Concrete Mechanisms Research Articles

N6-methyladenosine-modified circRPS6KC1 regulated cellular senescence in prostate cancer via FOXM1/PCNA axis.

Prostate cancer (PCa) gradually becomes the most common cancer in men in many countries, of which circRNAs and methylated modification exert an essential role in PCa progression. However, the concrete mechanisms of N6-methyladenosine (m6A) modification of circRNAs in PCa remain unclear. In our study, we identified circRPS6KC1, a novel and up-regulated circular RNA in PCa, through circRNA sequencing. We discovered that METTL3 and YTHDF1 were involved in the m6A modification of circRPS6KC1 and the stabilization. Furthermore, we found that suppression of circRPS6KC1 contributed to cellular senescence in prostate cancer. CircRPS6KC1 acted as the miR-761 sponge to regulate the FOXM1 expression. FOXM1 mediated the transcription of PCNA and influenced the p21 degradation, which resulted in up-regulation of p21 protein in a p53-independent manner. In conclusion, our findings showed that N6-methyladenosine modification by METTL3 and YTHDF1 stabilized circRPS6KC1, and circRPS6KC1 played an essential role on cellular senescence via FOXM1/PCNA axis in prostate cancer.

Workability of Nanomodified Self-Compacting Geopolymer Concrete Based on Response Surface Method

Geopolymer concrete is more low-carbon and environmentally friendly than Portland cement concrete. Nanoparticle modification can help to improve the mechanical and durability performance of concrete, but due to its large specific surface area and high activity, it may deteriorate its workability. However, there is currently limited research on the effect of nanomodification on the workability of freshly mixed self-compacting geopolymer concrete (SCGC). This article conducted SCGC workability experiments using the response surface methodology, which included 29 different mixtures. The effects of nano-silica (NS), nano-calcium carbonate (NC), alkali content (N/B), and water cement ratio (W/B) on the workability of SCGC were studied. The experimental results show that the addition of NS and NC can reduce the slump expansion of SCGC, and the combination of the two significantly increases the amplitude of slump expansion with the change in nanomaterial content. An increase in N/B will reduce the expansion time and clearance value of SCGC. As N/B increases from 4% to 4.4%, the slump extension of SCGC decreases, and with a further increase in N/B, the slump extension increases significantly to 68.1 cm, which means that the slump extension of SCGC increases by 9.5% as N/B increases from 4.4 to 5. This study can provide a reference for optimizing the fresh performance of geopolymer concrete and improving the mechanism of nanomaterial-modified geopolymer concrete.

Verbal and visual short-term memory predict performance in a multiplication production task: Evidence from a Malaysian sample.

Arithmetic requires the use of multiple cognitive processes, such as short-term memory (STM). However, findings on the association between STM and simple multiplication solving are mixed, potentially due to large interindividual differences in multiplication proficiency within and between samples. The present study aims to explore further the relationship between visual and verbal STM and simple multiplication solving with a large Malaysian sample (N = 230). Adults (age = 17-42) completed an online production-based multiplication-solving task, STM measures (verbal and visuospatial STM tasks), and a demographic survey. A mixed-model analysis found that verbal STM and visual STM predict multiplication performance, with lower span participants having longer reaction times during multiplication solving. Interestingly, we also observed the relationship between verbal STM and multiplication was moderated by interference, the impact of verbal STM was stronger in high-interference problems, while the visual STM-multiplication relation was moderated by problem size, high visual span participants took more advantage of their visual STM when presented with large size problems. Thus, our findings show that both verbal and visual STM in interaction with problem properties predict simple multiplication solving in adults. Hypotheses on the concrete mechanisms involved in these relationships are discussed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

4.A. Skills building seminar: Waves of community health engagement and governance: innovating through a design-as-policy approach

