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Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking. This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils. To validate the feasibility and efficacy of the proposed approach, direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents. Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance. During this period, the effects of W-OH treatment concentration and water content on tensile properties, soil suction and microstructure were investigated. The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil, which not only effectively enhances the tensile strength and failure displacement, but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior. The suction measurements and mercury intrusion porosimetry (MIP) tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores. Combined with the microstructural analysis, it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles. Moreover, desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking. With the increase of W-OH treatment concentration, the surface crack ratio and total crack length are significantly reduced. This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance.

Introduction. Domestic and foreign experience of full-scale tests is analyzed. The retrospective of development of standards for conducting full-scale tests in Russia and the USSR is presented. The review of the world regulatory documents regarding the requirements for conducting full-scale tests of structures is carried out, which showed insufficient research of this question both in our country and abroad. The obtained review can be the basis for the development of the national standard of the Russian Federation for conducting full-scale tests.Materials and methods. Analytical review.Results. The state of the issue and the application of stress tests (full-scale tests) in our country, as well as in Germany, the USA, Italy, Canada, Australia, Switzerland and other countries are shown. The minimum requirements for the target test load during testing, the loading mode and acceptance criteria for the experimental assessment of the load-bearing capacity of existing load-bearing structures specified in various standards are given. Specialized criteria for the acceptance of load-bearing structures, such as the permanency ratio and deviation from linearity index, mentioned in individual standards, are analyzed.Conclusions. The similarity of common approaches and the lack of unified requirements for conducting this type of research and evaluating their results are noted. The necessity to develop a national standard of the Russian Federation for full-scale tests of erected reinforced concrete structures is considered.

This is an article in the field of ceramics and composites. The performance of asphalt mixtures with different iron tailings content was analyzed. The rutting resistance, water stability and crack resistance of the asphalt mixture were analyzed. This verified the feasibility of iron tailings applied to the middle surface of low-grade roads. The results showed that the flexural strength decreased the most when the dosage was from 20% to 40%. The increase rate of immersion residue stability began to decrease after the dosage was 20%. As the content of iron tailings continued to increase, the FT-IR spectrum of iron tailings asphalt concrete showed a small, new absorption peak locally and an enhancement to the original absorption peak. This showed that after the addition of iron tailings, the asphalt concrete chemically reacted with it, and the internal structure of the original asphalt was changed and new functional groups were generated. With the increasing content of iron tailings, the proportion of the area of cycloalkane and alkane C-H functional groups in the asphalt concrete of iron tailings asphalt concrete showed a trend of first increasing and then decreasing. And when the iron tailings content was 20%, the area ratio of asphalt naphthenic and alkane C-H functional groups reached the maximum.

Introduction. The active introduction into practice of the system of volumetric and functional design (OFP) is aimed at the large-scale development by the Russian road construction industry of advanced foreign approaches to the technology of designing asphalt concrete pavements (Superpave). One of the fundamental differences between the OFP methodology and the previously established practice of evaluating technical, technological and operational indicators of road construction materials is the introduction of new methods that characterize quantitative indicators with a high degree of accuracy, based on the actual physical, chemical and mechanical properties of the components used. Thus, as methods for assessing the low-temperature properties of bitumen binders, it is proposed to use the bending beam method (BBR), which has proven itself quite well when working with traditional (ordinary) bitumen. However, the natural and climatic conditions of operation of highways in Russia clearly require the use of binders modified with high- and low-molecular compounds, including polymers. In this study, the task of applying the ABCD method to evaluate the low-temperature parameters of ordinary bitumen and polymer-bitumen binders was realized.Materials and methods. Samples of industrial batches of petroleum road viscous bitumen (GOST 33133-2014) and polymer-modified bitumen (GOST R 52056-2003) were used as objects of research. To determine the lowtemperature parameters, an ABCD 8.0 device and an air-cooled climate chamber were used. The study of bitumen binders according to the parameters laid down in the technical requirements of GOST R 58400.11–2019 ‘Automobile roads of general use. Petroleum-based bitumen binders. Method of determining the temperature of cracking using the device ABCD’ was carried out.Results. The values of the cracking temperature for ordinary and modified bitumen binders were determined. It is shown that the low-temperature parameters of polymer-bitumen binders significantly exceed similar properties of oxidized road bitumen.Discussion and conclusions. A comparative analysis of the low-temperature properties of ordinary and modified binders obtained during their determination by the direct method enables to confirm the effectiveness of the methodology developed in GOST R 58400.11-2019 for assessing the performance of binders of various component composition in difficult climatic conditions of Russia. The effectiveness of the domestic second-generation ABCD 8.0 device for direct assessment of the cracking temperature of bitumen binders of variable composition has been confirmed.

Abstract The effects of moisture and drying shrinkage can lead to uneven settlement, cracking, and other diseases in loess subgrade. The objective of this study was to investigate the effects of amide polymer (AP) on the permeability, mechanical properties and crack resistance of loess by orthogonal experiments. The basic properties of AP and the permeability, mechanical properties, and dry–wet variation properties of polymer-modified loess were tested, and a scale model verification and simulation analysis were conducted. In this paper, water migration in subgrade is regulated by improving the water sensitivity of loess. By reducing the variation range of subgrade water content, the stress accumulation in subgrade caused by water is weakened. The results show that the curing time and mechanical properties of AP are directly affected by the oxidant and reducing agent, and the mechanical properties of AP are compatible with the characteristics of loess. AP filled the grain gap and reduced the permeability of loess by 34.05–280.83%. The ductility of polymer-modified loess is significantly increased, and the strain of peak strength is increased by 17.21–126.36%. AP can regulate moisture change, reduce the surface tension between particles, and reduce stress concentration. The strength loss rate was reduced by 19.98–51.21% by enhancing the cracking resistance and weakening the strength loss caused by dry and wet cycling. The increase of upper layer moisture content in the scale model of polymer-modified loess subgrade is reduced by 31.38–36.11%.

Crack resistance of two types of glass was studied – cover glass (0.17 mm thick) and slide glass (2 mm thick) using an improved technique through the use of the probe methods, which makes it possible to increase the accuracy of determining the crack resistance of glass. Colorless silicate glass was used. Crack resistance was determined by the Vickers pyramid indentation method. Microstructure of glasses surface and deformation region after indentation were studied using an atomic force microscope. Mechanical properties of glasses were determined by nanoindentation. Surface relief of a glass slide is rougher than that one of a cover glass. Roughness Rz for a cover glass is less than for a slide glass. Specific surface energy value of 0.26 N/m is higher for the slide glass compared to the coverslip. One elastic modulus value E of the cover glass is 48 GPa, and that one of the slide glass is 58 GPa. The microhardness value H is almost the same for by the glasses and amounts to 6.7 GPa for a slide glass and 6.4 GPa for a cover glass. Atomic force microscope images of deformation region after indentation with a Vickers pyramid show that the first cracks appear at a load of 1 N on the slide glass, and at 2 N on the cover glass. At a load of 3 N, the cover glass is destroyed. Based on the results of crack resistance calculations it was found that critical stress intensity coefficient KIC values are 1.42 MPa∙m1/2 for a glass slide, and 1.10 MPa∙m1/2 for a cover glass.

