The early strength agent could increase the strength significantly, the strength could be increased from 6.4 to 10.8 MPa after 20 h at 10 °C and from 7.2 to 20.6 MPa after 14 h at 20 °C. All measures for promoting earlier strength did not have an evident negative effect. The results could be potentially referred for the formwork removal at a suitable moment.Knowing and promoting the strength development of concrete at an earlier age is essential for accelerating formwork circulation of the on-site construction and precast product manufacture. The strength development rate at earlier ages of less than the initial 24 h was investigated. The effect of measures of adding silica fume, calcium sulfoaluminate cement, and early strength agent on the strength development of earlier concrete at ambient temperatures of 10, 15, 20, 25, and 30 °C was studied. The microstructure and long-term properties were further tested. It is shown that the strength increases exponentially first and then logarithmically, different from what is commonly recognized. Increasing cement content exhibited a certain effect only above 25 °C. When the cement content increased from 420 to 460 kg/m Concrete is the most widely used construction material around the world ,2, commo2), lithium bromide (LiBr), and triisopropanolamine (TIPA), can increase the compressive strength from 2.4 MPa to 9.4 MPa at 1 d, and from 26.8 MPa to 47.7 MPa after 3 d [When compressive strength at an early age does not meet a practical requirement, some strength promotion methods need to be used ,17,18. After 3 d . Furtherfter 3 d ,22,23,24fter 3 d ,26, nanofter 3 d ,28,29,30fter 3 d ,32,33,34fter 3 d ,36,37,38fter 3 d ,39 and tfter 3 d ,41,42,43At present, studies on early age strength are mainly focused on 3 to 7 d, with little attention paid to strength at earlier ages of less than 1 d. However, the strength before 3 d, especially within 1 d, is becoming more and more important for modern civil engineering. For cast-in-place concrete, the earlier strength determines the time to remove the formwork and the timing for the next construction process . For preThe present study aims to investigate the compressive strength development rate and the effect of ambient temperature and early strength materials including silica fume, calcium sulfoaluminate cement, and early strength agent on strength development within 1 d. Long-term experiments on strength up to 3 years and chloride ion permeability were carried out, to clarify the effect of these technologies for promoting earlier strength on the long-term performance of concrete. Based on the strength development rate at an earlier age, it is expected to evaluate the effectiveness of different promotion technologies by measuring the impact of these measures on earlier age strength and long-term performance.3, marked as OPC. Two types of crushed rocks with different particle sizes were mixed in a mass ratio of 4:6, as coarse aggregate, and the particle sizes are 5~10 mm and 10~20 mm, respectively, the apparent density of both types of crushed rock is 2670 kg/m3. The OPC, sand, and crushed rock are all from Chongqing, China. A polycarboxylate water-reducing agent, marked as PCA, was added to improve the workability.Concrete was prepared with cement, manufactured sand, crushed rock, water, and superplasticizer, as a blank group. Ordinary Portland cement was PO42.5R with an apparent density of 3015 kg/m2/kg and the average particle size is about 0.15 μm. The calcium sulfoaluminate cement is from Henan, China, and the type is R-SAC42.5, marked as CSA. The early strength agent is a milky white liquid, with the core components of C-S-H-PCE nanocomposites [Silica fume, calcium sulfoaluminate cement, and early strength agent were also used for accelerating strength development. The specific surface area of silica fume (SF) is 24,500 mmposites , and theThe mixture proportions of blank group concrete are shown in All raw materials for preparing concrete, molds, mixer, and other tools which touch concrete mixture during mixing and casting were kept in the environment with a designed constant temperature. After mixing fully, cast the concrete mixture into concrete molds with the size of 100 mm × 100 mm × 100 mm, then vibrated for 30 s on the vibration table. After casting, the samples/specimens were cured in a box with the designed constant temperature and relative humidity of 90%. When testing the earlier strength, removed the molds 5 min before the test. When testing the long-term strength, the demolding time was 1 d, and then placed in the constant temperature and humidity box again for curing. After 28 d, the specimens were taken out and placed in an indoor environment.The compressive strength test was carried out according to GB/T 50081-2019 . The temIt can be seen from It also can be seen from The temperature rise of concrete is related to the hydration of cement. It is well known that cement has four stages of hydration with different characteristics. It is suggested that the strength development of concrete can be predicted by monitoring the temperature variation of concrete. The temperature curve can reflect several characteristics of the strength development rate. (1) The temperature begins to increase corresponding to the start of the strength increase (6 h). (2) The temperature reaches its peak corresponds to rapid strength development. (3) The period of several hours after the temperature peak is crucial, as it is a rapid increase stage of concrete strength. It is suggested that measures that promote the temperature rise of concrete would accelerate the strength development of earlier concrete.(1)Increasing content of Portland cement3, 440 kg/m3, and 460 kg/m3, respectively. The ratio of water to cement was kept at 0.30 constantly. Other components of concrete were adjusted correspondingly. 3 is relatively too high. Compared with the strength development in It can be seen from (2)Addition of SFThe addition of SF can usually promote the strength development of concrete significantly. Adding SF has become a common way of preparing high-strength concrete. The previous literature ,51 has sIt can be seen from (3)Addition of calcium sulfoaluminate cement (CSA)Concrete made from CSA can obtain higher early strength even in low ambient temperatures ,53. PrevIt can be seen from (4)Addition of early strength agent(5)DiscussionAmong the four ways above, increasing cement content is difficult to promote effectively the earlier strength of concrete, especially at a lower ambient temperature. This depends on the characteristic of hydration heat release because cement needs enough time to accumulate a certain amount of heat. However, additions of SF, CSA, and early strength agent CCP would provide extra driving heat to accelerate the hydration of cement. Compared with the other ways above, the addition of an early strength agent is a more effective way of promoting the earlier strength.It is worth noting that most experimental results of strength at ages of less than 24 h exhibit an exponential increase within a certain period varied with the ambient temperature.The experimental results above show that all measures for promoting the earlier strength could to some extent enhance the strength development of concrete at ages of less than 24 h. The early strength agent CCP exhibited the most promotion efficiency on the strength at an earlier age even at an ambient temperature of 10 °C. The promotion mechanism of CCP on earlier strength was analyzed with XRD and SEM at a micro level. All samples that hydrated to the specified age were crushed into small pieces and then immersed in ethanol to terminate hydration. To prevent the very quick hydration rate of cement at an early age, ethanol was exchanged every 5 h, and the total soaking time was 24 h. After that, the sample was dried in a vacuum drying oven for 3 d. In the preparation of XRD test samples, the hydrating cement paste from the dried concrete was separated and sifted through 250 mesh. When observing the microscopic morphology with SEM, tests were directly carried out on the crushed concrete specimens.The concrete samples with and without the early strength agent at the ambient temperatures of 10 °C and 30 °C were investigated. The concrete sample without the early strength agent hydrated for 18 h at 10 °C was marked as the 10 °C-18 h-blank group, and the sample with early strength agent was marked as 10 °C-18 h-CCP, similarly for those at 30 °C.(1)XRD(2)SEMGenerally, when the early strength of concrete develops quickly, the long-term strength will slow down to some extent. Inappropriate early strength enhancement measures will even reduce the long-term strength and durability of concrete. Thus, it is necessary to investigate the long-term compressive strength and durability of concrete with the measures for promoting the earlier strength of concrete. (1)Effect of measures for promoting earlier strength on the long-term strength of concreteAs can be seen from (2)Effect of measures for promoting earlier strength on chloride migration coefficientThe resistance to chloride ion permeability can reflect the compactness of concrete and is a commonly used method to characterize its durability . Figure This paper mainly investigated the development rate of concrete strength at an earlier age within 1 d under different ambient temperatures, especially at 10 °C, and the effect of some typical measures on strength promotion at an earlier age. The long-term strength and durability of concrete with the measures were tested at the same time. The following conclusions can be drawn:(1) The strength of concrete at an earlier age within 1 d develops with a latent stage first, following an exponentially rapid rise stage, and then a logarithmically slow rise stage. The start time of an exponentially rapid rise corresponds to the highest temperature rise inside the concrete. The occurrence of the highest temperature within 1 d can be a key moment for the formwork removal of on-site concrete construction and precast concrete product manufacture.(2) The ambient temperature dominates the earlier strength development of concrete. Increasing cement content is not effective for promoting earlier strength when the ambient temperature is lower than 20 °C.(3) Measures including the addition of SF, CSA, and early strength agents can promote the earlier strength of concrete to different extents. The promotion effect is relatively evident under high ambient temperatures. The early strength agent CCP used in this work exhibits an evident effect even at a temperature of 10 °C.(4) All measures for promoting earlier strength of concrete do not have evident negative effects on microstructure, long-term strength, and chloride migration coefficient of concrete, even the addition of SF exhibits positive effects. There is a good correlation between the early age strength and hydration heat of cement-based materials , but the


The study of the strength and failure modes of construction components has become increasingly important with the advent of industrialized construction. Recently, because of the need to promote the survivability of both structures and persons, it has encompassed failure modes associated with seismic threats. This study reports the seismic behavior of precast segmented columns designed with both unbonded prestressed tendons (UPTs) and energy-dissipating (ED) bars. A physical specimen was subjected to a quasi-static cyclic test; this permitted the evaluation of the damage mode and behavior of the energy dissipation mechanism, and permitted the establishment and verification of a fiber beam element simulation model. The model was then used to evaluate the effects of the variation of the design parameters on the behavior of precast assembled columns. The test specimen exhibited stable energy dissipation and a pinching effect during cyclic loading. An analysis using the fiber beam element model with varying design parameters revealed that high-strength concrete could mitigate the concrete damage and residual deformation after an earthquake, and that the concrete strength and steel bar strength should be matched when enhancing the seismic resilience of precast columns with high-strength steel bars. It was determined that increasing the prestress mechanism, namely the ratio of the UPTs, could greatly improve the residual deformation, while the ratio of ED bars is the key factor in enhancing the energy dissipation capacity of the precast columns. Suitable ratios of UPTs and ED bars are the keys to ensuring stable energy dissipation and low residual drifts. Moreover, an increased axial load ratio and prestress level are able to restrain the joint opening and improve the bearing capacity of the precast columns; however, an excessive axial load or prestressing force would result in the rapid degeneration of the carrying capacity and larger residual displacements. To ensure reliable connections in joints, researchers have mainly focused on the construction convenience, flexural or shear properties, and seismic performance of prefabricated architectures2. Wet and dry connections are commonly used in precast concrete structures. Wet connections refer to construction with cast-in-place (CIP) concrete after the placement of the linking reinforcements. Because the application of wet connections requires time-consuming on-site operations and curing times, it usually leads to long construction periods3. As an alternative to wet connections, unbonded prestressed tendons and anchor bolts have been utilized in dry connections without pouring concrete on-site, thus providing excellent construction convenience and efficiency4. However, because the joint behavior is relatively unknown, the characteristics of dry connections have been researched extensively in recent years.To overcome the labor shortage and promote reconstruction after World War II, building industrialization became critical for the reconstruction program in Europe. Related technology achieved high efficiency through standardized design, industrialized prefabrication, and