Abstract In this workshop we will engage our participants in a practice oriented exercise to experiment with a collaborative design-as-policy approach for a community health action plan. The exercise will be based on the lessons learned in two large evaluation projects: 1) an 8-year evaluation of the Dutch All about Health (AaH) platform of social health initiatives on the local, regional and national level; and 2) a comparative multiple case study, including Portugal, building a framework for sustainable citizen engagement, published in the WHO Handbook ‘Voice, Agency, Empowerment: The Handbook on Social Participation for UHC’. Both projects show striking similarities in findings, and developed guidance for devising collaborative action through (a) the use of community platforms, (b) concrete engagement mechanisms and (c) mediating civil society organizations. These will be brought together in a Guidance Tool that participants will work with in the exercise. The aim of the tool is to support initiatives to bring together both top-down participatory efforts and bottom-up grassroots movements in order to anchor community and minority voices into policy decision-making for a more level playing field for policy influence. The aim of the workshop is to let participants experiment with the Guidance Tool and develop collaborative design-as-policy skills. The outline of the skills building exercise: 1. Group introductions using Mentimeter and invitation to pick a particular complex health issue from participants’ own work or community setting (5 mins). 2. Three pitches on the projects, the Portugal case and the Guidance Tool (10 mins). 3. Exercise instructions (5 mins). 4. Exercise (35 mins) a. Upon room entrance participants receive a colored badge based on their professional background: public health professional/practitioner, community resident, researcher or policymaker; b. Form small sub groups of 6-8 participants with different backgrounds (2 mins); c. Introduce with key words on paper their respective complex community health issues and sub group jointly selects one issue for which most information and experience is present (6 mins); d. First round in duos within sub group: participants work through the guidance steps to an initial idea for the collaborative action approach consisting of a community platform, engagement mechanisms, and mediating civil society organizations, drawn out on paper (10 mins); e. Second round in duos within the sub group: duos review another duos initial design idea and conduct an intuitive SWOT analysis of feasibility, acceptability, and practicability (8 mins); f. Third round in sub group: compare the three proposals in SWOT perspective, select the most salient one, and improve with strong elements from other proposals (8 mins); g. Summarize in key words the final proposal and enter into Mentimeter. 5. Plenary wrap up using Mentimeter: select the winning proposal, and evaluate the exercise (5 mins). Key messages • Collaborative action is enhanced considerably through (a) the use of community platforms, (b) concrete engagement mechanisms and (c) mediating civil society organizations. • The Guidance Tool offers concrete steps for designing a reflexive and adaptive structure and process for community collaborative action and self-governance. Speakers/Panelists Marleen Bekker Wageningen University & Research, Wageningen, Netherlands Dheepa Rajan WHO, Brussels, Belgium Goncalo Figueiredo Augusto National Health Council, Lisbon, Portugal

A Review on Research Progress of Corrosion Resistance of Alkali-Activated Slag Cement Concrete.

China is the largest producer and user of Ordinary Silicate Cement (OPC), and rapid infrastructure development requires more sustainable building materials for concrete structures. Portland cement emits large amounts of CO2 in production. Given proposals for "carbon peaking and carbon neutralization", it is extremely important to study alternative low-carbon cementitious materials to reduce emissions. Alkali-activated slag (AAS) cement, a new green cementitious material, has high application potential. The chemical corrosion resistance of AAS concrete is important for ensuring durability and prolonging service life. This paper reviews the hydration mechanism of AAS concrete and discusses the composition of hydration products on this basis, examines the corrosion mechanism of AAS concrete in acid, sulfate, and seawater environments, and reviews the impact of its performance due to the corrosion of AAS concrete in different solutions. Further in-depth understanding of its impact on the performance of concrete can provide an important theoretical basis for its use in different environments and provides an important theoretical basis for the application of AAS concrete, so that we can have a certain understanding of the durability of AAS concrete.

Spontaneous symmetry breaking, gauge hierarchy, and electroweak vacuum metastability

The so-called metastability bound asserts that an unnaturally small Higgs mass is a necessary condition for electroweak vacuum metastability, offering a new approach toward solving the hierarchy problem. So far, this result relies on the assumption of a negative Higgs mass parameter, or equivalently, on electroweak spontaneous symmetry breaking. We derive a new, corresponding bound for the case of a positive mass parameter. When the new bound is significantly more restrictive than or comparable to its established counterpart, it may offer an explanation for the sign of the Higgs mass parameter, and thus, spontaneous symmetry breaking itself. New physics at scales O(1–10) TeV can lower these bounds as far as the TeV scale. As an illustration, we consider vacuum stability in the presence of additional TeV-scale fermions with Yukawa couplings to the Higgs, as well as a dimension-six term parametrizing new physics in the UV. This scenario requires new physics that couples strongly to the Higgs, and can potentially be probed at future colliders. Finally, to allow for comparison with concrete mechanisms predicting metastability, we provide the mass-dependent lifetime of the electroweak vacuum for this model. Published by the American Physical Society 2024

