Search

Fine powders of yttrium orthoniobate activated by Eu, Sm, Tb, Er have been synthesized by the sol-gel. The synthesized powders have been calcined at different temperatures (1000, 1100 and 1180 °C). Luminescent ceramics (Y 0.96 Еu 0.01 Sm 0.01 Tb 0.01 Er 0.01)NbO 4 were prepared from fine powders by uniaxial hot pressing (UHP) via various technological modes. For the first time, the crystal structure, microstructure, spectral composition, photoluminescence properties of (Y 0.96 Еu 0.01 Sm 0.01 Tb 0.01 Er 0.01)NbO 4 ceramics have been studied depending on the temperature conditions of the synthesis of powders and UHP conditions during sintering of ceramics. The mechanical properties of these ceramics (Young's modulus, microhardness and critical stress intensity factor for the mode I K IC) have been evaluated. [ABSTRACT FROM AUTHOR]

[Display omitted] The industry has always strived to design "hard" and "crack-resistant" glass. However, simultaneously realizing these properties in oxide glasses has been rare. Although Al 2 O 3 -rich hard and crack-resistant oxide glasses have been reported in the last decade, they exhibit two significant technological challenges that hinder their translation from laboratory to industry: (1) high processing temperatures (>2000 °C) and (2) small glass-forming regions (near eutectic). The present study reports the structural design of a hard and high modulus glass with high crack initiation resistance designed in the peraluminous region of rare-earth containing MgO–Al 2 O 3 –B 2 O 3 –SiO 2 system. The glass can be processed at a temperature ≤1650 °C and exhibits Vickers hardness (H v) of 7.84 GPa (at 1.96 N load) and indentation crack resistance (ICR) of 26.5 N. These H v and ICR values are significantly higher than most commercial or non-commercial glasses (prior to thermal tempering, densification near T g , or chemical strengthening). The glass has been scaled up to successfully produce slabs of dimensions 100 mm × 100 mm × 8 mm at laboratory scale with optical transmission of 90 ± 2 %. The results presented here are scientifically intriguing and have considerable tangible implications, as they pave the path for the design and development of stronger glasses for functional applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

The brittleness of oxide glasses remains a critical problem, limiting their suitability for high‐performance and safety‐critical applications. In this study, we attempt to address this by synthesizing nanostructures in sodium borosilicate glasses through phase separation. While most previous work on the mechanical properties of phase‐separated glasses has focused on phase separation through nucleation and growth, we here create interconnected structures through spinodal decomposition. Interestingly, this leads to improvements in Vickers hardness (from 5.8 to 6.2 GPa), crack initiation resistance (from 4.9 to 8.1 N), and fracture toughness (from 0.85 to 1.09 MPa⋅m1/2). We show that the interconnected glassy phases deflect the propagating cracks, causing the required energy for cracks to cross phase boundaries to increase when subjected to external stress. This study deepens the understanding of how to address the brittleness problem of oxide glasses and provides a promising way to design high‐performance glass materials. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article presents the results of experimental studies of the stress–strain state of volumetric blocks based on the underlying frame structures. The aim of the research is to evaluate the stress–strain state and the nature of damage development as a result of an increase in the load up to a critical level. Based on the analysis of the nature of the damage, recommendations have been developed to strengthen the destruction zone. Data were collected on the redistribution of stresses and deformations, the formation of cracks and joint openings, the magnitude of horizontal displacements, and the failure mode of volumetric blocks and floor frames. Five full-scale volumetric blocks were tested under the loading of hydraulic jacks, differing in concrete type, reinforcement, presence of doors, and dimensions of the stylobate beams. When the volumetric modules were supported by a frame floor the results revealed that the maximum destructive load of 10,462 kN was observed in the first specimen; the horizontal displacements of the walls decreased by 13–18 mm, and there was a decrease in the crack opening width to 0.5 mm. The cracks decreased the strength of the walls, leading to a redistribution of the compressive stresses and their increase in the support zone. The most significant compressive strains in concrete in the corner parts of longitudinal walls were in the range of (600–620) × 10−6, and in the middle part of the walls, 370 × 10−6 were observed. Furthermore, the largest cracks caused significant horizontal displacements (deplanation) of the walls, which decreased the stiffness of the conjunction of longitudinal walls with the floor slab and created an additional eccentricity of the vertical force. Based on the findings, the correlation between the measured parameters of each specimen at all stages of vertical load increase is demonstrated and illustrated in graphs of the measured parameters. The importance of quantity compliance with the initial rigid connection between the longitudinal wall and ceiling plate has been estimated. [ABSTRACT FROM AUTHOR]

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.