The most important factor in increasing the efficiency of the development of forest tracts is the development and improvement of the transport and operational condition of the network of logging roads. Inert road construction materials, such as sand, crushed stone, crushed stone-sand mixture or gravel-sand mixture, are traditionally used for the construction of pavements for logging roads. However, in the areas with a shortage of these materials, the cost of road construction increases significantly. An alternative technology that can significantly reduce or completely eliminate the use of inert road construction materials is the stabilization of local soils for the construction of pavement structural layers. The soil stabilization technology consists in mixing them with binders and compacting them at the optimal moisture content of the mixture. In doing so, the resulting material acquires the desired strength and frost resistance. The most effective and common binder for soil stabilization is Portland cement. However, along with high strength properties and frost resistance, cement soils, due to their crystalline structure, have low crack resistance, which worsens transport and operational performance and shortens the service life of road pavements. One of the rational solutions for increasing the security of soil stabilization for the construction of road pavements is the installation of fiber cement soil layers. The object of this research is fiber cement soil for the construction of structural layers of road pavements for logging roads. The aim is to improve the physical and mechanical properties and frost resistance of soils stabilized with Portland cement with the addition of the material based on basalt fiber. Laboratory tests of compressive and tensile strength during splitting, as well as frost resistance of fiber cement soils of various compositions were carried out in accordance with GOST R 70452–2022. According to the data obtained, fiber cement soil has higher strength and frost resistance compared to cement soil. The fibers distributed throughout the cement-soil matrix effectively perceive external loads, providing high physical and mechanical indicators, and therefore crack and frost resistance of the material. The use of fiber cement soil for the construction of pavements for logging roads will increase the durability and reliability of their operation, as well as reduce the costs of construction and operation of road transport infrastructure of forest tracts.

Introduction. Aluminium alloys are characterized by the absence of a cold fracture threshold, have high strength and ductility characteristics at low temperatures. However, the norms do not provide the design of aluminium structures that take cyclic force effects at low temperatures. In this regard, there is a need to study the properties and mechanisms of deformation and destruction of aluminium alloys to assess the possibility of their use in the Far North, as well as well as for the inner shells of isothermal reservoirs.Materials and methods. The mechanical properties of structural aluminium alloys 1915, 1565ch and 6082 (similar to AD35) were studied. The specimens were tested for uniaxial tensile strength, impact toughness and fatigue strength, and the characteristics of static crack resistance were determined. The tests were carried out using Instron 8802, Instron 1000HDX, LabTex machines and Instron 450 MPX pendulum coper according to the relevant GOST standards of Russia.Results. Experimental dependences of strength and elastic characteristics (tensile strength, offset yield strength, modulus of elasticity), as well as deformative ones (relative elongation and contraction of the cross-sectional area of specimens) of the studied alloys on the test temperature are obtained. The change of character of deformation of aluminium alloys with decrease in temperature is shown. The results of deformation and fracture resistance under conditions of impact bending and eccentric tension in the temperature range from –104...+20 °C are presented. Fracture toughness (crack resistance) was estimated according to the criteria of fracture mechanics when testing standard specimens with fatigue cracks. The paper also shows the limited limits of endurance based on 2 · 106, 107 cycles of the studied alloys at positive and negative temperatures.Conclusions. The obtained results make it possible to reasonably select materials, assign loads when designing structures made of aluminium alloys and evaluate their service life.

The scale of heterogeneity of the structures of steels and alloys can be rather large both within one sample and within a product. The procedure adopted in practice for determining the integral values of crack resistance characteristics cannot always reflect this circumstance. In this regard, it is necessary to develop methods for assessing the crack resistance of a medium with a heterogeneous structure. In this work, the authors determined the crack resistance of large forgings made of heat-hardenable 38KhN3MFA-Sh steel (0.38%C–Cr–3%Ni–Mo–V) based on the critical crack opening δс and the J-integral. The presence of critical stages in the development of a ductile crack during testing was assessed by acoustic emission measurements. In combination with the obtained methods of digital fractography of 3D images of fractures, this allowed relating the shape and position of the leading edge of each crack jump to the load-displacement diagram. Measuring the crack opening geometry during the test showed the possibility of determining directly the coefficient of crack face rotation when estimating δс. In general, this allowed constructing a map of the distribution of parameter δс values over the thickness of the sample and estimating the scale of the scatter in crack resistance within one sample – up to 30 %. Such a localization of measurements, primarily of the δc parameter, is comparable to the scale of heterogeneity in the morphology of various types of structures, which was assessed based on the measurement of digital images of the dendritic structure, the Bauman sulfur print, non-metallic inclusions on an unetched section, and ferrite-pearlite banding in the microstructure. This makes it possible to link local crack resistance values to various fracture mechanisms and their accompanying structural components.

This paper reports an experimental on the flexural performance of prestressed concrete-encased high-strength steel beams (PCEHSSBs). To study the applicability of high-strength steel (HSS) in prestressed concrete-encased steel beams (PCESBs), one simply supported prestressed concrete-encased ordinarystrength steel beam (PCEOSSB) and eight simply supported PCEHSSBs were tested under a four-point bending load. The influence of steel strength grade, I-steel ratio, reinforcement ratio and stirrup ratio on the flexural performance of such members was investigated. The test results show that increasing the I-steel grade and I-steel ratio can significantly improve the bearing capacity of PCESB. Increasing the compressive reinforcement ratio of PCEHSSB can effectively improve its bearing capacity and ductility properties, making full use of the performance of HSS in composite beams. Increasing the hoop ratio has a small improvement on the load capacity of the test beams; setting up shear connectors can improve the ductile properties of the specimens although it does not lead to a significant increase in the load capacity of the combined beams. Then, combined with the test data, the comprehensive reinforcement index considering the location of reinforcement was proposed to evaluate the crack resistance of specimens. The relationship between the comprehensive reinforcement index and the crack resistance of specimens was given.

To understand the microstructural factors controlling deformability during the forming process, a comprehensive analysis using in-situ scanning electron microscopy (SEM) with digital image correlation (DIC) for hot-dip Zn–6 %Al–3 %Mg alloy coatings on steel sheets in bending deformation was performed. The Zn–Al–Mg alloy coating exhibited two major microstructural constituents: the primary solidified Al (fcc) phase with dendritic morphologies and a fine ternary eutectic (TE) microstructure of the Zn (hcp), Al, and Zn2Mg phases. Major cracks were initiated on the tensile-strained coating surface, where the strain was localized in the TE regions, whereas the softer dendritic Al phases prevented the crack propagation. Microcracks were initiated in the binary eutectic (BE) Zn/Zn2Mg phases (Al-poor region) localized around the dendritic Al phases, whereas they were arrested in the TE region containing fine granular Al phases. The dendritic Al and fine granular Al phases embedded in the TE microstructure contributed to the high crack resistance.

Lightweight fibre-reinforced concrete integrates the advantages of lightweight aggregates with the strength-enhancing properties of fibres, resulting in a lighter composite with enhanced impact and mechanical performance. However, achieving an optimal balance between structural weight, and performance remains a challenging endeavour. This study investigates the mechanical properties, impact energy absorptions, flexural toughness, and crack resistance of lightweight fibre-reinforced concrete with the coarse aggregate entirely replaced with lightweight expanded clay aggregate (LECA). Concrete mixes containing 0 %, 0.5 %, 0.75 %, and 1.0 % Polypropylene fibre (PPF) and 10 % micro-silica were experimentally investigated. Predictions for concrete mixes with up to 2 % PPF were made using regression models developed from experimental data. The experimental and predicted results were analysed using response surface methodology. The findings reveal significant enhancements of up to 300 % and 570 % in toughness indices I5 and I10 at 1 % PPF, coupled with a 55.4 % increase in residual strength. Furthermore, an optimised slab thickness of 47 mm containing 1.73 % PPF yielded optimal impact energy absorption of 680 J and 2384 J and crack resistance of 3823 MPa and 16279 MPa at service and ultimate loading, respectively. These metrics represent improvements of 4.8, 15.2, 37, and 56 times, respectively, compared to the control samples. These substantial advancements highlight the potential of lightweight fibre-reinforced LECA concrete in engineering applications where balancing impact energy absorption, crack resistance, and structural weight is crucial. This innovative approach promises a transformative impact on the construction industry, paving the way for more efficient and resilient infrastructure.