Advanced monitoring of damage behavior and 3D visualization of fiber distribution in assessing crack resistance mechanisms in steel fiber-reinforced concrete

This study presents a novel approach to understanding the reinforcing mechanisms of steel fiber-reinforced concrete, particularly its crack resistance and toughening effects. By integrating dynamic surface strain monitoring with advanced three-dimensional visualization techniques, new insights are provided into how steel fibers enhance concrete's structural performance. X-ray computed tomography (CT) technology enabled detailed 3D visualization and analysis of steel fibers embedded within the concrete matrix, facilitating an in-depth examination of their distribution patterns, orientation, and positioning. Additionally, the Digital Image Correlation (DIC) three-dimensional full-field strain measurement system was utilized to dynamically monitor the loading process during three-point bending tests on semicircular concrete specimens. The findings indicate that the uniform distribution of steel fibers significantly reduces stress concentration and effectively delays crack initiation and propagation. Steel fibers bridge cracks, mitigate local stress concentrations, and substitute for the tensile components of concrete after macro-crack formation, thereby inhibiting further crack propagation. Quantitative analysis of fiber distribution through 3D image reconstruction and coordinate extraction confirmed a strong correlation between fiber orientation and crack resistance. This study contributes to the field by offering a comprehensive analysis of key parameters such as fracture process strain monitoring, 3D visualization, and quantification of fiber distribution, advancing the understanding of crack propagation mechanisms and failure processes in fiber-reinforced concrete.

Investigating the Role of Adaptivity in Video Games for Attitude Change

Video games have become one of the most widespread forms of media in the 21st century, bringing interactive digital narratives to over 3 billion people globally. Like other media, video games feature topics from our society, culture, and history. Research has shown that narrative-driven video games have a unique potential to influence explicit and implicit attitudes toward the topics they depict. However, the concrete mechanisms through which video games shape our attitudes remain unclear. Identifying the mechanisms behind the attitude-shaping effect would help to design more effective educational games and simulations. One aspect that reduces the potential of video games to change attitudes is a so-called credibility bias, a phenomenon where information contradicting one’s pre-existing beliefs is deemed less credible. For this reason, our work focuses on employing adaptivity to improve the attitude-shaping effect of video games. We hypothesize that adapting gameplay elements based on players’ pre-existing attitudes will mitigate the credibility bias, leading to greater attitude changes and enhanced game enjoyment compared to a static presentation. We propose assessing players’ attitudes before playing and adapting the game content accordingly, utilizing in-game metrics to track players’ actions to further refine the content. This work focuses on adapting highlights in user interfaces, narrative-related messages, and in-game goals. To empirically test our hypothesis, we have developed two versions of a video game – an experimental version featuring adaptive game elements and a control version with static content. For this proof-of-concept experiment, we have chosen the topic of electromobility, but we designed the adaptive elements to be usable with any topic. The experimental game is a delivery manager simulator featuring electric and combustion engine cars, with the aim of showcasing the usability and advantages of electric cars. Our experimental design involves a pretest-posttest setup with an experimental and a control group. We utilize measures for implicit and explicit attitudes and game enjoyment. This empirical study will bring valuable data reacting to the identified research gap. Should the adaptive approach prove to be usable, it could be widely utilized to improve the attitude-shaping potential of educational games.

Study on the deterioration mechanism of hybrid basalt-polypropylene fiber-reinforced concrete under sulfate freeze-thaw cycles

