Implementing green development is important to realizing a harmonious relationship between humans and nature, and has attracted the attention of governments all over the world. This paper uses the PMC (Policy Modeling Consistency) model to make a quantitative evaluation of 21 representative green development policies issued by the Chinese government. The research finds: firstly, the overall evaluation grade of green development is good and the average PMC index of China’s 21 green development policies is 6.59. Second, the evaluation of 21 green development policies can be divided into four different grades. Most grades of the 21 policies are excellent and good; the values of five first-level indicators about policy nature, policy function, content evaluation, social welfare, and policy object are high, which indicates that the 21 green development policies in this paper are relatively comprehensive and complete. Third, most green development policies are feasible. In twenty-one green development policies, there are: one perfect-grade policy, eight excellent-grade policies, ten good-grade policies, and two bad-grade policies. Fourthly, this paper analyzes the advantages and disadvantages of policies in different evaluation grades by drawing four PMC surface graphs. Finally, based on the research findings, this paper puts forward suggestions to optimize the green development policy-making of China. Since the reform and opening up in 1978, China’s economic development has accomplished great achievements and is ranked second in the world. However, China’s economic development has faced severe challenges, especially climate change and environmental pollution, which have become issues of great concern to the Chinese government. The frequent occurrence of natural disasters and social crises caused by environmental degradation and climate change has seriously restricted the sustainable and circular development of China’s society and economy. Although China has the second largest economy in the world, it faces daunting pressure and challenges in ecological and environmental protection. According to statistics, the health and economic loss caused by air pollution in China in 2017 was equivalent to 2.5% of that year’s GDP [Policy evaluation starts from the formulation of policies, evaluates the effect of policy implementation, and finds the advantages and disadvantages of policies . In the Green development policy plays a very important role in promoting green development. At present, there is scant literature on the quantitative evaluation of green development policies. A scientific evaluation of China’s green development policies can objectively judge the current situation and provide suggestions to adjust China’s green development policy in the future. Therefore, this paper uses the PMC Index model to evaluate China’s green development policies. The PMC (Policy Modeling Consistency) Index model can analyze internal consistency and intuitively displays the advantages and disadvantages of the various dimensions of policies through the PMC curved surface. The specific process is as follows: firstly, collect green development policy texts issued by the Chinese government and use a text mining method to deeply identify the policy’s contents and eliminate the parts that are not highly relevant. Secondly, use the content and nature of the green development policy text to design an evaluation index system of green development policies. Then, the value of the first-level evaluation index and the value of the PMC Index of each policy are calculated and a multi-input–output table is established. Finally, four PMC surface maps of green policy were drawn; the concave and convex of the surface map were observed to reflect the internal consistency of green policies and corresponding suggestions were put forward. The marginal contribution of this paper is to apply the PMC index model to assess green development policies, which is helpful to understand the status of China’s green development policies and promote the research boundary of green development policies. China is the largest developing country in the world and therefore, its green development policy evaluation can also provide inspiration for other developing countries to make better green development policies.The second part of this paper is the literature review, which evaluates the literature on green development and policy evaluation. The third part is the research design, wherein we introduce the data source of this paper, the PMC index model, the design of the index system of green development policies, and the PMC surface graph. The fourth part is the research results, including the multi-input–output table and four PMC surface graphs of different level policies. The fifth part is the conclusion, which summarizes this paper and puts forward suggestions to optimize China’s green development policy.The theme of this paper is the evaluation of China’s green development policy. Therefore, this paper reviewed the literature on green development and public policy evaluation.Firstly, as far as the study of green development, the study about green development can trace back to the 1970s, when people realized the disadvantages of the economic development model at the cost of resource consumption. People began to think about how to coordinate the relationship between economic development and ecological environment, then the concept of green development was born . In 2012Secondly, in terms of the research on public policy evaluation, policy evaluation runs through the process of policy formulation and implementation, which can be divided into pre-evaluation, in-process evaluation, and post-evaluation. Whether the results of policy evaluation are scientific and accurate directly affects policy formulation in the future. In the early studies, scholars mainly used the qualitative evaluation method to evaluate public policies, but the qualitative evaluation method is no longer applicable to the evaluation and analysis of policy because of its lack of feasibility and science. At present, most scholars adopt quantitative evaluation methods to evaluate policy. Quantitative evaluation methods include a multidimensional evaluation model, multiple difference method, entropy weight method, etc. In particular, there are a lot of studies on public policy evaluation using the synthetic control method and double-difference method. For example, Castillo et. al used an integrated control method to analyze the long-term impact of tourism development policies on employment in Salta Province of Argentina and found the average annual impact of tourism on employment was 11% . BrossarBased on the literature review, it can be found that there are a lot of studies related to green development and public policy evaluation but there are few studies on green development policy evaluation by using quantitative methods. Moreover, the existing studies on policy evaluation mostly focus on the effect of policy implementation, and few start from the policy formulation and conduct the prior evaluation of policy. A good level of green development policy is the premise to promote green development. Therefore, this study decides to use the PMC index model to evaluate China’s green development policy in order to provide inspiration for the adjustment of China’s green development policy in the future.The purpose of this paper is to evaluate green development policies issued by the Chinese government. Therefore, the data in this study come from the green development policies issued by the Chinese central government. A total of 90 related policy documents were collected in this study. Considering the rigor and feasibility of the evaluation of policy texts, the 90 texts collected were screened and some informal policy texts such as letters and replies were eliminated. Finally, 21 green development policies were obtained see .The traditional quantitative policy evaluation model uses quantitative methods to analyze the implemented effect of policy, while the PMC index model analyzes policy itself, not the effect of policy implementation. PMC index model is a new method to quantitatively evaluate policy proposed by Estrada, which analyzes the internal consistency of policy and emphasizes the importance of all variables in policy text being equal. In the PMC index model, all relevant variables should be included as far as possible and those weakly correlated variables should not be ignored. PMC index models can avoid the phenomenon that exists in policy evaluation methods, paying too much attention to some variables while ignoring others, because the status of all variables is equal. Therefore, all variables are regarded as binary variables in the policy evaluation process. In other words, the variable is assigned a value of 1 if it is covered by the policy, and 0 if it is not . In addiFirstly, assign a value to the secondary index. Equations (1) and (2) are used to assign binary values to the second-level index of the evaluation index system of green development policy. If the secondary index of green development policy meets the criteria in In Equation (3), i = 1,2,3… n, and i is first-order index, j is second-order index.1~X10 are first-level indices, including policy nature, policy function and timeliness of policy, evaluation of policy content, the social benefit of the policy, policy incentive, policy subject, policy object, implementation guarantee of policy, and openness degree of policy.After sorting out the contents of 21 green development policy texts, the evaluation index system of green development policy in this study is established by referring to the research of Estrada, Dai et al., Khalil et al., and Laurence et al. ,21,22,23Different first-level indicators in the policy evaluation index system represent different evaluation criteria but they are closely related to the policy. 10) for measuring policy openness in all 21 policies is 1. Considering the symmetry and operability of matrix construction, the variable of X10 is eliminated. Finally, a 3 × 3 surface matrix is formed by nine first-level indices to draw PMC surface maps of different levels of policies. 