To achieve the resource utilization of waste ceramic particles and promote the application of recycled concrete in cold regions, this study systematically investigates the effects of waste ceramic particle replacement ratios on the freeze-thaw resistance and service reliability of recycled concrete. Six groups of specimens with ceramic particle replacement ratios of 0%, 20%, 40%, 60%, 80%, and 100% were designed. Freeze-thaw cycle tests were carried out using the rapid freezing method, with mass loss rate and relative dynamic elastic modulus as the key evaluation indicators to determine the optimal mix proportion. Scanning electron microscopy (SEM) was used to observe the evolution of the microstructure, and a reliability function was established based on the Wiener distribution probability model to predict the remaining service life of the optimally proportioned specimens. The results show that during freeze-thaw cycles, the relative dynamic elastic modulus of all specimens decreases continuously, while the mass loss rate exhibits a variation trend of initial increase followed by subsequent decrease. The specimens with a 20% ceramic particle replacement ratio demonstrate the best freeze-thaw resistance, failing only after 398 freeze-thaw cycles. Microstructural analysis reveals that at early freeze-thaw cycles, the damage is dominated by the deterioration of the surface interfacial transition zone (ITZ), whereas at high cycles, severe degradation occurs, including pore connectivity and the collapse of the cementitious network formed by hydration products. When the ceramic particle replacement ratio exceeds 20%, the freeze-thaw resistance of the specimens decreases significantly. This study reveals the freeze-thaw deterioration mechanism of recycled concrete incorporating waste ceramic particles as aggregates, and the findings provide a theoretical basis and technical support for the mix optimization and engineering application of such recycled concrete in cold regions.

Regression equation analysis of dynamic and static elastic modulus and Poison's ratio of Paleogene sandstone reservoirs in Zhanhua sub-sag, Bohai Bay Basin

Cyclic freezing and thawing (FT) are a primary cause of cracking in concrete, yet current assessment procedures in Germany rely heavily on qualitative estimation using the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) capillary suction, internal damage and freeze-thaw (CIF) and Capillary de-icing freeze-thaw (CDF) tests. Although these standard tests provide a general overview of the condition of concrete damage in specimens through the estimation of water saturation through capillary suction, mass of surface delamination, qualitative open surface damage, and relative dynamic modulus of elasticity, they do not take quantitative analysis of voids, including cracks and air pores, directly into account. To address this, we propose a novel workflow utilizing deep learning-based semantic segmentation with Fourier-based slice-to-volume registration by combining 2D light microscopy (LM) of petrographic sections and 3D micro-computed tomography (μCT). We segment cracks, air pores, and aggregates in both modalities and employ feature matching alongside spatial harmonics analysis for 3D shape description. The best proposed 3D registration framework through feature matching demonstrated a success rate of 89.75%, achieving a dissimilarity of 5.21% in relative root mean square error (RRMSE) terms and thereby significantly surpassing the performance of compared 2D-only methods adapted from the body of research. Our approach enables precise, automated, and verifiable quantification of voids across CT and LM modalities and paves the way for advanced computational modeling-based methods to investigate moisture transfer mechanisms for more accurate assessments of frost damage in concrete, service life prediction models, deep learning applications for multimodal data fusion, and more comprehensive FT damage simulations.

To analyze the characteristics of acoustic emission (AE) and electromagnetic radiation (EMR) signals in specimens with different water contents during impact loading, impact tests were conducted on sandstone under dry, natural, and saturated conditions using the split Hopkinson pressure bar (SHPB) system. The results show that water reduces the dynamic compressive strength and elastic modulus of sandstone, changes the failure mode from tensile failure to tensile-shear failure, and increases the amount of small-sized fragments after failure. AE and EMR signals effectively reflect the entire deformation process of specimens with different water contents under impact loading. In the elastic stage, only EMR signals appear, indicating that EMR is more sensitive to crack generation. In the yield stage, the AE signal count and energy increase sharply, indicating that the response to specimen failure is better. By comparing AE and EMR signals at different stages, it was found that water inhibits both the propagation and energy of AE and EMR signals. The damage factor D, quantified by AE and EMR counts, accurately represents the damage suffered by specimens with different water contents during impact loading. This study significantly advances the understanding of failure mechanisms in specimens with varying water contents and contributes to practical engineering monitoring of water-bearing rock mass stability.