on-site erection. During construction, the structural type, load-transmitting performance, and failure modes of joints are of great significance6. The research results have shown that precast structures with unbonded tendon connections exhibit minor residual deformation and excellent self-centering capacity after earthquakes. Due to the outstanding seismic performance, this method has been suggested as possibly applicable to prefabricated segmented bridge columns.To understand the damage mechanisms and establish design methods using dry joints, experiments and simulations of post-tensioned unbonded prestressed connections have been conducted by many scholars7 performed quasi-cyclic tests on UPT connections with a medium drift ratio, and no damage was found to have occurred at a drift ratio of 4.0%. Liu et al.8 carried out research on UPT connections with different prestressing degrees. Compared to CIP columns, higher post-yield stiffness, lower residual drift, and reduced (less desirable) energy dissipation were observed. The quasi-static residual displacement and residual crack width were found to be around 66% and 73% of those of reinforced concrete columns, respectively. To define the deformation behavior under seismic ground motions, shaking table tests were employed by Ge and Wang9. The results showed that the damage mode was significant flexural cracking that occurred at the joints in the plastic hinge zones, while no cracks were observed in the body of the segmented columns. With a greater shaking magnitude, the opening of the joints became larger, and a swaying phenomenon was observed. Ou et al.10 acknowledged that the design must achieve good behaviors during earthquakes, and considered the maximum earthquake conditions; while the results revealed low damage and negligible residual displacement, they also indicated decreased energy dissipation.Because there are differences in the structural function, load characteristics, and reinforcement design of bridges as compared to buildings, the seismic performance of precast bridge columns with unbonded post-tensioned tendon (UPT) connections has been investigated. Perlamo et al.12 have carried out quasi-static cyclic tests to study the seismic performance of the columns, their makeup, and the methods of application. The research results indicate excellent energy dissipation, self-centering capacity, and low residual displacement with proper reinforcements. Based on existing research, Tong et al.13 proposed a connection with UPTs and high-strength energy-dissipating (ED) bars, and the results of experiments revealed good ductile behavior, satisfactory hysteretic energy dissipation, and acceptable self-centering capacity.To improve the energy dissipation capacity and avoid excessive deformation during earthquakes, steel bars have been used to enhance the damping ratio of the columns. To define the seismic mechanism, some scholarsBecause the design goal of this kind of pier is to take into account self-resetting and energy dissipation, although its seismic performance has been experientially investigated in previous research, the test results have been quite different due to the large differences in the design parameters of the test specimens, and an analysis of the degree of influence of the design parameters is lacking. In this research, based on the results of pseudo-static tests, the skeleton curve, residual offset ratio, and cumulative energy consumption of piers with variations in each design parameter are analyzed. This is of great significance for the identification of the main design parameters affecting the seismic performance and the realization of tough seismic design with both energy consumption and self-resetting capabilities.However, due to insufficient test results and scarce simulations, a knowledge gap still exists; there is a lack of information about the design parameters and design criteria of precast columns with UPT connections and ED bars. This study partially fills that gap by investigating the seismic performance and design parameters of such columns. To capture the damage mode and hysteresis curve, quasi-static cyclic tests were designed, a physical specimen was constructed, and the tests were performed. The analysis of the measured data, both observed and quantified, permitted the establishment and validation of a fiber beam element model. With the verified model, the design parameters were varied to investigate changes in behavior; the investigated parameters were the concrete strength, steel bar strength, UPT ratio, ratio of ED bars, axial load ratio, and prestress level. The results are meticulously analyzed and discussed, and are of great significance for understanding the seismic responses of, and establishing design methods for, precast columns with UPT connections and ED bars. This information reduces the knowledge gap concerning these structures.Specifications for Seismic Design of Highway Bridges (JTG/T 2231-01-2020)14. The specimen is depicted in Fig. 3. The steel bars used were HRB400 with a diameter of 12 mm, corresponding to a reinforcement ratio of 1.48%. The diameter of the stirrups was 6 mm, and the volumetric ratio of the bottom segment was 3.13%. The external diameter of the UPT was 15.2 mm, corresponding to a steel ratio of 0.59%, and the ultimate strength was selected as 1860 MPa. In the process of specimen fabrication, because the main reinforcements at the segments were continuous, plastic film was set at the segments during pouring, and the film was removed after construction was completed.The physical test specimen was designed according to the Chinese standard, namely JTG/T 223-01-20201E is the measured elastic modulus value, and To obtain the real mechanical properties of the material, the compressive properties of the concrete and the tensile properties of the rebar were tested. The concrete specimens used for compressive strength testing were three standard cylinders with a diameter of 150 mm and a height of 300 mm. The compressive strength and elastic modulus of the tested concrete are reported in Table The material characteristics of the steel bars are listed in Table 15, the axial load ratio in this study was determined to be 10%. Therefore, the prestress level was selected as 10%, which implied the tensile force of a single tendon of 56.4 kN. The loading protocol is depicted in Fig. To accomplish the experiments, the test setup was arranged as shown in Fig. The final state of the physical specimen is shown in Fig. 16, the hysteresis curve displayed an obvious pinching effect with stable energy dissipation and lower residual drift. At the displacement of 50 mm, the column responded with a maximum horizontal bearing capacity of 78.94 kN. As the loading continued, the horizontal force descended gradually. When the displacement reached 130 mm, the force descended to 62.50 kN, corresponding to 79.2% of the maximum force, as shown in Fig. The test data comprised a hysteresis curve, a backbone curve, residual drift, and energy dissipation, which were compiled and are depicted in Fig. Based on the test results, a fiber beam element model was established using Opensees software to investigate the design parameters, as shown in Fig. 17 was used to reflect the relative material properties of the cover and core concrete, as shown in Fig. To accurately reflect the strain distribution of the concrete, steel bars, and unbonded prestressed tendons, fiber sectioning was utilized, as shown in Fig. As presented in Fig. Using the verified model, analyses of changes in the characteristics of the precast column with unbonded prestressed tendons and energy dissipation capacity were conducted while varying the several design parameters, and the results were analyzed and discussed. The studied parameters were the concrete strength, reinforcement strength, UPT ratio, ratio of ED bars, axial load ratio, and prestress level.19 to mitigate structural damage and promote rehabilitation after earthquakes. To investigate the seismic performance of the precast column fabricated with various concrete strengths, concrete grades C40, C50, C60, C70, and C80 were analyzed. The research results showed that high-strength concrete enhanced the bearing capacity and initial stiffness, and the obvious pinching effect increased with the grade, as shown in Fig. A damage survey showed that concrete crushing is a typical damage mode under earthquake stresses. High-strength concrete has been put forward by scholars20. To study the bearing capacity, residual drift, and energy dissipation of precast columns fabricated with various reinforcement strengths, the steel bar strengths of HRB400, HRB450, HRB500, HRB550, and HRB600 were analyzed and compared, as exhibited in Fig. Regarding concrete crushing, steel bar yielding has been found to be an important failure mode of bridge columns during earthquakesDue to the large free length and effective elasticity of unbonded prestressed elements, they have the capability to supply self-centering capacity during earthquakes. To investigate the seismic performance of columns fabricated with various UPT ratios, the ratios of 0.59%, 0.88%, 1.18%, 1.48%, and 1.77% were selected for investigation and the results were calculated. The bearing capacity was found to be significantly improved with the increase of the UPT ratio, as shown in Fig. The ratio of ED steel bars is one of the most important factors for estimating the energy dissipation capacity of bridge columns. To demonstrate the seismic performance of columns fabricated with various ratios of ED bars, the ratios of 0.5%, 1%, 1.48%, 2%, and 2.5% were selected and analyzed. As the ED bar ratio increased from 0.5 to 2.5%, the hysteresis curves changed significantly, as depicted in Fig. The axial load ratio depends on the material and arrangements of superstructures, and usually ranges from 5 to 25%. The axial load serves to restrain the opening of several joints in a constructed multi-segment column, but high axial loads can also lead to the early failure of concrete in the compression zone. To effectively evaluate the influence of the axial load ratio on the seismic performance of the precast column, columns with various axial load ratios were analyzed. The analysis results reveal that the integrity, initial stiffness, and bearing capacity were enhanced as the axial load ratio was increased, as shown in Fig. As with the axial load ratio, the prestressing force of unbonded tendons is a significant design parameter of precast columns. To consider the seismic performance of precast columns under different prestress levels, preload ratios of 5%, 10%, 15%, 20%, and 25% were defined and analyzed. The analysis results reveal similar trends as compared with the axial load ratios. The increase of the prestress level increased the initial stiffness and bearing capacity, leading to larger residual displacements and a minor influence on energy dissipation, as displayed in Fig. Unlike a simpler precast column with only unbonded tendon connections, the test specimen with ED bars and UPTs exhibited stable energy dissipation and excellent self-centering capacity during cyclic loading. During the experiment, limited rocking was observed due to a slight joint opening that occurred in the bottom joint. The steel bars could not only increase the energy dissipation, but could also inhibit the excessive rotation of the joints. The failure mode of the column exhibited the steel bar yielding and concrete crushing of the bottom joint at a plastic hinge height of 15 cm. After the experiment, the ultimate displacement and residual displacement were 130 and 40.2 mm, respectively, corresponding to drift ratios of 5.9% and 1.8%.The initial stiffness and bearing capacity of the precast column were found to be greatly improved with the dual employment of high-strength concrete and high-strength steel bars. High-strength concrete could mitigate concrete damage and residual deformation after an earthquake. However, when using high-strength steel bars but leaving the concrete strength unchanged, the increased horizontal force will result in severe concrete crushing and excessive residual displacements. Therefore, the concrete strength and steel bar strength should be matched when enhancing the seismic resilience of precast columns with high-strength materials.The increase in the ratios of UPTs and ED bars effectively enhances the resistance of precast columns. The increased ratio of UPTs could greatly improve the residual deformation, but with negligible influence on energy dissipation. The ratio of ED bars was found to be the key factor for enhancing the energy dissipation capacity of the precast columns. However, as the ratio of ED bars increased, the residual deformation deteriorated rapidly. As a result, suitable ratios of UPTs and ED bars were found to be the keys to achieving both stable energy dissipation and low residual drifts.The increased axial load ratio and prestress level are available as design parameters to prevent joint opening and improve the bearing capacity of the precast column. However, excessive axial loads or prestressing force would result in premature crushing failure, the rapid degeneration of the carrying capacity, and larger residual displacements.This study investigated the seismic performance of precast columns with energy-dissipating (ED) bars and unbonded prestressed tendons (UPTs), as influenced by various design parameters. To capture the damage mode and hysteresis curve, force, residual displacement, and energy dissipation of a physical specimen, a quasi-static cyclic test was designed and performed. Using the measured data, a fiber beam element model was established and validated. Using the verified model, the effects of varying the individual design parameters were determined. The design parameters included the concrete strength, steel bar strength, UPT ratio, ratio of ED bars, axial load ratio, and prestress level. The results for each of the design parameters were analyzed and discussed meticulously. The conclusions drawn in this study are as follows.