3 × 3 surface matrix is shown in Equation (5).The PMC curved surface map measures the consistency of the internal structure of the policy in the form of three dimensions, which can present the advantages and disadvantages of the policy . Since a1 has supervision characteristics, so the value of X1.1 in policy P1 is assigned as 1. The specific value of secondary indicators of 21 green policies are shown in The multi-input-output table can reflect the value of various variables of different policies. The binary assignment method is adopted to assign secondary indicators of green development policies. If the content of the policy meets the evaluation criteria of secondary indicators, the value of the secondary indicator is assigned as 1; otherwise, it is 0 . For exaThe PMC index of green development policies can be obtained according to the values of second-level indicators of various policies. Then, the evaluation levels of 21 green development policies can be determined by referring to 1 is the highest, and the value is 9.17. Policy P1 is Opinions on Promoting Agricultural Green Development by Innovating Institutions and Mechanisms Promulgated by the General Office of the CPC Central Committee and The General Office of the State Council. Except for the policy timeliness (X3), the values of other eight first-level indicators in policy P1 are higher than the values of first-level indicators in the other twenty green development policies. The lowest PMC index value is P7, and the value is 4.58, referring 7 is bad. P7 is the Notice on Promoting Financial Support for County Industrial Green Development issued by the Ministry of Industry, the Ministry of Information Technology, and the Agricultural Bank of China. Most of the first-level indicators of policy P7 are lower than the average of the first-level indicators of twenty-one green development policies, so the content of policy P7 needs to be optimized and adjusted. It can be found from 5 is highest, and the value of X5 is 0.83. It can be seen from 7 (4.58), and the policy with the highest PMC index value is P1 (9.17). The PMC index value of P1 is 4.59 higher than that of P7 policy. In addition, it can be found from 10 is 1 and the mean value of X3 is 0.48, which indicate Chinese government needs to improve timeliness of green development policies in future.It can be seen from It can be seen from 1 (perfect grade), P3 (excellent grade), P17 (good grade), and P14 (bad grade) are selected and the PMC surface maps of four policies are drawn by using Matlab software to analyze the advantages and disadvantages of four green development policies  and policy subject variable (X6) are 0.67 and 0.5, indicating that P1 has deficiencies in policy timeliness and policy subject. In addition to the index of X3 and the index of X6 in policy P1, the values of the other eight first-level index are one, which indicate P1 is a comprehensive policy.The value of the PMC index of P3 is assessed as an excellent grade, the value of the PMC index of P3 is 7.33 and the rank fourth among twenty-one green development policies. P3 is “Notice on Special Management Measures for Investment from the Central Budget in Major Regional Development Strategy Construction (Green Development Direction of the Yangtze River Economic Belt)” issued by the National Development and Reform Commission. In the index of P3, the social benefit indicator (X5) and policy object indicator (X8) are first-order variables, and the values of X5 and X8 are the highest. The minimum value of X7 (policy incentive) is 0.33, which is not only the lowest among the 10 first-level indicators in P3 but also the lowest among all first-level indicators of twenty-one green development policies. This is because the theme of the P3 is investment management for the green development of the Yangtze River Economic Belt, focusing on the central budget investment projects in key regions and making specific provisions on financial subsidies. However, as P3 is highly targeted and related to the central government’s investment in green development of the Yangtze River Economic Belt, while policy P3 does not involve tax incentives and talent support. It can be seen from 3 is good in coordination.Policy P17 is 6.08, and the evaluation grade is good, ranking fourteenth among twenty-one green development policies. P17 is “The Notice of “Administrative Measures for the Construction of the Pilot Support System for the Green Development of Agriculture” issued by the General Office of the Ministry of Agriculture and Rural Affairs. The task of P17 is to effectively strengthen the construction of the national agricultural green development pilot zone, and it performs well in the aspect of social benefits (X5). P17 is issued from the aspect of environmental and economic benefits, which is conducive to implementing the green development concepts to some extent. However, the values of X1, X3, and X7 of the first-level index of P17 are 0.33, and the value of X2 is 0.5, indicating P17 is weak in the aspects of policy nature (X1), policy function (X2), policy timeliness (X3) and policy incentive (X7). The surrounding area of 17 needs to be improved. It is necessary to consider how to promote the green development of agriculture through overall coordination and local optimization in the future.The value PMC index of P14 is evaluated as bad, and its value of the PMC index is 4.83, much lower than the average value of the PMC index of twenty-one green development policies. P14 is the “Work Program of Agricultural Mechanization to Promote Agricultural Green Development” issued by the Ministry of Agriculture. P14 aims to play a central role in agricultural mechanization technology and equipment to promote the green development of agriculture. P14 not only has deficiencies in policy nature (X1), and policy timeliness (X3), but also needs to improve in policy incentive (X7), policy object (X8), and implementation guarantee (X9). It can be seen from 14 is low. This may be related to the policy nature and the focus of P14, so the contents of P14 need to be adjusted in the future.The grade of P1, P3, P14, P17) and analyzes the advantages and disadvantages of these four policies by PMC curved graph. In the future, it is necessary to carry out a specific analysis of the remaining policies by using a PMC curve graph.This part only selects four green development policies , policy incentive (X7), and implementation guarantee (X9) are relatively low, this study puts forward some suggestions to improve China’s green development policies: Firstly, pay attention to long-term planning of green development policy. In formulating policies, both short-term goals and long-term plans should be taken into account, and strong coordination among different departments to ensure a long-term blueprint of green development is implemented without distortion. Secondly, to increase policy incentives, all departments should focus on improving incentive and restraint mechanisms and strong financial support for green development. Finally, improve policy guarantee of green development policy. In the process of optimizing green development policy, it is necessary to improve green development policy from the aspects of law, social supervision, and technological innovation.Since the values of policy timeliness (XIn this paper, the PMC index model is adopted for the quantitative evaluation of twenty-one green development policies in China. The main limitation of this paper is that these twenty-one green development policies are issued by the central government, and the green development policies issued by the local governments of China are not evaluated. In addition, this paper mainly evaluates green development policies, there is no assessment of the actual effect of green development policy on green development. Therefore, it is necessary to expand the sources of green development policies in the future, it is not only necessary to evaluate green development policies issued by the central government, but also to evaluate green development policies issued by local governments. In addition, it is also necessary to evaluate the impact of green development policy on green development.


Due to the absence of specific interactions, carbosilane dendrimers are ideal models to study the effect of a hyperbranched regular structure on the molecular response to external influences. In this work, we have studied the conformational behavior of single polybutylcarbosilane dendrimers under confinement between impermeable flat surfaces using atomistic molecular dynamics simulations. Dendrimers of different generations belonging to two homologous series with a tetra-functional core and three- and four-functional branches were simulated. The analysis of the dependence of the internal energy of the dendrimers on the wall distance allowed us to determine the critical degree of compression at which the dendrimers are able to change their shape without energy loss. The effects of generation number and branching functionality on the number of wall contacts, density distribution and shape changes were elucidated. It was found that for high generation dendrimers, the inner layers are not accessible for external interaction. It was shown that the excess stresses occurring at high compressions are concentrated in the structural center of the dendrimer. The nature of the elastic response, which is strongly nonlinear, was analyzed at different compressions depending on the dendrimer architecture and generation. We believe that our results are useful for further studies of dendrimer films under compression and can also serve as a basis for developing model concepts to describe the dynamics of dendrimer melts. Dendrimers are hyperbranched synthetic polymers with a regular tree-like structure. The structural parameters of dendrimers are (i) the functionality of the core, i.e., the number of chains branching from the central atom or group of atoms, (ii) the length of the chains (spacers) with multifunctional end groups (branching points), (iii) the functionality of the branching points, and (iv) the generation, i.e., the number of branching layers ,2. Due tDespite a significant amount of work in the field of dendrimers, the fundamental understanding of the structure–property relationships of these highly branched macromolecules is not yet complete, but is crucial for the further development of new materials based on them. So far, the main practical applications have been at the level of individual macromolecules, mainly of low generations, which have the advantages of monodispersity and a tree architecture and, at the same time, do not require laborious and expensive synthesis. Thus, single dendrimer behavior in dilute solutions has been the focus of much theoretical, computer simulation and experimental research, and is now fairly well-understood ,15. Not Among a wide variety of chemical compositions of dendrimers, it is worth noting, especially for the class of dendrimers, in which branching occurs due to valence in silicon atoms, namely, carbosilane and siloxane dendrimers ,26,27, tThe purpose of this work is to study the elastic response of an individual polybutylcarbosilane dendrimer in dependence of its architecture and generation using atomistic molecular dynamics simulations. To the best of our knowledge, the conformational behavior of these dendrimers under confinement has not been consistently studied, yet. One can mention only one work  that touIn the next section, we describe the research objects and simulation methodology. We start the discussion of the results with the analysis of the potential energy of dendrimers under confinement and determine the range of deformations that do