Abstract With the development of recycled aggregate concrete (RAC), the recovery rate of construction waste is improved, and the pollution problem is alleviated. In particular, RAC beams strengthened with prestressed carbon fiber reinforced plastics (CFRP) can exhibit improved mechanical properties, expanding RAC application. Four groups of reinforced RAC beam specimens contained 0%, 40%, 70%, and 100% recycled coarse aggregate, respectively. Each group of beams was first pre-cracked and then strengthened by prestressed CFRP with one layer and two layers respectively. Finally, the bearing capacity tests were performed for these beams. The test results show that as the recycled coarse aggregate content increases, the cracking moment and ultimate load capacity of the beam decrease, while its crack width increases. As the CFRP layer increases, the deformation and crack width of the beam decreases, while the number of cracks increases. The prestressed CFRP also exhibited tensile and peeling failure. A beam deflection calculation model was established by introducing a coefficient k representing the interaction between recycled aggregate and CFRP. The influence coefficient of concrete elongation on the crack width and average crack spacing of the beam was modified, and the crack width analysis model of the beam was established. The calculated results are in good agreement with the experimental observations. It can provide reference for the application and design of recycled concrete beams strengthened with prestressed CFRP.

This paper presents the history of the development of the method for calculating the crack resistance of reinforced concrete elements according to Soviet and modern design standards, which was based on the work of the Soviet and foreign scientists, such as: A.F. Loleit, V.I. Murashev, A.A. Gvozdev, S.A. Dmitriev, A. Clark, J. Monier and others. Also, the article discusses the currently updated calculation methods for the formation and opening of normal cracks according to domestic and foreign standards.

Different variants of the hardness of the wheel/rail friction pair were investigated to determine the optimal hardness range of the wheel/rail that ensures the minimum wear under selected test conditions. A pair of tests was performed on an MI-2 machine with a cylindrical wheel steel roller and a rail steel liner. The hardness of the wheel steel specimens ranged from 275 to 900 HVw. The selected of the rail steel samples of 345-455 HVr covers the possible hardness variations (350-405 HVr) of R65 type long rails produced on the standard ST RK 2432-2013 “Railway Rails Differentially Hardened and Non-heat-strengthened.” Technical Requirements. The optimal ratio of wheel/rail hardness, which ensures minimum wear due to weight loss of the tested samples, is the interval HVw/HVr–1.41-1.59. This ratio of wheel/rail hardness is practically confirmed when linear wear is determined by micrometric measurement of the impression size with HVw/HVr–1.39-1.56. The results of the laboratory tests and the suggestions for the optimal ratio of wheel/rail hardness to improve wear resistance should be verified under field conditions. Oscillography of the destruction process of plasma-hardened and non-strengthened specimens was performed to evaluate the resistance to crack initiation and propagation.

Cracks in asphalt mixtures compromise the structural integrity of roads, increase maintenance costs, and shorten pavement lifespan. These cracks allow for water infiltration, accelerating pavement deterioration and jeopardizing vehicle safety. This research aims to evaluate the impact of synthetic fibers, specifically glass fiber (GF) and polypropylene fiber (PPF), on the crack resistance of Hot-Mix Asphalt (HMA). An optimal asphalt binder content of 5% was used in all sample designs. Using the dry mixing technique, GFs and PPFs were incorporated into the HMA at dosages of 0.50%, 1.00%, and 1.50% by weight of the aggregate. The effects of these fibers on the mechanical fracture properties of the HMA were assessed using Semi-Circular Bending (SCB), Indirect Tensile Asphalt Cracking Tests (IDEAL-CTs), and Three-Point Bending (3-PB) tests. This study focused on fracture parameters such as fracture work, peak load, fracture energy, and crack indices, including the Flexibility Index (FI) and Crack Resistance Index (CRI). The results from the SCB and IDEAL-CT tests showed that increasing GF content from 0.5% to 1.5% significantly enhances the flexibility and crack resistance of HMA, with FI, CRI, and CT Index values increasing by 247.5%, 55%, and 101.35%, respectively. Conversely, increasing PPF content increases the mixture’s stiffness and reduces its crack resistance. The PP-1 mixture exhibited higher FI and CT Index values, with increases of 31.1% and 10%, respectively, compared to the PP-0.5 mixture, based on SCB and IDEAL-CT test results. The SCB, IDEAL-CT, and 3-PB test results concluded that fibers significantly influence the fracture properties of bituminous mixtures, with a 1% reinforcement dosage of both PPFs and GFs being optimal for enhancing performance across various applications.

Pavement cracking is a primary cause of early damage in asphalt pavements, and fiber-reinforcement technology is an effective method for enhancing the anti-cracking performance of pavement mixtures. However, due to the multi-scale dispersed structure of pavement mixtures, it is challenging to address cracking and damage with a single fiber type or fibers of the same scale. To investigate the toughening mechanisms and damage behavior of hybrid-fiber-modified mixtures, we analyzed the fracture process and damage behavior of these mixtures using a combination of basalt fiber and calcium sulfate whisker hybrid fiber modification, along with semicircular bending tests. Additionally, digital imaging was employed to examine the fracture interface characteristics, revealing the toughening mechanisms at play. The results demonstrated that basalt fibers effectively broaden the toughness range of the modified mixture at the same temperature, reduce mixture stiffness, increase residual load at the same displacement, and improve crack resistance in the mixture matrix. While calcium sulfate whiskers enhanced the peak load of the mixture, their high stiffness modulus was found to be detrimental to the mixture’s crack toughness. The fracture interface analysis indicated that the three-dimensionally distributed fibers form a spatial network within the mixture, restricting the relative movement of cement and aggregate, delaying crack propagation, and significantly improving the overall crack resistance of the mixture.

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin–stringer sub-element is presented. The improvement in the crack resistance capability of skin–stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin–stringer specimen. A macro-scale pin–spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural response of PTTR laminate, including stiffness, adhesive strength, crack extension scenarios and progressive pin failure modes. This modeling approach can be beneficial for designing damage-tolerant structures by exploring various PTTR arrangements for achieving improved structural responses.

This paper investigates the effects of steel fiber and PVA fiber hybrid blending on the compressive strength (fcc), splitting tensile strength (fts), compression energy (W1.0), and shrinkage properties of concrete. It also establishes a multi-factor crack resistance index evaluation model based on the Analytic Hierarchy Process (AHP) to comprehensively evaluate the crack resistance of concrete. The results show that the steel–PVA hybrid fiber (S-PVA HF) further enhances fcc, fts, the compression energy, and the shrinkage suppression properties of the concrete. The crack resistance of the steel–PVA hybrid fiber concrete (S-PVA HFRC) is the best when the proportion of steel fiber is 1.0% and that of the PVA fiber is 0.2%, and it increases up to 143% compared to the baseline concrete. The established concrete crack resistance evaluation model has a certain reliability.