In the face of the problem of waste disposal in the demolition of concrete structures, a composite wall composed of recycled concrete bricks and fly ash blocks was proposed, and based on the previous thermal performance research, its axial compression performance were further studied. Four types of walls were designed and constructed: (1) clay brick masonry (CBM), (2) recycled concrete brick masonry (RBM), (3) bilateral clay bricks masonry with coal-ash blocks sandwich insulation wall (CFCM), and (4) bilateral recycled concrete bricks masonry with coal-ash blocks sandwich insulation wall (RFRM). The test results showed that recycled concrete brick masonry exhibited a higher bearing capacity than clay brick masonry. The ultimate load of RBM was 15% higher than that of CBM. Moreover, the ultimate load of CFCM was 21% higher than that of CBM. Following the addition of sandwich coal-ash blocks in RBM, its ultimate load increased by over 42% than that of CBM. Following the addition of coal-ash blocks sandwich in both clay and recycled concrete bricks masonry, both the bearing capacity and strain exhibited improvement, the yielding load and compressive strength of them increased. Thus, it could be concluded that coal-ash blocks improved its bearing capacity. Based on the analysis of the axial compression tests, a theoretical computational model was developed and a computational expression to explain the compressive bearing capacity of a two-sided brick with coal-ash blocks sandwich insulation wall. Comparisons between the test ultimate loads (FT) and the estimated ultimate loads (FE) confirmed the accuracy of the theoretical calculation model for the compressive bearing capacity. Thus, theoretical computational models are highly recommended for the design of two-sided bricks with insulating walls constructed from coal-ash blocks being sandwiched together. This study provides a theoretical basis for the engineering application of recycled concrete brick wall and fly ash block composite wall. Moreover, research on the new building materials and structural forms has been on the rise3. Khatib et al.4 studied the performance of reinforced concrete beams containing waste plastic straw fiber under three-point bending test. Some scholars have discussed the re-application of municipal solid waste incineration bottom ash in reinforced concrete beams5. Some scholars have studied the method of using waste glass sand to partially replace fine aggregate to produce low-cost, high-strength concrete6. The production of traditional wall materials has been proven to consume significant amounts of energy and contaminate the environment7. This has motivated the development of new types of wall materials using recycled materials or new forms of structures9. The considerable amounts of construction and demolition waste produced during urbanisation and new rural construction has resulted in a significant pressure on the environment11. Clay bricks, which are regarded as environmentally unfriendly building materials, have been regulated in terms of production according to the state plan in China since 200512. Recycled concrete bricks, which are primarily manufactured by adopting coarse aggregates from construction waste, as well as fine aggregates and cement, which can replace clay bricks, are being promoted. This strategy can significantly reduce the amount of waste at landfills14. It has been shown that recycled concrete bricks can be used in low-rise buildings in rural areas of China16. Moreover, coal-ash blocks can also be conveniently used for construction, as they facilitate efficient use and offer the advantage of high performance under low bulk density and insulation conditions17. Consequently, as a low-cost filling material, coal-ash blocks have been widely employed in filler walls of multi-story masonry and reinforced concrete structures18. In China, coal-fired power generation produces a lot of fly ash, which not only pollutes the environment, but also takes up land when piled up. The fly ash block made of waste fly ash has the advantages of light weight, good heat preservation and so on. It is an ideal wall material22.With the continued significant improvements in the living conditions of people, urbanisation and new rural construction have also been gradually expanding in China24.It is the fundamental measure to reduce the energy consumption of residential buildings to improve the energy efficiency of heating and air-conditioning by improving the thermal performance of the building envelope. The reuse of recyclable materials is also an important means to achieve the goal of energy conservation. In rural areas of China, seismic research and energy conservation research of buildings were mostly carried out separately in the past, and many houses were renovated for energy conservation after completion, resulting in waste of resources and poor integrity. With the rapid development of rural construction, it is urgent to develop new low-cost, eco-friendly and energy-saving earthquake-resistant integrated residential structure25. However, the compression performance of bilateral bricks with a sandwich insulation wall constructed using coal-ash blocks requires further validation. Therefore, the axial force performance of the new structure is studied in this paper.To solve these problems, the author proposes Bilateral bricks with the structural form of sandwich insulation constructed using coal-ash blocks. The thermal performance of the new structure was studied and analyzed26. Therefore, four types of specimens of the same size were tailored for the tests with width and length of 370 and 720 mm, respectively. The wire mesh layer of concrete steel with a thickness of 30 mm was set both at the top and bottom of each specimen to avoid local compression damage. In general, the thickness and structural forms of the four types were: (1) clay brick masonry (CBM) with a thickness of 240 mm; (2) recycled concrete brick masonry (RBM) with a thickness of 240 mm; (3) coal-ash blocks sandwich with a thickness of 120 mm with each bilateral clay brick (CFCM) measuring 115 mm in thickness; and (4) coal-ash blocks sandwich with a thickness of 120 mm with each bilateral recycled concrete brick (RFRM) measuring 115 mm in thickness 27 and autoclaved aerated concrete 28 )28 Fig. . The comUnder the vertical uniaxial loading tests, the load-strain curve was obtained to analyse the failure progression and damage mechanism of the specimens when performing the wall compression tests. By employing electronic dial indicators mounted on the two ends of the specimens, relevant measurements were conducted for the axial compression (in the height direction) of the four structure types. In addition, the displacements (in the thickness direction) of the bilateral bricks with sandwich walls constructed using coal-ash blocks (CFCM and RFRM) were measured. Moreover, with a design range of 240 mm . In addition, the widths and thicknesses at the heights of 1/4, 1/2, and 3/4 of each specimen were measured and the average was calculated (accuracy of 1 mm). Subsequently, before the specimen was hoisted and carefully placed on the platform, with the centreline coinciding with the axis of the apparatus employed for tests, the bottom of the specimen was cleaned.Thereafter, the sensitivity of the instruments and the soundness of the installation were examined using 5% of the estimated failure load prior to conducting the loading test. Subsequently, a repeated preloading (3–5 times) was employed with 5–20% of the estimated failure load. For the two sides, the relative errors of the axial deformation must be less than 10%; otherwise, the position of the specimen should be readjusted or levelled up.In the load tests, the hierarchical load mode was adopted, with 10% of the estimated failure load applied continuously for 1–1.5 min. Thereafter, 10% of the estimated failure load was increased each time, and the load was maintained for 1–2 min by adjusting the amount of oil pumped into the test machine. Moreover, the entire testing process was observed during the continuous constant loads. In addition, the amount of oil pumped into the testing machine was properly reduced to decrease the strain rate to determine the failure state of the specimen during the rapid expansion of the cracks of the specimen and when the pointer of the dynamometer travelled back. The peak load value obtained from the dynamometer was considered as the failure load value for the specimen.The CBM of the specimen went through three stages from the beginning of compression to failure: (1) from the beginning of compression to the initial crack. When the load is small, no damage phenomenon can be seen on the surface of the specimen. The load–displacement data curve collected by the acquisition system is approximately linear, and the specimen is in the elastic stage. When continued loading to 232 kN, vertical micro-cracks appeared in the middle brick of the specimen. (2) As the load continues to increase, cracks continue to develop along the longitudinal, the number of cracked bricks increases, and the cracks continue to develop and extend to converge. When the load reaches 300 kN, the test pieces appear through cracks, some bricks are crushed, and the skin is peeled off. (3) When the load reaches 383 kN, the load drops sharply, the axial displacement increases rapidly, the specimen is damaged, and the bearing capacity reaches the limit state.The process from initial compression to failure of specimen RBM is roughly the same as that of specimen CBM, with slightly different failure forms, such as small oblique cracks in the top brick and then small cracks in individual bricks at the bottom. With the development and extension of cracks, along with the sound of brick splitting, continuous load is applied, vertical through cracks appear, and some bricks begin to spalling. When the bearing capacity reaches the limit state, the microcracks in the test piece are less than those in the test piece CBM, and the number of spalling bricks on the surface is also less than that in the test piece CBM. The failure pattern of the test piece RBM is shown in Fig. The failure phenomena of the specimen CFCM from compression to failure are as follows: (1) when the load is small, the load–displacement curve changes linearly, and the specimen is in the elastic stage. When the specimen is loaded to 139 kN, the adhesive mortar