not cause any significant strains in the dendrimer internal structure, and gain some insight in the distribution of strains in highly deformed states. Then, we discuss the stress–strain curves, strain-stiffening effects and the influence of the dendrimer structure and generation on the effective elastic coefficients. The further analysis of the number of contacts of various structural elements of dendrimer molecules with the walls allows us to determine the availability of the dendrimer interior for interactions. The shape changes of the whole dendrimer and its interior and peripheral layers show the conformational variations depending on generation and strain degree. Finally, we calculate the linear and volume density profiles and formulate some conclusions.3) and tetrafunctional =Si=) have been studied (2)3- for both homologous series. The terminal layers of dendrimers 4-3 and 4-4 are also the same, consisting of two butyl -(CH2)3-CH3 groups and one methyl -CH3 group for each Si atom. As in our previous simulations  of the width Δz parallel to the walls and located at the distance z from the bottom surface, i-atom, and Δz = 0.2Å. In fact, the calculated value Monomer density profiles along the z-axis were calculated as It can be seen that for the larger slit D/2R = 0.8, the linear density profile has a bell shape, with a gentle maximum in the center of the slit, and a density decreasing to zero near the walls. The higher the generation, the higher the density. For higher compressions, D/2R = 0.5, the density tends to a constant value almost throughout the slit space, dropping to zero near the walls due to the excluded volume. Density oscillations appearing in the density profile of the 4-3G7 dendrimer and the dendrimers of the 4-4 series are probably related to the intramolecular positions of massive Si branching centers. It should be mentioned that at D/2R = 0.5 the 4-4 series dendrimers experience stresses in bonds and bond angles see b.g/2, with the axis of the cylinder oriented along the z-axis and passing through the center of mass of the dendrimer, To determine whether compression affects the volume density of the dendrimer molecules, we have also calculated the density distribution along the z-axis as the density within the cylinder of the radius RAtomistic molecular dynamics simulations of single polybutylcarbosilane dendrimers confined between two impenetrable planar surfaces were carried out. The distance D between the surfaces was varied in a wide range, so that the degree of dendrimer compression varied from light  to strong (D/2R << 1). Equilibrium dendrimer conformations were obtained at each D/2R. Dendrimers with the functionality of the central Si atom equal to 4, belonging to two homologous series differing in the functionality of the branched Si atoms (3 and 4), were studied. For the 4-4 series, the dendrimers were simulated from the 3rd to the 5th generation, while for the 4-3 series, the dendrimer generation was varied from the 4th to the 7th generation. The comparative analysis of the dendrimer behavior under compression allowed us to elucidate the effect of the generation number and branching functionality on the elastic response as well as on the internal structure of polybutylcarbosilane dendrimers.The critical degree of dendrimer compression has been found, above which significant stresses in chemical bonds and valence angles occur. Dendrimers of the 4-3 series can be compressed to 60–70% of their original size in the free state without internal deformation. At the same time, the chemical structure of the denser 4-4 dendrimers is more sensitive to deformation. Even the smallest 3rd generation dendrimer is stressed at less than 60% strain, while the 5th generation dendrimer can only deform 10% without disturbing the bond and valence angle equilibrium.At small compressions, only the peripheral layer of dendrimers interacts with the confining walls. A decrease in the wall distance causes an increase in the number of contacts of the inner layers of the dendrimers with the confining surfaces. At critical compressions for the 4-3 series, atoms of almost all branching layers interact with the walls. In contrast, the inner layers of the 4-4G4 and 4-4G5 dendrimers are not accessible for external interaction.The elastic response of all dendrimers investigated is strongly non-linear. It has been shown that a higher density of the molecular structure realized for 4-4 series due to the higher branching functionality results in (i) much larger values of the effective elastic constant, k, of these dendrimers compared to those for the 4-3 series and (ii) a tremendous growth of k with generation. In particular, only a fourfold increase in the effective coefficient is observed from G4 to G7 generations of the 4-3 series. At the same time, the k-value of the 5th generation of 4-4 dendrimers is more than an order of magnitude larger than that of the 3rd generation and it is an order of magnitude larger than the elastic modulus of the largest 4-3G7. A strain-stiffening effect is very pronounced for all dendrimers, it manifests itself in an almost three-orders of magnitude increase in the effective elastic constant with deformation.It was found that the effect of the confinement on the dendrimer conformations begins to appear at distances between compression planes exceeding the size of the dendrimer. The lower the dendrimer generation, the larger the deviation of the dendrimer shape from the spherical shape at D/2R = 1. At larger compressions, disc-like conformations of dendrimers are realized. The value of the sphericity parameter S correlates well with the dendrimer rigidity, i.e., softer dendrimers spread more over the surface when compressed. The sphericity parameter of the peripheral layer follows the behavior of S for the whole dendrimer while the shape of the core region of the dendrimer fluctuates to a large extent, so that it can adopt both prolate and oblate conformations at small compressions.It has been shown that the density profile changes from a standard bell-shaped one with a maximum at the center of the slit to the one characterized by an almost constant value decreasing to zero at the walls. It was demonstrated that excess stresses occurring at high compressions are concentrated in the structural center of the dendrimer.The work carried out helps to deepen the understanding of the behavior of dendrimer molecules under spatial restrictions.


The calculation formula of the stiffness and cohesion strength of the GFRP bar grouting body and the reinforcement scheme proposed in this paper can provide a reference for the construction of shallowly buried rock tunnels in soft surrounding rock.As a new type of pre-reinforcement material for tunnel faces, glass fiber-reinforced polymer (GFRP) bolts can effectively and safely improve the stability of tunnel faces in soft surrounding rocks and speed up excavation. Therefore, in this paper, systematic research is carried out on the bond strength of GFRP bolts in tunnel faces and their relative pre-reinforcement parameters. Firstly, the effects of rebar diameter, anchorage length, and mortar strength on the bonding properties of GFRP bars were studied by indoor pull-out tests. The bond strength–slip curves under different working conditions were obtained, and the curves showed that the ultimate bond strength between GFRP bars and mortar was negatively correlated with the diameter of GFRP bars but positively correlated with the strength of the mortar. In addition, the increase in anchorage length led to a reduction in bonding strength. Secondly, inverse analysis was used to analyse the mechanical parameters of the bond performance of the anchor bars by the finite difference software FLAC3D, and the results indicated that 1/5 of the compressive strength of the GFRP bar grouting body can be taken as the ultimate bond strength to calculate the cohesive strength of the grout. Additionally, the formula of GFRP bar grouting body stiffness was revised. Finally, based on the results of laboratory tests and the inverse analysis, the numerical simulation analysis results showed that the optimal reinforcement configuration for a shallow buried tunnel face surrounded by weak rock is to use GFRP bars with a length of 17 m arranged in the center circle of the tunnel face with a reasonable reinforcement density of 1.0 bolt/m Excavating a tunnel in soft surrounding rocks can easily loosen the core zone ahead of the tunnel face. The tunnel face would be deformed inward due to being subject to the pressure load arising from the overlaying soil and rocks and become unstable or even collapse. Therefore, it is critical to control the deformation of the surrounding soil and rocks during the excavation procedure. As verified by existing studies, the use of bolts as a reinforcement for the core soil and rocks could effectively control this deformation ,2, whichIn engineering projects, steel bars are not a preferred material for tunnel face bolts due to their high shear strength, resistance to cutting, and heavy weight. Conversely, GFRP is an ideal substitution for this purpose because of its light weight, high tensile strength, and easy-to-cut property. A number of researchers have carried out relevant studies on the anchorage performance and reinforcement parameters of GFRP bolts as a part of pre-reinforcement technology in tunnel engineering.The bonding behavior is paramount to characterizing the mechanical property of GFRP bolts. Xue et al.  conducteIn addition to the bonding behavior of GFRP bolts, a large number of studies have also focused on the application of pre-reinforcement technology in tunnel engineering. Chen et al. ,17 studiThe existing research mainly focuses on pull-out tests to study the bond behavior between steel/GFRP bolts and concrete. It should be noted that GFRP bolts and steel bolts greatly differ in bonding performance. Additionally, in tunnel construction, the cement mortar used in the bolt grout segments does not contain coarse aggregates. Considering the fact that the mechanical behavior of bolt grout  is generally different from that of concrete, the bonding performance between cement mortar and GFRP bolts should be further examined. Additionally, regarding the application of pre-reinforcement technology  in tunnel engineering, currently available studies mainly employed simulation-based methods, in which the bonding parameters are evaluated for the steel bolts instead of GFRP bolts. As mentioned previously, this may lead to significant discrepancies in the bond performance, entailing the need for a systematic investigation regarding the material parameters of GFRP bolts.In this study, the effects of rebar diameter, anchorage length, and mortar strength on the bonding properties of GFRP bars were studied based on the pull-out tests of GFRP bars. Then, the bond pull-out tests of GFRP bars were simulated by the finite difference software FLAC3D 7.0. An