Volume Change Behavior Research Articles

Nearly All-Active-Material Disordered Rock-Salt Cathodes for Ni- and Co-Free Li-Ion Batteries

The global shift towards electric vehicles and large-scale energy storage systems necessitates cost-effective and abundant alternatives to commercial Co/Ni-based cathodes, such as LiNi0.6Mn0.2Co0.2O2, for Li-ion batteries (LIBs). Manganese-based disordered rock-salts (Mn-DRXs) have shown promising potential to outperform conventional cathodes at a lower cost, achieving energy densities exceeding 900 Wh kg-AM (per active material, AM).[1-4] However, previous demonstrations of such performance have been conducted in cell constructions that are far from commercially viable, utilizing diluted electrode films (∼70 wt%-AM) containing excessive carbon and binder.[3] In this presentation, I will address the challenges associated with attaining AM-concentrated Mn-DRX cathodes (>95 wt%-AM).[5] It will be revealed that the failures observed in AM-concentrated electrodes of Mn-DRXs stem from their remarkably low electrical conductivity (ranging from 10−10 to 10−8 S/cm) and the subsequent collapse of the electrode's electrical network due to volume changes over cycling. I will then outline strategies to mitigate these challenges through electrical percolation engineering and the enhancement of electrode mechanical properties. Through these approaches, we have successfully demonstrated nearly all-AM Mn-DRX cathodes (∼96 wt%-AM) and achieved the highest application-level energy density (∼1050 Wh kg-cathode) reported to date.[5] Furthermore, I will discuss the trade-off associated with the manganese content in Mn-DRXs concerning their electrical conductivity and volume change behavior. This discussion will provide valuable insights and guidelines for material design aimed at advancing Co/Ni-free LIBs' technology readiness.Overall, this presentation will shed light on the current status, challenges, and breakthroughs in the development of Mn-DRX cathodes, offering a pathway towards more efficient and sustainable LIB technology. References J. Lee et al., Science 343, 519−522 (2014).J. Lee et al., Nature 556, 185–190 (2018).H. Li, R. Fong, D.-H. Seo, J. Lee et al., Joule 6, 53–91 (2022).E. Lee, H. Lee, J. Lee, D.-H. Seo et al., Adv. Mater. 35, 2208423 (2023).E. Lee, D.-H. Lee, D.-H. Seo, J. Lee et al., Energy Environ. Sci. (2024) https://doi.org/10.1039/D4EE00551A.

Revealing the Impact of Graphite Reaction and Binder Structural Changes on the Degradation of Silicon-Graphite Composite Electrodes via Differential Capacity and Stress Analysis