between the clay brick and the fly ash block has a slight crack; (2) with the increase of load, the width of bonding mortar cracks between fly ash blocks and clay bricks increases slowly and extends along the length direction of bonding layer. Small oblique cracks appear and increase in front clay bricks, accompanied by the sound of brick splitting; (3) as the load continues to be applied, the vertical cracks of the front clay bricks extend, and cracks also appear in the side bricks. Some bricks begin to flake off in small pieces, and the clay bricks are divided into many small unit blocks by cracks. The load increases slowly, and the fly ash blocks begin to crack and flake and break, and the axial deformation increases rapidly, resulting in the final failure of the specimen, as shown in Fig. The phenomena of RFRM from compression to failure of the specimen are as follows: (1) when the load is small, the load–displacement curve changes linearly, and the specimen is in the elastic stage. When the load reaches 121 kN, the adhesive mortar between the recycled concrete block and the fly ash block has a slight crack; (2) as the load increases, the bond mortar cracks between the fly ash block and the recycled concrete block extend, and the recycled concrete block at the front and bottom of the specimen appear small oblique cracks and gradually extend, accompanied by the sound of brick splitting; (3) as the load continues to be applied, the vertical cracks on the front side are extended, and cracks appear along the cement mortar bonding layer on the side. As a result, some bricks begin to flake off in small pieces. As the peeling area increases, the specimens lose their bearing capacity. The failure morphology of the specimen is shown in Fig. The axial load–strain curve obtained for specimens of different types are shown in Fig. The results of stress analysis based on the load-strain curves in case of the clay and recycled concrete bricks, as well as the coal-ash blocks from CFCM and RFCM, are shown in Fig. CBM) were compared. The results are summarised in Table The cracking loads comprising the cracking load of adhesive mortar (Fs) and that of bricks (Fc), as well as the ultimate loads (Fu), and the relative value of the ultimate loads of RBM, CFCM, and RFRM to CBM   2) as fo29:ψ denotes the stability coefficient of the masonry, which is specified in the code for the design of masonry structures 30.The compressive bearing capacity shown in the application of engineering can be calculated using Eq. 29:3\docufm is the average compressive strength of the masonry, f1 and f2 are the average compressive strength grades for blocks and adhesive mortar, respectively, k1 is a parameter relative to the block category, ɑ is a parameter relative to the block and masonry category, and k2 is the correction factor of the adhesive mortar strength to compressive strength of masonry. By adopting the design standard of masonry structures, the values of k1, k2, and ɑ were obtained as 0.78, 0.5, and 1.0, respectively30.Equation  was usedRegarding the brick masonry, the bearing capacity is typically expressed as follows:31, as well as the compressive strength of coal-ash blocks; therefore, its bearing capacity is expressed as follows:In case of coal-ash blocks masonry, the determination of the compressive strength is generally conducted based on the results collected from researchIn case of the adhesive mortar, it was assumed that it was homogeneous in the vertical direction and its bearing capacity could be directly obtained by employing its compressive strength and cross-sectional area.32 were verified. The calculation results are shown in Table The theoretical calculation model was used to calculate the four types of specimens, and the similar core column specimens in the referenceAs can be seen from Table Four types of specimens were tested to investigate their axial compressive property. The results showed that recycled concrete brick masonry exhibited a higher bearing capacity than clay brick masonry, which indicated the enormous development potential in terms of recycled concrete bricks for constructions in rural area. Moreover, following the addition of coal-ash blocks sandwich in both clay and recycled concrete bricks masonry, both the bearing capacity and strain exhibited improvement, the yielding load and tensile strength of them increased. The ultimate load of RBM was 15% higher than that of CBM. Moreover, the ultimate load of CFCM was 21% higher than that of CBM. Following the addition of sandwich blocks in RBM, its ultimate load increased by over 42% than that of CBM. In addition, the cracking and ultimate loads of both the CFCM and RFRM increased. Thus, it could be concluded that coal-ash blocks enhanced the brittle failure characteristics of brick masonry and improved its bearing capacity. The computation expression of bearing capacity for bilateral bricks with an insulation wall constructed using coal-ash blocks sandwich was subjected to a comparative analysis to test and calculate the values theoretically. The results confirmed the correctness and feasibility of the calculation model. Moreover, it can be employed for the design of similar wall types.In the face of the problem of waste disposal in the demolition of concrete structures, based on the previous thermal performance research of the composite wall of recycled concrete brick and fly ash block, the axial compression mechanical properties of the wall are studied in this paper. According to the research, the thermal insulation and mechanical properties of recycled concrete brick wall and fly ash block composite wall are improved compared with the traditional clay brick wall, and can replace the traditional clay brick wall. For the seismic area, further research on seismic performance is needed.


The effect of octaisobutyl-polyhedral oligomeric silsesquioxane (OIB-POSS) as a nanosized reinforcement on the cure kinetics, crosslinking density, and mechanical properties of styrene-butadiene rubber (SBR) nanocomposites was examined in this study. For this purpose, SBR compounds with various OIB-POSS nanoparticle loadings at 1, 3, and 5 phr were prepared and their results were compared with a reference compound without OIB-POSS. When 1 phr of OIB-POSS was added to the rubber matrix, the elongation at break values and tensile strength of the corresponding nanocomposite increased by 24.1% and 29.2% compared to the reference sample, respectively. The presence of OIB-POSS nanoparticles and their random distribution in the SBR matrix was confirmed by transmission electron microscopy. The crosslinking density of nanocomposites was calculated by the Flory-Rehner method and a decrease was observed with the addition of OIB-POSS nanoparticles. In addition, thermal aging process as 70 °C for 70 h was applied to vulcanized samples. It was noted that the mechanical properties of SBR/OIB-POSS nanocomposites remarkably improved, whereas their crosslinking densities gradually decreased after thermal aging. Rubber composites are generally prepared with various reinforcements having different particle size and surface energy according to the application areas of rubbers . The reiStyrene-butadiene rubber (SBR) is one of the synthetic nonpolar rubber types and synthesized from styrene and 1,3-butadiene monomers . BesidesThe POSS is a new-generation three-dimensional nanofiller having a silica-like core surrounded by a shell of organic groups and widely used in polymers as it provides reinforcement and stabilizing properties to polymer materials –13. The In this study, it was aimed to use OIB-POSS as a potential reinforcing agent for SBR, unlike our previous study, in which POSS nanoparticles containing reactive groups were chemically bonded to the SBR matrix and involved in the vulcanization mechanism. The effect of OIB-POSS nanoparticles added to the SBR matrix as nonreactive reinforcement nanofillers at 1, 3, and 5 phr on the rubber compounds was investigated through crosslinking, mechanical, physical, and rheological properties. The change in the properties of SBR nanocomposites after the thermal aging process was also examined.N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-Isopropyl-N′-phenyl-1,4-phenylenediamine , sulfur (S), tetramethylthiuram disulfide (TMTD), 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), and zinc oxide (ZnO) in rubber recipes were obtained from Rubber Chem, Turkey and used as received.Styrene-butadiene rubber  was supplied by Arlanxeo, Germany. Nonfunctional octaisobutyl POSS  was obtained from Hybrid Plastics Inc., USA and used as received without purification. The chemical structures of SBR and OIB-POSS are given in A laboratory type banbury was used for the preparation of SBR/OIB-POSS nanocomposites according to the procedure of our previous study . The detThe SBR/OIB-POSS compounds were successively vulcanized using a hydraulic hot press at 160 °C. During the vulcanization, their optimum cure times were determined by a moving die rheometer (MDR). Test specimens were obtained by cutting in accordance with the required dimensions and standards of tests to be applied to the compounds. Rubber nanocomposites were kept in an air-circulating oven for 70 h at 70 °C to investigate the effect of thermal aging.The rheometer parameters of the SBR/OIB-POSS nanocomposites and the reference compound were determined by a moving die rheometer  in accordance with ASTM D5289 (2019). The chemical structures of SBR/OIB-POSS nanocomposites were characterized by ATR technique using Spectrum Two, Perkin-Elmer (USA) Fourier-Transform Infrared Spectrum (FT-IR) equipment at room temperature. Mechanical properties of reference sample and rubber nanocomposites were determined with an Instron Universal Tester (Model 3345) in accordance with ASTM D412 (2019). The speed of the crosshead was applied to be 500 mm/min. Zwick Shore A type durometer in accordance with ASTM D2240 (2015) was used to test the hardness of vulcanized nanocomposites. Also, compressions set tests of samples were performed properly with ASTM D395 (2018). To examine the dispersion of OIB-POSS nanoparticles in the rubber matrix and the morphology of SBR/OIB-POSS nanocomposites, transmission electron microscopy (TEM) analysis was performed with the instrument Joel JEM-2100 (UHR) Gatan, (USA) at 300 kV.Crosslinking densities of cured and aged SBR/OIB-POSS nanocomposites were determined by equilibrium