inverse analysis was subsequently performed in order to reasonably quantify the mechanical parameters of GFPR bars with the mortar grouting body. Finally, the effects of length, reinforcement density, and range of GFRP reinforcement on the face of a shallowly buried tunnel in a soft stratum were studied by FLAC3D.The literature  pointed Before the bond pull-out test on GFRP, 6 specimens of bolts in each diameter were taken for the reinforcement pull-out test to obtain the basic mechanical parameters of the reinforcement bolts, summarized in All mortar samples in the test consisted of medium-grained sand, ordinary Portland cement, and polycarboxylic water reducer. For the mortar mix proportions in different strength grades, see The test shape of the specimen was cuboid, with four different sizes: 0.3 m × 0.3 m × 0.5 m, 0.3 m × 0.3 m × 1 m, 0.3 m × 0.3 m × 1.5 m, and 0.3 m × 0.3 m × 2 m. For each size, three samples were produced for each dimension following the ‘Standards for Test Method for Concrete Structures’ , as showA hollow jack was used for one-way, stepwise loading until the failure of the reinforcement bolts, with each loading step at about 0.2 MPa. In the test process, the bolt pull-out displacement The test results are shown in F is the pull-out resistance, l is the anchorage length, and d is the bolt’s diameter.The bond strength is calculated according to the following equation :(1)τ=FπlSpecimens with anchorage lengths of 0.5 m were selected for analysis. The ultimate bond strength of bolts with different diameters is shown in The test results of specimens with anchorage lengths of 0.5 m and GFRP bolt diameters of 22 mm are adopted for analysis. The bond strength-sliding curves in different mortar strengths are shown in There are three failure modes of specimens after loading: GFRP bolts pulling out, GFRP bolts breaking, and mortar splitting. The failure modes and their proportions are shown in In the process of pulling out, a relatively larger radial stress occurs on the ribbed GFRP bolts. If the specimen strength and mortar thickness are not adequate, mortar split failure can occur, and the bond behavior of GFRP bolts is yet to give a full play. Therefore, in real engineering, it is important to reasonably select the mortar strength and anchorage length to avoid split failure.In FLAC3D, it is common to set up grouting body parameters for cable elements so as to reflect the bond behavior between the steel bars and mortar. However, GFRP bolts and steel bars differ from each other essentially, and so do their bond behaviors. During the actual construction period, grade M20 mortar with an anchorage length of 0.5 m is often adopted for the grouting body of tunnel face bolts because of its safety and cost. Therefore, based on the results from the laboratory tests on specimens with anchorage lengths of 0.5 m, this paper adopts FLAC3D to simulate the bond behavior and conducts inverse analysis to propose the parameters of the GFRP bolt bond behavior that are suitable in FLAC3D.The numerical model for the pull-out test is shown in As shown in In FLAC3D, the bond strength between reinforcement bolts and mortar is mainly related to the four parameters of grout perimeter, grout frictional angle, grout stiffness in unit length, and grout cohesion in unit length, among which the grout perimeter is ascertained by the actual borehole diameter, D. Here, the borehole diameter D is taken as 60 mm as per engineering practices, and as the literature  points okg in unit length and the grout cohesion cg in unit length to ensure that the simulation results of the bond strength–slip relationship resulting from numerical calculations are as close as possible to those from the laboratory test.Therefore, the inverse analysis mainly focuses on the grout stiffness d is the reinforcement bolt diameter; Assuming that no failure occurs in the interface between the grout and surrounding rocks, and reinforcement bolts are bonded tightly in the mortar, the grout cohesion of ordinary steel bolts can be calculated as per the following equation :(3)cg=πdG is the grout’s shear modulus, d is the reinforcement bolt’s diameter, and t is the grout’s thickness.For ordinary steel bolts, assuming that the slippage and the pull-out resistance are in a linear relationship, the grout stiffness can be inferred by elastic mechanics and calculated as follows :(4)kg=2πMeanwhile, in FLAC3D, due to the influence of the relative shear displacement between the host-domain grid points and the borehole surface, it is a common practice in the calculation of grout stiffness to multiply Formula (4) by the reduction factor n as 0.1 .(5)kg=2cg1 when cg2 when cg2 is always greater than cg1, and the average specific value is 2.4.The grout cohesion is denoted as cg1 is multiplied by different reduction factors to study the influence of grout cohesion on the values of simulated extreme bond strength of reinforcement bolts. The simulation parameters are given in Based on the pull-out test results, the M20 mortar specimen was selected for this study. The grout stiffness remains unchanged in the process of the simulation. cg1, the ultimate bond strength corresponds with the test values. Additionally, from The inverse analysis indicated that the ultimate bond strength of the specimen increased with an increase in the grout cohesion. When the grout cohesion is taken as cg2 is taken as the grout cohesion, the ultimate bond strength of GFRP bolts in the numerical simulation is amplified by an average ratio of 2.4. Therefore, to ensure the simulation result is close to the real data, cg2 shall be divided by 2.4; in other words, in case of insufficiency of test data, the ultimate bond strength of reinforcement bolts shall be taken as 1/5 of the grout’s compressive strength.Equation (6) shows that if To obtain reasonable values of grout stiffness for GFRP bolts, the grout cohesion remained unchanged in the numerical simulation, and the bond strength–slippage curve in different grout stiffness was obtained by way of changing the reduction factors in Equation (5). The actual reduction factors can be determined by comparing them with the experimental data. The simulation results are shown in Based on the research into the bonding behavior of GFRP bolts in the previous sections, a case study based on the Chenggong tunnel in Kunming, China, is investigated to study the systematic influence of the reinforcement parameters, including reinforcement length, reinforcement density and reinforcement range, on the structural behavior of a shallowly buried tunnel.The numerical model is shown in (1)Failure mode analysis of shallow tunnel face in soft surrounding rockC is the buried depth of the tunnel, H is the tunnel’s height, As the face bolts are only arranged in the range of the tunnel face, this paper simplifies the model in (2)Analysis of reinforcement length based on theoretical valuesH =12 m, and the depth to which the tunnel is buried is C =10 m. The maximum depth of the fracture surface is obtained as follows:To make the reinforcement effective, the tunnel face bolts should pass through the fracture surface  Analysis of reinforcement length based on numerical simulationThe extrusion displacement of the target face while tunneling (y = 20 m) is shown in The reinforcement length of the tunnel face bolts should not only meet the specification requirements but also meet the requirements of the depth of the plastic zones and undisturbed surrounding rock. Therefore, based on the theoretical analysis and numerical calculation results, the reinforcement length of the tunnel face bolts is taken as 17 m.To prevent the extrusion failure of the tunnel face, the horizontal support stress provided by the tunnel face bolts should not be less than. Referring to existing studies ,40,41, t(1)Analysis of the face bolts’ number based on theoretical analysisC = 10 m, the tunnel face height H = 12 m, the volumetric weight 3, and the undrained shear strength The calculation model of n is the number of face bolts, A is the cross-area of a single GFRP bar, and The anchoring capacity of the tunnel face bolts is mainly dependent on the minimum value between the tensile strength of the reinforcement and the bond strength of the bolt–grout interface. Therefore, the number of tunnel face bolts shall be calculated according to Equation (10).For a single bolt, the pull-out force and the shear force provided by the grout can be obtained by Equation (11):Thereby, from Equation (12), we can obtain:As the tunnel face bolt technology is a kind of temporary pre-reinforcement support, its factor of safety is taken as 1.4 based on the provisions of Technical Specification for Retaining and Protection of Building Foundations Excavations .(13)n=8(2)Analysis of face bolts’ number based on numerical simulationBased on the theoretical number of tunnel face bolts, the effectiveness of reinforcement under five operating conditions, such as 77, 90, 112, 150, and 187 face bolts, is discussed to determine the optimized number of face bolts. The calculation model and bolt parameters are the same as above. Calculation results are shown in 2.The results indicate that the reinforcement effectiveness is proportional to the number of tunnel face bolts. When the number of bolts is less than 150, there is no obvious difference in reinforcement effectiveness under different working conditions. Additionally, when the bolt number reaches 150, the reinforcement effectiveness is significantly improved. However, when the bolt number continues to increase to 187, the reinforcement effectiveness does not improve significantly. Therefore, considering the safety and cost, the number of bolts should be 150; that is, the reinforcement density is 1.0 bolt/mAs shown in Reinforcement effectiveness under three kinds of reinforcement range, i.e., upper reinforcement a, lower 2, respectively. The calculation model and bolt parameters are the same as above.The reinforcement density and reinforcement area in three working conditions are assumed to be equal, which are half of the tunnel face area and 1.0 bolt/m(1)Laboratory test results show that when the anchorage length is constant, the ultimate bond strength between GFRP bolts and mortar is negatively correlated with bolt diameter and positively correlated with mortar strength, and when the bolt diameter and mortar strength are constant, the bond strength is in a nonlinear downtrend with the increase in the anchorage length.