Silicon-graphite (Si-Gr) composite electrodes, which are based on high-capacity silicon mixed with conductive graphite with low volume expansion, have garnered significant interest due to their excellent electrochemical performance and stability. However, increasing the silicon content in the composite electrodes accelerates degradation, leading to a limitation in achieving higher energy density. In addition, Si-Gr composite electrodes undergo multi-stage reactions of silicon and graphite, resulting in complex reaction kinetics and intricate volume change behaviors. Therefore, it is challenging to analyze the impact of each active material's reaction on the electrode degradation. Furthermore, as the degradation of composite electrodes has primarily been understood and studied in the context of silicon's significant volume expansion and degradation, there is a lack of research evaluating the influence of graphite reactions. Despite having a low volume expansion upon lithiation, graphite occupies a significant volume fraction in the composite electrode and exhibits a relatively consistent arrangement. Therefore, it is anticipated that graphite would also influence electrode structural changes and the consequent electrode defect formation.In this study, we observe the average stress corresponding to the electrochemical reactions of the charge/discharge processes of Si-Gr composite electrodes in situ. The average stress can be understood as the internal pressure build-up within the electrode due to the volume expansion of the reactions. The stress and the reaction capacity were differentiated with respect to potential to analyze the contributions of each reaction on the volume change and the internal force evolution. Interestingly, graphite reactions generally induced higher stress than those of silicon during the lithiation process, and their stress per capacity increased as the State of Charge (SoC) increased. These results indicate that graphite can significantly contribute to the stress inside the electrode even though it exhibits a much lower expansion rate than silicon. Moreover, stress behavior that contradicts the silicon volume contraction was also observed during silicon delithiation. This result can be attributed to the stress-relieving phenomenon of the binder, highlighting the importance of the interaction between the active materials and binders. To observe the initial degradation of the composite electrode, repeated charge-discharge cycles were conducted, revealing intervals of unstable stress variation. Subsequent examination using ex-situ SEM showed that debonding and fracture at the interface between graphite and silicon/binder were the primary causes. Furthermore, EDS, XPS, and indentation analysis showed that such structural defects were caused by changes in the silicon-binder structure due to SEI formation. As confirmed by the micro indentation test, the viscoelastic binder and silicon were transformed into a brittle silicon-binder structure. Consequently, it failed to sufficiently dampen the forces generated by the active materials’ volume change resulting in the defects. These research findings contribute to a fundamental understanding of the stability of Si-Gr composite electrodes and our method can be expanded to various energy electrodes of different materials and compositions to enhance understanding of their behavior and contribute to their stability improvement. Choi, J., G. Kim, and S.Y. Kim, Silicon Graphite Composite Anode Degradation: Effects of Silicon Ratio, Current Density, and Temperature. Energy Technology, 2023. Ghamlouche, A., M. Müller, F. Jeschull, and J. Maibach, Degradation Phenomena in Silicon/Graphite Electrodes with Varying Silicon Content. Journal of The Electrochemical Society, 2022. 169(2). Wetjen, M., et al., Differentiating the Degradation Phenomena in Silicon-Graphite Electrodes for Lithium-Ion Batteries. Journal of The Electrochemical Society, 2017. 164(12): p. A2840-A2852. Berhaut, C.L., et al., Multiscale Multiphase Lithiation and Delithiation Mechanisms in a Composite Electrode Unraveled by Simultaneous Operando Small-Angle and Wide-Angle X-Ray Scattering. ACS Nano, 2019. 13(10): p. 11538-11551. Yao, K.P.C., et al., Operando Quantification of (De)Lithiation Behavior of Silicon–Graphite Blended Electrodes for Lithium ‐Ion Batteries. Advanced Energy Materials, 2019. 9(8). Sethuraman, V.A., et al., Real-time stress measurements in lithium-ion battery negative-electrodes. Journal of Power Sources, 2012. 206: p. 334-342. Schweidler, S., et al., Volume Changes of Graphite Anodes Revisited: A Combined Operando X-ray Diffraction and In Situ Pressure Analysis Study. The Journal of Physical Chemistry C, 2018. 122(16): p. 8829-8835. Liu, X.H., et al., Size-dependent fracture of silicon nanoparticles during lithiation. ACS Nano, 2012. 6(2): p. 1522-31. Lee, H.-J., et al., Lithiation Pathway Mechanism of Si-C Composite Anode Revealed by the Role of Nanopore using In Situ Lithiation. ACS Energy Letters, 2022. 7(8): p. 2469-2476. Ogata, K., et al., Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy. Nature Communications, 2014. 5(1).

Quantifying Volume Change in Porous Electrodes Via the Multi-Species, Multi-Reaction Model

Automotive manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change1–7 is one of the more complex aspects that needs to be considered during this process. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods8, the need for coupled electrochemical/mechanical9 models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary. In this study, we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge10,11 and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions.

(Invited) Applications of a Mechano-Electrochemical Battery Model for Electric Vehicle Development

The electric vehicle (EV) revolution has prompted automotive manufacturers to develop new battery cell and pack technology at an extremely rapid pace--dictating the need to employ modeling methods to become resilient to material delays and remove strain from experimental capability. Automotive manufacturers are concerned with how material, electrode, cell, and pack design decisions impact each other, some of which are hard to measure until after development. Therefore, multi-scale models are of particular interest to help improve the EV and battery pack development process. One phenomenon that can greatly impact design decisions is the volume change of active material upon lithiation, especially considering the promising materials with high volume change, like silicon. The active material volume change can lead to changes in the electrode's porosity and volume, impacting performance. The volume change of the electrode can lead to swelling of the full pouch cell (or pressure generated in a prismatic cell). And finally, the cell volume and pressure change can impact design decisions at the full module or pack scales.To address this, the authors have launched an industrially-led project focused on the development of a multi-scale, mechano-electrochemical battery model, with particular focus on automotive applications. Initially, theoretical models were developed to capture how volume change may impact performance in a single electrode[1] and dual insertion electrodes.[2] Then, applied models were developed to account for volume change impacts on the cell and pack scales[3], incorporate realistic, thermodynamically non-ideal active material volume change[4], and accurately simulate electrodes with blended active materials to account for preferential lithiation and unique volume change behavior.[5] In this presentation, the development of these models will be briefly summarized. Throughout the presentation, the discussion will have a particular emphasis on how each modeling topic may be useful to automotive manufacturers. Additionally, brief discussion will be provided on concepts that would improve the usefulness of this type of model, such as accounting for the impact of battery aging.[6,7] The authors thank the GM Global Propulsion System's team for computing resources and partial funding. This work was partially funded by the IGERT Program at University of South Carolina under NSF Award #1250052.

