand the strength degradation due to the load eccentricity, another comparison of eN/fN0, where fN0 is the axial strength for unconfined concrete with the same load eccentricity as that of eN. The comparison results are shown in eN/fN0. A high value of eN/fN0 represents a higher efficiency due to the FRP confinement because this ratio represents the strength enhancement by the FRP confinement. For most FRP-confined square concrete specimens, it can be found in eN/fN0 increases when the load eccentricity increases. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. This is reasonable because the circular section has less compressive area than that of square columns for a fixed load eccentricity or natural axis. This trend is more significant for a large eccentricity because of the small height of the natural axis.The contribution from the FRP confinement can be further investigated by studying the effect of the load eccentricity on e/b = 0, which means the concrete is under concentric loading, a greater corner radius can result in a higher value of eN/fN0, as shown in r = 15 mm  is applied to determine the axial strength of FRP confined concrete under eccentric loading, Equation (3) can be written as:c-fN and c-0N are the eN and f0N values for 2r/b = 1 , respectively.However, Equation (2) was proposed for the ultimate strength of the stress-strain relationship of FRP-confined concrete. Jiang et al.  extendedeN/fN0 values for the various corner radii with a fixed number of FRP layers are plotted in c-fN/c-0N in Equation (4) takes the average test values in The The compression tests on a total of 78 FRP-confined square concrete columns subjected to eccentric loading were reported in this work. The degradation of the axial load capacity due to the load eccentricity was investigated. After analyzing the test results, the following conclusion can be drawn.(1)e/b = 0.13), the axial strength reduction degree is limited and is occasionally close to 0. However, when the load eccentricity increases, the decrease in the axial strength is more significant.When the load eccentricity is small FRP confinement can reduce the axial strength degradation compared with that of unconfined concrete specimens. While different confinement levels  do not have a significant influence on the strength degradation.(3)For FRP-confined square concrete specimens, the strength enhancement due to FRP confinement increases with increasing load eccentricity. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. This is because the circular section has a much less compressive area than that of square columns for a fixed natural axis.(4)The relationship between the structural behavior of FRP-confined square columns and their corner radii (Equation (4)) can basically describe the effect of the corner radius on the axial strength of FRP-confined concrete subjected to eccentric loading.


This paper carries out the assessment of load-carrying capacity of prestressed concrete sleepers, in accordance with Brazilian Standard (ABNT NBR 11709) and AREMA Standard. In a lot of railways around the world, many prestressed concrete sleepers have failed due to Rail Seat Abrasion (RSA) and corrosion. RSA is the wear degradation underneath the rail on the surface of prestressed concrete sleepers. In this paper, a numerical study was carried out to evaluate the load-carrying capacity of the prestressed concrete sleepers, using ABAQUS software. The nonlinear using Concrete Damage Plasticity model was validated by 18 experimental results, in accordance to standards. Using the validated model, the influence of different wear depth RSA, combined with corrosion of the prestressed wires, is investigated. The sleeper is one of the fundamental elements of the superstructure of the railway tracks. In summary, its main functions are to support the rails, keep the axis of the track constant and transmit to the ballast the actions of the axles of the vehicles. These functions make it necessary to provide the sleeper with a high level of strength, which in general leads to great stiffness; at the same time, it is also necessary to have a certain level of elasticity, since it must be able to withstand extremely high impact forces ,2,3. In In order to overcome this deficiency, with a bigger nominal concrete cover, to avoid corrosion of the reinforcement concrete, it was applied in concrete the corrosion inhibitors. Corrosion inhibitors are useful in cases where it is not possible to achieve full concrete cover on the reinforcement; however, they raise the price of the sleeper ,9,10,11.Thus, with the development of prestressed concrete, the possibility arose to combat cracks in concrete, giving rise to a new stage in the design of concrete sleepers. Prestressed concrete sleepers used in railways emerged historically from World War II, and recently there was an increase in their use due to their technical superiority, in order to replace wooden sleepers .The purpose of the prestressed force on the rebars is that the stress applied to the steel wires allows the material to remain compressed, even under bending, thus avoiding the opening of tensile cracks. Recently, the need for sleepers’ replacement in old railroads has been increasing, as well as the average increase of the speed guide provided by increasingly modern trains, which economically justifies the large amount of studies on this theme around the world ,12,13.The sleepers are subjected to cyclic loads during their whole life; the materials that comprise them are subjected to an intense process of fatigue. It is desirable that the sleeper is free of cracks under dynamic loading, because if cracks occur, there is a great increase in stresses in the prestressing reinforcement and an increase of up to 50% in the transfer length ,15,16. TThus, this paper aims to evaluate the mechanical behavior of prestressed concrete sleepers, in accordance with the Brazilian and American standards and the common pathologies they are submitted to over their design life. A comparison is made between the results obtained numerically by the software ABAQUS and the experimental curves obtained through the tests, as recommended by ABNT NBR 11709  and AREMEighteen sleepers were taken from the Brazilian railway and were tested in in the Infrastructure Laboratory—INFRALAB and in the Structures Laboratory—LABEST of the University of Brasilia, using the Brazilian Standard  .The sleepers were designed for a positive moment of 2856 and 1786 kN.cm for the negative moment in the center of the sleeper. An initial prestressing force of 51 kN was applied to the 13 ϕ 6.3 mm wires. For the concrete compressive strength test, two specimens were extracted from five sleepers of the same batch, using a drill bit with a water-cooled diamond drill, which was capable of extracting specimens with a diameter of 68 mm and a height of up to 200 mm see .fc), the analysis corrections indicated by Item 6.2 of the Brazilian standard ABNT NBR 7680 [k1, k2, k3 and k4, given by the following equation:k1 represents a correction for the relationship between the height of the specimen (h) and the diameter (d); k2 would be the correction of the boring effect according to the diameter of the specimen; k3 is the direction of extraction in relation to the casting of the concrete, considered equal to zero because it was adopted that the direction of the concreting was parallel to the casting of the concrete; and k4 is the effect of moisture in the core; for structures without contact with water, this value is equal to 0.04, so it was possible to obtain the strengths of the concrete and the modulus of elasticity.After the extraction of the specimens, the surfaces at the end of the specimens were leveled with the aid of a grinding machine with a diamond disc, and then the compression test was carried out by using the procedure of the Brazilian standard ABNT NBR 5739 ; the resNBR 7680  were perjP was applied at a speed of less than 50 kN/min, until the