(2)Split failures occur in all M15 mortar specimens when the anchorage length is 0.5 m. As a result, that grade mortar shall be avoided as the grouting body during real construction. In addition, by analyzing the proportion of failure modes of specimens, it is concluded that in engineering practice, the strength of the mortar used as grouting material shall be greater than M20. When M20 mortar is used as grouting material, the minimum anchorage length of GFRP bolts with diameters of 22 mm, 25 mm, and 28 mm are 1.0 m, 1.5 m, and 2.0 m, respectively.Based on the ultimate bond strength of GFRP bars and mortar obtained from laboratory tests, the mechanical parameters of GFRP bars and the mortar grouting body are obtained by inverse analysis. Among them, the cohesive strength of the grouting body can be calculated by 1/5 of the compressive strength of the grouting body as the ultimate bond strength. The stiffness of the grouting body can be obtained by multiplying the stiffness formula of the grouting body of the reinforced bolt-concrete pull-out model with the reduction factor, and the range of the reduction factor is (4)2, and the GFRP bolts are anchored in the range of the central round.A failure model of a shallow tunnel face in a soft stratum is established to determine the reasonable reinforcement length by simplifying the tunnel face failure model proposed by Davis. Considering the construction safety and cost, the optimum reinforcement length is taken as 17 m, the reasonable reinforcement density is 1.0 bolt/mThe effects of rebar diameter, anchorage length, and mortar strength on the bonding properties of GFRP bars were studied based on the indoor bond pull-out tests of GFRP bars. Then, the bond pull-out tests of GFRP bars were simulated by the finite difference software FLAC3D, and the inverse analysis of related anchorage parameters in numerical calculations was carried out. We also presented formulas for calculating the stiffness and cohesive strength of the GFRP bar grouting body. Based on the results of inversion analysis, the optimal reinforcement length, the reasonable reinforcement density, and the reasonable reinforcement range of the GFRP bar anchors were analytically determined in the shallow soft surrounding rock. The main conclusions include the following:


The effect of TiC on the microstructure, hardness and wear resistance of the coatings was investigated. It was found that the phase structure of the coating with 10 wt.% TiC was a single BCC phase with no other precipitated phase. When 20 wt.% TiC was added, the phase structure of the coating was a BCC phase and TiC phase. When the TiC content increased to 30 wt.%, more TiC-reinforcing phase was formed. With the increase in the TiC content, the hardness of the high-entropy alloy coating was enhanced and the wear loss clearly decreased, which was closely related to the change in the coating structure. The addition of TiC to high-entropy alloys plays the role of fine-grain strengthening and dispersion strengthening.Al Laser cladding is an additive manufacturing technology that can be used to optimize the quality and performance of the workpiece surface. With the continuous development of laser and mechanical technology, the application of laser cladding is more and more extensive ,2. In or1.8CrCuFeNi2 HEA is a typical high-entropy alloy with excellent wear resistance and a high hardness [High-entropy alloys (HEAs) with high hardness, outstanding wear resistance and excellent corrosion resistance ,4,5 are Relevant reports show that a change in elements or the addition of strengthening particles will improve the strength and wear resistance of materials. Changes in the carbon content also affect the quality of the laser cladding coating ,10,11. I1.8CrCuFeNi2 high-entropy alloy powder, and then the laser cladding experiment was carried out. The effect of TiC on the microstructure, hardness and the wear resistance of the Al1.8CrCuFeNi2 high-entropy alloy coating prepared using laser cladding was analyzed.The purpose of this study was to obtain materials with better wear resistance. In this study, TiC particles with 10 wt.%, 20 wt.% and 30 wt.% content were added into the AlDue to the excellent strength and hardness of 65 Mn high-carbon spring steel, it has become the main material for wear-resistant parts. In this study, 65 Mn spring steel was selected as the matrix material to investigate the wear resistance of the coating.1.8CrCuFeNi2 HEA exhibited high hardness and excellent wear resistance in our previous study [1.8CrCuFeNi2 HEA was selected as the main coating material. The 200 mesh Al1.8CrCuFeNi2 HEA powders prefabricated using an aerosol method  were used.The Al3). Its excellent microstructure makes it a high-quality nucleation core in the alloy system to promote grain refinement. Moreover, the high hardness and high melting point of TiC particles enable them to be pinned between grains, which plays the role of second-phase strengthening and greatly improves the hardness and wear resistance of the material [TiC was selected as the strengthening phase due to its extremely high hardness (above 3000 HV) and low density  from the Netherlands. The working voltage was 35 kV, the working current was 50 mA, the scanning speed was 4°/min and the scanning angle was 20–100°.The microstructure was analyzed using an energy dispersive spectrometer (X-MAX 50) equipped with an electron microscope.The microhardness was measured using a tmvp-1 hardness tester. Five areas on the sample surface and four hardness values in each region were selected to measure the hardness. The trim mean was the final hardness value.The wear resistance of the samples was measured using a mms-2a friction and wear testing machine under the conditions of dry friction and room temperature. The experimental load was 100 N, and the test time was 0.5 h and 2 h, respectively.1.8CrCuFeNi2 HEA-based coatings with different TiC contents. The results showed that a single solid solution of BCC was formed in the Al1.8CrCuFeNi2 HEA, which was consistent with previous research [research . After aresearch . In addiresearch . When 20research .The results of the EDS mapping of the coatings are shown in It could be seen from the high-magnification metallographic diagram that when the TiC content increased from 10 wt.% to 20 wt.%, the amount of intergranular structure in the coatings increased, the color became darker and the shape of the grain changed from columnar dendrite to small dendrite. When the TiC content increased to 30 wt.%, the distribution of the grain was more regular than that of the 20 wt.%, and the grains gradually became columnar dendrite, which was mainly related to the increase in the TiC content. When the TiC content was 10 wt.%, the TiC dissolved in the high-entropy alloy to form the BCC phase. However, when the content increased to 20 wt.%, the TiC content dissolving in the high-entropy alloy was too high, resulting in the formation of the agglomerated particles, which was TiC. Moreover, with the increase in the TiC content to 30 wt.%, more TiC-agglomerated particles were formed.In order to further investigate the hardness of the coatings, the TiC-agglomerated particles were also studied. The increase in the hardness of the coating was related to two strengthening mechanisms, which were dispersion strengthening and grain refinement ,17,23. DIn this study, with the increase in TiC, the hardness increased and the wear loss decreased. Therefore, the coating with 30 wt.% TiC not only exhibited a high hardness, but also presented a low wear loss, which indicated that the coating with 30 wt.% TiC exhibited the best comprehensive performance among the coatings studied.1.8CrCuFeNi2 HEA coatings were fabricated onto the 65 Mn surface using laser cladding. The influence of TiC on the structure and wear resistance of the coatings was studied. The main conclusions could be summarized as follows:(1)1.8CrCuFeNi2 HEA. The 10 wt.% TiC coating was still a single solid solution of BCC without obvious TiC agglomeration particles. The TiC-agglomerated particles appeared in both the 20 wt.% TiC and the 30 wt.% TiC coating. After adding TiC, the grain size clearly decreased.A single solid solution of BCC was formed in the Al(2)Due to the fine-grain strengthening and dispersion strengthening of TiC, with the increase in TiC content, the hardness of the high-entropy alloy coatings clearly increased. The hardness of the 30 wt.% TiC coating was the highest.(3)1.8CrCuFeNi2 HEA coatings could be significantly enhanced with the addition of TiC. Due to the increase in hardness, the 30 wt.% TiC/Al1.8CrCuFeNi2 composite coating had the best wear resistance.The wear resistance of the AlIn this study, the TiC-reinforced Al


The control concrete was made from quartz sand and tap water, and the sea concrete was made from sea water and sea sand for the purpose of applying local building materials to construction sites in the coastal area. The properties of a self-compacting concrete mixture, as well as concrete and textile-reinforced concrete based on it, were determined. It was found that at the age of 28 days, the compressive strength of the sea concrete was 72 MPa, and the flexural strength was 9.2 MPa. The compressive strength of the control concrete was 69.4 MPa at the age of 28 days, and the flexural strength was 11.1 MPa. The drying shrinkage of the sea concrete at 28 days exceeded the drying shrinkage of the control concrete by 18%. The uniaxial tensile test showed the same behavior of the control and marine textile-reinforced concrete; after the formation of five cracks, only the carbon textile reinforcement came into operation. Accordingly, the use of sea water and sea sand in combination with a cement with reduced CO The minimum amount of water to ensure cement hydration is about 25% of the cement weight [Today, concrete remains the most popular building material in the world . In addiIt is worth noting that only about 2.5% of the world’s ocean water is fresh water, and about 40% of the world’s population lives within 100 km of the sea coast . Moreove2 in terms of climate impact. This is a measurement scale developed and implemented by the United Nations’ Intergovernmental Panel on Climate Change [2 equivalents are also referred to as global warming potential (GWP) and abbreviated to CO2-eq in mass units (kg). For a product , these values can be found in its respective environmental product declaration (EPD), which is defined by ISO 14025 [Today, it is widely recognized that concrete is one of the greatest contributors to global warming, and different strategies to produce environmentally efficient concretes already exist and are implemented in practice. Its environmental sustainability can be assessed on the basis of the European standard EN 15978 [e Change  to repreSO 14025 . The comSO 14025 .Lately, the material technology has offered various possibilities for the replacement of cement with other binders, such as calcium sulphate aluminates (CSA) and geopolymers, which can lead to a relative reduction of approximately 30% or 80%, respectively . Replaci2,e/ton compared to the extraction from pits and quarries with 0.276 and 0.737 kg CO2,e/ton, respectively [Sand has for a long time been considered an easily accessible and seemingly abundant raw material, which can be extracted from mines and deposits, including deserts. Vast quantities, in the range of 50 billion tons annually, are consumed globally in the production of various industrial products, such as glass, filters, microchips/electronics, shale oil from fracking, but also in construction as a filler or a concrete aggregate . In receectively . 