This paper focuses on the deterioration mechanism of hybrid basalt-polypropylene fiber-reinforced concrete (HBPRC) under the coupling of sulfate freeze-thaw cycles. The changes in the macroscopic properties of HBPRC under the influence of different volume contents of basalt fiber (BF), polypropylene fiber (PF) and hybrid BF-BF were investigated. The microstructure of HBPRC was characterized using the nuclear magnetic resonance (NMR) technique, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the deterioration models of the BF- matrix interfacial transition zone (BF-ITZ) and the PF- matrix interfacial transition zone (PF-ITZ) in HBPRC were developed. The results showed that the fibers effectively reduced the cracking and macroscopic property damage induced by sulfate freeze-thaw cycles as the number of freeze-thaw cycles increased. When both BF and PF volume contents are mixed at 0.05 %, they can produce complementary effects, and their formation of a uniformly distributed three-dimensional mesh structure is more conducive to reducing the damage to the concrete, and their relative dynamic modulus of elasticity and compressive strength after 300 times of sulfate freeze-thaw cycles were increased by 67.10 % and 46.92 % compared with control concrete. At the same time, the addition of fibers resulted in a more stable evolution of the pore structure of the concrete, and the porosity of the specimens with fibers added at a volume admixture of 0.05 % and 0.1 % was reduced by 13.69–21.35 % after 300 cycles of sulfate freeze-thaw cycling, compared with control concrete. From the BF-ITZ and PF-ITZ deterioration models, it was concluded that the differences in the bonding performance of BF and PF to the concrete matrix affected the degree of frost damage to which they were subjected to coupling and the efficiency of salt solution replenishment, which in turn led to differences in the damage of each group of HBPRC. The reliability of the model was further verified by SEM observation of the morphological changes of different fiber-matrix ITZs before and after sulfate freeze-thaw cycles.

Research on mechanical properties and microscopic mechanism of multi-based geopolymer concrete under combined action of pre-curing and nano-silica

In order to study the combined action of curing conditions and nano-silica (NS) on geopolymer concrete (GPC), the multi-based geopolymer concrete (FSSGC) was prepared with fly ash (FA), slag (SG) and steel fiber (SF), the experiments were carried out in three stages. Firstly, the mechanical properties of FSSGC was tested by monofactor analysis, with pre-curing temperature (20, 40, 60, 80, and 100 °C) and pre-curing time (6, 12, 18, 24, 30, and 36 h) as parameters. The compressive strength and splitting tensile strength initially increased and then decreased with the increase of parameters, and there was an optimal value for subsequent experimental research (80 °C and 18 h). Secondly, the effects of NS content (0, 0.5, 1.0, 1.5, and 2.0 wt%) on the mechanical properties of FSSGC under different curing conditions were analyzed. The results indicated that the mechanical properties of the FSSGC exhibited a trend of initially increasing and then decreasing with the increase of NS content, with the optimal mechanical performance observed under the combined action of high-temperature pre-curing conditions and the incorporation of NS (1.0 wt%). Thirdly, X-ray diffraction, scanning electron microscopy, image analysis, and microhardness tests had been conducted, and the results were consistent with the mechanical properties. The pre-curing temperature affected the rate of geopolymerization, while the pre-curing time influenced the degree of geopolymerization by maintaining this rate. The small particle size and high Young's modulus of the NS effectively filled pores and inhibited the propagation of microcracks. High-temperature pre-curing enhanced the nucleation effect and pozzolanic effect of NS, resulting in a combined action that formed a denser microstructure in the matrix and interfacial transition zone (ITZ).

Mechanical behavior and microscopic damage mechanism of hybrid fiber-reinforced geopolymer concrete at elevated temperature

Geopolymer concrete (GPC) that is prepared from eco-friendly materials exhibits much more excellent resistance on high temperature compared with ordinary Portland cement concrete. In this study, hybrid fibers containing varying proportions of steel fiber (0.5%-2.0%) and polyvinyl alcohol (PVA) fiber (0.2%-0.8%) were incorporated in GPC. The hybrid fiber-reinforced geopolymer concrete (HFRGC) was subjected to temperatures ranging from 200 °C to 800 °C. The physical properties tests, mechanical properties tests, and microstructure tests of HFRGC were carried out at elevated temperatures, while the environmental impact and cost-effectiveness of HFRGC were assessed. The results of physical properties tests showed that the appearance and mass loss of the HFRGC were mainly affected by temperature, while hybrid fibers had a negligible effect on both. The appearance of HFRGC gradually transformed from gray to brick red with increasing temperature, and the mass loss of HFRGC at 800 °C was as high as 9.4%. The mechanical performance test results indicated that the mechanical strength of HFRGC increased at 200 °C and then decreased with elevated temperature. At 200 °C, the compressive strength, splitting tensile strength, and flexural strength of HFRGC containing 1.5% steel fibers and 0.6% PVA fibers were respectively increased by 13.1%, 14.7%, and 4.4% as compared with ambient conditions. The microstructure test results showed that further geopolymerization at 200 °C promoted the densification of the matrix. The matrix was damaged at higher temperatures violently while the porosity of HFRGC was dramatically increased from 13.35% at 25 °C to 27.83% at 800 °C. Based on the thermal behavior, environmental impact, and cost-effectiveness of HFRGC, a reference for future research in the fire prevention of GPC was provided.