appearance of the first bending crack. Such moment generated with the first crack simulates the field conditions. Subsequently, a load was applied at a rate of 60 kN/min, until the sleeper failure. Although the concrete strength adopted in the design is 50 MPa, it was found that condition of the concrete in the test age of about 1 year obtained an average strength of 63.67 MPa. The prestressing tendons are the chevron-patterned indented wires with ultimate strength of prestressed steel 1750 MPa. From visual inspection, it could be observed that the high-strength prestressing wires were of high quality, and thus the strength would not change so fast during the time. For carry out the experimental tests, the loading Two test systems were developed; in the first test, eight sleepers were subjected to a positive moment test with load application at midspan of the sleeper supported on concrete blocks in the reaction frame. In the second, the load was applied on the base plate, which is attached to the rail of the railway, with ten experimental tests. In adherence tests, LVDT  was used to obtain the displacements at the load application point, and also in the prestressing wires at the end of the sleeper. Z. Subsequently, the results were plotted for comparison with a numerical model.For the simple bending test, this paper shows the details of the experimental tests by using one LVDT to measure the displacement in the center of the sleeper. The load was applied and controlled with a system set consisting of a three-phase motor responsible for pumping the hydraulic oil, a key that controlled the pressure outlet and a hydraulic actuator with a capacity of 1000 kN coupled in a load cell of 1500 kN. The reading was automatic by means of a system that recorded the data at a rate of 2 HThe sleepers with one year of use were removed from the railroad for testing. Ten sleepers were chosen to test the resistance in the rail support. In the load test of positive moment at the support, shown in In the positive moment test at the midspan with increasing load, the tensile failure stress was reached in the midsection, and the first vertical cracks with an average load of 278 kN appeared, covering half the height of the sleeper, or up to one just below the neutral line. In this phase, the tension forces were absorbed by the prestressed wires. After the beginning of this stage, the extreme sections of the concrete have not yet reached the breaking stress, but with the progressive increase in the load, the concrete began to have inclined cracks, until the failure of the lower wires. At this stage, the concrete showed crushing in the upper fibers, and the failure occurred with the increase of bending and shear cracks see . Figure As shown in In the first test, when the loads reached 566 kN, there was a total of plastification of the sleeper section with yielding of steel wire and concrete failure by crush of the compressed section. In the simple bending test, the plastic load that causes the failure of the sleeper was between 350 and 400 kN. At this stage of the test, the loss in tension strength of the concrete, the tension stresses were not completely resisted by steel wires, and consequently, it yields. Therefore, the failure range of the sleeper had a difference of 10.80% b. In allIn the concrete crack model, it is assumed that cracking is the most important factor in the material’s behavior. A “completely non-isotropic” behavior will govern the material after it has cracked. However, cracks influence the process of the computations and create problems for convergence of the results. Using the concrete crack model is advisable in cases where the concrete is under relatively low stresses . Therefore, in this study, we used the Concrete Damage Plasticity (CDP) model, with ABAQUS . The Con0, is reached. Failure stresses in concrete block are converted to replace microcracks in it. Beyond the state of the failure stress in concrete, stress–strain response is designed by softening characteristics εtpl=E0 = 38 GPa, and the Poisson ratio as v = 0.17. By using Equations (4) to (7), it was possible for us to obtain the curves shown in In the FEM analysis, the Young’s modulus of concrete was adopted as This model includes combinations of non-associated plasticity with hardening and scalar isotropic elastic damage, to determine irreversible changes that occurred during the loading and unloading cycles. The CDP model is based on the brittle–plastic degradation model created by Lubliner et al. ,33 and lThe concrete, in turn, was described by using the Abaqus Concrete Damage Plasticity model , which iThe Concrete Damage Plasticity (CDP) model was used in the modeling of concrete, present in the ABAQUS material library and also the parameters in Lubliner et al. ,33 and . This coThis constitutive model is present in the ABAQUS material library, under the name PLASTIC. The PLASTIC model adopts the flow criterion of Von Mises, with an associative flow rule, ideal for the modeling of ductile materials such as steel.t = 0.01E.EThe uniaxial behavior implemented in the model consisted of the bi-linear stress–strain ,33. TablThe explicit dynamic analysis used in this paper was a strategy due to the greater possibility of numerical convergence, based on the nonlinear analysis method with time control. Despite being a dynamic analysis, this method is capable of performing quasi-static analyses, provided that small increments of loads are applied, so that the low effect of inertia prevails. It is very efficient in the analysis of complex numerical models that involve material damage, large deformations and contact interactions between components.The loading points for external loads were selected for the standard one-point beam-bending configuration, in such a way that the bending moment was combined with shear see . In the The models were carried out by using eight-node reduced-integration solid elements (C3D8R—concrete sleeper) and two-node linear truss elements (T3D2—prestressed wires in concrete). Both were modeled discretely as elements embedded in the concrete of the sleeper. In all computations were considered both the physical nonlinearity of the materials and the geometric nonlinearity resulting from high deformation. The numerical models were verified based on the list of calculated displacements, ultimate loads and failure modes of the investigated sleepers and numerical model. For the simulation, we used the Riks  method, zU). The highest displacements determined in the numerical analysis  were similar to the results of laboratory tests . The largest difference between the numerical and experimental deflections) was 5%  and bottom chord. The compressed diagonals, called connecting rods, represent the concrete between the cracks. The bottom chord of the truss represents the prestressing wires. The first recurring problem that can result in structural failure in sleepers, especially in heavy-rail prestressed sleepers, is the failure by Rail Seat Abrasion (RSA). This deterioration is the result of an abrasion process, which is a gradual wear of the concrete cement paste, exposing the aggregate of the sleeper surface below rail foot ,36,37. Rd) were applied . The location and dimension of abrasion are shown in In order to analyze the RSA, the concrete abrasion of the sleeper was simulated in the ABAQUS program. Four damage cases of abrasion by reduction of depth , for failure with numerical simulation of the sleeper in ABAQUS . The eleA decrease in the load capacity was expected, since the bending strength is provided mainly due to the active reinforcement located in the tension regions of the concrete; this fact is observed in the The experimental results pointed out that the sleepers were designed in accordance with Brazilian standards.The use of the CDP model for concrete behavior was considered satisfactory. The numerical mechanical behavior was similar to experimental ones from the beginning of plastification up to the final failure stage.Simulations of the post-buckling behavior of the structure  were carried out, using the Riks analysis available in the Abaqus software , which eThe size of the calculation step in the modified Riks method  depends It was also possible to evaluate the impact of local pathologies in the sleeper’s load-carrying capacity. These deleterious effects of reinforcement degradation are responsible for reducing the sleeper strength, which may lead to a loss of more than 50% of the load-carrying capacity.It is important to highlight the relevance of prestressing, good construction practices (well-performed cure and low water/cement ratio) and other anti-cracking mechanisms in the durability of the sleeper in order to get a good response from the sleepers over their service life.The numerical model carried out could be used to predict static responses of prestressed concrete sleepers.This paper presents the experimental results of positive moment tests of prestressing sleepers and numerical results of finite analysis to investigate the static behavior of the sleepers. Based on the results, the following conclusions can be drawn in this paper:


The axial compressive behaviour of an innovative type of square concrete filled steel tube (CFST) column to reinforced concrete (RC) beam joint was experimentally investigated in this paper. The innovative joint was designed such that (i) the steel tubes of the CFST columns were completely interrupted in the joint region, (ii) the longitudinal reinforcements from the RC beams could easily pass through the joint area and (iii) a reinforcement cage, including a series of reinforcement meshes and radial stirrups, was arranged in the joint area to strengthen the mechanical performance of the joint. A two-stage experimental study was conducted to investigate the behaviour of the innovative joint under axial compression loads, where the first stage of the tests included three full-scale innovative joint specimens subjected to axial compression to assess the feasibility of the joint detailing and propose measures to further improve its axial compressive behaviour, and the second stage of the tests involved 14 innovative joint specimens with the improved detailing to study the effect of the geometric size of the joint, concrete strength and volume ratio of the steel meshes on the bearing strengths of the joints. It was generally found from the experiments that (i) the innovative joint is capable of achieving the design criterion of the ‘strong joint-weak member’ with appropriate designs, and (ii) by decreasing the height factor and increasing the volume ratio of the steel meshes, the axial compressive strengths of the joints significantly increased, while the increase of the length factor is advantageous but limited to the resistances of the joint specimens. Because of the lack of existing design methods for the innovative joints, new design expressions were proposed to calculate the axial compression resistances of the innovative joints subjected to bearing loads, with the local compression effect, the confinement effect provided by the multi-layers of steel meshes and the height effect of concrete considered. It was found that the proposed design methods were capable of providing accurate and safe resistance predictions for the innovative joints. The concrete-filled steel tube (CFST) structure is a high-efficiency solution for high-rise buildings and bridges due to its high bearing capacity, excellent ductility and great energy dissipation capacity . In CFSTRecently, through-beam joints connecting the CFST columns and RC beams have attracted the interest of researchers because of their simple detailing in the joint area, with a brief review of the recently developed through-beam joints summarised herein. Nie et al.  and Bai Because of the lack of existing experimental investigation on the compressive behaviour of innovative joints, a two-stage experimental study was first conducted to investigate the compressive behaviour of the innovative joint subjected to bearing loads, where the first stage of the tests included three full-scale innovative joint specimens to assess the feasibility of the joint detailing and propose measures to further improve the axial compressive behaviour of the joint, and the second stage of the tests involved 14 innovative joint specimens with the improved detailing to further study the effects of the geometric size of the joint, concrete strength and volume ratio of the steel meshes on the bearing strengths of the joints. Because of the lack of existing design methods for innovative joint, new design expressions for the bearing strengths of the innovative joints were developed and validated by the experimental results.The Series I axial compression tests included three geometrically identical full-scale specimens, namely SC1, SC2, and SC3, and were designed with various rebar diameters of the steel meshes in the joints. Each specimen included the upper and lower CFST columns and the joint, as shown in During the fabrication of the specimens, four concrete cube specimens were respectively reserved when casting the concrete of the lower CFST column, joint area and upper CFST column. Compression tests were conducted on the concrete cubes to derive their cubic strengths at the day of the column tests, with the average cubic compressive strength of each part of the specimen reported in The Changchun CSS-254 15 MN universal testing machine was employed to apply axial compression force to the specimens, with the test setup shown in All the specimens exhibited similar overall behaviour under axial compression during the tests, as summarised below. The first vertical crack was found on the side surface of the joint when the upper load reached 44~57% of the peak loads. With the load increased, the horizontal cracks occurred and gradually crossed the first vertical crack. The dilation and local buckling of the steel tubes were observed when the specimens reached their peak loads, while the concrete in the joint area remained intact without series spalling, which indicates that the specimens were failed by the local buckling of outer steel tubes of the CFST columns and thus satisfied the design criterion of the ‘strong joint-weak member’. The crack patterns on each side surface of the joint at failure are shown in Nu , the first crack was found at the middle of the side surface of the joint in the vertical direction. As the load increased to about 50% of Nu, the vertical crack developed with a maximum width of about 0.1 mm, and a short horizontal crack occurred on the side surface of the concrete at the same time. At about 70% of Nu, the maximum widths of the vertical and horizontal cracks on the side surface of the joint reached 0.25 mm and 0.15 mm, respectively. When the specimen reached its maximum load Nu, dilation and local buckling of the steel tubes of the CFST columns were observed. At the post-peak loading stage, the steel tubes of the CFST columns continued to dilate with the load capacity of the specimen gradually dropped to about 85% Nu.Taken specimen SC2 as an example to illustrate the experimental observation in detail, when the load reached about 45% of Ncr and the peak loads Nu for all specimens are listed in Ncr for SC1 is 1.13 and 1.18 times than those of SC2 and SC3 respectively, which indicates that the crack resistance of the joint is enhanced by improving the volume ratio of steel meshes in the joint (ρv). However, the ultimate axial compressive strength of SC1 is smaller than those of SC2 and SC3. It may be attributed to the discreteness of concrete material in the CFST columns, as all specimens eventually failed in the CFST columns.The axial load-deformation curves of the three specimens are shown in Nu when the first crack appeared, the strains developed dramatically and subsequently reached the yield strains at the peak loads. It was also found that as the volume ratio of the steel