Comparative analysis of volume change behavior of expansive road subgrades stabilized with waste paper sludge

Expansive soils have a high tendency for volume change in case of fluctuations in moisture content, potentially causing significant damage to light structures, particularly road pavements. This paper investigates the influence of waste paper sludge () as an alternative sustainable stabilizer on the volume change behavior of expansive road subgrade soils of different origins. For this purpose, was added to the expansive soils at ratios of 3%, 6%, 9%, 12%, and 15% by dry weight of the soils. A series of Atterberg’s limit, swelling, shrinkage, compaction, and consolidation tests were performed on pure soils and soil specimens with to attain a comprehensive understanding of the role that plays in the volume change behavior of expansive soils. The experimental test results showed that the addition of led to a considerable decrease in the plasticity and swell-shrink potentials of subgrade soils. The consolidation settlement of expansive road subgrades was also reduced to some extent with . Moreover, the statistical analysis of the test data indicated a significant relationship among different swelling-shrinkage parameters. The experimental results presented here suggest that the may be a cost-effective, environmentally friendly, and sustainable stabilizer to reduce the volume change sensitivity of expansive road subgrade soils.

Laboratory assessment of the effect of rice husk, groundnut shells and RHA on the shear, permeability and consolidation of clayey sands

Utilizing waste materials to improve soil properties can result in cost savings and environmental benefits. This study aims to determine the effect of adding agricultural wastes like rice husk ash (RHA), rice husk (RH), and groundnut shells (GS) to clayey sands from Mysore district, India. The study focused on the undrained strength, permeability and volume change behaviour of soils mixed with RHA, RH and GS. The soil samples were mixed with varying amounts of RHA (5%, 10%, 15%, and 20%) and RH-GS (1%, 2%, 3%, 4%, and 5%) and cured for 1, 7, 14 and 21 days. These blended specimens were then used to determine the maximum dry density (MDD), optimum moisture content (OMC) and unconfined compressive strength (UCS). The soil mixture containing 5% RHA and 4% (RH + GS) yielded optimal results in the UCS test. Further tests, including unconsolidated undrained (UU) triaxial, permeability and consolidation tests, were conducted on the parent soil and the soil composite with 5% RHA and 4% (RH + GS). From the undrained test, the strength increased for the soil admixture, with a reduction in the cohesion and an increment in the friction angle, compared to that of the parent soil. The experimental results also showed improvement in the permeability and consolidation characteristics of the blended soil. As RH, GS, and RHA are abundant and considered to be agricultural waste products, using them represents an innovative, sustainable, and cost-effective solution with promising potential for soil improvement.

Experimental investigations of the shear strength and deformation behavior of a frozen unsaturated silt

There are limited studies in literature with respect to the deformation and shear strength behavior of frozen unsaturated soils that consider sensitive changes in temperatures below 0 °C. For this reason, the focus of the present study is directed towards investigating the shear strength and deformation behavior of a frozen unsaturated silt. As a part of the study, one-dimensional freezing tests were performed on compacted silt samples with various initial water contents and dry densities. The pulsed nuclear magnetic resonance (P-NMR) method was used to obtain distribution of unfrozen water content of silt samples; this information was used to explain the deformation behavior during freezing. The volume change behavior in unsaturated soils due to freezing can be associated to three primary factors: expansion caused by the ice-water phase transition and shrinkage induced by ice-cementation and dehydration. A critical water saturation was also observed at which the frost heave is minimum, or no volume change occurs. In addition, conventional direct shear tests were performed on compacted unsaturated silt samples both in frozen and unfrozen conditions to determine and quantify the shear strength contribution arising from the different cohesion components. The investigations in this study provide valuable information that can be used in rational explanation of the strength and deformation behavior of unsaturated frozen soils.

Highly Porous Co-Al Intermetallic Created by Thermal Explosion Using NaCl as a Space Retainer.