Confinement Mechanism of Basalt TRM-Confined Concrete: The Role of the Mortar Matrix

Confinement Mechanism of Basalt TRM-Confined Concrete: The Role of the Mortar Matrix

Experimental study on constitutive relation of coal gangue coarse aggregate concrete under uniaxial compression

As an efficient method for utilizing coal gangue (CG), concrete incorporating coal gangue as coarse aggregate has significantly reduced the reliance on natural aggregates, offering substantial environmental and economic benefits. In this study, coal gangue concrete was prepared with coal gangue replacement rates of 0, 20, 40, 60, 80, and 100%, and mechanical tests under unconfined compression were conducted to evaluate the stress-strain behavior and failure mechanism of coal gangue coarse aggregate concrete (CGC). Utilizing scanning electron microscope (SEM) microscopic characterization, the microscopic failure mechanism of CGC was further elucidated. With increased coal gangue replacement, the CGC's uniaxial compression failure mode shifts from shear to longitudinal splitting failure. The slope, peak stress and elastic modulus of the stress–strain curve's rising section are negatively correlated with the coal gangue content, while the falling section's slope, peak strain and ultimate strain are positively correlated. Next, building upon the classical constitutive model, we adjust the constitutive parameters utilizing the uniaxial compressive strength and coal gangue content. Finally, we introduce a predictive model for the CGC's constitutive compressive behavior across various content levels. There is a notably high agreement between the model and experimental data.

Drying-Wetting Correlation Analysis of Chloride Transport Behavior and Mechanism in Calcium Sulphoaluminate Cement Concrete.

In response to rising CO2 emissions in the cement industry and the growing demand for durable offshore engineering materials, calcium sulphoaluminate (CSA) cement concrete, known for its lower carbon footprint and enhanced corrosion resistance compared to Ordinary Portland Cement (OPC), is increasingly important. However, the chloride transport behavior of CSA concrete in both laboratory and marine environments remains underexplored and controversial. Accordingly, the chloride ion transport behaviors and mechanisms of CSA concrete in laboratory-accelerated drying-wetting cyclic environments using NaCl solution and seawater, as well as in marine tidal environments, were characterized using the rapid chloride test (RCT), X-ray diffraction (XRD), mercury infiltration porosimetry (MIP), and thermogravimetric analysis (TGA). The results reveal that CSA concrete accumulates more chloride ions in NaCl solution than in seawater, with concentrations 2-3.5 times higher at the same water-cement ratio. Microscopic analysis indicates that calcium and sulfate ions present in seawater facilitate the regeneration of ettringite, thereby increasing the density of the surface pore structure. The hydration and repair mechanisms of CSA concrete under laboratory conditions closely resemble those in marine tidal conditions when exposed to seawater. Additionally, this study found that lower chloride ion concentrations and pH levels inhibit the formation of Friedel's salt. Therefore, laboratory experiments with seawater can effectively simulate CSA concrete's chloride transport properties in marine tidal environments, whereas NaCl solution does not accurately reflect actual marine conditions.

Exploring cement content's impact on self-healing in super absorbent polymer-modified concrete