meshes in the joint decreases, the strain values corresponding to the peak loads increase, which exhibits more adverse elongation deformation of the steel meshes.The load-strain relationships of the steel meshes in all specimens are similar, as According to the experimental results and analysis of the Series I tests, it can be concluded that the axial load carrying capacity of the joint can be higher than those of the CFST columns by proper design, which verifies the feasibility of the innovative joint. However, the multi-layers of steel meshes in the joint is difficult to rig up because of the lack of efficient supports. Moreover, square CFST columns are extensively used as structural members due to aesthetic consideration. In order to improve the construction operability of the joints, an improved joint detailing specifically for square CFST columns is developed. In the improved joint detailing, the stirrups were added in and arranged radially around the multi-layers of steel meshes to assemble into a steel cage, as shown in ρv), the dimension of the joint and the concrete strength. The test specimens were named based on the following parameters, where C20 and C30 represent the cubic compressive strengths of the concretes are 15.34 MPa and 32.96 MPa respectively, L1, L2 and L3 refer to α = 1.6, 1.8 and 2.0 respectively; H1, H2 and H3 indicate β = 0.6, 0.8 and 1.0 respectively; and S1, S2 and S3 represent ρv = 1.0%, 1.5% and 2.0% respectively.In order to study the axial compressive behaviour of the innovative joints with the improved detailing of the steel meshes, the tests of Series II were conducted subsequently. A total of 14 full-scale specimens were designed and fabricated. The details of the joint specimens are shown in a of 300 mm. In order to examine the actual bearing strengths of the joints, the upper and bottom CFST columns adopted in the Series I tests were removed and replaced by a pair of thick steel plates, with their cross-section dimensions identical with the local compression area. A total of 3 (β = 0.6) or 4 (β = 0.8 and 1.0) layers of steel meshes were horizontally and symmetrically arranged in the joint area. The diameters of the rebars in each steel mesh were determined according to the volume ratio of the steel meshes in the joint (ρv) and the joint volume, with the detailed steel bars adopted in each layer of the steel mesh listed in The specimens were all loaded concentrically. The compression zones on surfaces of the joints were square with the side length The test setup for the Series II tests is shown in Ncr, the loads when the maximum crack width developed to 0.2 mm N0.2 and the loads when the maximum crack width developed to 0.3 mm N0.3. It can be concluded that all the specimens had similar performance during the tests, with cracking of the concrete, yielding of the steel meshes and eventual spalling and crushing of the concrete. At the ultimate loads, several vertical penetrating cracks occurred on the surface of the joint. However, the distributions of the horizontal cracks were different with various height factor β. Accordingly, three different crack patterns  on the surface of the specimens can be classified according to the distributions of the horizontal cracks, as shown in β increases from 0.6 to 1.0, the horizontal cracks begin to generate, and the number of horizontal penetrating cracks gradually rises. The crack pattern modes of all the 14 specimens are summarised in β of 0.6 were categorised as the crack pattern of Mode I. Taking specimen C30-L2-H1-S2 as an example to describe the experimental observation in detail, the first vertical crack appeared when the upper load reached 800 kN. The crack extended gradually and became a penetrating crack when the load reached 1200 kN. The steel meshes started to reach the yield strains as the load increased to about 4000 kN. After that, the specimen reached its maximum load-carrying capacity of 7800 kN. During the post-peak loading stage, the concretes began to spall and crush. The test was terminated when the bearing capacity of the specimen declined to 85% of its peak load. Regarding the crack pattern of Mode I, several vertical penetrating cracks can be found on the surfaces of the joint. The horizontal cracks may appear on the surfaces of the joint, but they were not penetrating . The speβ of 0.8 were categorised as the crack pattern of Mode II. Taking specimen C30-L2-H2-S2 as an example to describe the experimental observation in detail, the first vertical crack occurred at the load of 1200 kN and developed into a penetrating crack at the load of 1500 kN. When the upper load reached 3300 kN, several horizontal cracks began to appear and gradually developed into a penetrating crack at the load of 5000 kN. At the load of about 6500 kN, the specimen reached its maximum load-carrying capacity. The test was ended when the upper load dropped to 85% of its peak load.Regarding the crack pattern of Mode II, several vertical penetrating cracks and a main horizontal penetrating crack can be observed on each side surface of the joint see . The speβ of 1.0 were categorised as the crack pattern of Mode III. Taking specimen C30-L2-H3-S2 as an example to describe the experimental observation in detail, the first vertical crack appeared at the load of 900 kN. When the upper load reached 2700 kN, the first horizontal crack occurred. After that, several horizontal cracks could be observed on each side surface of the specimen and eventually generated two main horizontal penetrating cracks when the load increased to 5000 kN. The specimen reached its load-carrying capacity of 5550 kN. The test was terminated when the load dropped to 85% of its peak load.Regarding the crack pattern of Mode III, several vertical penetrating cracks and more than one horizontal penetrating cracks could be found on each side surface of the specimen see . The speThe comparison of failure modes between different concrete strengths is displayed in N) versus longitudinal displacement (Δ) curves for typical specimen series are plotted in α. It can be observed that the curves are quite close to each other. As shown in α is advantageous but limited to the peak loads of the specimens in this experiment. β are 0.6, 0.8 and 1.0 for specimens C30-L2-H1-S2, C30-L2-H2-S2 and C30-L2-H3-S2, respectively. As shown in β is a significant parameter affecting the behaviour of the specimen. The increase of β could evidently reduce the initial stiffnesses and the peak loads of the specimens. ρv for specimens C30-L2-H2-S1, C30-L2-H2-S2 and C30-L2-H2-S3 are 1.0%, 1.5% and 2.0%, respectively. As shown in ρv could significantly increase the peak strengths of the specimens. However, the strengthen efforts could be weakening once ρv is larger than 1.5%. In addition, the effect of ρv on initial stiffness of the specimen is limited.The load  the resistances of the joints were sustained or declined slowly after the peak loads, indicating excellent ductility of the joints when subjected to bearing loads, and (ii) with the decrease of height factor Because of the lack of existing guidelines for the design of the innovative joints, a theoretical investigation was conducted in this section to determine the axial compression resistances of the innovative joints subjected to bearing loads, based on the test observations and analysis in Nplain is the design bearing compression of unconfined concrete; fc is the characteristic compressive cylinder strength of unconfined concrete; A1 is the loaded area; A2 is the area of the lower base of the largest frustum of a pyramid, cone or tapered wedge contained wholly within the support and having its upper base equal to the loaded area.Several experimental studies have been conducted to investigate the resistances of plain concretes under local compression ,20,21,22It is certified from the experimental results that the ductility and the bearing strength of concrete improved due to the confinement from the multi-layers of