solvent-swelling ratios in toluene, densities of the rubber matrix and toluene , volume In this study, influence of nonfunctionalized OIB-POSS nanoparticles on the rheological, physical, mechanical, morphological, and crosslinking properties SBR nanocomposites were investigated. For this purpose, the OIB-POSS nanofiller at 1, 3, and 5 phr was intensively mixed with SBR and then were vulcanized at 160 °C. The effect of thermal aging (70 hours at 70 °C) on SBR/OIB-POSS nanocomposites was also investigated.Rheometer data with important parameters of the reference compound and rubber nanocomposites were determined at 160 °C. The average results of rheometer tests repeated three times are presented in 90) values of SBR/OIB-POSS nanocomposites did not change significantly with the increase of OIB-POSS amount compared to the reference compound. The absence of a significant change in optimum curing time in the presence of OIB-POSS could be attributed to the fact that sulfur was not consumed in the early stage of vulcanization and there was no dominant reaction between OIB-POSS and sulfur.The ML values of the SBR nanocomposites and the reference sample were quite similar; however, the maximum torque (MH) values were remarkably decreased by increasing OIB-POSS loading. In addition, the cure extent (CE) value, which is related to the crosslinking degree of rubber and calculated from the difference between MH and ML values in the literature, decreased as the amount of OIB-POSS increased . This maOne of the important parameters characterizing the vulcanization of rubber compounds is the cure rate index (CRI) and it was calculated with the given equation.According to the rheometer test performed at 160 °C, the CRI values of SBR/OIB-POSS nanocomposites were significantly lower than those of the reference sample. Therefore, it could be concluded that the presence of OIB-POSS in the SBR matrix reduced the curing rate. The decrease in CRI values during the vulcanization reaction indicated to reduce the crosslink density in the rubber nanocomposites .−1 assigned to double bond of SBR matrix was the proof of the successful curing process (REF V). Moreover, the increase in peak intensity of bonds of hydroxyl and carbonyl groups in the aged reference compound spectrum (REF A) verified oxidative aging ). In the literature, thermal oxidative aging of SBR results in the formation of oxygenated chemicals such as anhydrides, peresters, carboxylic acids, ethers, and alcohols [The insertion of OIB-POSS into the SBR matrix was studied by FT-IR spectroscopy equipped with a diamond attenuated total reflection (ATR) instrument at room temperature. The FT-IR spectra of the reference and SBR/OIB-POSS-1 nanocomposite samples in nonvulcanized, vulcanized (V), and aged (A) steps are given in ve aging . Additio698 cm−1 –26. The omposite –29. The alcohols , 31. TheThe mechanical properties of SBR/OIB-POSS nanocomposites, in comparison with the conventional SBR reference compound, are shown in The elongation at break and tensile stress values of the obtained nanocomposites gradually decreased due to possible agglomerations and lower degree of crosslinking with the addition of more OIB-POSS, which could be supported by previous rheological data . HoweverThe 50% and 100% tensile modulus values of the SBR/OIB-POSS nanocomposites were lower than the reference compound . The addShore A hardness and compression tests were performed according to ASTM D2240 (2015) and D395 method B (2018) to determine the effect of OIB-POSS nanoparticle loading on the resistance to indentation, permanent deformation of samples and to observe how the elastic properties change after prolonged compression at room temperature for 22 h and after thermal aging process at 70 °C for 70 h . It was The crosslinking densities (ν) of both vulcanized and aged SBR/OIB-POSS nanocomposites were determined by swelling measurements in toluene solvent using Flory-Rehner equation. The average results of the crosslink densities calculated from the three swelling tests are given in The reinforcement mechanisms in rubber nanocomposites are complex due to the multicomponent heterogeneous system and cross-linked structure. In addition to the interactions between filler-filler and filler-rubber, the particle size, specific area and dispersion level also affects the reinforcement of composites. Therefore, the decrease in crosslinking density cannot normally be explained by a single simple theory. Currently, the reinforcing mechanisms of the rubber nanocomposites have drawn significant interest with an emergence of novel fillers and various matrix/filler combinations .The morphological properties of the SBR/OIB-POSS nanocomposites were evaluated by TEM analysis from the rupture surface of the corresponding tensile sample. TEM images of the SBR/OIB-POSS-5 nanocomposite demonstrated fairly continuous and homogeneous distribution with some very rare OIB-POSS aggregates visible as black clusters between 50–200 nm . These d−1 for the POSS groups in the FT-IR spectrum of the SBR/OIB-POSS-1 nanocomposite. The successful vulcanization process was also verified by the absence of the peak at 1638 cm−1 in the FT-IR spectrum of vulcanized nanocomposite. As a result of the rheological test, it was determined that the addition of OIB-POSS to the rubber recipe reduced the CE value. The mechanical strength increased with the addition of 1 phr OIB-POSS to the SBR matrix, but further increase in the amount of POSS nanoparticle led to a negative effect on the mechanical properties due to possible agglomerations. The tensile strength of SBR/OIB-POSS-1 nanocomposite increased from 1.41 MPa to 1.75 MPa, with an improvement of 24.1% and the elongation of break values of corresponding nanocomposite increased by 29.2% compared to the reference sample, respectively. This increase in mechanical properties implied that the reinforcement effect was more dominant than the negative crosslinking effect. Accordingly, the crosslink densities of nanocomposites calculated by the Flory-Rehner method decreased with the addition of OIB-POSS, as predicted. TEM micrographs verified the presence and random dispersion of OIB-POSS in the SBR matrix. In addition, after the thermal aging process, the rigidity of the SBR/OIB-POSS nanocomposites increased while the mechanical strength decreased.In this study, a series SBR/OIB-POSS nanocomposites with 1, 3, and 5 phr on the rubber compounds were prepared using a laboratory type banbury mixer, and their rheological, physical, mechanical, and crosslinking properties were investigated along with the reference SBR compound without nanofillers. The presence of OIB-POSS in the SBR nanocomposites was confirmed by detecting the Si-O stretching band at 1129 cm


Immunoglobulin G4-related disease (IgG4-RD) is a systemic inflammatory disease and affected individuals typically present with an increased infiltration of IgG4-positive plasma cells in the pancreas, hepatobiliary tract, and liver but rarely in the gastrointestinal tract.A 12-year-old girl presented with vomiting and poor weight gain. Gastroscopy revealed duodenal stenosis and ulceration. Computed tomography revealed edematous duodenal wall thickening and air-fluid levels on the right side of the duodenum, which suggested duodenal perforation or penetration. She underwent pancreaticoduodenectomy, and IgG4-RD was diagnosed via histopathology.This is the first pediatric case of isolated duodenal IgG4-RD resulting in duodenal obstruction after multiple ulcers. Gastrointestinal IgG4-RD should be among the differential diagnoses of unexplained gastrointestinal obstruction or ulceration even in children. Immunoglobulin G4-related disease (IgG4-RD) is a systemic inflammatory disease which is characterized by an abundance of IgG4-positive plasma cell infiltration in the affected organs and an elevation in the serum IgG4 levels . This coThe patient was a 12-year-old girl with no comorbidities and no oral medications. She fainted after hematemesis and hematochezia and was rushed to the ER. She received a blood transfusion for severe anemia and underwent gastrointestinal endoscopy, which detected a hemorrhagic duodenal ulcer Fig.A. She waEdematous duodenal wall thickening and air-fluid levels on the right side of the duodenum were observed via abdominal computed tomography (CT), which suggested the presence of duodenal perforation or penetration. The wall of the common bile duct was thickened with enhancement. There was no swelling or mass in the pancreas Fig. A–C.She had high serum levels of IgG4 214 mg/dl) but no other tumor marker level was remarkable . Serum helicobacter pylori antibody was negative. Serum gastrin was normal (87 pg/ml). C-reactive protein (0.19 mg/dl), total bilirubin (0.3 mg/dl), and amylase (115 U/l) were not elevated  characteristic diffuse/localized swelling or masses in single or multiple organs upon clinical examination, (2) a serum IgG4 concentration of ≥ 135 mg/dl, and (3) a remarkable degree of lymphocytic and plasma cell infiltration along with fibrosis and the infiltration of IgG4-positive plasma cells, with a ratio of IgG4/IgG-positive cells of > 40% and > 10 IgG4-positive plasma cells/HPF on histopathological examinations .Steroid therapy can be considered a viable treatment strategy when the diagnosis of gastrointestinal IgG4-RD is achieved without surgical resection. If a definitive diagnosis was obtained by examinations such as core needle biopsy or laparoscopic exploration and biopsy, we could try the steroid therapy. High-risk surgical resections such as pancreaticoduodenectomy would have been performed only when steroid therapy was ineffective. However, isolated gastrointestinal IgG4-RD is particularly difficult diagnose before surgical resection owing to the fact that it is a considerably rare condition and presents with features similar to malignancy. IgG4-RD is diagnosed via histopathology with IgG4 staining . As descGastrointestinal IgG4-RD should be among the differential diagnoses of unexplained gastrointestinal obstruction or ulceration even in children. If there is a situation in which IgG4-RD is suspected, a biopsy should be performed to make the diagnosis whenever possible, especially in children. Once IgG4-RD is definitively diagnosed, medical treatment including steroids should be administered, and surgical resection should be performed only if the disease is refractory to medical therapy.