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%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aims to develop a prefabricated flexible ultrathin overlay that can quickly and effectively repair cracks, particularly reticulation cracks, in old asphalt pavements while improving skid resistance. The overlay consists of a combination of an aggregate, a binder, and a geotextile; its unique structure results in a thickness of only about one-third of that of traditional ultrathin overlays. Its tensile strength, skid resistance, flexibility, waterproofing, interlayer bonding, and long-term service performance were evaluated through a series of tests. The results indicated that basalt, styrene butadiene styrene–modified emulsified asphalt, and warp-knitted polyester fiberglass fabric was the best combination. The proposed steady-state equation could reduce the test duration by more than 20%. The best interlayer binder was rubber asphalt with an optimum dosage of 0.9 kg/m2. The effect of temperature on interlayer bonding properties was more significant than that of the loading rate. The overlay maintained good waterproofing, skid and crack resistance, and interlayer bonding properties after a medium-scale accelerated loading test. [ABSTRACT FROM AUTHOR]

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steel–concrete composite beams, essential for large-span structures, benefit from connectors that reduce cracking at the supports. The crack resistance and alignment with sustainable building trends of high-strength bolted connectors have been extensively researched. Nevertheless, only a few studies exist on their load–slip behavior in hogging sections. In this study, the shear performance of high-strength bolted connectors subjected to tension due to hogging moments was studied based on experiments and numerical modeling according to numerous reverse push-out tests. The results revealed that tensile and splitting cracks were produced in the concrete. Their distribution was affected primarily by the concrete strength and bolt diameter; this distribution became denser at decreasing concrete strengths and increasing bolt diameters. Subsequently, an analysis of the out-of-plane displacement and load–slip response was performed to investigate the phenomenon of anchor rod sliding. A cost-effective and time-efficient finite-element (FE) model was developed to investigate the internal microstates of the specimens. It revealed a correlation between bolt cracking, specimen hardening, steel yield, and failure. A correction factor is also proposed for the shear capacity of bolts within concrete subjected to tension. The findings offer insights into the load–slip response of high-strength bolted connectors subjected to hogging moments, aiding in safer, more durable supports for steel–concrete composite beams. [ABSTRACT FROM AUTHOR]

To study the crack resistance of steel slag crumb rubber modified asphalt mixture (CR-steel slag) under salt freeze–thaw cycles, we selected styrene-butadiene-styrene (SBS)-steel slag and CR-basalt as the reference group. The relationship between CR-steel slag interfacial adhesion properties and crack resistance under salt freeze–thaw (FT) cycles was investigated through semicircular bending (SCB), pull-out, and contact angle tests. The results show that the salt FT will accelerate the process of micro-cracks in the mixture to macro-cracks. With the increase of FT cycles, the crack resistance will gradually deteriorate, and significant damage will occur in the mixture at 15 freeze–thaw cycles. The mutation point of freeze–thaw times will move forward in different degrees under the action of salt solution. At the same time, with the increase of salt solution concentration, its anticracking performance first decreases and then increases, reaching an extreme value of 8%. The magnitude of the crack resistance of the three asphalt mixtures is CR-steel slag > SBS-steel slag > CR-basalt. The macroscopic cracking index of asphalt mixtures has an excellent positive correlation with the matching index, and the matching index model has sufficient accuracy in evaluating the cracking resistance of three asphalt mixtures under the action of salt freeze–thaw cycles. Based on the surface energy theory to evaluate the crack resistance of the mixture from a microscopic perspective, combined with macroscopic evaluation indexes, the evaluation results are accurate and more reliable. [ABSTRACT FROM AUTHOR]

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 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To better reveal the performance development of bitumen emulsion-based cold in-place recycling (BE-CIR) mixture over curing, a semi-sealed laboratory curing method was proposed in this research to simulate the in situ moisture evaporation process and cracking resistance of the BE-CIR specimen at different depths during a curing time of 28 days, which was also investigated by the semi-circular bending (SCB) test. The influencing factors of cement content (1.5% to 2.5%), initial moisture content (3.5% to 4.5%), curing temperature (25 °C to 45 °C) and relative humidity were investigated, and the significance of different factors affecting the performance development was also analyzed. The results indicate significant variations in cracking performance parameters at different depths, with the top part exhibiting notably higher tensile strength and fracture energy compared to the bottom part, and a gradient index (GI) is proposed to describe the difference. Cement content affected early tensile strength and fracture energy, while the initial moisture content affected the development rate of the performance. The influence of curing temperature was extensive, and as the temperature increased beyond 40 °C, the strength of the effect decreased. High humidity during the early stage of curing inhibited the strength formation and development of fracture energy. The performance development of the BE-CIR mixture is more significantly influenced by the moisture migration process, which is governed by curing temperature and relative humidity, as opposed to the cement content and initial moisture content. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

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.