steel meshes. However, the advantage contribution of the confinement effect on the concrete strength is not included in Equation (1), as set out in ACI 318-08 , which wlf is the lateral pressure provided by the transverse reinforcements and assumed to be uniformly distributed in the concrete core; fy is the yield strength of the reinforcing bars; ke is the confinement effectiveness coefficient, which takes into account the reduction in the confinement effect due to the spalling off of the cover concrete. Although vertical and horizontal cracks were observed on the side surfaces of the joint specimens, the concrete in the loaded area remained intact in the experiments. Therefore, the reduction in the confinement effect due to the spalling of the cover concrete is neglected, with the confinement effectiveness coefficient ke = 1, leading to the expression to calculate the lateral pressure given by Equation (4).Given that the amount of the reinforcements in both directions of the multi-layers of steel meshes are approximately the same, the effective lateral confining pressure tion (3) , where fβ is a critical factor affecting the ultimate strength of the joint [h/d ratio and displayed in d is the width of the local compression zone. As shown in h/d ratio results in a downtrend of Existing experimental results have demonstrated that the height factor he joint ,20. Withhe joint  and Yi ehe joint . The lath/d = 2, which represents the frictional force between the loading plates and specimens is neglected if the height-to-width ratios of the concrete specimens are greater than 2. According to Equations (2) and (5), when h/d = 1, the value of In Equation (5), it is discovered that specimen .Through considering the local compression effect, the confinement effect provided by the multi-layers of steel meshes and the height effect of concrete, the formulas for calculating the compressive resistances of the joints are summarised in Equations (6)–(8).Nu and the predicted results Ncal, as listed in Ncal for the joint specimens in Series I are higher than the corresponding experimental counterparts, which could be attributed to the fact that all the specimens in Series I failed by the CFST columns, and the ultimate strengths of the joints were higher than those of the CFST columns. For Series II, the resistance predictions derived by Equations (6)–(8) are in good agreement with the experimental ones for normal strength concrete (C30), with a mean value and standard deviation of Ncal/Nu equal to 1.038 and 0.100, respectively. However, the ultimate strengths were overestimated for the specimen series with low strength concrete (C20). It may be because the outer concrete of the specimens with lower concrete strength was prematurely spalled and crushed when the specimens were reaching their ultimate strengths, which would weaken the favourable effect of local compression.Assessment of the accuracy of the new proposal was then conducted, through the comparisons between the experimental ultimate strengths Therefore, the calculation model for the ultimate strengths of the joints subjected to bearing loads for practical engineering design is recommended herein. The confinement effect provided by the multi-layers of steel meshes and the height effect of concrete are considered in the model, while the effect of local compression is neglected because of its uncertainty, leading to the final formulations for the design of the ultimate strengths of the square joints given by Equations (9) and (10).The axial compressive behaviour of square through-beam joint between CFST column and RC beams with multi-layers of steel meshes was experimentally and theoretically investigated in this paper. The following conclusions can be drawn based on the results of this study.The first stage of the tests included three full-scale innovative joint specimens, indicating that the innovative joint is capable of achieving the design criterion of the ‘strong joint-weak member’ with appropriate designs. β of the joint specimens from 0.6 to 1.0, the axial compression strengths of the joints significantly decreased with a maximum reduction ratio in strength equal to 28.9%. The increase of the volume ratio of the steel meshes in the joint ρv is advantageous for the axial compression strengths of the joints. As ρv increased from 1.0 to 2.0, the axial compression strengths of the joints increased by 26.4% and 15.2% for the specimens with concrete grades of C20 and C30, respectively. The increase of the length factor α is advantageous but limited to the peak loads of the specimens. The second stage of the tests involved 14 innovative joint specimens with the improved detailing to study the effects of the geometric size of the joint, concrete strength and volume ratio of the steel meshes on the bearing strengths of the joints. It is shown that by increasing the height factor Because of the lack of existing design methods for the innovative joints, new design expressions were proposed to calculate the axial compression resistances of the innovative joints subjected to bearing loads, with the local compression effect, the confinement effect provided by the multi-layers of steel meshes and the height effect of the concrete considered. The strength predictions of the joints are in good agreement with the experimental ones for normal strength concrete. Through the discussion of the calculated results, recommended formulations for the design of the joints were proposed, which is capable of providing accurate and safe resistance predictions for the innovative joints. However, because of the limited range of variables chosen for the specimens in the tests, extensive applications of the proposed calculation method should be verified by further experimental researches.


Compressive strengths at the age of 28 days were equal to 17.0 MPa and 16.6 MPa for the supersulfated binder of 3500 cm2/g specific surface and CEM 32.5, respectively. Shrinkage deformation of hardening concrete, indicators of fracture toughness, frost resistance, and thermal conductivity were determined during the experimental works. The coefficient of thermal conductivity decreased up to 12% compared to the use of CEM 32.5. An enhancement in concrete properties was associated with the increase of supersulfated binder fineness.The physical and mechanical characteristics of expanded-clay lightweight concrete based on a supersulfated binder in comparison with lightweight concrete based on ordinary Portland cement were studied. In replacing CEM 32.5 with a supersulfated binder of 6000 cm The issue of environmental protection is becoming global with active human intervention in natural resources. Two equally important problems should be highlighted: first, protection from depletion as well as reproduction of natural resources and, second, protection from pollution of the environment due to production processes associated with the extraction, transport, storage, and processing of raw materials as well as with the formation of harmful waste ,2.Trends in the development of industrial production and the construction industry in particular provide the widespread use of secondary raw materials. Multi-tonnage wastes from the chemical and metallurgical industries are important raw materials for construction ,4,5.