In this study, accelerated chloride diffusion tests are performed on ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBFS), and fly ash (FA) concretes aged 4–6 years. Passed charge is evaluated according to ASTM-C-1202 for 12 mixtures, considering water–binder (W/B) ratios , GGBFS replacement rates , and FA replacement rates (0% and 30%). The effects of aged days on passed charge reduction behavior are quantified through repetitive regression analysis. Among existing machine learning (ML) models, linear, lasso, and ridge models are used to analyze the correlation of aged days and mix properties with passed charge. Passed charge analysis considering long-term age shows a significant variability decrease of passed charge by W/B ratio with increasing age and added admixtures (GGBFS and FA). Furthermore, the higher the water–binder ratio in GGBFS and FA concretes, the greater the decrease in passed charge due to aged days. The ML model-based regression analysis shows high correlation when compressive strength and independent variables are considered together. Future work includes a correlational analysis between mixture properties and chloride ingress durability performance using deep learning models based on the time series properties of evaluation data. Concrete offers several engineering benefits in addition to being a cost-effective building material. Globally, more than 5.5 billion tonnes of concrete are used every year . HoweverNumerous studies in the field of materials, design, and engineering have attempted to control the deterioration caused by chloride ingress. Methods using industrial byproducts such as ground granulated blast furnace slag (GGBFS) and fly ash (FA) as alternatives to cement are known to be effective ,9,10. FuInternational concrete structure design standards perform chloride ingress durability performance designs based on Fick’s second law ,14,15. ICurrently, machine learning (ML) and deep learning (DL) algorithms are actively used in a variety of fields, and they can be used to devise new techniques for the performance prediction and evaluation of concrete quality, considering several variables ,26,27,28ML is used to analyze the relationship between independent and dependent variables using linear and nonlinear regression analyses ,31. DealIn the field of concrete performance, most of the existing studies conducted using ML and DL algorithms are limited to predicting mechanical and durable performances based on specific aged days and mix design ,23,24,28This study quantifies the evaluation results of passed charge and compressive strength for OPC, GGBFS, and FA concretes aged 4–6 years. The test results obtained before 4 years of age are quoted from existing studies ,39. Furtck) for each mixture were set at 41 MPa (W/B: 0.37), 38 MPa (W/B: 0.42), and 33 MPa (W/B: 0.47) based on the respective W/B ratio. The slump for all mixtures was set at 150 cm, and to achieve this, varying amounts of super plasticizer were applied to each mixture. Due to the differences in the unit weight of binders , there were slight variations in the aggregate quantities in 12 types of mixtures. All concrete specimens were subjected to temperature-controlled water curing (20 °C) until the target aged day. The physical and chemical properties of the binders used are listed in In this study, three levels of W/B ratio , three levels of GGBFS content , and two levels of FA content (0% and 30%) were used for the concrete mix. The W/B ratio and substitution ratio of admixtures (GGBFS and FA) were considered to quantitatively analyze their impact on strength and resistance of chloride ingress. The designed strengths ) was used to obtain the accelerated chloride diffusion coefficient from the resulting value of the passed charge .2 s−1) and For 6 h, a voltage of 60 V was supplied to an apparatus consisting of two cells and a disk specimen of thickness 5 cm, whose sides were coated with epoxy. Cell I (negative electrode) was filled with 3% sodium chloride (NaCl) aqueous solution, while Cell II (positive electrode) was filled with 0.3 M sodium hydroxide (NaOH) aqueous solution. The passed charge was measured and calculated every 30 min for a continuous supplied voltage using Equation (2). On each evaluation day, the amount of passed charge was calculated thrice, and the values were averaged to derive the final result. An image of the apparatus used to evaluate the passed charge is shown in The compressive strength was evaluated in accordance with KS F 2405 for OPC, GGBFS, and FA concretes aged 4–6 years . Based oThe compressive strength evaluation results for the OPC, GGBFS, and FA concrete specimens aged 28–2190 days (6 years) are shown in After 3 years, the last aged day in previous studies ,39, no s3S and C4AF, which could lead to strength recovery. This phenomenon, termed the dilution effect, was substantiated in prior research [Regression analysis of the aged day effect on the compressive strength behavior showed that the higher the W/B ratio, the larger the effect on all mixes. Particularly, aged days had the most effect on the OPC concrete, with a root mean square difference of 1.81 times between the W/B ratios of 37% and 47%. For the GGBFS concrete, the effect was at a similar level as the replacement rate increased. The values of FA concrete were between those of the OPC and GGBFS concretes. Even in OPC concrete, the specimen with a lower W/B ratio (0.37) appeared to be less influenced by the curing period. In the specimens containing GGBFS and FA, higher strengths compared to OPC concrete were showed from the early aged days. Consequently, even in concrete with a relatively low binder content (W/B ratio: 0.47), the impact of aged days on strength was at a low level. In the case of substituting cement with GGBFS or FA, reducing the amount of cement may cause a reduction of strength. However, a decrease in the amount of cement increases the free water available for reacting with the cement, promoting reactions of Cresearch . MoreoveIn accordance with ASTM C 1202, the passed charge evaluation results for the OPC, GGBFS, and FA concretes aged 4–6 years are shown in Based on the last aged days of the previous studies, the rate of passed charge decrease for age days of 6 years was assessed based on the age days of 3 years, and the results were 7.9 to 20.7, 5.3 to 9.7, 10.0 to 14.7, and 13.6 to 16.5% for the OPC, GGBFS30, GGBFS50, and FA30 concretes, respectively. Comparatively, OPC concrete showed a greater passed charge decrease than the others. However, the decreased rate in other concretes was underestimated because a major decline had already occurred before the age of 3 years. In concrete mixed with admixtures such as GGBFS and FA, the passed charge variations among the 3 levels of W/B ratio decreased as age increased. In the case of OPC concrete, the variation by W/B ratio was relatively large, even at the final age of 6 years. Moreover, the high Blaine in GGBFS resulted in a packing effect, enhancing the durability performance of specimens containing GGBFS from the early aged days.The design criteria for chloride ingress resistance performance in different countries consider the extent to which the behavior of the chloride ions penetrating into the concrete decreases over time. When the durability performance was analyzed without considering the diffusion behavior that was improved with dependence on time, the analysis results were very highly conservative, requiring crucial consideration ,15,16. TThe effect of aged days on the passed charge was analyzed through regression analysis, and the higher the W/B ratio for the GGBFS and FA concretes, the greater the effect of aged days. In the specimens containing GGBFS, there was not a significant difference in the impact of curing period due to varying W/B ratios. However, in FA concrete, the effect of curing period was high, due to the relatively higher passed charge in 28 aged days. OPC concrete showed the highest value in the OPC-37 mix. Even when the formulation only used OPC as the binding material and the unit binder quantity was achieved through a low W/B ratio, a greater improvement in chloride ingress resistance performance with the age days was expected. For GGBFS and FA concretes, even when the W/B ratio was relatively high, their material properties of latent hydraulic and pozzolanic reactions were observed to significantly improve the chloride ingress durability performance over the long-term. The obtained results aligned with those observed in previous studies .For this study, three multiple regression models were used to analyze the correlation between mix properties and concrete performance. The models included linear, ridge, and lasso regression. A multiple regression model was used to analyze the relationship between a dependent variable and one or more independent variables. This model was used as the multicollinearity showing that correlations between independent variables did not exist in the data used in this study . The thrAs the number of explanatory variables in regression analysis increases, model selection difficulties arise, and with more variables included in the model, the complexity of the problems increases and interpretation becomes difficult. Methods of subset selection and shrinkage exist as statistical solutions to provide modeling convenience by arbitrary selection of variables.Tibshirani proposed lasso regression as a shrinkage method for regression models, where a penalty equal to the square of the estimated regression coefficient was imposed . AccordiThe dataset for regression analysis was constructed by considering the mix properties, compressive strength, and passed charge evaluation results of 12 formulations discussed in The correlations of concrete compression strength and passed charge with the mix properties were analyzed using the linear, lasso, and ridge regression models, considering the three cases listed in 2), which was an indicator of how well the independent variables explained the dependent variable in a regression model. The value ranged between 0 and 1, and higher values indicated better explanation [The performance evaluation of the correlation of compressive strength and passed charge of concrete with the mix properties was verified by comparing the coefficient of determination , aged days, and compressive strength were set as independent variables, while passed charge was the dependent variable. Thus, considering compressive strength in addition to mix properties and age can better explain the correlation between passed charge and mix properties. In the future, further analysis of the correlation between mix properties and chloride ingress durability performance through DL algorithms based on the time series characteristics of the data will be conducted.In this study, the compressive strength and passed charge of 12 concrete mixes at 4 to 6 years of age were evaluated considering different admixture replacement rates. The effect of aged days on the mechanical and durability performance behavior was quantified by citing the results of previous studies that analyzed aged days. Furthermore, ML algorithms were used to analyze the correlation of compressive strength and passed charge with mix properties. The conclusions of this study are as follows.