Abstract 3D-printed concrete (3DPC) construction has gained global attention as an innovative and promising technique. However, the high cement content in 3DPC raises sustainability concerns, presenting a challenge for implementing sustainable processes. To address the issue, this research uses a low water-to-binder (w/b) ratio and incorporates silica fume (SF) and fly ash (FA) as partial cement replacements to reduce cement consumption and enhance sustainability. Three w/b ratios (0.33, 0.35, 0.37) and varying superplasticizer (SP) doses (0%, 0.25%, 0.5%, 0.75%, 1%) were tested, with 10% SF and 20% FA. The study investigated the physical, chemical, and morphological properties of the mix, alongside fresh, hardened, and durability properties, including workability, dry bulk density, compressive strength, dynamic modulus of elasticity, water absorption, and sulfate resistance. The results showed that a higher w/b ratio increased workability, with the w/b 0.37 mix exhibiting 50.71% higher workability than the w/b 0.33 and 45.09% higher than the w/b 0.35 for SP0 at 0 min. Besides, both a lower w/b ratio and increased SP content improved dry bulk density, compressive strength, and dynamic modulus of elasticity, with performance peaking at a 0.5% SP dosage in mix SP2. Additionally, reducing the w/b ratio decreased water absorption from 5.54% at 0.37 to 4.22% at 0.33 and lowered mass loss across all mixes; notably, the 0.33 mix with SP2 achieved the lowest mass loss (0.89%) and strength loss (3.12%). Despite these improvements, the use of SP increased production costs by 14.32%, while $$ {CO}_{2}$$ emissions rose only slightly by 0.89%.

Experimental determination of dynamic and static elastic modulus of high-performance lightweight concrete

The ultrasonic pulse velocity (UPV) method is widely used for determining the dynamic modulus of elasticity of concrete. Traditionally, this approach requires assuming Poisson’s ratio (arbitrary values ranging from 0.1 to 0.25), regardless of the actual properties of the tested material. Such assumptions can lead to inaccurate estimations of the elastic modulus and limit the reliability of the method. In this study, an experimental methodology is proposed to enhance the accuracy of the estimation of the elastic modulus of concrete by combining digital image correlation (DIC) with UPV testing. The DIC technique is used during axial compression tests to directly measure the Poisson ratio of cubic concrete samples, while the dynamic modulus of elasticity is determined through UPV measurements. Subsequently, conversion models from the literature were applied to estimate the static modulus of elasticity from the dynamic modulus. The obtained values are compared with the experimental measurements of the static modulus, showing strong consistency and validating the proposed approach. The results highlight two key findings: (i) incorporating the actual Poisson ratio of the material significantly improves the precision of modulus predictions obtained via UPV, and (ii) DIC provides a reliable and adaptable tool for measuring Poisson’s ratio in concrete. Overall, the integration of DIC and UPV offers a robust and non-destructive framework for improving the assessment of mechanical properties of concrete.

Thermally modified wood is primarily used in exterior applications due to its enhanced resistance to biotic degradation. However, reduced mechanical performance limits its structural use. This study investigates the structural potential of high-temperature-treated European beech timber (Fagus sylvatica, L.) and evaluates its mechanical properties and grading models for structural design. Timber from 32 beech logs was air-dried and divided into untreated (NoTMW) and thermally modified (TMW) groups. Thermal modification was carried out commercially in an oxidizing atmosphere at 190 °C. All specimens were visually graded according to DIN 4074-5 and assessed using acoustic non-destructive methods before testing in four-point bending following EN 408. Modulus of elasticity (MOE), modulus of rupture (MOR), and density were determined, and characteristic values were calculated according to EN 384. On average, TMW exhibited a 17% reduction in bending strength compared to untreated wood, while both static and dynamic MOE were not significantly affected. The multiple regression model only slightly improved bending strength prediction compared with single linear regression based on global modulus, as the R2-value increased from 17% to 19%. The prediction of stiffness of thermally treated beech timber was greatly improved by combining local and acoustic moduli, explaining 76% of the total variation.