-making the production of binders based on secondary resources cheaper than the production of binders from natural raw materials ,9;-ensuring environmental cleanliness and waste-free production ;-obtaining binders with sufficiently high quality and with stability of the main characteristics ,12,13.Modern methods of utilization of such wastes and by-products confirm the possibility of their use in various directions in construction, in particular, for producing low-energy non-burning binders such as supersulfated slag binders ,7. Thus,Supersulfated cements consist of ground granulated blast furnace slag, gypsum, and a hardening activator. Lime or Portland cement are traditionally used as slag hardening activators in so-called alkaline activation. Natural gypsum is also used as a sulfate component, i.e., combined (sulfate) activation . A superStructure formation, namely ettringite formation, is of great importance in the hardening of SSBs. Accordingly, it is necessary to select a binder composition to exclude ettringite formation in the hardened matrix that can lead to strength decreases ,20.42− ions. Under these conditions, the high-sulfate form of calcium hydrosulfoaluminate ettringite (C3A·3CS·31H) is formed by the through-solution mechanism with the formation and development of crystallohydrates. The crystallohydrates are placed in the intergranular space, compacted, and strengthens the cement matrix in these conditions without expansion and destruction [A favorable course of dissolution processes for the binder will be provided when sufficiently intensive dissolution of the slag alumina is realized under conditions of high saturation of the solution with SOtruction .It is important that the formation of crystalline high-base calcium hydrosulfoaluminates ends in the initial period of hardening. During this period, the matrix still has plastic properties and volume changes that occur during crystallization do not disrupt the matrix structure ,22,23.Stresses in the solidified structure are especially dangerous when the initial substances in the aqueous solution react with the components of the solid phase of the binder. In this case, the particles of newly formed compounds lead to a disturbance of the matrix structure ,25,26.The hydration products do not cause dangerous stress values and contribute to matrix hardening when such reactions occur in the liquid phase. The nature of the reaction flow depends on the amount of dissolved alumina, which is the function of the lime concentration in the liquid system of the slag—calcium sulfate—water ,28,29,30It is known that regulated structure formation of hardening cement pastes results in an increase in concrete durability ,32,33. CThe aim of the paper is theoretical and experimental justification of technological approaches for improving the concrete properties of lightweight concrete based on expanded-clay gravel and a supersulfated binder.The developed technology is a model of circular economy when it is profitable to reuse resources closing the chain: resources–goods–waste–resources. The improvement of mechanical and physical properties of lightweight concrete was obtained by increasing the fineness of supersulfated cement based on secondary resources that contributed to the increase of the adhesive strength of the contact zone between expanded clay and the matrix.The supersulfated binder was obtained by mixing the ground granulated blast furnace slag (ggbfs) from Public Joint Stock Company  “Magnitogorsk iron and steel works”, the sulfate component—phosphogypsum (fg)—from JSC  “Meleuzovskie mineral fertilizers” as well as cement kiln dust (ckd) from JSC “Bashkir soda company”. The cement kiln dust was used as a hardening activator. Chemical compositions of components have been confirmed by manufacturer’s product bulletins provided by manufacturers. Characteristics of the slag are given in The hydraulic properties of blast-furnace granulated slag were evaluated using the K quality coefficient according to . This co2 + Al2O3. The activity modulus of slag is the ratio of the amount of Al2O3 to SiO2.The basicity modulus of slag is the ratio of the amount of alkaline oxides CaO + MgO to the sum of the oxides of silicium and aluminum SiOThe preliminary study of wastes from the chemical industry in the Southern Urals region in Russia showed the presence of a number of components that can be used as lime- and sulfate-containing hardening activators for clinker-free binders without significant refinement . These w2O + Na2O. The chemical composition of the cement kiln dust is shown in The cement kiln dust has 6–7% of free lime and up to 1.5% of K4·2H2O. The yield of dry phosphogypsum waste is 4–5 t per 1 t of P2O5 since the ratio of mass fractions of CaO/P2O5 in the phosphate raw material varies from 1.35 to 1.65.Phosphogypsum is the waste of sulfuric acid treatment of apatite and phosphorite concentrates obtained in the process of orthophosphoric acid production. The most common process of dihydrate decomposition of calcium–fluorapatite in industrial conditions is carried out at the temperature 65–80 °C. The resulting product contains phosphoric anhydrite in a quantity of 28–32% and sludge of CaSO4·2H2O—94.6%, CaHPO4—traces, Ca3PO4—1.31%, and H3PO4 and Ca(H3PO4)2—0.47% as shown in The phosphogypsum from JSC “Meleuzovskie mineral fertilizers” used in these experiments as a sulfate-containing activator is characterized by the following composition: CaSOfree, up to 2% of the binder mass. According to research in [The maximum content of alkaline additives was assigned to ensure intensive dissolution of slag aluminates and uniform change of the binder volume at hardening, which is achieved by limiting the amount of calcium oxide, CaOearch in , the conExpanded-clay coarse and fine aggregates have been used in the lightweight concrete compositions according to the data in The water demand of lightweight aggregates was defined as absorption at mixing to ensure a water–binder ratio. Water absorption is determined in percent as the difference in the mass of the aggregate before and after saturation with water. The aggregate is placed in a container with holes and a lid. The container is slowly submerged in water and shaken to remove air bubbles from the aggregate. The container with the aggregate is kept in water for 1 h, then removed from the water, and suspended so that the excess water is draining for 10 min. Then, the aggregate mass is determined. The average value of the results of two parallel tests is taken as the test result.Experimental binder compositions were prepared with separate grinding of slags and activators followed by mixing the dry ingredients in the laboratory drum and ball-type mill with the diameter of the balls at 30 mm. The fineness of component grinding was chosen to achieve both a high activity of the binder and economic feasibility. The specific surface was determined using the Blaine method.2/g as a sulfate component of the binder gives a lower matrix strength especially in the early stages and after heat-steaming treatment. Repulping and heat treatment of phosphogypsum make it possible to obtain the binder with higher activity. The sample strength in this case exceeds the sample strength of the SSB with natural sulfate components.The use of dump phosphogypsum with a natural moisture content of about 25% and specific surface area of 3000 cmsp = 3500 cm2/g and Ssp = 6000 cm2/g were made at water-to-binder ratios equal to W/B = 0.55 and W/B = 0.50 for the B15 and B25 strength classes, respectively. The slump was 5–7 cm. The compositions of concrete are presented in Samples of lightweight concrete based on SSBs with S3 for the B25 concrete strength class. Water was assigned in the amount of 10–15% of the mass of the dry components depending on the aggregate porosity and the required workability. The total amount of aggregates per 1 m3 can be determined by the following formula:Lightweight concrete composition can be calculated by different methods. Three series of test mixes were prepared to determine the optimal composition of the required grade according to the average density and compressive strength class. The following recommendations were used for choosing the composition. The recommended amount of cement of CEM 32.5 strength class was 300–400 kg/m3A—the total amount of coarse and fine aggregates, kg/m3D—the required grade of the average density of concrete, kg/m3C—the cement amount, kg/m3 of concrete with the 5–7 cm slump is 0.85–0.9 m3. The increase of the volume of expanded-clay gravel per 1 m3 leads to strength decrease. The mass of the coarse and fine aggregates can be defined by taking