3 of water on earth, only 2.5% is drinkable fresh water, 0.3% of which is directly accessible via rivers, streams or lakes on the continental surface [Regarding water, as another significant constituent of concrete, out of the 1.4 billion km surface . At the  surface  indicate surface . As withIn experiments ,24,25,26It should be noted that for construction in the coastal zone, it is important to ensure sufficient sulphate resistance of concrete structures, according to . A separ2 emissions through the use of sea textile-reinforced concrete.Textile-reinforced concrete (TRC) contains a rectangular arrangement of fiber bundles made of non-corroding materials, such as carbon, glass or basalt. Textile reinforcement is produced from continuous fibers (filaments) in the form of rovings, which can contain more than 40,000 individual filaments. Textile reinforcement has close-meshed openings, which increase the ductility of concrete. Stresses and cracks are distributed over a larger area, thereby reducing cracking in the structure elements. The smaller diameter of the cross-section of textile reinforcement (1–2 mm) allows to reduce the thickness of structures and consequently reduce their total weight ,40. A fe3) for the control concrete mixture and Dyckerhoff CEM III/B 42.5 N-LH/SR (bulk density = 1180 kg/m3) for the sea concrete mixture. The use of CEM III/B 42.5 cement results in a 47% reduction in CO2 emissions (CEM I 42.5 N/CEM III/B 42.5 N-LH/SR = 661/311 kg CO2-Eq/t). Normal and sea sand were used as fine aggregates; the particle size distribution was determined according to Ref. [3; using https://reefapp.net/de/salinity-calculator (accessed on 23 April 2023), this corresponds to a salinity of 3.5%.Two types of cement were used to prepare self-compacting concretes: Dyckerhoff CEM I 42.5 N , 2 plates with a size of 1300 mm × 420 mm × 10 mm were produced based on the compositions of self-compacting concrete from First, a 6 mm layer of concrete was placed; then, the carbon mesh was laid and slightly troweled; then, a second layer of 4 mm concrete mixture was placed and then troweled . The man-compressive strength at age of 3, 7 and 28 days according to the methodology in , load ap-flexural strength at age of 3, 7 and 28 days according to the methodology in  . This may be due to the high air content of the fresh concrete mixture and the consequent formation of more open pores on the surface of the hardened concrete. Additionally, refs. ,59,60 co3A, which contributes significantly to early strength development. At the age of 7 days, the difference in compressive strength decreased to 2%—65 MPa for control concrete and 63.7 MPa for sea concrete. At the design age, the strength of sea concrete exceeded the strength of control concrete by 3.7% and amounted to 72 MPa. Six samples for each batch were used for compressive strength tests. The compressive strength of the control self-compacting concrete at the age of 3 days was expectedly higher than the compressive strength of sea self-compacting concrete; the difference was 29.2%. This is due to the fact that the sea concrete was made on a CEM III/B 42.5 N-LH/SR base with a low clinker content, and consequently, a lower content of tricalcium aluminate CThe authors in ,63,64 coThe data obtained on the flexural strength of the studied self-compacting concretes are shown in the diagram in The modulus of elasticity of concrete is an important parameter, which is used in the calculation of building structures and characterizes the ability of concrete to retain its elastic properties under external load. c at the age of 28 days was 39.1 GPa, and for the control concrete, it was 38.9 GPa. This is due to the lower compressive strength of the control concrete composition. Other studies [For sea concrete, the modulus of elasticity E studies ,68 also Shrinkage is one of the most important parameters for the durability of concrete. In this study, the drying shrinkage was determined using the linear method . The tensile tests were carried out according to the load application scheme shown in The diagram shows that the tensile strength of sea concrete was 3.6 MPa, and the tensile strength of control concrete was 3.3 MPa. This area on the diagram has a linear character. With the development of the first crack, textile reinforcement is included in the work, and the stage of multiple cracking begins—a sawtooth section in the diagram. It was experimentally established that the number of cracks on both types of concrete was five pieces. The average distance between cracks on the samples of sea TRC was 9.6 cm, and on the samples of control TRC, the distance was 10 cm. With a further increase in the load, the bond between the reinforcing mesh and concrete is broken, and only textile reinforcement continues to work.The absorption energy of sea and control TRC was also calculated for specimen displacement at 10 mm. For this purpose, the average area (three samples) under the stress–strain curve for each TRC type was determined. For the sea TRC composition, the fracture energy was 874.56 kJ, and for the control TRC composition, it was 835.12 kJ. Thus, 4.7% more energy was required to achieve a displacement length of 10 mm for the sea TRC compared to the control TRC.The obtained data on the performance of textile-reinforced concrete are consistent with the research ,42,69. S2 emissions per 1 m3 of concrete in the extraction and production stages (A1–A3), according to [Since the purpose of this study was to determine not only the physical and mechanical properties of concretes but also their impact on the environment, this section determined the amounts of COrding to , which arding to ,73,74,752 emissions by 91.5% compared to the control SCHSC. In turn, the use of slag cement has the most impact on decreasing CO2 emissions. Additionally, the use of sea sand up to 50 km from the coast would generate much less emissions than the transportation of sand from a quarry.The data show that the use of Type III low clinker cement, sea sand and sea water for SCHSC production can reduce CO2 emissions are recorded at the component level compared to steel in the following research works [A direct comparison between steel reinforcement and textile reinforcement with carbon rovings via their global warming potential does not seem appropriate due to an energy-intensive process. However, it should be considered that carbon reinforcement is much lighter in weight, in addition to the fact that the bearing capacity can be up to six times higher . There ich works ,78,79.-the flowability of the sea concrete was more viscous than the control concrete because of the amount of sea shells, which are contained in the sea sand, and because of the salt in the sea water, which accelerated the hydration. Therefore, a higher content of superplasticizer for the concrete mixture with sea water and sea sand can be expected. Additionally, the air content test confirmed that, although self-compacting concrete was produced, which usually has a higher air content, in this case, it was below the limit of 5–6% and had no negative influence on the pore structure;-the use of sea sand and sea water for the production of SCHSC based on slag cement makes it possible to produce concretes with comparable mechanical properties while significantly improving the life cycle assessment. At the age of 3 days, the compressive strength of the sea concrete composition was 37.3 MPa, which was around 10.9 MPa lower than the compressive strength of the control concrete composition at 48.2 MPa, due to the slower hydration rate of the slag cement. However, this cannot be considered a negative effect because, in new construction, early strength is not paramount. It was experimentally established that at the age of 28 days, sea concrete had a compressive strength of 72 MPa, which corresponds to the concrete grade of C45/55. The strength of the control concrete was 69.4 MPa, which corresponds to the concrete grade of C40/45. The flexural strength at the age of 3, 7, 28 days of sea concrete was slightly lower  than the flexural strength  of control concrete due to the weak surface contact between the shells and the cement matrix;-after 28 days, the modulus of elasticity for the sea concrete showed a higher value of 39.1 GPa in comparison to the control concrete value of 38.9 GPa, which showed that sea water had no effect on it;-the studies on durability in the form of drying shrinkage show that at the early ages (3 days), the sea concrete shrinkage deformations exceed 122% with 0.6 mm/m in comparison to the control concrete. This is explained by the fact that, with the use of sea water, the pore structure is refined, and the capillary pores (>100 nm) are reduced . Due to -the combination effect of sea concrete as an SCHSC with textile reinforcement on the tensile strength (3.6 MPa) shows equal results to the control concrete (3.3 MPa) with a slightly increasing trend. The obtained data on the performance of textile-reinforced concrete based on sea and control concrete matrices show the same result.-2 emissions can be significantly reduced. The ability to use sea sand as an aggregate also eliminates the need to deliver this material to the construction site, which further reduces CO2 emissions. 2 emissions for 1 m3 of concrete would be more than 90% in total. In addition, the use of textile-reinforced concrete allows us to reduce the cross-sectional thickness of structural elements, which makes it possible to reduce the material consumption and bypass corrosion of steel reinforcement due to sea sand/water.the raw materials used for the production of concrete in our experiment can be recommended for the construction of facilities near the sea coast, which makes it possible to obtain SCHSC. It is important to note that by using slag cement in the production of textile-reinforced structures, COThis paper provides an overview of the use of sea water and sea sand in combination with textile reinforcement with the following conclusions:Further research should be directed to the study of the microstructure of sea concretes. Of particular interest is the study of the effect of different salinities of sea sand and sea water on the properties of sea concrete. The possibility of reducing shrinkage deformations of sea concrete by using dispersion reinforcement must also be considered. Special attention should be paid to durability indicators, such as frost resistance, sulphate resistance and water permeability. This will expand the existing data and, in the future, will allow the use of concrete based on slag cement, sea water and sea sand not only for residential construction in the coastal zone but also for the construction of coastal protection and offshore structures.