This study shows the impact of varying cement content while maintaining a constant water-to-cement (w/c) ratio on the performance of self-healing concrete. It also explores the effect of F-type fly ash on the self-healing mechanism of concrete. Self-healing concrete, incorporating super absorbent polymers, offers a viable remedy to diminish the detrimental effects of cracks, enhancing the durability and lifespan of concrete structures. While the w/c ratio is a crucial factor influencing concrete properties, the impact of varying cement content under a constant w/c ratio in self-healing concrete remains understudied. Therefore, this experiment involved preparing 18 different concrete mixtures using three distinct cement contents under three specific w/c ratios. Fly ash was mixed in half of the specimens. Super absorbent polymers are incorporated into all mixtures to facilitate autonomous healing by absorbing and retaining water, which is released upon crack formation. Specimens were pre-cacked using a stress-controlled UTM machine. To evaluate the self-healing mechanism, low water pressure permeability test, water absorption test, and image analysis were conducted at 7, 14, 28, and 56 days. The findings of this study show that a w/c ratio of 0.35 yielded the best performance which indicates a lower w/c shows a higher self-healing performance. Additionally, the specimen containing a higher cement content exhibited enhanced healing capacity compared to other specimens. However, the specimens with fly ash failed to show a satisfactory result on self-healing capacity because the addition of silicon-based fly ash (F type) created an adverse effect on the self-healing mechanism.

CT imaging‐enhanced numerical simulation of microscopic structure and resilient safety of asphalt concrete

AbstractAsphalt concrete is a foundational material in water conservancy projects, serving a critical function in the construction of impermeable structures such as dams. The seismic response characteristics and resilient safety of concrete dams are heavily influenced by the arrangement and evolution of the microscopic structure of the dam material. In this study, a high‐precision computed tomography (CT) scanning technique, in conjunction with advanced numerical simulations, was employed to analyze the internal damage and crack extension mechanism of asphalt concrete. Microstructural images of the asphalt concrete specimen were accurately captured by CT scanning, followed by the construction of corresponding numerical models. Presented simulation results show that the displacement deformation of asphalt concrete reaches its maximum value in the top region of the model and subsequently decreases with depth. Material damage was first observed at the interface between aggregate and asphalt matrix, where microcracks emerge and extend to the entire asphalt matrix, resulting in a gradual deterioration of the model performance. The simulation results indicate that the overall strength of asphalt concrete is primarily influenced by the strength characteristics of its aggregates. The stress–strain curves obtained from the numerical simulations exhibit a hyperbolic relationship, which is in high agreement with the physical test results. This study not only enhances our comprehension of the mechanical behavior of concrete but also contributes to the analysis of seismic response and risk assessment in dam engineering through dynamic experimental testing and numerical simulation.

Progress in Researching the Ability of Geopolymer Concrete to Withstand a Penetration of Chloride Ions

Geopolymer concrete is an innovative environmentally friendly construction material, and the transportation of chloride ions plays a crucial role in determining its durability. This study provides a summary of the characteristics and limitations of the test techniques used to measure the resistance of geopolymer concrete to the permeability of chloride ions, based on the introduction of the chloride ion transport mechanism in geopolymer concrete. This text provides an overview of the features and constraints of the test techniques used to assess the resistance of geopolymer concrete to chloride ion permeability. It also explores the connections between the mechanism of chloride ion transport and the resistance of geopolymer concrete to chloride ion permeability. This paper provides a concise overview of the properties and constraints of the test methods used to measure the resistance of geopolymer concrete to chloride ion permeability. It also discusses the factors that can affect the chloride ion permeability resistance of geopolymer concrete and presents a comparison between different methods. The article continues by highlighting that the chloride transport model of geopolymer concrete is complex. The essay continues by highlighting the chloride transport model of geopolymer concrete, specifically focusing on the impact of individual parameters such as high temperature, freezing-thaw cycles, and the resistance of geopolymer concrete to chloride ion permeability. The study investigates the impact of freeze-thaw cycles, alkali admixture, and water glass modulus on the resistance of geopolymer concrete to chloride penetration. The infiltration of chloride, as well as the precision of determining the concentration border of chloride ions for colour rendering, require further in-depth investigation.

Fracture evolution characteristics of asphalt concrete using digital image correlation and acoustic emission techniques