into account the bulk density of coarse aggregate (ρb):The coefficient 1.15 takes into account chemically bound water that is involved in cement hydration. The recommended volume of expanded clay gravel per 1 m3 was determined by the following formula:Test mixes were performed, and the water amount was corrected to obtain the required workability. The average density of fresh concrete mix (ρ) was checked after compaction, and the actual material consumption per 1 m3, kgM—amount of a component in 1 mm—amount of the same component in bath, kg∑—sum of all components in bath , kgThe graph of the strength dependence on the average density and on the cement amount was performed on the data of three series of test mixes and the optimal composition was selected from the graph.Calculation example for concrete of D1500 and B25:3. Then, the composition was calculated for each cement amount, for example, for 380 kg/m3:Three cement amounts were assigned based on the recommendations: 360, 380, and 400 kg/mCalculation example for concrete of D1300 and B15:3. Then, the composition was calculated for each cement amount, for example, for 280 kg/m3:Three cement amounts were assigned based on the recommendations: 260, 280, and 300 kg/mThe concrete frost resistance was determined according to . The coe3 size with compressive axial load until failure to determine the prism strength. Loading was done at the level of 30% of the failure load by measuring the sample deformation to determine the elasticity modulus. The sensors were attached to the sample. The measurement accuracy of the sensors was 0.001 mm. The sensor base for determination the longitudinal deformation was 150 mm. The prismatic strength Rpr was calculated for each sample by the following formula:The elasticity modulus test was done by stage loading of prism specimens of 100 × 100 × 400 mmp—is the failure load measured on the press scale;PF—is the average value of the cross-sectional area of sample.δ was calculated for each sample at the load level of 30% of the failure load according to the following formula:1 = P1/F is the stress increment from conditional zero to the level of the external load equal to 30% of the failure load;The elasticity modulus E1—is the external load increment; andP1—is the increment of the elastic-instantaneous relative longitudinal deformation of sample at the load level equal to P1 = 0.3Pp and measured at the beginning of each stage of loading.εSeveral steady and transient methods can be used to measure the thermal conductivity of building materials ,50. In t3 size for each composition according to [l—base for measuring deformations, mm.For shrinkage test, the specimens were three prisms of 40 × 40 × 160 mmrding to . The devThe presence of fine aggregates of expanded clay contributes to increased strength in the case of a binder with higher specific surfaces, as shown in tb) to compressive strength (Rcomp) was characteristic of defects reduction and structure improvement [An increase of the ratio of tension strength in bending  surface . There atb/Rcomp ratio corresponds to defect reduction in the concrete structure. In replacing Portland cement CEM 32.5 with SSB of higher specific surface, one can increase the Rtb value up to 20% and can increase the ratio of Rtb/Rcomp as shown in The increase in the RThe increase of deformability of a lightweight concrete based on SSB is caused by changing the pore structure of concrete, namely, the uniform distribution of conditionally closed pores that act as dampers in this case.The compressive strength at the ages 3–24 months, the coefficient of water resistance, and frost resistance of lightweight concrete on SSB are not lower than the same characteristics of lightweight concrete on OPC according to δ) of studied lightweight concrete is slightly higher than the elasticity modulus of lightweight concrete based on CEM 32.5. The ratio Rtb/Eδ indirectly characterizes the fracture toughness of concrete. The ratio Rtb/Eδ increases by 1.14–1.18 times when using the SSB, as shown in The uniform pore distribution in concrete structure improves its deformative properties and increases the structure resistance to internal pressures. It was stated that the elasticity modulus  to the compressive strength, which indicates the crack resistance increase of concrete.The improvement of durability characteristics of concrete was proven experimentally. Increasing the specific surface area of the supersulfated binder from 3500 to 6000 cmThe most significant shrinkage deformations, 0.36 mm/m, of concrete on CEM 32.5 were observed during the first 5 days when samples intensively lose water. During further air storage, shrinkage deformation was attenuated and, after two months, reached values of 0.55 mm/m. Samples based on the supersulfated binder had shrinkage equal to 0.01 mm/m after first 5 days and shrinkage equal to 0.04 mm/m by the end of the second month. The compressive strength at the age of 3–24 months, coefficient of water resistance, and frost resistance of lightweight concrete on the supersulfated binder were not lower than the same characteristics of lightweight concrete on CEM 32.5. F50 and F75 frost resistances were found for the B15 and B25 concrete strength classes, respectively. It was stated that the elasticity modulus (E) of the studied lightweight concrete is slightly higher than the elasticity modulus of lightweight concrete based on CEM 32.5. The ratio Rtb/E indirectly characterizes the fracture toughness of concrete. The ratio Rtb/E increases by 1.14–1.18 times when using the supersulfated binder. The coefficient of thermal conductivity decreased up to 12% compared to the use of CEM 32.5.


The workability, density, compressive strength (per curing days), and water absorption of the sample loaded at 10% glass bubble (loading level determined to satisfy the minimum strength requirement of a load-bearing structure) were 70 mm, 2165 kg/m3, 52.58 MPa (28 days), 54.92 MPa (60 days), and 65.25 MPa (90 days), and 3.73 %, respectively. The thermal conductivity for geopolymer concrete decreased from 1.47 to 1.19 W/mK, while the thermal diffusivity decreased from 1.88 to 1.02 mm2/s due to increased specific heat from 0.96 to 1.73 MJ/m3K. The improved physicomechanical and thermal (insulating) properties resulting from embedding a glass bubble as an insulating material into geopolymer concrete resulted in a viable composite for use in the construction industry.This paper details analytical research results into a novel geopolymer concrete embedded with glass bubble as its thermal insulating material, fly ash as its precursor material, and a combination of sodium hydroxide (NaOH) and sodium silicate (Na Current research endeavours are heavily invested in addressing energy and environmental issues due to the global emphasis on sustainability ,2. BuildThe thermal (insulating) properties of concrete buildings are crucial for environmental sustainability via respective energy consumption ,11. The 3) and low thermal conductivity (0.044 W/mK) resulted in a net benefit to the geopolymer concrete it was embedded into to act as insulation materials. The literature on using glass bubbles as insulation materials in composites reported loadings of 0–60% , it is related to the number of sources in the sensor. The transient (dynamic) methods can be used for measuring thermal diffusivity of good-conducting solid materials, thermal conductivity, or both, for a broader range of temperatures and thermal properties [operties . The TPS method or thermal constant analyser consists of various transient plane source probes connected to a computerised control unit measure, which respond as a signal and is sent out to create heat in the sample. This method adheres to the ISO standard (ISO22007-2). These methods are distinguished mainly by quick measurements (100–120 s) within −100 to 1000 °C and can discern thermal conductivities between (0.016–6 W/mK), thus making it suitable for various materials ,56. The This method is generally quicker when it comes to reaching the required equilibrium for obtaining the results relative to other methods, especially in determining the thermally insulating properties for concrete .The samples’ physicomechanical properties such as its workability, density, compressive strength, and water absorption will be discussed based on the optimal loadings of the glass bubble in the geopolymer concrete that satisfies the minimum strength requirement of the load-bearing structure. The thermal (insulating) properties determined in this study were the thermal conductivity, specific heat, and thermal diffusivity, which will also be discussed within the abovementioned context.The workability of the glass bubble loaded geopolymer concrete is shown in It is evident in The presence of the glass bubble in the geopolymer concrete decreased its overall density . The upp3 could theoretically result in a thermal conductivity decrease of 0.04 W/mK [The decrease in the overall density of the geopolymer concrete due to the presence of glass bubble was also accompanied with decreases in air void or bubbles generated by air entrainment of the closed-shell structure, as concrete density is dictated by the volume fractions of its constituent materials and the respective volume of voids present within the concrete. These are some of the factors that make the geopolymer concrete’s density vital for its thermal properties, as a density of 100 kg/m.04 W/mK .3). The lightweight nature of the geopolymer concrete could be indicative of the fact that in the case of some percentages , the glass bubble reacted with the geopolymer binder as the main composition of the glass bubble is silica (Si), which is also the main components involved in the geopolymerisation process. This assumption is supported by the images shown in The experimental values were not in agreement with the lower bounds or minimum values of the calculated  density, where the former resulted in the categorisation of the geopolymer concrete as a lightweight  on the compressive strength based on effect of aging days  has shown in As per the results shown in Most studies involving insulation posited that the density, compressive strength, and thermal conductivity are main factors dictating the viability of the geopolymer concrete of insulation applications ,67,68,69The water absorption percentage slightly increased but remained within a comparable percentage of 3–6.5% of standard concrete. A slight increase of water absorption can be attributed to the increase in the glass bubble content in the geopolymer concrete, leading to decreased aggregates in the system. It also contributed to the spherical configuration that developed into capillary voids, making transportation in the geopolymer concrete possible.3. The general trend in the plot seems to be an inverse relationship between glass bubble loading and thermal conductivity, where the thermal conductivities of 1.47, 1.41, 1.35, 1.19, 1.34, and 1.31 W/mK corresponded to 2.5%, 5.0%, 7.5%, 10.0%, 20.0%, and 30.0% glass bubble loading, respectively, resulting in an overall decrement of 20.44% in thermal conductivity. It is also evident in The results confirmed that the geopolymer concrete’s effective thermal conductivity decreases with increasing loading of the glass bubble (inverse relationship). The thermal conductivity of the glass bubble itself helps decrease the overall thermal conductivity of the geopolymer concrete. The thermal conductivity of the gas within the glass bubble is 0.04 W/(mK)  and its 3K for 2247 kg/m3, and 2.28 MJ/m3K for 2118 kg/m3 relative to its 30% glass bubble loading counterpart, which translated into a 58% decrease in specific heat at a 5.7% decrease in density (The measured specific heat of control (zero loadings of glass bubble) was 0.95 MJ/m density .3K) at the same density.The specific heat of the geopolymer concrete increased with increasing loading of glass bubble due to the presence of an interior gas core in the glass bubble, which increases the thermal storage capacity that delays the heat transfer or convection in the thermal insulation system (illustrated in 2/s) decreased by 6% relative to the control sample . Both the thermal diffusivity and density are inversely related  confirmed that the thermal conductivity and diffusivity decreases while the heat capacity increases with an increasing volume fraction of thermal insulation materials in building materials .This paper reported the physicomechanical and thermal insulation properties of a new insulation material, the glass bubble, embedded in geopolymer concrete to enhance the latter’s thermal insulation while also preserving its functional physicomechanical properties. The physicomechanical properties such as the workability, density, compressive strength, and water absorption, and thermal insulation properties such as the thermal conductivity, specific heat, and thermal diffusivity of the geopolymer concrete embedded with glass bubble were determined and analysed.3, its compressive strengths (based on curing days) 52.58 MPa (28 days), 54.92 MPa (60 days), and 65.25 MPa (90 days), and its water absorption at 3.73% at a 10% glass bubble loading, which was determined to be the most suitable configuration that satisfies the minimum strength requirement adequate for load-bearing structures. The decreases in the thermal conductivity (1.47 to 1.19 W/mK) and thermal diffusivity (1.88 to 1.02 mm2/s) due to the increase of void ratio from the glass bubble and the thermal conductivity of the glass bubble itself significantly improved the thermal properties of the concrete. The presence of an interior gas core of glass bubble resulted in high specific heat (0.95 up to 1.73 MJ/m3K) of the geopolymer concrete, leading to increased heat absorption and longer heat storage times before heat dissipation to its surroundings.The workability of the samples were determined to be 70 mm, its density 2165 kg/mTherefore, the potential of using glass bubble as a thermal insulation material was affirmed due to its low thermal conductivity, low thermal diffusivity, high specific heat, and comparable concrete performance vis-à-vis the standard recommended strength for concrete applications.


We have recently reported that the continuous exposure of rats to a concrete building environment under cool temperatures had adverse effects on general health parameters and embryo-fetal development. This study examined to compare the potential effects of concrete and wood building environments on pregnant dams and embryo-fetal development in rats. Groups of 10 mated females were exposed to polycarbonate (control), concrete, or wood cages from gestational days (GD) 0 to 20 under cool temperatures (11.9∼12.3°C). All the females underwent a caesarean section on GD 20, and their fetuses were examined for any morphological abnormalities. The temperatures in the cages were similar in all groups but the relative humidity in the concrete and wood groups were higher than in the control group. The concentration of volatile organic compounds in the wood group was higher than in the control group. In the concrete group, maternal effects manifested as an increase in the incidence of clinical signs, a lower body weight, and a decrease in the thymus and ovary weights. Developmental effects included increased post-implantation loss and decreased litter size. Infrared thermal analysis showed that the skin temperature of the rats in the concrete group was lower than that in the control group. In contrast, there were no exposure-related adverse effects on the maternal and developmental parameters in the wood group. Overall, the exposure of pregnant rats to a concrete building environment under cool temperatures has adverse effects on the clinical signs, body weight, skin temperature, organ weight, and embryo-fetal development. On the other hand, exposure to a wood building environment does not have any adverse effects in rats.