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. [ABSTRACT FROM AUTHOR]

Cold mix asphalt (CMA) is emerging as an environmentally friendly alternative to traditional hot mix asphalt (HMA). It offers advantages such as lower costs, reduced energy demands, decreased environmental impacts, and improved safety aspects. Among the various types of CMA, the cold bitumen emulsion mixture (CBEM) stands out. The CBEM involves diluting bitumen through emulsification, resulting in lower bitumen viscosity. However, this process has certain drawbacks, including extended setting (curing) times, lower early strength, increased porosity, and susceptibility to moisture. This study focuses on enhancing CBEM properties through the utilization of low-energy heat techniques, such as microwave technology, and the incorporation of a polymeric additive, specifically acrylic. These innovations led to the development of a novel paving technology known as a half-warm bitumen emulsion mixture (HWBEM). The research was conducted in two phases. First, the study assessed the impact of low-energy heating on the CBEM. Subsequently, it explored the combined effects of low-energy heating and the addition of an acrylic polymer. CBEM samples containing ordinary Portland cement (OPC) as an active filler were utilized in the sample manufacturing process. The effectiveness of these techniques in enhancing crack resistance was evaluated by analysing the results of the indirect tensile strength test. Notably, CBEM samples containing an amount of 2.5% of acrylic polymer and OPC exhibited the highest resistance to cracking. Furthermore, significant improvements were observed in their volumetric and mechanical properties, comparable to those of HMA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the engineering application potential of waste cigarette butts and to investigate the effect of waste cellulose acetate (WCA) as reinforcement material on the performance of asphalt mixtures. A performance prediction model was also constructed to explore the optimal mixture preparation scheme. In this study, a scanning electron microscope (SEM) was used to visually characterize the surface morphology of WCA. The elemental composition of the cellulose surface was determined semiquantitatively using an energy dispersive spectrometer (EDS). The experimental design was carried out following the face-centered central composite design (FCCD) of the response-surface methodology (RSM), taking WCA shearing time, WCA content, and asphalt-aggregate ratio as variable factors, and the splitting strength (Rdry), freeze–thaw splitting strength (Rsaturated), and tensile strength ratio (TSR) of the mixtures as response variables. The software Design-Expert was adopted to construct and optimize the model under multiple responses. The road performance was verified by rutting test, low-temperature bending test, and water immersion Marshall test. The results showed that WCA is a kind of organic cellulose with a smooth surface and cloverlike cross section, which can significantly improve the mixture's crack resistance and water stability. The performance prediction models all achieved a fit of 90% or higher. The best parameters recommended by Design-Expert were WCA content of 0.201%, WCA shearing time of 11.847 min, and asphalt-aggregate ratio of 5.683%, and the WCA-reinforced asphalt mixture Rdry , Rsaturated , and TSR values were 1.38 MPa, 1.24 MPa, and 89.86%, respectively, all of which were within the 95% prediction interval of the model predicted values. In addition, the road performance tests showed that WCA significantly improved the mixture's flexural strength and water stability, but harmed the high-temperature rutting resistance. WCA has a significant reinforcing effect on asphalt mixture, which has a certain reference value for recycling waste cigarette butts and developing green road materials. In addition, the FCCD model has high accuracy and can effectively guide the road material preparation process. [ABSTRACT FROM AUTHOR]

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.

The crack resistance of asphalt pavement mixtures directly impact pavement service condition and pavement distress. And characterizing the crack resistance of a pavement mixture can reflect the crack resistance potential of asphalt pavement. This study analyzes several representative highway sections based on time, material, and service conditions to identify the mixture type of three layers. Semi-circular bending tests are conducted at 15 °C, and load–displacement curves are recorded. Factor independence analysis is performed, and combinations showcasing the cracking performance of the surface layer, middle layer, and bottom layer are selected. Analysis of variance (ANOVA) evaluating the indices versus selected factors for the three layers identifies significant influencing factors, and the crack resistance is analyzed based on these significant factors. The crack resistance of the middle layer with the highest truck loads is significantly lower than the two other lanes and the shoulder. Transverse crack spacing (TCS) can be used to directly evaluate the crack resistance of the mixture. The Factor dots upper rate (FUDR) and absolute Factor dots upper rate (absFUDR) indices are introduced to quantify the percentage deviation of a factor specimen from the average crack resistance index–fracture energy ratio, indicating whether the crack curve becomes sharper or flatter. The factor dots upper rate index is then applied to characterize the factors, and the results are reasonable. It is found only on the surface and middle layers that the service age has significant impacts on crack resistance, the Transverse crack spacing has significant impacts on crack resistance index, and the Factor dots upper rate can identify the brittleness of mixtures with different factors. [ABSTRACT FROM AUTHOR]

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 Nonheat-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 nonstrengthened specimens was performed to evaluate the resistance to crack initiation and propagation. [ABSTRACT FROM AUTHOR]