MET gene encodes a receptor critical for cell growth and repair. It plays diverse roles in processes like organ development, wound healing, and blood vessel formation. Genetic alterations in MET contribute to cancer progression, enabling tumor spread and resistance to treatment. Scientists are studying how to target MET to treat cancer. Despite progress, the complexity of MET’s functions in cancer challenges our understanding. This review explores recent discoveries about MET in cancer, its effects, potential therapies, and future directions.The MET proto-oncogene encodes a pivotal tyrosine kinase receptor, binding the hepatocyte growth factor  and governing essential biological processes such as organogenesis, tissue repair, and angiogenesis. The pleiotropic physiological functions of MET explain its diverse role in cancer progression in a broad range of tumors; genetic/epigenetic alterations of MET drive tumor cell dissemination, metastasis, and acquired resistance to conventional and targeted therapies. Therefore, targeting MET emerged as a promising strategy, and many efforts were devoted to identifying the optimal way of hampering MET signaling. Despite encouraging results, however, the complexity of MET’s functions in oncogenesis yields intriguing observations, fostering a humbler stance on our comprehension. This review explores recent discoveries concerning MET alterations in cancer, elucidating their biological repercussions, discussing therapeutic avenues, and outlining future directions. By contextualizing the research question and articulating the study’s purpose, this work navigates MET biology’s intricacies in cancer, offering a comprehensive perspective.The  MET protooncogene encodes the tyrosine kinase receptor for the hepatocyte growth factor/scatter factor (HGF/SF) [α and β subunits of, respectively, 50 kDa and 145 kDa [MET-expressing epithelial cells [The human (HGF/SF) ,2,3. It al cells ,7. This al cells ,9,10. MEal cells ).MET is altered in multiple cancer types and behaves as a pivotal regulator of invasive growth, a complex and intertwined sequence of events including epithelial-to-mesenchymal transition (EMT), scattering, migration, and growth [The broad range of critical biological responses induced by MET awards this oncogene as a crucial oncogene in tumor progression, enabling cancer cells to survive and escape the hostile primary tumor microenvironment and form distal metastases . MET is d growth ,15,16,17d growth ), therefd growth ,18,19. Rd growth .However, it should be noted that the path to efficient MET-targeted therapy for patients is long and covered with complications. Despite the presumed ‘addiction’ to MET, many patients do not respond to therapy ,21,22,23MET alterations in cancer, their impact on invasive growth, and their therapeutic potential. The lessons from the disappointing results of targeted therapies will be investigated to propose more accurate strategies to extend disease-free survival time.This review reminds the overall structure of MET and summarizes the observed α subunit (50 kDa) linked via disulfide bonds to the 145 kDa transmembrane β subunit. The extracellular portion of the β chain comprises a semaphorin (SEMA) domain, a Plexin–Semaphorin–Integrin (PSI) homology domain, and four immunoglobulin-like IPT domains [MET is the receptor tyrosine kinase (RTK) for SF. The translated precursor protein of 175kDa matures through proteolytic cleavage by FURIN protease in the Golgi apparatus , promoting MET monoubiquitylation , receptoProteomics-based studies have been invaluable in understanding conventional RTKs like EGFR, where signaling typically shows rapid activation and deactivation in response to ligand binding . In contMET gene in cancer. Here, we present some of the features of this observatory; notably, the catalog of alterations results from data collection from The Cancer Genome Atlas (TCGA), Catalogue of Somatic Mutations in Cancer (COSMIC), and ClinVar datasets.Recent advances in next-generation sequencing technologies allowed a significant reduction in their cost, ultimately leading to an inflation of publicly available ‘OMICS’ data. Additionally, improvements in the standardization of data curation, analyses, and presentation offered researchers an unprecedented quantity of comprehensive information regarding genetic alterations during cancer onset and progression. In line with this, we developed an auto-updatable ‘MET observatory’ to catalogue genetic alterations of the MET is an excellent example of an oncogene because of its critical involvement in cell migration, metastasis, and cell survival. Unsurprisingly, MET is altered in many cancers, including but not limited to non-small cell lung cancer (NSCLC), lung squamous carcinoma, gastric cancer, colorectal adenocarcinoma, melanoma, gliomas, and renal cancer [MET is gene amplification, exhibiting a prevalence rate of approximately 4% across various tumor types, as illustrated in MET amplification surges to nearly 20% in kidney papillary cell carcinomas (KIRP), a data point presented in MET amplification has been shown to confer resistance to therapies targeting the epidermal growth factor receptor (EGFR) in malignancies such as NSCLC and colorectal cancer, underlining its role in both cell survival and acquired resistance to EGFR-targeting therapies [An oncogene can be defined as an entity that can transform cells by conferring some attributes of a cancer cell. l cancer ,49,50,51herapies ,58,59.MET amplification because both are related, but have distinct genomic alterations affecting cellular phenotype and treatment response. Unlike chromosome 7 trisomy, which is not a primary cancer driver, MET amplification acts as a driver and represents a true biological selection [MET gene drives addiction, thus justifying targeted therapies [MET amplification. In the case of polysomy, the MET-to-centromere of the chromosome 7 ratio (MET/CEN7) remains constant, whereas it increases for biologically selected true MET amplification, identifying a patient subgroup that could benefit from targeted therapies. Current advances in next-generation sequencing (NGS) techniques can also offer invaluable information for better patient stratification. Indeed, recent studies have demonstrated the efficiency of MET inhibition when patients were classified using either the MET/CEN7 ratio or NGS-based detection of the MET copy number, as shown in While interpreting these findings, it is crucial to place MET amplification in the broader context of common chromosomal aberrations in cancer, such as cellular aneuploidy. Specifically, the trisomy of chromosome 7 is often observed across multiple cancer types and serves as a pan-cancer genetic marker ,61,62. Telection . In vitrherapies . AlthougEGFR, fibroblast growth factor receptor (FGFR), for review, see [MET mutations in the kinase domain or regulatory regions (Exon14 were by far the most common MET mutations. These mutations (complex or simple) are a consequence of the loss of acceptor or donor sites, resulting in Exon14 ‘skipping’. Indeed, the latter was described in a significant number of patients: 13% in pulmonary sarcomatoid carcinoma, 6% in adenosquamous carcinoma, 3% in lung adenocarcinomas, 2% in lung squamous cell carcinomas, 0.4% in gliomas, and 0.4% in cancers of unknown primary origin (CUP) [MET Exon14 encodes for the juxtamembrane domain. Because of the regulatory role of the JM described above, it was thought that its loss would lead to increased receptors, and the subsequent ligand-independent uncontrolled activation of MET, thus driving invasive growth. Accordingly, the re-insertion of Exon14 into the oncogenic gene fusion (TPR)–MET, which consists of the MET sequence downstream from the juxtamembrane domain fused to the dimerization motif of TPR, resulted in decreased oncogenic potential [MET Exon14 deletion (MET∆14) [Exon14 does not result in constitutive activation of the kinase. MET∆14 activity requires SF and drives a robust and selective AKT activation, rendering cancer cells more prone to survival and migration [MET Exon14 ‘skipping’ in 14% of cancer patients [It was thus proposed that other mutations might drive ligand-independent activation of MET. Surprisingly, for an RTK , very fin (CUP) ,107. METotential . Therefo(MET∆14) ,114,115.(MET∆14) ,117. Recigration . Therefopatients ,120. BasMET are sporadic but do exist. The first activating mutations of MET were identified in hereditary papillary renal carcinoma (HPRC), and the authors suggested that the mutations affecting the kinase domain of MET  were causal in HPRC [MET mutations  spanning the critical Y1234 and Y1235 were described in the sporadic renal carcinoma [MET allele [As shown in  in HPRC . SimilarT allele , leadingInterestingly, tumors formed in mice were not restricted to the kidney; animals developed lymphomas, carcinomas, or aggressive mammary tumors ,127. Impα and β chains, Exon2 encoding for the SEMA domain [MET mutations were detected in 9% of advanced breast cancer (8/88 patients). Six of eight MET mutations affected the SEMA domain . Despitpatient, ,138, ourh factor —MET mutath E168D ). MET alterations in cancer and their biological significance, opening new avenues for targeted therapies.Point mutations, although rare, should not be overlooked. With recent advancements in genomic screening technologies, we might find a growing number of these mutations. By combining in silico, in vitro, and in vivo findings, we aim to have a sharper picture of MET in mouse liver induces hepatocellular carcinomas [For RTKs, it is generally accepted that gene amplification leads to a higher number of receptors at the cell surface, priming kinase activation in the presence of small amounts of ligands. MET challenges this concept; an overexpression of human rcinomas . Since hrcinomas , these rMET gene rearrangement in human tumors has been TPR-MET, mostly occurring in gastric cancers [For decades, the only known  cancers . Recentl cancers : the MET cancers .MET and the PTPRZ1 gene, encoding a tyrosine phosphatase [PTPRZ1–MET fusions include almost the entire MET sequence fused at its 5′ end with a variable number of exons of the PTPRZ1 gene [PTPRZ1-MET fusions have been found in brain tumors, such as low-grade gliomas, secondary glioblastomas arising in adults from the progression of lower-grade gliomas, and pediatric glioblastomas at a remarkably high frequency . Notabltivation . The mecMET gene  and the d to MET  are two PTPRZ1-MET in a pediatric glioma [KIF5B-MET in lung cancers [MET gene fusions also happen in melanomas, where six different N-terminal partners fused in-frame with the intracellular MET domain have been described [Experiments show that MET fusion proteins respond to anti-MET monotherapy: c glioma  and KIF5 cancers . MET genescribed . MET genetic alterations can induce either ligand-independent (or hypersensitive) or SF-dependent (MET∆14) activation of the kinase , partially explaining these frustrating results. Nevertheless, targeting SF should not be dismissed; their ability to sequestrate the ligand could be exploited to inhibit SF-dependent invasion and survival in tumors without MET amplification . Furthermore, it should be reminded that SF acts on the tumor micro milieu on cancer-associated fibroblasts and macrophages to foster angiogenesis [Targeting the ligand is an alternative option to impede MET signaling. The benefit of the SF antibodies AMG 102  and AV-ogenesis ,174,175;MET alterations (mostly amplification) respond to the MET blockade. The cell cycle is arrested, and/or apoptosis is induced in vitro [MET alterations must be assessed in patients before assigning them to the group receiving targeted therapies. This is indeed a golden rule to follow, as targeted therapies can only benefit patients presenting MET alterations. Nevertheless, their unambiguous identification is challenging. In many clinical trials, MET levels were assessed by immunohistochemistry [MET amplification and ‘addiction’. Because of the inducible nature of the MET promoter [Identifying the target population for treatment might look self-evident, but it is laborious and critical for setting the scene for success in a clinical trial. More than three decades of basic research guided drawing an overall picture of patients that can benefit from MET inhibition. Studies using cell lines or patient-derived xenografts have shown that only tumors harboring in vitro , and comin vitro . MET althemistry ,92, a stpromoter ,150,151,promoter ). Indeedpromoter , demonstMET (the vast majority of patients), a priori ineligible for MET-targeted therapies, it should be noted that hampering the MET signaling reduces migration and metastatic dissemination drastically without affecting the growth of cancer cells [For tumors expressing wt er cells ,177,178.MET alterations must be assessed before the initiation of the clinical trial. Liquid biopsies also enable longitudinal evaluation of tumor evolution in a non-invasive manner, crucial for understanding mechanisms hidebound to drug resistance, the major challenge in targeted therapy.With the progress in next-generation sequencing technologies , genomic interrogations of liquid biopsies (circulating tumor DNA and circulating tumor cells) are largely feasible ,180 to aTargeted therapies were a breakthrough in cancer research, emphasizing our cutting-edge understanding of cancer cells’ vulnerabilities. The design of appropriate treatment strategies was thus achievable. However, they suffer a significant limitation: resistance frequently occurs ,182,183 MET genetic alterations