Experimental results are compiled to show apparent hysteresis seen in hydride thermal precipitation–dissolution cycling in zirconium alloys using X-ray diffraction, dynamic elastic modulus techniques, and differential scanning calorimetry (DSC). Gibbs’ phase rule is used to justify a description of a stable hydride in the H-Zr system in terms of a control volume with a hydride at its core, surrounded by a stress gradient that produces a stabilizing gradient of hydrogen in the solution. The conditions for a stable hydride are derived when the flux of hydrogen in solid solution is zero. DSC heat flow curves are analyzed with a thermodynamic model that predicts concentrations of hydrogen in a solution during temperature cycling and a description of experimental results that show how concentrations evolve at a constant temperature to the same final state when cycling is paused, from which hysteresis is deemed an illusion. The control volume is supported by previous energy calculations, performed with density functional theory. Implications of replacing the order parameter for phase field methods with the gradient of the yield stress are discussed. A practical method for forming a stable hydride is presented.

The main objective of this study was to investigate the relationships between stress-wave velocity measured in logs and small clear specimens and the bending strength of Pinus massoniana trees planted in northern Vietnam. Stress-wave velocity (SWVL) and green wood density (WDL) were measured on logs collected from different heightlevels of 23-year-olds P. massonianatrees. Stress-wave velocity (SWVS), wood density (WDS), and bending strength (MOR) were subsequently determined on small clear specimens prepared from the logs. Regression analyses revealed significant correlations between SWVL and MOR (r = 0.73, P < 0.001) and between SWVS and MOR (r = 0.80, P < 0.001). These results show that stress-wave velocity measurements, whether taken on logs or small specimens, are effective for segregating P. massoniana lumber resources based on MOR. A more accurate prediction of strength was obtained when stress-wave velocity and log or specimen wood density were used together to calculate the dynamic modulus of elasticity of logs (DMOEL) or specimens (DMOES), respectively. The correlation coefficients were 0.82 (P < 0.001) between DMOEL and MOR, and 0.93 (P < 0.001) between DMOES and MOR.

The paper investigates an assessment of mechanical strength in relation to dynamic and static MOE of Antrocaryon micraster stemwood from the semi-deciduous ecological zone in Ghana. The objective was to assess the strength variation of Antrocaryon micraster stemwood along the axial direction, using destructive and non-destructive methods. Antrocaryon micraster stemwood that was divided into bottom, middle and top positions were prepared for the study. The results reveal that the stemwood bottom position obtained maximum density (530.43 kg/m³) representing 10% and 16.02% higher when compared to other corresponding positions (middle and top) respectively. For stemwood along the axial direction, the static MOE mean values were 18.54%, 22.82%, and 27.48% more than the dynamic MOE obtained in the bottom, middle and top positions, respectively. At 1% and 5% levels of significance, the position of the stemwood along the tree height has a significant effect on dynamic MOE and static MOE. Statistical evaluation with regression and Pearson correlation also indicates positive relationship with the variability of 50.4% and 71%, respectively. In a whole, the mechanical behaviour of the Antrocaryon micraster stemwood, especially the bottom position along the axial plane is considered wealthy to be selected for furniture applications.

Aim of study: Analyze the behavior and predictive capacity of different non-destructive testing (NDT) methods—ultrasound, longitudinal and transverse vibrations, and static bending— for estimating the MOEGTO in two species of great forestry interest in Europe: Pinus sylvestris and Populus × euramericana. Additionally, this study focuses on developing global prediction models for MOEGTO using the NDT modulus of elasticity from both species, and on improving the reliability of prediction through the cross-validation process. Area of study: Provenance Region 8 (Northern Iberian System, Spain) and Ribera del Carrión (Palencia, Spain). Material and methods: A total 75 sawn lumber samples (45 of Pinus sylvestris and 30 of Populus x euramericana) with dimensions of 60 × 40 × 1200 mm were analyzed using ultrasonic testing, longitudinal and transverse vibration methods, and both destructive and non-destructive static bending tests performed with a universal testing machine. Regression models were developed to predict the static modulus of elasticity (MOEGTO). Main results: The prediction model using the NDT method of longitudinal vibrations with Fast Fourier Transform (FFT) software for Pinus sylvestris showed the highest coefficient of determination with R2= 0.56, while for Populus × euramericana, the ultrasound method with the Sylvatest 4 device yielded R2= 0.67. For both species, the best-fit global prediction model was obtained with the ultrasound method using the Sylvatest Trio device, achieving R2= 0.60. Additionally, the application of cross-validation improved the predictive performance of the global models, particularly for the three ultrasound methods and the longitudinal vibration method, all of which attained R2 values above 0.6. Research highlights: This study confirms the reliability of ultrasound and longitudinal vibration techniques for estimating MOEGTO and contributes new insights by comparing multiple NDT methods across two species and developing robust cross-validated global prediction models.

To address the freeze-thaw (F-T) durability of concrete structures in severely cold plateau regions, this study investigates recycled coarse aggregate concrete (RCAC) by designing mixtures with varying replacement ratios of recycled brick aggregate (RBA). Rapid freeze-thaw cycling tests are conducted in combination with macro- and microscale analytical techniques to systematically elucidate the frost resistance and damage mechanisms of mixed recycled coarse aggregate concrete. When the RBA content is 50%, the concrete demonstrates relatively better frost resistance within the mixed recycled aggregate system. This is evidenced by the lowest mass loss rate coupled with the highest retention ratios for both the relative dynamic elastic modulus (RDEM) and the compressive strength. Micro-analysis indicates that an appropriate amount of RBA can optimize the pore structure, exerting a “micro air-cushion” buffering effect. Blending RBA with recycled concrete aggregate (RCA) may create functional complementarity between pores and the skeleton, effectively delaying freeze–thaw damage. A GM (1,1) damage prediction model based on gray system theory is established, which demonstrates high accuracy (R2 > 0.92). This study provides a reliable theoretical basis and a predictive tool for the durability design and service life assessment of mixed recycled coarse aggregate concrete engineering in severely cold regions.

ABSTRACT To investigate the dynamic response mechanism of deep mine surrounding rock under complex stress and cyclic impact loading, this study takes granite as the research object and systematically conducts dynamic mechanical tests on samples with different aspect ratios (0.5 and 1) under three‐dimensional cyclic impact loading using a Split Hopkinson Pressure Bar system. The study considers different impact air pressures (0.4, 0.5, and 0.6 MPa) and combinations of pre‐applied axial and confining pressures (simulating in situ stress conditions at depths of 400 and 600 m). The dynamic stress–strain behavior, energy dissipation patterns, damage evolution characteristics, and failure modes of the samples are analyzed. The results indicate that aspect ratio and impact air pressure significantly affect the dynamic peak stress, peak strain, and elastic modulus of the samples. The dissipated energy density increases linearly with the number of impacts, with samples of smaller aspect ratios exhibiting higher dissipated energy. The damage variable increases with the number of impacts, and high confining pressure can inhibit damage development. The failure mode transitions from “tensile‐dominated” to “shear‐composite,” with aspect ratio influencing the crack distribution morphology. Based on energy and strain characteristics, a rockburst propensity index D r is proposed, which comprehensively considers peak stress, peak strain, and energy ratio, and its normalized relationship with the number of impacts is established, providing a theoretical basis for rockburst risk assessment in deep mines.

Extensive research has addressed concrete deterioration and its countermeasures; however, studies on responsive repair methods and materials remain comparatively limited and less systematic. In this study, six mixtures of repair mortars (RMs) were formulated using aluminate-based binders, specifically calcium sulfoaluminate (CSA) and amorphous calcium aluminate (ACA) cements. The experiment evaluated the mechanical properties and freeze–thaw resistance of these mortars. To accelerate hydration, a controlled amount of anhydrite gypsum was incorporated into each mixture. The fluidity and setting time of fresh RMs were measured, whereas the compressive strength, flexural strength, and ultrasonic pulse velocity (UPV) of hardened RMs were evaluated at 1, 7, and 28 days. In addition, freeze–thaw resistance was assessed as per ASTM C666 by determining the relative dynamic modulus of elasticity. Additionally, the hydration products and microstructural characteristics of paste specimens were qualitatively analyzed. The mechanical performance, including strength and UPV, and freeze–thaw resistance of RMs containing ACA were superior to those of RMs containing CSA. In particular, compared to the CSA-containing specimens exposed to freeze–thaw action were significantly deteriorated, the ACA-containing specimens showed excellent resistance with relatively less cracking and spalling. This may imply that ACA is effective as rapid repair materials for concrete structures in cold regions. Microstructural observations revealed variations in hydration products depending on the aluminate binder employed, which significantly influenced the mechanical and durability properties of the RMs. These results may aid the selection of optimal repair materials for deteriorated concrete structures.

Abstract The objective of this study was to evaluate three commercially available self-leveling mortars. Mixing was performed using a Pheso rheometer, which enabled the assessment of mixing efficiency. In the fresh state, the evaluated properties included fluidity, spreadability, rheological parameters, and regeneration time. In the hardened state, flexural tensile strength, compressive strength, and dynamic modulus of elasticity were measured. The results revealed significant variations in mixing efficiency, influenced by the physical characteristics of the mortars. Among all the fluidity and spread tests, the time measured using the Spanish cylinder exhibited the strongest and most consistent correlations. This greater precision was supported by the number of significant relationships observed across physical, mixing, and rheological parameters. The variations found among the mortars demonstrate that each formulation exhibits distinct characteristics, including variations in regeneration time. For example, mortar 1, with a shorter regeneration time, exhibited higher yield stresses and viscosity, with greater flexural strength. This finding highlights that the absence of specific Brazilian standardization require the users of this mortar type to have good knowledge about the material properties to ensure correct application and compliance with project specifications.

Abstract The degradation mechanisms of concrete in bridge structures under prolonged fire exposure represent a critical safety challenge in addressing multihazard environmental interactions. Although existing research predominantly employs single-index assessment systems, these approaches fail to meet the technical requirements for post-fire rehabilitation decision-making. This study proposes a multivariate assessment framework to quantify thermal damage in bridge concrete through systematic experimental investigations. Through in-depth research, the characteristics, causal mechanisms, and degree of sensitivity of damage evaluation indicators with temperature changes were derived. The results of the study indicate that the characteristics of various damage evaluation indices are not only closely related to the absence, decomposition, and interaction of the internal components of concrete at high temperatures, but are also significantly affected by the intrinsic properties of the indices themselves; dynamic elastic modulus (measured by dynamic testing methods that reflect the response of materials to alternating loads or vibrations) and compressive elastic modulus (obtained by uniaxial compression tests that reflect the stress–strain relationship of the material under quasistatic loading) show superior sensitivity, with damage variables reaching 96.80 % and 92.86 %, respectively. at 700°C, demonstrating monotonic degradation patterns; considering the limitations of on-site sampling or testing conditions in practical engineering applications, nondestructive testing (NDT) indicators such as ultrasonic pulse velocity, impact-echo stress wave velocity, and infrared thermal image average temperature rise (69.81 %, 81.47 %, and 62.07 % of damage variables at 700°C, respectively) can be used as alternatives. There may be limitations in the use of these NDT indicators when applied individually, and it is recommended that they be combined with compressive modulus testing results for comprehensive analysis to ensure the accuracy and reliability of damage evaluation outcomes.

Experimental study on dynamic elastic modulus of thawing subgrade sandy loam soil under vibration load

Abstract The particles and dust generated during the processing and crushing of construction waste aggregates continue to pose considerable environmental challenges. To achieve the comprehensive utilization of construction waste in concrete materials, this study investigates the damage evolution characteristics of recycled composite micro-powder concrete (RCMC) under freeze-thaw-bending load coupling. The relative dynamic elastic modulus test, axial compression test and acoustic emission test of RCMC specimens were carried out to analyze their mechanical properties and damage development. Based on the cumulative energy of acoustic emission, an axial compression damage model considering the compaction stage was established. Combined with the initial damage under the freeze-thaw-bending load coupling environment, a segmented damage constitutive model for the whole process of RCMC axial compression was established. The results show that the cumulative energy of acoustic emission can accurately describe the damage evolution law of RCMC specimens. With the intensification of freeze-thaw-bending load coupling, the increase rate of cumulative energy of acoustic emission in the compaction stage gradually increases, and the relative dynamic elastic modulus of RCMC decreases faster. The damage constitutive model established in this paper can accurately reflect the damage characteristics of RCMC specimens under freeze-thaw-bending load coupling environment and axial compression load. These findings not only confirm the reliability of acoustic emission cumulative energy in characterizing RCMC damage, but also provide a theoretical basis for the practical application of the established damage constitutive model in engineering scenarios involving freeze-thaw and bending load coupling.

To address the engineering challenge of durability deterioration in concrete structures in the cold and saline regions in northern China, this study investigated PVA fiber-reinforced concrete under combined sulfate attack and freeze–thaw cycles using PVA fiber volume fractions (0%, 0.1%, 0.3%, 0.5%) and salt-freeze cycles (0, 25, 50, 75, 100, 125, 150 cycles) as key variables. By testing the mechanical and microscopic properties of the specimens after salt-freeze, the degradation law of macroscopic performance and the evolution mechanism of microscopic structure of PVA fiber concrete under different volume fractions are analyzed, and the salt-freeze damage evolution equation is established based on the loss rate of relative dynamic elastic modulus. The results show that the addition of PVA fibers has no significant inhibitory effect on the surface erosion of concrete, and the degree of surface spalling of concrete still increases with the increase in the number of salt-freeze cycles. With the increase in the number of salt-freezing cycles, the mass, relative dynamic elastic modulus and cube compressive strength of the specimens first increase and then decrease, while the splitting tensile strength continuously decreases. The volume fraction of 0.3% PVA fibers has the most significant effect on improving the cube compressive strength and splitting tensile strength of concrete, and at the same time, it allows concrete to reach its best salt-freezing resistance. PVA fibers contribute to a denser microstructure, inhibit the development of micro-cracks, delay the formation of erosion products, and enhance the salt-freezing resistance of concrete. The damage degree D of relative dynamic elastic modulus for PVA fiber concrete exhibits a cubic functional relationship with the number of salt-freeze cycles N, and the correlation coefficient R2 is greater than 0.88. The equation can accurately describe the damage and deterioration law of PVA fiber concrete in the salt-freeze coupling environment. In contrast to numerous studies on single-factor exposures, this work provides new insights into the degradation mechanisms and optimal fiber dose for PVA fiber concrete under the synergistic effect of combined sulfate and freeze-thaw attacks, a critical scenario for infrastructure in cold saline regions. This study can provide theoretical guidance for the durability assessment and engineering application of PVA fiber concrete in cold and saline regions.