The cracking damage of asphalt concrete significantly affects the service life of pavement. The objective of this research is to investigate fracture mechanisms of asphalt concrete by employing a synergistic approach combining digital image correlation (DIC) and acoustic emission (AE) techniques under three-point bending tests. Firstly, the crack tip opening displacement (CTOD) and the fracture process zone (FPZ) derived from DIC were utilized to classify fracture stages and describe the entire crack propagation process. Meanwhile, AE-related parameters were applied to detect the internal damage and fracture characteristics. Subsequently, the results from DIC and AE were utilized for comparative analysis to evaluate the cracking resistance of different materials. Finally, the fractal dimension and AE b-value were used to distinguish the characteristics of the critical damage conditions. The results indicated that both techniques are effective in classifying the fracture stage of asphalt concrete. DIC can visualize and analyze crack propagation processes and paths on concrete surfaces, especially at the stage of macrocrack initiation and propagation. AE allows for continuous monitoring and highly sensitive detection of early-stage damage inside concrete. The distinct advantages of DIC and AE result in different fracture stage identification results at the early stage, but consistent after the appearance of macrocracks. Based on the relationship between CTOD and AE cumulative count, a simple approach is proposed to directly evaluate the cracking resistance of different asphalt concretes. The formation of macrocracks in asphalt concrete can be reflected by a shift where the correlation dimension drops steeply to the minimum value, and a minimum inflection point in the AE b-value curve acts as a precursor of complete fracture. The research offers an in-depth insight of both surface deformation and internal damage, thus enhancing the understanding of crack growth behavior and fracture process in asphalt concrete.

Study of Damage Mechanism and Evolution Model of Concrete under Freeze–Thaw Cycles

Researching the mechanical characteristics of concrete subjected to the freeze–thaw cycle is crucial for building engineering in cold climates. As a result, uniaxial compression tests were performed on concrete samples exposed to various freeze–thaw (F–T) cycles, and the measurements of the pore size distribution, porosity, and P-wave velocity of the saturated concrete samples were obtained, both before and after being exposed to the F–T cycles. Concrete’s F–T damage mechanism and damage evolution model were thoroughly examined. Using rock structure and moisture analysis test equipment to observe the T2 spectrum, the results showed that the F–T cycles can cause the internal structure of the samples to deteriorate. Porosity and F–T cycles have a positive correlation, although P-wave velocity has a negative correlation with the F–T cycles. As the F–T cycles increased, the specimens’ peak strength and elastic modulus steadily declined, while the peak strain clearly exhibited an increasing trend. A microscopic F–T damage model that takes into account the pore size distribution was developed, based on the relative changes in the pore structure distribution (PSD), before and after the F–T cycles. The concrete sample damage evolution law under various F–T cycles was examined using the following metrics: total energy, pore size distribution, static and dynamic elastic moduli, porosity, and P-wave velocity. Uniaxial compressive strength (UCS) and peak strain tests were used to evaluate the accuracy of the pore size distribution damage model, as well as that of five other widely used damage models.

Study on mechanical properties and corrosion damage mechanism of mixed sand concrete

In order to address the excessive utilization of river sand resources in Inner Mongolia, an investigation is being conducted on the utilization of wind-blown sand and machine-made sand for the production of mixed sand concrete. A study is conducted to examine the influence of including mixed sand in concrete on its mechanical qualities, working performance, and erosion resistant durability. The findings suggest that when the proportion of wind-blown sand in the mixed sand mixture increases, the compressive strength of the mixed sand concrete exhibits a general pattern of initially increasing and subsequently dropping. At a ratio of 1:1 between wind-blown sand and machine-made sand, there is a maximum point. Nevertheless, the capacity for stretching under tension, resilience, and the strength of the connection all demonstrate a consistent decline. The wind-blown sand content of 50 % in the mixed sand is the critical value. When the wind-blown sand content exceeds 50 %, the tensile deformation capacity, toughness, and bond strength experience a steep decline. Utilizing a combination of different types of sand diminishes the efficiency of concrete. Nevertheless, the efficacy of concrete can be enhanced by modifying the water-cement ratio and the quantity of water-reducing admixtures. It is worth mentioning that although the work performance can be improved, there might be a little reduction in the mechanical qualities of the concrete. The erosion depth in mixed sand concrete has a growth rate that is 0.027 mm/d lower compared to ordinary river sand concrete under erosion conditions. The compressive erosion resistance coefficient and saturated surface dry water absorption rate show significantly reduced damage in mixed sand concrete compared to standard river sand concrete. Moreover, when erosion-freeze-thaw coupling circumstances are present, the structural deterioration of mixed sand concrete is less significant in comparison to ordinary river sand concrete. By using a mixture of sand, the concrete's ability to withstand erosion is improved, resulting in a longer lifespan. This discovery establishes a theoretical foundation for the secure utilization of concrete in aquatic environments in Inner Mongolia.