The studied membranes are composites of ion-exchange polymers with polyethylene and nylon reinforcing mesh. The external influences provoke the aging of IEMs and the deterioration of their characteristics. The transport properties of IEMs are quantitatively described using five physicochemical parameters: counterion diffusion and equilibrium distribution coefficients in the membrane, characteristic exchange capacity, which depends on the microporosity of ion-exchanger particles, and macroscopic porosity at a known exchange capacity of IEMs. Calculations of the physicochemical parameters of the membranes were performed according to a specially developed fitting technique using the experimental concentration dependences of integral diffusion permeability and specific electrical conductivity, and their model analogs. This made it possible to identify and evaluate changes in the membrane micro- and macrostructure and examine the process of artificial aging of the IEM polymer material due to the abovementioned external impacts.For the first time, based on the joint application of the fine-porous and cell models, a theoretical analysis of the changing transport and structural characteristics of heterogeneous polymeric ion-exchange membranes (IEMs) MK-40, MA-40, and MA-41 after exposure to elevated temperatures in water and aggressive media (H During the electrodialysis of dilute solutions, due to low values of limiting currents, significant overheating of the membrane system does not occur. It was found that 0.02 M NaCl solution was heated to 5 °C at the outlet of the channel with the same type of MK-40 membranes at a sixfold excess of the limiting current density [Ion exchange membranes are widely used in electrodialysis processes for the desalination of natural, industrial, and wastewater, as well as the separation and concentration of solutions ,2,3,4,5.thors of , the temthors of , at currNot only the production of Joule heating but also the uneven distribution of current density over the membrane area, a decrease in electrical conductivity, as well as an increase in the thickness of the membrane due to the sediment formation on it, lead to a significant increase in the heat load on ion-exchange membranes . This in3, NaOH, H2SO4, and oxidants of different natures at room and elevated temperatures. Experiments on the artificial aging of membranes usually reveal a decrease in exchange capacity and resistance, but an increase in water content and permeability, and to a greater extent for anion-exchange membranes. Changes in these properties are caused (i) by the transformation or cleavage of ionogenic groups [In the case of the application of elevated temperatures or intensive current regimes, the main influence is exerted by the processes of degradation of membranes, in particular the destruction of their surface layer ,20,21,22c groups ,29,30;  .When studying only the temperature exposure, the membrane samples were thermostated for 50 h at temperatures from 20 to 100 °C in distilled water. Such operating conditions of membranes are realized in the process of high temperature electrodialysis at low currents. Thermochemical pretreatment of membranes at 100 °C in solutions of 5.0 M sodium hydroxide  or 2.5 M sulfuric acid  simulated their operating conditions under intense current conditions during conventional and high-temperature electrodialysis. More stringent conditions are chosen to accelerate the processes that may occur during prolonged processing of the electrodialysis stack or violation of its operating mode.3) and sulfates (1.37 g/dm3). The total salt content was 12.87 g/dm3, with a hardness of 49 mmol/dm3, and pH 7.5 [2 in the center of the working package of a concentrator for obtaining brines with concentrations of 180–200 g/dm3 from the underground water of the Tyumen region (Russia). The treated water with a total salt content of 17.29 g/dm3 contained 10.582 g/dm3 of chlorides and 0.19 g/dm3 of hydrocarbonates [3, and the total hardness was more than 50 mmol/dm3.Samples of the MK-40 cation-exchange membrane and the MA-40 anion-exchange membrane after prolonged processing in electrodialyzers of various types during desalination and concentration of natural waters were also examined. The long-run trials were carried out by the enterprise “Membrane Technologies S.A.”  , which ad pH 7.5 . Other srbonates . The dur3) was calculated considering the density of swollen membrane samples, which was measured pycnometrically. The water content of the membranes  was determined as the mass ratio of water to the swollen membrane by the method of air-heat drying. The membranes were dried at temperatures of 80 °C (AEMs) and 100 °C (CEMs) to reach a constant weight of the sample.The ion-exchange capacity  of the membranes was evaluated by acid–base titration under static conditions by determining the total number of counterions that participate in ion exchange with the neutralization reaction . The valPm was calculated by the equation2·s); C1 and C2 (C1 > C2) are the concentrations of the substance in the giving and receiving sections of the chamber, respectively, mol/m3; and l is the thickness of the membrane, m. The working solution was fed into the section at a speed of 9 × 10−5 m/s. The chosen rate of solution supply in the section ensured the independence of the determined Pm value in hydrodynamic conditions [The diffusion permeability was studied using a two-chamber flow cell: the studied NaCl solution was fed into one of the chambers, and deionized water into the other. The concentration of NaCl solution in the first chamber was sequentially increased from 0.05 to 1.00 M. The membrane under study was equilibrated with each of the solutions for 24 h. The value of the integral coefficient of diffusion permeability of the membrane nditions . The conmκ (S/m) was calculated by the formulaR is the difference in the electrical resistances of one and two membranes, Ohm; S is the area of the membrane or electrode, m2; and l is the membrane thickness, m.A contact-difference method was used to measure the specific electrical conductivity . The met2–Pearson criterion was used to correctly compare the experimental and theoretical calculated characteristics of the membranes [f was assumed to be equal to the number of compared quantities n. The value of the criterion χ2 was calculated by the formulaχ2 to f. Further, the calculated values of the criterion χ2 or P, which reflects the reliability of the agreement of experimental and theoretical values.The χembranes . A pairwC0 is the electrolyte concentration in the giving chamber of the measuring cell. It is assumed that the receiving chamber of the measuring cell contains distilled water. In this paper, we used a simplified formula for calculations, neglecting the difference in the diffusion coefficients of electrolyte ions inside the membrane, The theoretical values of the diffusion permeability of ion-exchange membranes were calculated using the formula obtained in the framework of a homogeneous model of a fine-porous membrane for 1:1 electrolyte (4)Pm=DmTo calculate the theoretical values of the specific electrical conductivity of the membrane, we used an approximate formula for electrical conductivity obtained within the framework of the cell model in  for ideaF0 is the Faraday constant, R is the universal gas constant, and T is the absolute temperature.Here ® software package. Thus, the fitting procedure assumed the determination of two parameters by the experimental dependence of the integral coefficient of diffusion permeability The calculation procedure consisted of determining five physicochemical parameters of the problem: Samples of the MK-40 cation-exchange membrane (8–10) and the MA-40 anion-exchange membrane  were studied after prolonged use in electrodialyzers of various types during desalination and concentration of natural waters. The physicochemical characteristics of the heat-treated membranes were compared with the samples thermostated at 20 °C.As can be seen from The strongly basic anion-exchange membrane MA-41 undergoes the deamination reaction when heated in water, with the cleavage of the tertiary amino group from the polymer matrix ,48‚(9)CThe tertiary bases are then transformed into secondary and primary amines and split off from the main chains of the polymer matrix.Weakly basic anion-exchange polymers are more stable than strongly basic ones, which is explained by the greater stability of secondary and tertiary amino groups compared to quaternary amino groups. It is known  that theχ2 showed their good agreement. The calculated values of the criterion χ2 were less than χ2crit = 2.73 with reliability p = 0.95 and the number of degrees of freedom f = 8. For the concentration dependences of the diffusion permeability, a consistent agreement of theoretical and experimental values has been proved with reliability p = 0.90, χ2crit = 1.61, and the number of degrees of freedom f = 5.It is known that changes in the concentration of ionogenic groups (IEC) and the water content in membranes determine their transport and selective properties. The diffusion permeability and the specific electrical conductivity of the membranes naturally increase with an increase in the concentration of the solution . With ankD of ion-exchange resin particles, decreases 3.0 times for the cation-exchange membrane, and 6–7 times for both anion-exchange membranes  increases with an increase in the temperature of the thermostating due to changes in both the micro- and macroporous structure of the membrane.It should be noted that the calculated values of the macroscopic porosity embranes . In aniomembrane a. Thus, Pm and κm for membranes of different natures  increases by more than an order of magnitude with an increase in the temperature of the membrane thermostating. This fact is a consequence of an increase in porosity and a corresponding weakening of the steric effect in the membrane phase.The coefficient of the equilibrium distribution of the Naostating b. This c2SO4 at T = 100 °C are presented in 2SO4 solution leads to an intensive transformation of fixed sulfo groups because of acid catalysis, and an even greater decrease in the degree of crosslinking of the polymer matrix of ion-exchange particles [m0 increases most significantly for the MK-40 membrane. At the same time, for all membranes, this value m0 differs from the macroporosity when processed in distilled water at the same temperature of 100 °C. The microporosity of ion-exchange resin particles, which is determined by the parameter Dm+ of the counterions (Na+) for the MK-40 membrane, thermostated at 100 °C in the alkaline and acid solutions, practically does not differ from the value in the case of thermostating at the same temperature in water. This means that the chemical reagents used mainly affect the change in the microporosity of the cation-exchange membrane. For anion-exchange membranes, thermostating in the acid or alkaline solutions has a different effect on the change in the value of the diffusion coefficient Dm− of the counterions (Cl−). Prolonged exposure to sulfuric acid for the MA-41 membrane increases the value of Dm− (Cl−) by 1.5 orders of magnitude compared to the original membrane  and 3.6 times compared to thermostating in water at 100 °C. For the MA-40 membrane, an increase in the value of Dm− (Cl−) in comparison with the original membrane is only 8.7 times and practically coincides with the thermostating in water at 100 °C. During the temperature exposure of membranes in the alkaline solution, the change in transport properties depends on the type of fixed groups. For the MA-40 membrane, the diffusion coefficient Dm− (Cl−) is slightly more than 3 times higher compared to the original membrane, but 2.8 times lower compared to the membrane thermostated in distilled water at a temperature of 100 °C. For the MA-41 membrane, this difference is much greater, being 24.4 and 1.6 times higher. The value of the equilibrium distribution coefficient γm increases with exposure to the alkaline and acid solutions in comparison with membranes thermostated at 20 °C. For the MK-40 and MA-40 membranes, this effect is less pronounced (about 2–3 times) than for the MA-41 membrane (about 7–13 times). This means a more significant loss of the selective properties of the MA-41 membrane under thermochemical action since the energy of the surface interaction of counterions with the charged walls of the membrane pores decreases more strongly for it. The fact of the minimal thermochemical stability of fixed groups of the strongly basic MA-41 membrane in comparison with the MK-40 membrane is confirmed by the experimental results in [The results of calculations of the physicochemical parameters of the studied membranes after 50 h thermostating in solutions of alkali NaOH and acid Harticles . An incrsults in .It can be seen from 2–Pearson criterion revealed the reliability of their matching p in the range of 0.95–0.99. Minimum values of p = 0.90 are set for theoretical and experimental values of diffusion permeability of MA-40 and MK-40 membranes after processing in a reverse electrodialyzer.Dm+ (Na+) decreased 1.5 times, and the value of Dm- (Cl−) increased 1.4 times for the MK-40 and MA-40 membranes, respectively.The most pronounced change in the physicochemical parameters was found after the processing of the MK-40 cation-exchange membrane in the near-electrode section of the desalination stack for 2 months. In particular, the exchange capacity decreased by 40%, macroporosity increased by 20%, and microporosity, 3.4 times, and the distribution coefficient decreased 2.2 times (selectivity even increased slightly). In the case of membranes that have been operating in the concentrator for 500 h, the exchange capacity dropped less (by 16%) than after processing in the desalination stack. At the same time, the macroporosity increased by 10%, and the microporosity increased about 2 times due to the destruction of the ion-exchange resin. The difference between the characteristics of cation-exchange membranes is caused by the fact that in the desalination stack, the MK-40 membranes worked under the harsh conditions of near-electrode sections, and the membranes in the concentrator were in the center of the working package of the electrodialyzer. A comparison of the characteristics of membranes of different natures from the concentrator showed that the distribution coefficient for the MK-40 membrane decreased 2.5 times, and for the MA-40 membrane, it increased 1.5 times. In comparison with the pristine membrane, the diffusion coefficient of the counterion Analysis of the calculated physicochemical parameters of the membranes revealed that prolonged (1000 h) reverse electrodialysis, using MK-40 cation-exchange membranes, slightly changes their properties. A decrease in the exchange capacity by 10% was found, the micro- and macroporosity of the membrane practically did not change, and the distribution and diffusion coefficients decreased 1.8 and 1.7 times, respectively. For the anion exchange membrane MA-40, after its use in reverse electrodialysis, the macroporosity increased 1.8 times. In this case, by contrast, microporosity decreased 2.3 times. The distribution coefficient increased 1.6 times, and the diffusion coefficient decreased 1.3 times. The reason for the anti-bath changes in the main characteristics of the membranes from the reverse electrodialyzer compared to the membranes from the concentrator and the desalination stack is the formation of a continuous layer of sediment on the surface, blocking the transfer. The hypothesis of sedimentation not only on the surface but also in the volume of the membrane during electrodialysis of groundwater in the Aral region was proved by the SEM method in .Dm±, the coefficient of the equilibrium distribution of electrolyte molecules in the membrane γm, the characteristic exchange capacity kD), and macroscopic porosity m0 at a known exchange capacity Based on the joint application of the homogeneous model of a fine-porous membrane and the heterogeneous cell model, a theoretical analysis of changes in the transport properties of heterogeneous ion-exchange membranes of different natures after exposure to elevated temperatures in water and aggressive media , as well as after long-term processing in electrodialyzers of various types, was carried out. The calculations were performed using experimental concentration dependences of the integral diffusion permeability and the specific electrical conductivity of the membranes. The mentioned effects provoke the aging of the membrane material and deterioration of its operational characteristics. These processes are quantitatively described using five physicochemical parameters: the diffusion coefficient of the counterion in the membrane The calculated physicochemical parameters of the membranes made it possible to identify and evaluate changes in the membrane structure due to the partial destruction of their constituent polymers .Growth in the micro- (ion exchange resin particles) and macro- (interparticle space) porosity of membranes during thermochemical exposure was revealed. This is the main reason for the increase in the diffusion permeability and electrical conductivity of membranes against the background of a drop in their exchange capacity.A comparison of theoretical and experimental results suggests the possibility of successful theoretical prediction of changes in the transport characteristics of membranes with changes in electrolyte concentration and the presence of external temperature, thermochemical, and electrical influences.Thus, the novelty of this work is that for the first time, a combination of the cell and fine-porous membrane models was successfully used to study the aging of the polymer material of the MK-40 cation-exchange membrane and the MA-40 and MA-41 anion-exchange membranes during thermostating at high temperatures, including in aggressive environments.Knowing the physicochemical parameters of the combined model made it possible to describe the nature of aging and changes in the transport and structural characteristics of the studied membranes.The suggested approach can also be applied to the study of the aging of any other charged membranes—for example, reverse osmotic, nano-, and ultrafiltration membranes.In future works, we intend to establish a methodology for calculating the physicochemical parameters of negatively and positively charged membranes using exact formulas for electrical conductivity instead of the approximate ones applied here and consider the difference between ion diffusivities.