During the operation of structures, stress and deformation fields occur inside the materials used, which often ends in fatal damage of the entire structure. Therefore, the modelling of this damage, including the possible formation and growth of cracks, is at the forefront of numerical and applied mathematics. The finite element method (FEM) and its modification will allow us to predict the behaviour of these structural materials. Furthermore, some practical applications based on cohesive approach are tested. The main effort is devoted to composites with fibres and searching for procedures for their accurate modelling, mainly in the area where damage can be expected to occur. The use of the cohesive approach of elements that represent the physical nature of energy release in front of the crack front has proven to be promising not only in the direct use of cohesive elements, but also in combination with modified methods of standard finite elements.

The orthotropic steel bridge deck (OSBD) has been widely used in recent decades, benefiting from its advantages of lightweight and easy assembly. However, the longitudinal and transversal stiffeners of OSBDs are connected to the top flange plate through dense welds, which will easily introduce fatigue cracks. Hence, the composite bridge deck (CBD) system was proposed, adding a concrete layer over a steel plate to increase the sectional stiffness of OSBDs and reduce the fatigue stress amplitude. Furthermore, some new materials with extraordinary properties such as ultra-high-performance concrete (UHPC) and engineering cementitious composites (ECC) were used to replace the normal concrete, to improve the bearing capacity and crack resistance of CBDs. In this review, four kinds of bridge deck systems with different structural types including OSBD, steel–concrete, steel–UHPC, and steel–ECC CBDs were discussed. The flexural performance of four systems under sagging and hogging moments was reviewed, and close attention was paid to the crack resistance of the CBD system. In addition, the shear connection used in the CBDs was concentrated, and the shear behavior of some connectors including studs, perforated rib (PBL), and modified clothoid (MCL) shape shear connectors was investigated. The CBD structure assembled by duplicate profile steel parts proposed recently was introduced and discussed.

Low-temperature cracking is one of the main causes of pavement distress in colder areas with below-freezing temperatures. Resistance of asphalt to this cracking depends on a number of factors. A complex knowledge about this phenomena is a key factor during the design process, the building and the use stage of roads. Among the leading drivers are the type of bitumen and air voids in the bituminous mixture. In this research project, both the bituminous binders and mixtures were tested to determine the influence of these components on the low-temperature performance of asphalt pavements. A wide range of bituminous binders were tested, including 20/30, 35/50, 50/70, 70/100 and 100/150 grades. This approach allowed for an in-depth evaluation of the impact of bitumen type and air voids on the low-thermal susceptibility of asphalt mixture. The basic tests for bitumen were performed such as the penetration value at 25 °C (EN 1426), the softening point with the Ring & Ball method (EN 1427) and the group composition with SARA analysis using the Thin Layer Chromatography with Flame Ionization Detector (TLC/FID) method. Both neat bitumen and bitumen after Rotating Thin Film Oven Test (RTFOT) short-term simulated ageing (EN 12607–1) were tested. Next, bituminous mixtures based on mentioned bitumen with 2.2%, 3.5% and 6.5% air voids were prepared and subjected to uniaxial tension in Thermal Stress Restrained Specimen Test (TSRST) to determine their low-temperature performance. The test results point to the binder type as the key determinant of the low-temperature performance of asphalt. Softer bitumens of a higher penetration have a better low-temperature performance and the group composition is the determinant of the TSRST failure temperature. The effect of air voids were of secondary importance in this respect.

A B S T R A C T: Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture, the semi-circular bending (SCB) test has attracted a lot of attention in the academic road engineering community because of its simplicity, stability, and flexibility in testing and evaluation. The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years. This paper mainly summarizes the overview of the SCB test, summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years, and predicts and suggests the research direction of the SCB test in the future. It is found that the research on the monotonic SCB test is more comprehensive, and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode, characterization parameter selection, and so on. Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens, and conduct comprehensive analysis combined with the results of numerical simulation. The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy, fracture toughness, stiffness, flexibility index and other fracture indicators, combined with the crack propagation of the specimen. The analysis of numerical simulation can confirm the test results. In order to standardize the setting of fatigue parameters for future application, it is necessary to standardize the setting of bending performance.

The crack resistance of concrete structures with low reinforcement ratios requires a broader examination. It is particularly important in the case of foundations working in changing subsoil conditions. Unfavorable phenomena occurring in the subsoil (e.g., ground subsidence, landslips, non-uniform settlement) can lead to unexpected cracking. Therefore, it is necessary to check the effectiveness of the low reinforcement provided. As there are limited studies on lightly reinforced concrete structures, we performed our own experimental investigation and numerical calculations. In the beams analyzed, the reinforcement ratio varied from 0.05% to 0.20%. It was found that crack resistance in concrete members depends on the reinforcement ratio and steel bar distribution. A comprehensive method was proposed for estimating the crack resistance of lightly reinforced concrete members in which both the reinforcement ratio and the reinforcement dispersion ratio were taken into account. Furthermore, the method considered the size effect and the fracture properties of concrete. The proposed method provides the basis for extrapolation of the test results obtained for small elements and conclusions for members with large cross-sections, such as foundations, which frequently use lightly reinforced concrete.

The poor early shrinkage and cracking performances of manufactured sand concrete, waste powder concrete, and recycled aggregate concrete are the main difficulties in engineering applications. To solve these problems, early shrinkage and cracking, strength, and impermeability tests were performed on high-volume stone powder manufactured sand concrete mixed with fly ash and slag powder (FS), a shrinkage-reducing agent (SRA), polyvinyl alcohol (PVA) fibers, and a superabsorbent polymer (SAP). Furthermore, the microstructures and pore structures of these concretes were revealed using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The results showed that the mixture of FS, SRA, PVA fibers, and SAP could effectively inhibit the shrinkage strain and cracking area of the concrete. The effect of the SAP on reducing the early shrinkage of the concrete is the greatest, and the shrinkage strain can be reduced by 76.49%. The PVA fibers had the most obvious effect on inhibiting the early cracking of the concrete, and the total cracking area was reduced by 66.91%. Significantly, the incorporation of the FS can improve the particle gradation and the pore structure and improve its compactness. The PVA fibers not only provide good carriers for cement-based materials but also enhance the bonding force between the particles inside the concrete, filling the pores inside the concrete, inhibiting the loss of water, and reducing the generation of internal microcracks. The FS and PVA can reduce the shrinkage and cracking risk and improve the strength and impermeability of the concrete. Although the SRA and SAP can reduce the shrinkage and cracking risks, it will lead to a significant decrease in the later strength and impermeability. The main reason is that the SRA leads to an increase in micropores in the matrix and microcracks near the aggregate, which are not conducive to the development of the strength and penetration resistance of the MS. Similarly, the SAP can promote the rapid formation of ettringite (Aft) at an early age and improve the early shrinkage, early cracking, and early strength of the concrete. However, with an increase in age, the residual pores, after SAP dehydration, will cause the deterioration of the concrete pore structure, resulting in the deterioration of the strength and impermeability.