might dominate the majority of tumor cells and dictate drug sensitivity; however, minor subclones harboring other mutations that confer resistance to MET blockade may coexist and be positively selected under drug pressure. Resistant subclones must be promptly detected . In line with this idea, many efforts have been made to characterize the molecular profile of emerging resistant clones [Tumors can be defined as pseudo-organs constituted of heterogeneous clones presenting highly diverse genotypes and phenotypes. Some might prosper while others regress depending on their ability to face microenvironmental selection pressures . MET gent clones ,185,186.In current clinical practice, the line of treatment is dismissed when resistance arises. In many patients, discontinuation of kinase inhibitors results in rapid tumor regrowth: this phenomenon is known as disease ‘flare’ or tumor ‘rebound’ ,189,190,We recently presented a mechanistic elucidation of the ‘flare’ effect . Within MET translation upon MET inhibitor withdrawal [A captivating observation emerged as mTOR swiftly augmented thdrawal , uncoverthdrawal . ConsequMET’s translational control in the context of cancer demands further exploration, it might provide insight into the apparent paradox between sporadic MET amplifications (accounting for 3–5% of cases) and the nearly ubiquitous MET overexpression observed in cancer [In a broader context, the intricate interplay between the mTOR axis and MET biology underscores the pivotal role of translational regulation in governing MET expression within the realm of cancer. Translational control, distinct from the transcriptional regulations, operates on pre-existing mRNA, facilitating swift adaptability to the dynamic shifts within the tumor microenvironment. While a comprehensive evaluation of the relevance of n cancer ,202,203.MET mutations in cancer [MET genetic alterations before patient selection. On the contrary, when patient stratification was appropriately performed a priori or during post hoc analyses, a general picture of the target patients’ genomic profile can be pictured: MET alterations are an absolute prerequisite for the success of targeted therapies. MET is a potent oncogene driving invasive growth ,15,16,17n cancer ,138. TheMET sustain oncogene ‘addiction’. For the large majority of cancer patients, where MET is not mutated, preclinical comprehension of the role of MET can be directly translated to the clinic: MET has anti-apoptotic and pro-invasive functions [These lessons bear witness to crucial importance of the functional preclinical insights in guiding clinical practice. Indeed, it was already clear from studies in cell lines and animal models that substantial reduction of cancer cell viability in vitro and tumor shrinkage in vivo occur only in settings where stable and heritable genetic alterations of unctions ,178. AdjMET promoter: ionizing radiations, hypoxia, and cytotoxic reagents enhance MET expression [MET gene. The number of previously unidentified MET mutations is constantly increasing thanks to the advances in next-generation sequencing techniques and comprehensive publicly available databases . Thus, efforts aiming at the identification of new variants in cancer must be encouraged. The primary task should be to functionally characterize these mutations to broaden the panel of MET ‘addicted’ tumors and increase the number of patients eligible for next-generation precision medicine. Another unexplained phenomenon is the relatively poor frequency of MET-amplified tumors ,57,107, pression ,150,151,pression . Translapression . Another


Fracture behavior is one of the key properties to study concrete cracking under sodium chloride attack exposed to the freeze–thaw cycles environment, which is frequently neglected. In this paper, 24 single edge notch beam specimens and 24 cubes were poured. The corresponding freeze–thaw cycles test in sodium chloride solution, standard cube compressive strength of concrete test, and three-point-bending tests were carried out. The research revealed that the fracture toughness, fracture energy, relative dynamic modulus of elasticity, and standard cube compressive strength were decreased by increasing freeze–thaw cycles under sodium chloride attack, and the damage degree of concrete caused by sodium chloride solution was deeper than that of pure water. In particular, there existed good linear correlation between the fracture behavior and imposed freeze–thaw damage for various solution. Accordingly, a more reliable damage model using fracture control parameters as damage factors was proposed. Using concrete as a building material is widely accepted for its good versatility and relatively low cost. However, a large number of micro cracks are produced due to the non-uniform shrinkage deformation of aggregate and mortar in forming stage, which creates the possibility of aggressive material invasion into itself . The detAccordingly, existing research on the concrete properties exposed to FTC environment have been abundant conducted ,10,11,12strength . To summThe fracture behavior is helpful to analyze the response of concrete structures with cracks to external loads and to estimate the actual bearing capacity of concrete structures, which is suitable for the analysis of concrete in FTC environment. Additionally, concrete ,15. Loadconcrete ,17. The concrete . MoreoveLately, considerable progress has been made in the fracture behavior of concrete without consider the affection of environmental factor. However, the fracture properties of concrete under Na-Cl attack exposed to FTC environment is rarely provided. Furthermore, the corresponding test method and calculation of fracture behavior under Na-Cl attack exposed to FTC environment require further investigation.For the current study, basic experimental research on the performance of concrete subjected to FTC in pure water and Na-Cl solutions was conducted based on three-point-bending (TPB) test and standard cube compressive strength test. Firstly, a new test method for single edge notch beam (SENB) under Na-Cl attack exposed to FTC environment was proposed. The fracture behavior of SENB specimens in Na-Cl solution were further explored and compared with that of SENB specimens in pure water. Accordingly, the relationship of concrete fracture behavior between freeze–thaw damage in Na-Cl solution and pure water was investigated. Ultimately, a more reliable damage model using critical fracture toughness In this paper, 24 SENB (single edge notch beam) specimens (250 mm × 50 mm × 50 mm) and 24 Standard Cube specimens (150 mm × 150 mm × 150 mm) were poured, which strictly followed the Norm DL/T 5332 . The preAs shown in According to the Norm GB/T 50082-2009 [Because of the incremental freeze–thaw cycles from 0 times to 30 times, 5 groups of specimens (contain 4 SENB and cubes) were named as D, YD10, YD15, YD20, and YD30, respectively. An additional group of specimens was immersed in water with 30 FTC (SD30) to study the relationship of concrete fracture behavior between freeze–thaw damage in Na-Cl solution and pure water. A concentration of 5% Na-Cl solution was used for FTC test, as is shown in The pool was placed in an environmental simulation laboratory with net dimensions of 5000 mm × 4000 mm × 3000 mm, and the inside temperature could change from −40 °C to 80 °C. One cycle of the FTC test included a temperature decline from 10 ± 2 to −18 ± 2 °C with the speed of 10 ± 1 °C/h, then the temperature should be brought back to 10 ± 2 °C (and hold for one hour) with the same speed after 3 h of sustained low temperature. Moreover, a Pt  sensor was embedded in the center of the specimen. According to every 5 cycles, the specimens were dried and weighed, then covered by a reconstituted solution. The maximum number of cycles was set as 30 times, which is nearly equal to the corresponding termination rules of the Norm GB/T 50082-2009 [In the TPB test, a closed-loop servo-controlled hydraulic jack with a maximum capacity of 50 kN was employed. The clip-on extensometers were fitted at the mouth of the notch to measure the crack mouth opening displacement (CMOD), as is shown in Compared with group YD30, the SENB of group YD30 in pure water exhibited a distinct experimental phenomena. A slight spalling of the surface mortar was observed on the specimens of group SD30 exposed to the pure water.Several explanations exist for the diversity of denudation degree in various FTC solution. First, the freezing of water in the large pores of concrete was expanded by FTC. It follows that the concentration difference between the unfrozen area in the large pore and the solution in the surrounding small pore were formed. Second, the water translation between the small hole and the large pore was generated by the concentration gradient. Hence, the concrete damage was primarily promoted by that translation. Third, the water content and concentration difference in the pore were exacerbated by Na-Cl, which led to more serious concrete damage. Therefore, a further study was required to obtain more reliable results.Additionally, the coarse aggregate exposed in some severely scaled specimens immersed in the solution even peeled off. Naturally, the above results show that the Na-Cl&FTC surroundings caused serious erosion, which were even discovered universally on the coarse aggregate with high strength. An essentially deduction was put forward, that the strength difference and bond strength between mortar and aggregate is closely related to the FTC resistance of concrete. The results corroborate the findings of other researchers   was revealed in The following Equation (1), which was mentioned in , was appThe weight loss of SENB submerged in Na-Cl in For the cube compressive test, a universal testing machine with a maximum capacity of 500 kN was employed, and the testing rate was fixed at 0.2 mm/min until failure. The dynamic modulus of elasticity (DME) was calculated by the followed Equation (2).For the specimens attacked by FTC, due to the existence of numerous micro cracks and severe surface erosion damage, it was reasonable to use Equation (2) to obtain Young’s modulus by concrete cubic compressive strength, but not the conventional test method. The RDME, which was determined by Equation (3), is the ratio of DME value to the initial DME value after 5n FTC:According to the test procedure, the deterioration of the specimens was investigated by determining the RDME loss, weight loss, and compressive strength loss, and the results are shown in In order to prove the validation of double-K fracture model to the concrete attacked by Na-Cl in FTC circumstance. As shown in The flexibility coefficient The calculated elastic modulus Then, the critical notch depth of the specimen 0.5) was calculated by Equation (6).2) is the acceleration of gravity, 2, The initial fracture toughness 0.5) was calculated by Equation (7).The critical fracture toughness The calculation formula for fracture energy is shown in Equation (8), Fracture energy is the product of load and deflection under applied load conditions; therefore, load-deflection curves can express the fracture properties of concrete. The structures of concrete specimens changed by the freeze–thaw cycles in salt solution; estimates showed that more microcracks are formed with ceaseless Osmotic pressure, which develop with increased FTC times. Furthermore, the independent microcracks gradually developed, and more unobstructed cracks were created. Energy was consumed with the collection and propagation of microcracks in FTC environment, which led to a decrease in fracture properties. Thus, freeze–thaw damage in Na-Cl solution significantly decreased the toughness and fracture behavior of concrete. Crack performance is well reflected in the fracture properties of concrete in Na-Cl solution.In addition, there exists a linear correlation between fracture energy and applied FTC, as shown in The characteristics of the FPZ are described by the softening constitutive curve of concrete, which is one of the important parameters to simulate the nonlinear behavior of concrete. Three indirect methods were shown and compared to obtain the appropriate softening curve. ode 1990 , and Reiode 1990  and ReinAnother widely accepted method for testing the applicability of softening curves was proposed. The cohesive fracture toughness The CEB-FIP Model Code 1990  was usedCrack stability of specimens in Na-Cl&FTC environment were studied by method of It can be concluded that the double-K fracture criterion and Griffith’s criterion are still applicable in the analysis of the crack stability of the specimens in salt freeze–thaw cycles environment.The RDME, SEM was used to observe the surface of concrete specimens after salt freeze–thaw by researchers  Compressive strength and RDME both decrease with increasing FTC times; specimens in the Na-Cl solution have lower compressive strength and FTC resistance compared with specimens in pure water. The reduction relationship of concrete fracture behavior between freeze–thaw damage in Na-Cl solution and pure water were three times.(2)The feasibility of double-K fracture model was confirmed, (3)The CEB-FIP Model Code 1990 was used to calculated the strain-softening curves. This model is more accurate than Petersson and Reinhardt. The value (4)The damage of specimens in salt freeze–thaw is currently underestimated, and using In this paper, the fracture behavior of concrete attack by Na-Cl&FTC was mainly studied. Based on the results of this experimental work, the following conclusions are drawn: