Ultrasonic Velocity Research Articles

Density, Viscosity, Refractive Index, Speed of Sound, Molar Volume, Isobaric Thermal Compressibility, Excess Gibbs Activation for Fluid Flow, and Isentropic Compressibility of Binary Mixtures of Methanol with Anisole and with Toluene at 298.15 K and 0.1 MPa

Density, viscosity, refractive index, and ultrasonic velocity were measured for the pure materials anisole, methanol, and toluene, and for the binary mixtures: methanol—anisole and methanol—toluene. Excess molar volume VE, isobaric thermal compressibility α, excess Gibbs activation energy for fluid flow ΔGE*, and excess isentropic compressibility κSE were calculated from the measured quantities. For both binary mixtures VE and κSE were <0 while Δn > 0 and ΔGE* > 0 over the entire mole fraction composition range. Anisole mixtures exhibited more negative values for VE and κSE while more positive values were displayed for Δn and ΔGE* compared to toluene mixtures. For Δη, negative values were observed at low alcohol concentrations but positive values at high alcohol concentrations for both systems.

Evaluating Recycled Concrete Aggregate and Sand for Sustainable Construction Performance and Environmental Benefits

This research investigates the potential of utilizing recycled concrete aggregate (RCA) and recycled sand (RS), derived from crushed concrete cubes, as sustainable alternatives in construction materials. The study comprehensively evaluates the properties of RCA and RS, focusing on workability, impact resistance, abrasion resistance, and compressive strength to determine their viability as substitute construction materials. A notable finding is RS’s enhanced fire and heat resistance when used as a fine aggregate in mortar blends, mixed with cement and Sinicon PP in a 3:1 ratio. The experimental analysis included thorough assessments of uniformity, durability, and curing time, alongside Scanning Electron Microscopy (SEM) for structural examination. Results show that RCA has an Aggregate Impact Value (AIV) of 5.76% and a Los Angeles Abrasion Value (LAA) of 21.78%, demonstrating excellent strength of the recycled aggregates. The mortar mix was also prepared using recycled sand, cement, and Sinicon PP, and its stability was confirmed through soundness tests, which resulted in a 0.53 mm expansion and a satisfactory consistency level of 44%. Ultrasonic pulse velocity (UPV) tests also indicated high-quality concrete formation using RCA and RS. SEM imaging corroborated this by revealing a bond between the cement paste and the aggregates. Incorporating RS and RCA in concrete mixtures impressively yielded a compressive strength of 26.22 N/mm2 in M20-grade concrete. The study concludes that using RCA and RS waste materials in the construction sector underlines that sustainable practices can be integrated without compromising material quality. This approach aligns with sustainable development goals and fosters a more environmentally friendly construction industry.

Engineered Cementitious Composites with Super-Sulfated Cement: Mechanical, Physical, and Durability Performance

This study aimed to bridge a research gap by exploring the utilization of super-sulphated cement (SSC) in engineered cementitious composites (ECCs) as a sustainable alternative to ordinary Portland cement (OPC)-based mixtures. The SSC was designed with slag, gypsum, and a small amount of OPC. The primary objective was to investigate the effects of incorporating SSC, both with and without fly ash (FA), at various FA/SSC ratios between 0 and 1.5. A comprehensive evaluation was conducted to assess the performance of the ECC-SSC mixtures, including the compressive and flexural strengths, ductility, ultrasonic pulse velocity, rapid chloride permeability, and drying shrinkage. Additionally, advanced microstructural evaluation techniques such as scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis as well as X-ray diffraction (XRD) analysis were employed to analyze the reaction products in selected mixtures. The results showed that the ECC mixture produced with SSC exhibited comparable strength to the ECC-OPC. In general, all the SSC-based ECCs fulfilled the criteria for various engineering applications, especially when the fly ash to SSC ratios were 0 and 0.8. In addition, ECCs with FA/SSC ratios of 1.2 and 1.5 showed ultra-ductile performance higher than the control ECC. Interestingly, all the FA-based ECC-SSC presented lower shrinkage characteristics than the control OPC-based ECC.

Early thrombus detection in the extracorporeal membrane oxygenation circuit by noninvasive real-time ultrasonic sensors

Thrombus formation in extracorporeal membrane oxygenation (ECMO) remains a major concern as it can lead to fatal outcomes. To the best of our knowledge, there is no standard non-invasive method for quantitatively measuring thrombi. This study’s purpose was to verify thrombus detection in an ECMO circuit using novel, non-invasive ultrasonic sensors in real-time, utilizing the fact that the ultrasonic velocity in a thrombus is known to be higher than that in the blood. Ultrasonic sensors with a customized chamber, an ultrasonic pulse-receiver, and a digital storage oscilloscope (DSO) were used to set up the measuring unit. The customized chamber was connected to an ECMO circuit primed with porcine blood. Thrombi formed from static porcine blood were placed in the circuit and ultrasonic signals were extracted from the oscilloscope at various ECMO flow rates of 1–4 L/min. The ultrasonic signal changes were successfully detected at each flow rate on the DSO. The ultrasonic pulse signal shifted leftward when a thrombus passed between the two ultrasonic sensors and was easily detected on the DSO screen. This novel real-time non-invasive thrombus detection method may enable the early detection of floating thrombi in the ECMO system and early management of ECMO thrombi.

Experimental Study on Strength Enhancement and Porosity Variation of 3D-Printed Gypsum Rocks: Insights on Vacuum Infiltration Post-Processing

AbstractThree-dimensional printing (3DP) technology has shown great potential in rock mechanics and mining engineering due to its ability to create complex and customized objects with high precision and accuracy. At present, an emerging research focus is improving the mechanical properties of 3D-printed samples, which originally has low strength and stiffness, to match those of natural rocks. The objective of this study was to investigate the effectiveness of different post-treatments on the strength enhancement of 3D-printed gypsum samples. To achieve this goal, 3D-printed gypsum samples were subjected to different post-treatments including dipped infiltration treatment and vacuum infiltration treatment using different infiltrants: water, saltwater, ColorBond, and StrengthMax. Subsequently, each sample was subjected to ultrasonic wave velocity testing and uniaxial compression experiments to characterize their mechanical properties, CT scans to investigate their microstructural characteristics. Additionally, X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) tests were conducted to explore the underlying reasons for changes in macroscopic strength. Finally, the physical characteristics and mechanical properties of untreated and post-processed 3D-printed gypsum samples were compared with natural rocks. The results showed that the strength of samples treated with water and saltwater was much lower than that of those treated with ColorBond and StrengthMax, while the porosity was the opposite. In water-treated and saltwater-treated samples, water or saltwater treatment can alter particle characteristics, but weak adhesive bonding and numerous pores result in low mechanical strength. Samples treated with Colorbond or StrengthMax exhibit improved strength due to effective gap filling and cohesive structure formation, with StrengthMax-treated samples showing higher strength despite having more pores than Colorbond-treated ones. Moreover, the physical and mechanical properties of these treated samples matched a wider range of natural rock types compared to the untreated samples.

Experimental Investigation of the Structural Performance of Concrete Containing Cellulose Fibers and the Anti-corrosive Effect of Green Corrosion Inhibitors

This research was aimed to find the structural behaviour of Calotropis procera fibres added concrete and the effect of Azadirachta indica leaf slurry blended to concrete and exposed to seawater. Conventional and fibre reinforced concrete samples fabricated keeping the curing time as 7, 14 and 28 dayswere subjected to compression, split tensile, rebound hammer and ultrasonic pulse velocity test. Increase in curing time increased the structural properties and Calotropis procerafibres added samples produced respectively 19.5%, 15%, 10.3 and 14.5% improvement in the compression, tensile, rebound hammer and ultrasonic pulse velocity values. These fibres reduced the brittleness of the specimen and avoided unprecedented failures. Accelerated corrosion and gravimetric mass loss test conducted to estimate the anti-corrosive property of Azadirachta indica leaf slurry showed decrease in corrosion rate. The corrosion rate of concrete samples without and with inhibitors was 0.0654 ± 0.008 and 0.056 ± 0.011 mm/year respectively evincing the anti-corrosive effects of Azadirachta indica leaves. Thus green materials are compatible with concrete and can be used in making sustainable concrete structures.

Introducing the area under stress–velocity curve: Theory, measurement and association with rock properties

AbstractSince many years ago, ultrasonic velocity has been used to investigate the physical and mechanical behaviour of rocks, thereby playing an important role in reservoir characterization and seismic interpretation. In order to develop the knowledge of ultrasonic tools, we performed a noble analysis on the ultrasonic behaviour of rocks under confining stress and evaluated a distinctive property of porous media that is measured as the area under the stress–velocity curve (here defined as S*). We further investigated its relationship with elastic and mechanical behaviours of rock. To validate the theoretical framework developed in this work, 20 core plugs from various rock units with complex microstructures were subjected to triaxial compressional tests to calculate their area under the curve. Calculations were made for crack‐closing, elastic and post‐elastic stages (e.g. pore collapse) along the ultrasonic velocity–stress curve. Moreover, the selected samples had their microstructure investigated by thin‐section studies to quantify their porosity and pore type. The results were analysed to check for the effect of pore type on S* in different stages of the stress–velocity curve. Based on the outputs of the analysis of variance and Pearson's correlation coefficient analysis, the curve had its shape and underlying area closely related to the porosity and pore geometry. Indeed, the results showed that the shale and sandstone with micro cracks and carbonate with stiff pores correspond to smaller and larger areas under the curve in crack‐closing and inelastic stages, respectively. Cross‐correlating the results to compressibility (inverse of bulk modulus), it was figured out that the calculated area under curve was well consistent with the compressibility. In addition, S* represents both static and dynamic behaviours of the rock, and the results revealed that the shape and curvature of the stress–velocity curve give valuable information about the rock microstructure. Another finding was the fact that the type of fluid and wave velocity seemingly affect the S*. Our findings can help interpret wave velocity behaviour in reservoir rocks and other stressful porous media.

Damage to monumental masonry buildings in Hatay and Osmaniye following the 2023 Turkey earthquake sequence: The role of wall geometry, construction quality, and material properties

This article reports on the findings of an investigation on 29 historic stone masonry buildings located in the cities of Hatay and Osmaniye following the 2023 Turkey earthquake sequence. The earthquake couplet on 6 February (with moment magnitudes 7.8 and 7.5) and the following events (including another earthquake which occurred on 20 February with a moment magnitude of 6.3) resulted in significant damage to the buildings. To understand why, the examined buildings were assigned an EMS-98 damage level (ranging from 1 to 5) and descriptive response categories (masonry disaggregation, local mechanism, and global response). Overall damage statistics indicated that masonry disaggregation was common and coterminous with local mechanism response. Wall geometry and construction quality indices were then investigated to explore why these were the dominant damage mechanisms. Wall geometry indices highlighted insufficient amount of walls to resist the local seismic demands, particularly in the transverse (e.g. short) direction of buildings. This deficit promoted the formation of local mechanisms. Construction quality indices suggested that stone layouts did not enable interlocking and that the walls were prone to disaggregation. To further investigate the role of material properties on the observed damage, materials were characterized using three non-destructive testing techniques: ultrasonic pulse velocity (UPV) measurements to estimate the static elastic modulus of stones, Schmidt rebound hammer (SRH) tests to estimate the compressive strength of stones, and the mortar penetrometer (MP) tests to estimate the compressive strength of mortar. The measurements indicated poor mortar quality, which may have expedited failures. Using established correlations, various other important material parameters (e.g. mortar cohesion and homogenized masonry strength) are derived. It is envisioned that the damage observations and the material measurements in this article will inform detailed modeling efforts on the behavior of historic masonry buildings during the earthquakes.

Mechanical properties and water resistance study of basic magnesium sulfate cement-emulsified asphalt composite materials

This study introduces a novel semi-flexible composite material (BMSC-EA), formed by merging the favorable properties of emulsified asphalt (EA), known for its high flexibility and crack resistance, with basic magnesium sulfate cement (BMSC), recognized for its high rigidity, early strength, and toughness. The research systematically explores the impact of varying EA dosages on BMSC properties. Furthermore, the study analyzes the phase composition, pore structure, and microstructure of BMSC-EA materials. Results indicate that an increase in EA dosage leads to a corresponding extension in the setting time of BMSC, accompanied by a gradual decrease in compressive and flexural properties. Interestingly, the flexural compression ratio of BMSC increases, suggesting that EA addition significantly enhances BMSC toughness. The principal hydration product of BMSC comprised crystals of 5Mg(OH)2∙MgSO4∙7H2O (5∙1∙7 phase). However, the introduction of EA exerted an inhibitory influence on the generation of Mg(OH)2, leading to a scenario where more MgO remained uninvolved in the hydration reaction. The porosity of the BMSC matrix increases with higher EA content. After subjecting the BMSC-EA material to water immersion treatment, a noteworthy observation emerged: exceptional water resistance was evident when the EA dosage reached 10%. This phenomenon was primarily ascribed to the heightened densification (ultrasonic velocity) observed in the BMSC-EA samples under these conditions. Additionally, the study observes further growth of Mg(OH)2 in BMSC after water immersion treatment, but excessive Mg(OH)2 negatively impacts BMSC-EA. These findings serve as both experimental and theoretical foundations for advancing innovative semi-flexible composite pavement materials.

Optimization and Characterization of Cementitious Composites Combining Maximum Amounts of Waste Glass Powder and Treated Glass Aggregates

This work investigates the combined use of waste glass aggregates (GA) and glass powder (GP) in cementitious mortars. For this reason, the optimized incorporation of GA by natural aggregates (NA) replacements was first studied after applying a surface roughening method with hydrofluoric acid. The compressive strength results were utilized to select the best mixture with GA. Then, different GP contents were added by cements substitutions to the optimized GA-based mortar. A control mortar without GA and GP amounts was also casted as a reference for comparison. The detailed mechanical, physical and durability properties of the resulted mixtures with combined GA and GP were assessed by considering the compressive and flexural strengths, ultra-sonic pulse velocity, alkali-silica reaction (ASR), rapid chloride permeability test (RCPT), magnesium sulphate attack and sulfuric acid resistance. The microstructure of different optimized (GA + GP)-combinations was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS)in order to analyse the interfacial transition zone (ITZ) between glass materials and the surrounding matrix. The results showed that the optimized composition with 75% GA and 25% GP was shown with high compacity and durability characteristics due to the increased GA/matrix ITZ and the formation of C–(N,K)–S–H products with C–S–H.

Evaluating the fresh and mechanical properties of steel slag aggregate concrete reinforced with steel fiber

In this study, steel slag (SS) and steel fiber (SF) were used to make environment-friendly high-strength concrete. Natural coarse aggregate (NCA) was initially substituted partially with SS at various substitution levels, i.e., 25 %, 50 %, 75 %, and 100 %, respectively, for getting the optimum substitution levels of SS in concrete. Afterward, SF, having an aspect ratio of 60, was considered with volume fractions of 0.15 %, 0.3 %,0.45 %, 0.6 %, 0.75 %, 0.90 %, 1.05 %, and 1.2 % in concrete. The water-to-binder ratio was taken as 0.35 for all the concrete mixes. For the fresh property, slump and compaction factor of concrete were determined. Similarly, for the mechanical property compressive strength (CS), split-tensile strength (STS), and flexural strength (FS) have been tested after the curing age of 28 and 56 days. Additionally ultrasonic pulse velocity (UPV) test was conducted to measure the quality of concrete. X-ray diffraction (XRD) was also performed to analyze crystalline phases and identify mineralogical composition within the concrete matrix. All the tests were compared with the standard concrete made with NCA. It has been found that the addition of steel slag aggregate (SSA) and SF enhances the mechanical properties of concrete, whereas it reduces workability. Substituting 50 % of SSA for NCA alongside 1.05 % of SF results in the highest CS, while employing 1.2 % SF achieves maximum STS, FS, and UPV.

Reassessment of Birch's Law on hcp‐Fe From Ultrasonic Sound Velocity Measurement and Implications on the Velocity Profiles of Earth's Inner Core

AbstractWe performed in situ X‐ray diffraction and ultrasonic sound velocity measurements on hcp‐Fe up to 15 GPa, 873 K in a multi‐anvil apparatus. The elastic moduli and their pressure and temperature derivatives were determined by fitting the velocity and density data to the third‐order finite strain equations, yielding KS0 = 169.0(57) GPa, KS0′ = 5.4(6), (∂KS/∂T)P = −0.031(3) GPa/K, G0 = 104.5(27) GPa, G0′ = 1.7(2), (∂G/∂T)P = −0.060(2) GPa/K. Within the experimental P‐T range, we find significant temperature effect on the density‐velocity (ρ − VP or S) relations and caution the use of the temperature‐independent Birch's law for extrapolation to core conditions. Furthermore, temperature‐induced velocity decrease is more significant in VS than in VP, offering a possible explanation for the high Poisson's ratio in the core. Extrapolations based on our results together with previous experimental data suggest that VP of hcp‐Fe aligns with PREM at Earth's core conditions, while Vs and density are approximately 10% and 2.7% higher than PREM, respectively.

Towards Sustainable Construction: Performance Evaluation of Slag-Cenosphere Geopolymers Under Different NaOH Concentrations

The incorporation of industrial wastes into construction materials, such as geopolymers, is highly desirable to improve their environmental impact. The choice of source materials, such as slag and cenosphere, and the amount of activator used significantly impact the properties of geopolymers. For instance, including high-reactivity precursors and optimizing activator composition may enhance mechanical strength and durability. However, no studies have evaluated the effect of cenosphere addition on the properties of geopolymer composites. This research study aims to unveil the synthesis of a binary geopolymer material by integrating slag and cenosphere as precursors, activated by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). Geopolymer composites were prepared to assess the impact of cenosphere addition (by substituting the slag with cenosphere in different percentages of 25, 50, and 75%) and NaOH concentration (specifically 6M, 9M, and 12M) on the material’s properties. Additionally, one conventional mortar with a water-to-cement ratio of 0.5 was also prepared. Compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity, water absorption, density, and thermogravimetric analysis were conducted. Results showed that increasing the cenosphere percentage increased the water absorption and decreased the compressive strength, UPV, electrical resistivity, and density compared to the geopolymer mixture with 100% slag content. However, up to 50% substitution of cenosphere, the geopolymer mix performed better than conventional mortar. Notably, results suggest a potential increase in CO2 uptake due to the addition of cenosphere, further enhancing the environmental performance of geopolymer composites. The findings of this study suggest the potential use of slag-cenosphere geopolymer as an alternative and sustainable construction material.

Cyclic Loading Behavior of Concrete with Thermally-Induced Damage

The paper reports a study on concrete specimens that were subjected to constant amplitude, low-strain cyclic (LSC) and high-strain cyclic (HSC) tests to evaluate their cyclic behavior after they had been subjected to either ambient or elevated temperatures. Parameters examined included maximum normal stress, dynamic modulus, and extent of damage observed in specimens. An equation is proposed to help quantify the extent of damage in specimens, which accounts for both thermal and cyclic loading effects. Ultrasonic Pulse Velocity (UPV) measurements were also used to quantify the damage in both the LSC and HSC tests. Results show that losses in compressive strength and dynamic modulus are greater in cases with higher temperature exposures due to thermally induced damages. Also, cyclic characteristics of the specimens were found to be significantly influenced by the strain amplitude used in cyclic loading tests.

Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art.

With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR's capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material's complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced.

Velocity Measurements of Powdered Rock at Low Confining Pressures and Comparison to Lunar Shallow Seismic Velocity

AbstractSeismic methods will be useful for future lunar near‐surface characterization, and high‐fidelity elastic models will be required to aid interpretation of seismic observations. To develop an elastic lunar near‐surface model, we performed ultrasonic velocity measurements of lunar regolith simulant at low confining pressure and developed a rock physics model calibrated to these measurements. Grain contact models based on Hertz‐Mindlin theory produce accurate results at high confining pressure (i.e., several hundred meters or more burial depth) but historically fail to predict observed velocities in unconsolidated media at low pressure. Therefore, we heuristically modified existing models to fit our measured data over a range of porosities and confining pressures. To compare with Apollo 14 and 16 active seismic experiments, we used our new heuristic rock physics model to produce lunar subsurface velocity profiles. We performed ray tracing through our velocity profiles to calculate seismic traveltime, which results in good agreement with first arrivals interpreted from the Apollo experiments. Our model suggests a slightly higher velocity‐pressure dependence than inferred from in situ measurements, which may be due to porosity reduction in the lunar regolith from impact‐induced and natural vibrations.

Study on improving the crack self-healing width and depth based on microbial mineralization modified by Ca-Al bimetallic hydroxides

In-depth research was conducted on the application of an inorganic mineral composite microbiological remediation agent in mortar specimens with varying crack widths. Firstly, the remediation agent's efficacy in repairing cracks was validated through surface observations and macroscopic performance tests, including methods such as crack surface image capture, crack water permeability recovery rate testing, and crack ultrasonic velocity recovery testing. Subsequently, this study investigated whether the inorganic mineral and microbiological components in the remediation agent played a role by examining the repair products within the cracks. Material composition was identified using techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). The primary minerals identified were layered double hydroxides and calcium carbonate. Furthermore, it was found that CI- and SO42- ions were immobilized within the interlayers of layered double hydroxides, aligning with the expected objectives of the experiment, thus confirming the feasibility of this study. Finally, the self-healing mechanism of cracks in this experiment was elucidated through a schematic diagram, demonstrating that the use of layered double hydroxides as inorganic minerals improved the microenvironment of the crack area, lowered the pH in the crack region, providing a favorable environment for microbial growth and mineralization. Additionally, these minerals could adsorb erosive ions such as CI- and SO42-, thereby enhancing the durability of cement-based materials.

Sustainable reuse of waste ceramic tiles powder and waste brick powder as a replacement for cement on green high strength concrete properties

Nowadays, reducing construction waste has grabbed the attention. As bricks and ceramic tiles represent more than 50% of the ceramic waste in many European countries. Thus, the recycling of this waste type is one of the most significant challenges within the paradigm of the circular economy. This paper investigated the impact of substitution levels of cement by waste ceramic powder (WCP) and waste brick powder (WBP) at 0%, 5%, 10% and 15%, on the HSC characteristics. The WBP and WCP materials were characterized in detail by laser granulometry, XRF and XRD measurements, followed by standard mixing, production, and curing of concrete samples. The experiments on dry density, modulus of elasticity, flexural strength, splitting tensile strength, compressive strength, resistance to sulfate attack, water absorption and ultrasonic pulse velocity were conducted to evaluate the hardened properties of concrete. It was demonstrated that the durability and strength of concrete containing WBP and WCP as partial replacements for cement are marginally inferior to those of the control sample. On the other hand, samples containing WBP had a lesser negative effect on HSC properties in comparison with samples containing WCP. However, employing a 5% WBP with 10% WCP mixture enhanced the characteristics of the HSC in comparison to samples containing various percentages of WCP individually. In addition, the microstructure analyses revealed that the addition of 10% WCP and 5%WBP to HSC specimens resulted in higher hydration products and a slightly denser concrete matrix compared to samples containing various percentages of WCP individually. Research findings indicate that a 15% substitution of cement with WCP or WBP illustrated an environmental benefit in concrete production due to a 13.1% reduction in specific energy consumption.

ANOVA-guided assessment of waste glass and limestone powder influence on ultra-high-performance concrete properties

Ultra-high-performance concrete (UHPC) possesses remarkable structural and durability characteristics, yet its widespread acceptance is hindered by cost inefficiency and environmental concerns. To address these challenges, this study investigates the impact of waste glass and limestone powder as partial substitutes for silica fume and cement in UHPC. For this, three distinct formulations are studied (Control, Optimized-1, and Optimized-2), representing different dosages of waste glass and limestone powder. The research focuses on six critical properties (compressive strength, modulus of elasticity, ultrasonic pulse velocity, initial surface absorption, density absorption, voids, and chloride ion penetration) evaluated at different ages (1, 7, 28, and 90 days for compressive strength, and 7, 28, and 90 days for the remaining properties). So, a total of 171 test specimens were examined, with 3 samples for each age and formulation. Statistical analysis, using ANOVA, assessed and confirmed the significance of the factors in the experimental results. The findings provide comprehensive insights into the UHPC formulations, highlighting the influence of waste glass and limestone powder on specified properties over varying ages. The research reveals that, despite the optimized blends exhibiting lower compressive strength values, all mixes surpass the 150 MPa threshold for cylindrical samples at the 90-day mark. Moreover, the Control mix consistently outperforms the optimized blends in modulus of elasticity at all ages, meeting ACI 239 criteria. The void content analysis shows encouraging trends, with all formulations displaying voids of less than 5% on the seventh day, improving during the curing process. Notably, Optimized-2 demonstrates superior performance over the Control mix after 90 days. Chloride ion penetration is minimal for all blends after 90 days, confirming the effectiveness of mineral admixtures. ANOVA analysis confirms significant impacts of formulation and age on various UHPC characteristics, emphasizing the consistent reduction in performance with alternative mineral additions. The interaction between formulation and age implies variations in property evolution, suggesting potential convergence with alternative formulations.

Simulation of Shear and Tensile Fractures Using Ductile Phase Field Modelling with the Calibration of P Wave Velocity Measurement and Moment Tensor Inversion

AbstractThe appropriate understanding and formulation of rock discontinuities via FEM is still challenging for rock engineering, as continuous algorithms cannot handle the discontinuities in rock mass. Also, different failure modes of rock samples, containing tensile and shear failure, need to be computed separately. In this study, a novel double-phase field damage model was introduced with two independent phase field damage variables. The construction of the proposed model follows the thermodynamics framework from the overall Helmholtz free energy, with elastic, plastic and surface damage components. The proposed model is calibrated via traditional damage variables, based on ultrasonic wave velocity measurement and acoustic emission monitoring, and both show great consistency between simulation results and laboratory observations. Then the double-phase field damage model is applied to COMSOL software to simulate microcrack propagation in a pre-fractured rock sample. Both lateral and wing cracks are observed in this study, manifested as shear- and tensile-dominated cracks. We also observed different microcracking mechanisms in the proposed numerical models, such as tensile and shear cracking, the influence of plastic strain and the percolation between tensile and shear microcracks. Overall, this study provides valuable insights into the mechanics of microcracking in rocks, and the proposed model shows promising results in simulating crack propagation.