【Objective】 Cellulose fiber is a material increasingly used to reinforce concrete and this paper investigates its improvement of concrete slabs against cracking. 【Method】 Concrete slabs made by cement mixed with fly ash, cement mixed with fly ash and MgO, were compared with slabs made by cement-fly ash reinforced by cellulose fiber. For each slab, we measured its strength, deformation property, resistance against macro-cracks and emergence of micro-crack. 【Result】 Concrete slab reinforced by cellulose fibers are mechanically best, and its splitting tensile strength and ultimate tensile strength are both higher than other slabs. The cellulose fibers not only delays the initiation of cracks but also reduces cracking density (numbers of cracks per unit area). Ninety days after the slab is casted, SEM analysis shows that the structure of the reinforced slabs is relatively compact and a large number of short-rod clusters are formed inside it. Energy spectrum analysis shows that the cellulose fiber reduces the proportion of calcium while increasing the proportion of silicon and aluminum in the slabs. Fly ash hydration consumes a certain amount of calcium, thereby reducing the calcium-silicon ratio and increasing the strength of the slabs. 【Conclusion】 Comparison shows that reinforcing concrete slabs by cellulose fiber can significantly improve their resistance against cracking and tensile strength.

Introduction. The purpose of the study was to evaluate the effectiveness of dispersed concrete reinforcement in terms of strength and crack resistance.Materials and methods. When conducting research, test methods were used, regulated by the provisions of national standards, equipment specially designed for this study was used.Results. The results of testing fiber-reinforced concretes made using low-modulus and high-modulus fibers are presented.Discussion and conclusions. As a result of the analysis of the data presented, it is shown that in order to assess the effectiveness and the correct choice of reinforcing fibers, it is not enough to characterise fiber-reinforced concrete only by tensile strength in bending. For a more accurate assessment, it is proposed to use crack resistance characteristics, for example, the critical stress intensity factor, or to supplement the description of the advantages of dispersed reinforcement with the features of the behavior of fiber-reinforced concrete under load.

To further understand self-healing behaviors of cracks in fiber reinforced asphalt mortar, shape memory polyurethane/styrene butadiene styrene modified asphalt mortar (PSAM) was first prepared. Then shape memory properties of lignin fiber reinforced PSAM (LFAM) and polyester fiber reinforced PSAM (PFAM) were characterized. The effects of filler-asphalt ratio and fiber type on the multi-cycle self-healing results of LFAM and PFAM were discussed. The self-healing effectivenesses in each crack-healing cycle and whole multi-cycle self-healing process were evaluated. Results indicate that shape memory properties of LFAM and PFAM are lowered as their filler-asphalt ratios are increased. LFAM and PFAM show satisfactory shape memory properties, but PFAM has better shape memory performance than LFAM, and its higher shape recovery force further improves its self-healing effectivenesses. Also, when the filler-asphalt ratio is raised, both creep deflection and creep slope of LFAM and PFAM are decreased, but their creep stiffnesses are increased. The self-healing mostly restores the mechanical properties of LFAM and PFAM. PFAM shows higher low-temperature crack resistance than LFAM. Meanwhile, the creep deflection and creep slope of PFAM are higher than those of LFAM as the filler-asphalt ratio is the same one, while the creep stiffness of PFAM is smaller than that of LFAM. LFAM shows a brittle failure at low temperature, but PFAM shows a flexible failure. Additionally, the self-healing effectiveness of LFAM and PFAM in each crack-healing cycle is decreased as the crack-healing cycle is increased. Finally, PFAM shows a higher self-healing rate than LFAM. The mechanical and self-healing characteristics of PFAM are more stable than those of LFAM. The multi-cycle self-healing test indexes can assess the multi-cycle self-healing effectiveness of LFAM and PFAM.

This study develops a new type of decorative bridge panel by ultra-high-performance concrete (UHPC) based on the project of the Guangyangwan Bridge. First, the numerical analysis was carried out using MIDAS and ABAQUS to find the critical position of the bridge and decorative panels. The numerical results showed that the last concrete cantilever segment had the greatest vertical deflection, and the corresponding panel had the greatest stress response. Based on the numerical results, this study conducted a series of full-scale, self-balanced bending tests to examine the crack resistance of six UHPC panels and six glass fiber-reinforced concrete (GRC) panels with varying curved section thicknesses (from 25 to 40 mm). The experimental results indicate that, due to the high strength of the UHPC matrix and the wall effect of steel fiber distribution, the crack resistance of UHPC panels is significantly superior to that of GRC panels. UHPC panels possessed superior stiffness and ductility, while GRC panels showed brittle fracture when the curved section thickness reached 34 mm. The uniaxial tensile cracking strength of UHPC with a steel fiber volume fraction of 1.6% was 14.7% greater than that of GRC with a glass fiber volume fraction of 5%. At the same curved section thicknesses, UHPC decorative panels exhibit cracking loads and ultimate loads that are 64.3% to 123.0% and 29.2% to 115.0% greater than GRC panels, respectively. Hence, UHPC is more suitable to produce ultra-thin decorative panels for bridges that are subjected to severe environmental action and external forces.

Cement-stabilized macadam (CEM-SM) base layers on highways are prone to early shrinkage cracking in extremely cold and arid regions, mainly caused by the large drying shrinkage of traditional cement-stabilized base materials. A multi-component solid waste cementitious material (SWCM) was designed based on the response surface method. The synergistic reaction mechanism of SWCM was analyzed using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). A shrinkage testing system was developed to evaluate the anti-cracking characteristics of stable macadam using multiple solid waste cementitious materials (SWCM-SM), and the strength growth law and frost resistance were analyzed. The results show that the Box–Behnken response surface model was used to obtain the optimal parameter combination for SWCM, including 60% slag, 30% steel slag, and 10% desulfurization gypsum. The compressive strength and flexural strength of SWCM-SM were 24.1% and 26.7% higher than those of CEM-SM after curing 180 days. The frost resistance of SWCM-SM was basically equivalent to that of CEM-SM, and the dry shrinkage strain of SWCM-SM was reduced by 30.7% compared to CEM-SM. It can be concluded that steel slag and desulfurization gypsum stimulate the hydration reaction of slag, thereby improving the bonding strength. Compared to CEM-SM, SWCM-SM exhibits slower hydration reaction and longer hydration duration, exhibiting characteristics of low early strength and high later strength. The early microstrain of the semi-rigid base layer is mainly caused by the occurrence of early water loss shrinkage, and the water loss rate of SWCM-SM is lower than that of CEM-SM. This study concludes that SWCM has good early crack resistance performance for stabilized crushed stones.

Plastic shrinkage cracking is a complex and multifaceted process that occurs in the period between placement and the final setting. During this period, the mixture is viscoplastic in nature and therefore possesses rheological properties. The investigation of the relationship between rheological behavior and its propensity to undergo cracking during the plastic phase presents an intriguing subject of study. However, many factors influence plastic cracking, and the corresponding interaction of its effects is complex in nature. This study aimed to evaluate the impact of rheological and physicomechanical properties on the occurrence of plastic cracking in high-performance shotcrete containing various supplementary cementitious materials. To achieve this, plastic cracking was evaluated employing the ASTM C 1579 standard and a smart crack viewer FCV-30, and the rheological parameters were controlled using an ICAR rheometer. In addition, a study was conducted to assess the strength development and fresh properties. Further, a relationship was established via statistical evaluation, and the best predicting models were selected. According to the study results, it can be concluded that high-yield stress and low plastic viscosity for colloidal silica mixtures are indicators of plastic cracking resistance owing to improved fresh microstructure and accelerated hydration reaction. However, earlier strength development and the presence of a water-reducing admixture allowed mixtures containing silica fume to achieve crack reduction. A higher indicator of yield stress is an indicator of the capillary pressure development of these mixtures. In addition, a series containing ultrafine fly ash (having high flow resistance and torque viscosity) exhibited a risk of early capillary pressure build-up and a decrease in strength characteristics, which could be stabilized with the addition of colloidal silica. Consequently, the mixture containing both silica fume and colloidal silica exhibited the best performance. Thus, the results indicated that rheological characteristics, compressive strength, and water-reducer content can be used to control the plastic shrinkage cracking of shotcrete.

When using the technology of long-line formwork-free shaping for the manufacture of reinforced concrete structures, industrial engineering can be conducted in accordance with the requirements of modern regulatory documents. This allows projects to be developed individually, and production lines can be readjusted in a short time in accordance with emerging needs. In this regard, the possibility of using reinforced concrete posts produced by the technology of long-line formwork-free shaping for 0.4-10 kV overhead line supports is being considered. The designs of such supports are developed on the standard basis of the product range. The problem of establishing the minimum number (two) of cross-sections with different geometric dimensions for all brands of the offered posts is solved, subject to the operational requirements and technological specifications of production. The cross-sections of the proposed posts represent trapeziums, with the dimensions of the upper bases smaller than the dimensions of the lower bases in order to maintain the shape of the freshly formed concrete body of the posts made using long-line formwork-free shaping technology. For posts up to 11.0 m long, a solid cross-section with trapezoid edges is proposed: h = 245 mm; b = 150 mm (an upper base); b1 = 180 mm (a lower base). In the middle part of the cross-section of posts with a length of 11.0 to 16.4 m there is a cavity along the entire length of the posts. Cross-sectional dimensions of such posts are h = 300 mm; b = 205 mm, b1 = 235 mm. Long-line formwork-free shaping technology provides for the reinforcement of prestressed structures with high-strength wire or rope reinforcement. The proposed posts are rein-forced with 5Вр1400 rods, therefore, during their operation, the formation of cracks in the tensile zone of concrete is not fore-seen. The rods are located in groups at all corner sections along the cross-section of the post with an equal number of rods in each group, taking into account the technological features of the long-line formwork-free shaping. For the proposed cross-section of hollow posts, produced by long-line formwork-free shaping for 0.4–10 kV overhead line supports, a patent for autility model has been obtained from the Agency for Intellectual Property of Uzbekistan. Qualitative characteristics of the posts for overhead line supports are low material consumption, versatility, manufacturability, innovation, which lies in the fact that their implementation is associated with the design, manufacture and testing of experimental products for use by specific consumers, i. e. with the commercialization.

The article dwells on a comprehensive method for determining concrete strength and crack-resistance in sample testing with varying loading rate. The method allows for receiving simultaneously kinetic parameters of the microstructure defects and length and rate of the main crack growth. The authors consider the impact of effective involved volume on the formation and growth of minor structural defects in cement gel with their eventual phased transition to larger defects. It facilitates increased stress concentration and the development of main cracks at the matrix-aggregate interface. Control over the development of the main crack allows for determining the time till destruction for concrete (longevity). The suggested method and the obtained formula helped applying a wide range of loading rates for determining the critical length of the main crack in concrete. The testing results were used to identify the coefficients of dynamic strengthening for the sample sets with and without an artificially created main crack. These coefficients were applied for calculating the main crack critical length. The article presents the results of experiments aimed at development of concrete compositions comprising fibre fillings and modifying additives including nano-additives followed by determination of their strength and crack-resistance as per the presented comprehensive method. The found values of efficient involving volume, activation energy characterise the microstructure parameters and critical length of the main crack in concrete. The resulting conclusion was that the main crack length in all of the developed concrete compositions exceeded the half of the section in the sample where it developed. Comprehensive assessment of concrete strength and crack-resistance and accumulation of experimental data improve the reliability of scientific research due to the emerging integrated approach to determining quantitative parameters of crack-resistance and longevity of the developed concrete compositions with forecasted properties.

Objectives. The study assessed the possibility of using optical-polarization methods to test quantitatively the stress state and residual stress in polycarbonate (PC) monolithic sheets. This stress is the leading cause of the cracking of PC sheets and the products made of them.Methods. The objects were samples of monolithic PC sheets made by various manufacturers (Monogal and Novattro). The birefringence method was used to study the stress state of the samples, and the interference images obtained in polarized light in crossed polaroids were analyzed.Results. The efficiency of optical-polarization research methods, such as the birefringence and the analysis of the interference images of stretched PC samples combined into an additive spectrum, was shown. The residual stress in the monolithic PC sheets made by various manufacturers was estimated.Conclusions. The quantitative relationship between the stress acting on the PC samples, their birefringence, and the characteristics of their additive spectrum of interference images of stressed samples obtained in polarized light in crossed polaroids was established. The possibility of a quantitative assessment of the residual stress in monolithic PC sheets based on an analysis of their additive spectrum of interference images was shown. The measured residual stress did not exceed 1 MPa.

Abstract The harsh environment will reduce the interlayer bonding quality of mass concrete and cause plastic cracking. These defects will seriously affect the safety and durability of the structure. This study tested the layer state (water content and penetration resistance), interlayer mechanical properties, and early-age crack resistance of concrete to evaluate the impact of extreme weather on concrete interlayer properties and crack resistance. Furthermore, the interlayer splitting tensile strength of concrete under different treatment measures (covering insulation quilts and artificial grooves) was analyzed to find a method to reduce the construction risk of mass concrete. At the same time, the early-age crack resistance of concrete under different treatment measures (covering insulation quilts and adding PVA fibers) was evaluated. The results showed that the interlayer splitting tensile strength of concrete decreased by 50%, 40%, 29%, and 70%, respectively, compared with bulk concrete under extreme weather conditions (high temperature, strong winds, steep descent in temperature, and short-time heavy rainfall). Covering insulation quilts can reduce the construction risk of concrete under extreme weather conditions such as high temperature, strong winds and steep descent in temperature. This is mainly due to the fact that insulation quilt reduces the impact of the external environment on the concrete and effectively prevents the evaporation of moisture inside the concrete. In addition, covering insulation quilts can reduce the total cracking area of concrete under extreme weather conditions (strong winds and dry-heat, strong winds and cold waves, and short-time heavy rainfall) by 85–100%. At the same time, adding PVA fibers can inhibit the generation and expansion of micro-cracks on the concrete surface. This is due to the bridging and cracking resistance of PVA fibers.

The advantages of rubber concrete (RC) are good ductility, fatigue resistance, and impact resistance, but few studies have been conducted on the effects of different rubber admixtures on the strength of RC and the cracking performance of rubber mortar. In this study, the compressive and flexural tests of rubber concrete and the crack resistance test of rubber mortar were carried out by changing the rubber content and adding expansion agent and retarder in this test. The test results show that the strength of RC decreases with the increase in rubber admixture. At 15% of rubber admixture, the expansion agent and retarder increase the compressive strength and flexural strength of RC the most; the compressive strength increased to 116% (22.6 MPa) and 109% (21.2 MPa), and the flexural strength increased to 111% (4.02 MPa) and 116%. (4.21 MPa). At the same rubber admixture, the expander improves the cracking time of the rubber mortar by about 3 times, and the retarder improves the cracking time of the rubber mortar by about 1.6 times. The BP neural network (BPNN) was established to simulate and predict the compressive and flexural strengths of RC with different admixtures and the cracking time of rubber mortar. The simulation results show that the predicted 7-day compressive strength of RC fits best with the actual value, with a value of 0.994, and the predicted 28-day flexural strength was closest to the measured value, with an average relative error of 1.7%. It was shown that the calculation results of the artificial intelligence prediction model are more accurate. The simulation results and test results show that the expander and retarder significantly improve the strength of RC as well as the cracking performance of rubber mortar.

Reflective cracking is a common distress of old pavement overlaid with an asphalt layer. The asphalt rubber stress-absorbing membrane interlayer can effectively mitigate and prevent reflective cracking. However, the existing test methods and evaluation indices for the crack resistance of the asphalt rubber stress-absorbing membrane interlayer are insufficient and unsystematic. They do not account for the significant effect of gradation parameters on the crack resistance in a comprehensive way. Therefore, this research aims to explore the impact of gradation parameters on the performance of the asphalt rubber stress-absorbing membrane interlayer. Based on the Chinese and U.S. standards, three kinds of 10 types of gradation were selected, forming a total of seven groups. The asphalt rubber stress-absorbing membrane interlayer was subjected to −10 °C and 15 °C beam bending test, low-temperature semi-circular bend test, crack expansion semi-circular bend test, and overlay test to evaluate its cracking resistance. The correlation and influence law between the key sieve hole method, graded fractal method, and Bayley method parameters of different grades and beam bending test, low-temperature semi-circular bend test, crack expansion semi-circular bend test, and overlay test indexes were quantitatively analyzed by the coefficient of variation and Pearson correlation analysis method. The results showed that the performance of the mixtures with different gradation ranges varied significantly in different tests, as indicated by the maximum difference of 56.07% in stress absorption. This implied that gradation is a critical factor that affects the stress absorption performance of mixes. The different sensitivities of different tests to the parameters of the key sieve method, the graded fractal method, and the Bailey method indicated that the stress absorption performance was affected by a combination of factors. Therefore, in order to evaluate and optimize the stress absorption performance, it was necessary to comprehensively consider the interactions among the parameters of the key sieve method, the graded fractal method, and the Bailey method. The stress absorption performance included crack resistance and crack expansion resistance, which were inversely related and needed to be balanced and optimized during design. The −10 °C beam bending test and crack expansion semi-circular bend tests were more suitable test methods for evaluating stress absorption performance, and maximum flexural–tensile strain, strain energy density, fracture energy, and flexibility index were recommended as evaluation indicators. This research provides a reference for the optimization of the grading design of asphalt rubber stress-absorbing membrane interlayers, and provides test methods and indicators for the evaluation of crack resistance.

Plasticizers are common additives used to enhance the flexibility and workability of polymer materials. Recent findings suggest a great potential for typical plasticizers being used as rejuvenators to recycle oxidized paving asphalts. This study investigated the rejuvenating effectiveness of two plasticizers via rheological evaluation and explored the underlying mechanism by analytical characterizations and molecular dynamics (MD) simulations. A conventional plasticizer dibutyl phthalate (DBP) and an environmentally friendly tributyl citrate (TBC) were selected given the discrepancies in their molecular structures. Both plasticizers were effective in restoring the rheological performance of the aged asphalt; TBC was relatively more efficient which was attributed to its higher molecular polarity and the formation of hydrogen bonds with the oxidized asphalt molecules. Analyses based on the gel permeation chromatography and differential scanning calorimetry suggested the capability of the plasticizers in dissociating the oxidized asphalt molecules and improving the molecular mobility. The improved molecular mobility was considered responsible for the reversing effect of the plasticizers, as compared to aging, in terms of widening the relaxation spectrum and broadening the glass transition region. The plasticizers’ dissociating effect was confirmed and visualized in the simulations by inspecting their impacts on the spatial arrangement and distribution of the asphaltenes.

This paper aims to analyze the interface property between fibers and asphalt, and study its influence on the crack resistance of the asphalt mixture. Four fibers (basalt fiber A (BF-A), basalt fiber B (BF-B), polyester fiber (PEF) and polyacrylonitrile fiber (PAF)) were selected in the study. The interface adhesion parameters were obtained by conducting the novel fiber-asphalt pullout test, and the micromorphology of the fiber-asphalt interface area was also observed. The crack resistance of the mixture was determined using the indirect tensile asphalt cracking test (IDEAL-CT) and the semi-circular bending test (SCB). Basic crack resistance indicators such as CTIndex and flexibility index (FI) were used for analyzing. Meanwhile, digital image correlation (DIC) technology was adopted to quantitatively characterize the crack inhibition mechanism of fibers in the fiber-asphalt mixtures. The results showed that the interface adhesion strength between BF-A and asphalt is the largest at 25 ℃, followed by BF-B, PEF and PAF. The addition of fibers can effectively improve the CTIndex and FI of asphalt mixtures, and it is found that the interface adhesion characteristics between fibers and asphalt have a great influence on the crack propagation process. The crack opening velocity curve obtained from the DIC analysis can quantitatively characterize the crack development law of the asphalt mixture. The coefficient of determination R2 between the interface adhesion strength and the DIC index (stage I velocity change rate and timing point 1 time) exceeded 0.85. The results can provide scientific references for the design and application of fiber reinforced asphalt mixture.

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

This article develops three transverse rib setting schemes for a 20 m wide cantilever segmental box girder of a particular engineering bridge deck, analyzes the stress rules under loads such as dead load, live load, and temperature, and studies the lateral deformation characteristics of the three schemes under symmetrical and eccentric live load arrangements on the bridge deck. Research has shown that setting transverse ribs can significantly improve the transverse stress, crack resistance, and reduce vertical deformation of the cross-section. However, its effect gradually weakens with the increase in the number of transverse ribs. Considering the convenience and simplicity of construction, installing a transverse rib structure for the large cantilever section box girder in this project is recommended.

Pure self-compacting concrete has many disadvantages, such as early shrinkage and cracking. The addition of fibers can effectively improve the properties of resistance to tension and cracking of self-compacting concrete, thereby the effect of improving its strength and toughness can be achieved. Basalt fiber is a “new green industrial material” that has unique advantages, such as high crack resistance and being lightweight compared with other fiber materials. In order to study the mechanical properties and crack resistance of basalt fiber self-compacting high-strength concrete intensively, the self-compacting high-strength concrete of C50 was designed and obtained using the absolute volume method with multiple proportions. Orthogonal experimental methods were used to study the influence of the water binder ratio, fiber volume fraction, fiber length, and fly ash content on the mechanical properties of the basalt fiber self-compacting high-strength concrete. Meanwhile, the efficiency coefficient method was used to determine the best experiment plan (water binder ratio 0.3, fiber volume ratio 0.2%, fiber length 12 mm, fly ash content 30%), and the effect of fiber volume fraction and fiber length on the crack resistance of the self-compacting high-performance concrete was investigated using improved plate confinement experiments. The results show that (1) the water binder ratio had the greatest impact on the compressive strength of basalt fiber self-compacting high-strength concrete, and as the fiber volume fraction increased, the splitting tensile strength and flexural strength both increased; (2) there was an optimal value for the effect of the fiber length on the mechanical properties; (3) with the increase in fiber volume fraction, the total crack area of the fiber self-compacting high-strength concrete significantly decreased. When the fiber length increased, the maximum crack width first decreased and then slowly increased. The best crack resistance effect was achieved when the fiber volume fraction was 0.3% and the fiber length was 12 mm. Therefore, basalt fiber self-compacting high-strength concrete can be widely used in engineering fields, such as national defense construction, transportation, and building structure reinforcement and repair, due to its excellent mechanical and crack resistance properties.

This article presents a literature review into the current state of the theory and practice of spraying complex titanium and zirconium nitride on steel P6M5, as well as a study of the effect of spraying time on the structural and mechanical characteristics of the applied coating. With the help of microstructural analysis and the measurement of the mechanical properties of the sprayed layers, it was found that the size of the voids and their number per unit surface area decreases with the spraying time. The highest values of hardness and crack resistance of the coating were obtained during the technological process – 15 minutes. It was found that the duration of vacuum-condensation spraying with Ti-Zr-N alloy significantly increases the wear resistance of structural steels, and the best results among the considered parameters showed a sample with a spraying time of 15 min, this figure can be considered optimal.

A vast amount of nylon waste is being generated as paintbrushes, and how to reuse post-consumer nylon waste is a new crisis. The eco-friendly development of fiber reinforced concrete (FRC) is a major challenge in the construction industry considering the high cost of engineered fibers. Thus, owing to high tensile strength, recycled nylon fiber (RNF) derived from nylon waste can be used in FRC as an eco-friendly and cheaper alternative to engineered fibers. This study assessed the influence of RNF on the properties of medium-strength concrete. Therefore, concrete mixes were prepared and studied with various volume fractions of RNF i.e., 0.05%, 0.1%, 0.15%, 0.25%, 0.5%, 0.75%, 0.85% and 1%. Physical (density, and ultrasonic pulse velocity-UPV), mechanical (compressive strength-CS, splitting-tensile strength-SPS, and flexural-tensile strength-FS), and permeability (water absorption-WA and chloride penetration depth-CPD) properties of all mixes were examined and compared. The experimental findings proved that higher volume fractions of RNF showed a ‘reducing effect’ on CS. For best SPS and FS, results recommended doses of RNF are 0.25%, and 0.75%, respectively. At optimum RNF doses, net improvements of 24.2% and 14.1% were noticed in FS and SPS, correspondingly w.r.t control mixture. RNF enhanced the crack-resistance of plain concrete by delaying the failure under tensile and flexural load. The incorporation of a 0.05–0.5% volume fraction of RNF was beneficial to minimize the WA and CPD. Minimum permeability is achieved at the incorporation of 0.1–0.15% of RNF, for instance, at 0.15% RNF, WA and CPD of concrete were reduced by 11.5% and 29.2%, respectively w.r.t control mix.

The fill mining method has become more widely used due to its advantages of a high resource recovery rate, reliability and safety, and reduced surface tailings storage. However, the mechanical properties of the cemented fillings in fill mining are similar to those of ultra-low strength plain concrete, and there are problems such as high brittleness, low bending and tensile strength, and sudden failure. Using a flexible grid as reinforcement material, uniaxial compression, tensile, and shear tests of a flexible grid filling body were carried out, and the results were compared with the mechanical properties of the filling body without the flexible grid. We drew the following main conclusions: the uniaxial compressive strength of the flexible grid filling body gradually increased with the decrease in the grid spacing (the increase in the grid density); the grid dimension had little effect on the uniaxial compressive strength of the flexible grid filling body. The uniaxial tensile strength and shear strength of the flexible grid filling body increased with the increase in the grid dimension; and they first increased and then decreased with the increase in the grid spacing, and there was an optimal grid spacing. From the perspective of the macroscopic failure mode, the flexible grid filling body specimen after the uniaxial compression test had a conjugate shear failure, forming a “dumbbell shape” with two large ends and a small middle. After the uniaxial tensile test, the macroscopic failure mode of the specimen was tensile failure. After the shear test, the macroscopic failure mode of the specimen was shear slip failure. It is proposed that the tensile strength, shear strength, cohesion, and internal friction angle strengthening coefficients of the flexible grid filling body with different dimensions and spacing are higher than the elastic modulus strengthening coefficients. The experimental results can provide a certain reference and guidance for mine filling.

The study object is a prototype of a composite bridge prestressed concrete beam with a length of 42.0 m for road bridge desks for perception of impact from motor vehicles in the form of A14, NK-120 and NK-180 loads.

The paper deals with the results of multi-method test studies of the bearing capacity, stress-strain behaviour and crack resistance of the 2000х200х100 mm reinforced concrete beams and basalt fibre reinforced concrete beams subjected to high-level static and low-cycle loads. Specifically, the test-statistical curves illustrating strengths of the inclined cross-sections (collapsing transverse force). There are examined moments and the developed transverse forces for normal and inclined cracks, the deflection and crack widths subjected to service and collapsing loads. The projection lengths of the dangerous inclined cracks on the longitudinal axis and the average distances between normal cracks along the element lengths versus the design factors of the concrete beams similarly reinforced with steel and basalt-plastic were compared. Comparative analysis was made to check the impact of the main design factors on the indicated load-bearing capacity parameters of the reinforced concrete beams and basalt fibre reinforced concrete beams manufactured and tested in accordance with the experimental design theory and D-optimum plan of Box B3.

Abstract Cracking caused by shrinkage deformation of cement-based materials at early age is a major problem leading to material failure in restrained conditions. Carbon nanotubes (CNTs) are incorporated into cement-based materials, and the autogenous shrinkage and crack resistance of the new composite materials obtained by linear shrinkage and ring tests are studied to solve the destruction of the materials caused by the shrinkage of cement-based materials. The results showed that addition of CNTs significantly inhibited the autogenous shrinkage of cement-based materials with maximum reduction rate above 40%. CNTs also significantly improved the cracking resistance of cement-based materials. The optimal effect was noticed at CNTs content of 0.1 wt%. The incorporation of CNTs not only inhibits the autogenous shrinkage of cement-based materials, but also inhibits the drying shrinkage of cement-based materials to some extent. Therefore, carbon nanotubes have the potential to solve the destruction of materials caused by shrinkage of cement-based materials.

Introduction. The paper is devoted to the analytical determination of general criteria for predicting the wear resistance of heavily loaded friction couples, in particular, stamping tools, operating under various loading conditions. The proposed system of criteria is based on physical dependencies that link the basic wear index, i.e. the number of loading cycles NF with crack resistance parameters n and C. The work objectives were the development and analytical foundation of the calculation technique that provides for predicting the wear resistance of the stamping tool for various loading conditions, as well as the predetermination of experimental verification of the efficiency of the developed methodology.Materials and Methods. Mathematical models that link the key criterion of wear-resistance, the number of loading cycles NF with crack resistance parameters nand C, are proposed. An analytical verification of the proposed models is carried out.Results. Mathematical models are developed for predicting the wear resistance of a stamping tool operating under various loading conditions. In particular, for the following cases: under sliding and rolling friction of the tool on a plastically deformable metal, for conditions of thermo-mechanical contact fatigue, for high-cycle brittle contact damaging, for pulsating contact on a plastically deformable metal, as well as for combined types of frictional contact. Discussion and Conclusions. The results obtained can be used in the design and structural optimization of the stamping tool operating under various loading conditions, as well as in predicting its life cycle.

The article considers the peculiarities of the model for predicting the crack resistance characteristics of pipe material taking into account the influence of corrosion-erosion processes during long-term operation with an estimation of one of the major characteristics of cyclic crack resistance, threshold stress intensity factor. A methodical description is given for the experimental determination of the values of cyclic crack resistance characteristics (threshold stress intensity factor, parameters of Paris equation of fatigue fracture kinetic diagram) of the pipe material under the direct corrosion-erosion effect of a liquid medium on fatigue crack front in laboratory compact specimen.