Co-Al porous materials were fabricated by thermal explosion (TE) reactions from Co and Al powders in a 1:1 ratio using NaCl as a space retainer. The effects of the NaCl content on the temperature profiles, phase structure, volume change, density, pore distribution and antioxidation behavior were investigated. The results showed that the sintered product of Co and Al powders was solely Co-Al intermetallic, while the final product was Co4Al13 with an abundant Co phase and minor Co2Al5 and Co-Al phases after added NaCl dissolved out, due to the high Tig and low Tc. The open porosity of sintered Co-Al compound was sensibly improved to 79.5% after 80 wt.% of the added NaCl dissolved out. Moreover, porous Co-Al intermetallic exhibited an inherited pore structure, including large pores originating from the dissolution of NaCl and small pores in the matrix caused by volume expansion due to TE reaction. The interconnected large and small pores make the open cellular Co-Al intermetallic suitable for broad application prospects in liquid-gas separation and filtration.

Quantifying Volume Change in Porous Electrodes via the Multi-Species, Multi-Reaction Model

Automotive manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary[1-9]. In this study[10], we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge[11-16] and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions. References T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016).T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017).D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019).D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020).T. R. Garrick, J. Gao, X. Yang and B. Koch, J Electrochem. Soc., 168 (1) 010530 (2021)D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez and J. W. Weidner, J Electrochem Soc, 170, 100513 (2023).T. R. Garrick, M. A. Fernandez, M. Verbrugge, C. Labaza, R. Mollah, B. J. Koch, M. Jones, J. Gao, X. Gao and N. Irish, J. Electrochem. Soc., 170 060548 (2023)M. Verbrugge, D. Baker and X. Xiao, J Electrochem Soc, 163, A262 (2016).M. Verbrugge, D. Baker, B. Koch, X. Xiao and W. Gu, J Electrochem Soc, 164, E3243 (2017).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 165, A3952 (2018).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 167, 013504 (2019).D. R. Baker, M. W. Verbrugge and W. Gu, J Electrochem Soc, 166, A521 (2019).M. W. Verbrugge, X. Xiao and D. R. Baker, J Electrochem Soc, 167, 080523 (2020).

Biopolymer and Gypsum Added Na Bentonite for a More Effective Clay Liner

AbstractBentonite soil is frequently utilized as a compacted clay liner, which is a critical component of municipal waste landfill systems. This study aims to investigate the feasibility of treating sodium bentonite (NAB) with natural biopolymers to obtain an effective clay liner. The NAB was treated with three biopolymers: sodium alginate (SA), agar gum (A), and xanthan gum (X), at different replacement percentages (2%, 4%, 6%, and 8%). Additionally, an investigation was conducted to determine the extent to which replacing 50% of these additives with gypsum (G) would improve the biopolymer treatments. Fourier-transform infrared spectroscopy (FTIR), pH, one-dimensional swelling, and unconfined compressive strength (UCS) were carried out in this study. The FTIR results indicated the presence of intermolecular hydrogen bonding when NAB was treated with biopolymers and gypsum, which is crucial for enhancing the UCS. Furthermore, the thermal treatment of biopolymers significantly contributes to improving the UCS. Among the various biopolymers tested, agar gum demonstrated the most significant improvement, specifically, replacing 8% of the NAB with agar gum resulted in a 55% increase in UCS. Volume change behavior was most influenced by replacement of NAB with gypsum by 8%, which reduced the vertical swelling to 21% as opposed to 79% for the untreated NAB. The use of SA conversely resulted in an increased vertical swelling of 91%.

Effects of vegetation growth on soil microstructure and hydro-mechanical behaviour

Literature studies are presenting counterposed effects of vegetation on soil hydraulic behaviour. Besides, root impacts at the micro-scale are rarely correlated to phenomenological observations due to the complexity of adopting up-scaling factors. In this study, the microstructural causes behind observed changes in vegetated compacted clayey sand’s hydraulic and volume change behaviour were explored. Laboratory experiments were carried out on compacted samples seeded with Cynodon dactylon. Significant changes in soil water-saturated permeability, water retention and shrinkage upon drying were observed after root growth. Laboratory measurements were complemented by the quantification of root morphological features and observations at the micro-scale for different soil hydraulic states. X-ray scans and mercury intrusion porosimetry allowed to cover seven orders of magnitude of pore sizes, shedding light on soil fabric changes at the soil–root interface and the clay aggregate scale. The effects of roots on the soil pore size distribution consisted of Multiphysics phenomena: fissure generation, void clogging and soil aggregation due to roots’ chemical interaction. Furthermore, a good correlation was found between the normalised volume of roots and the micro-pores volume. This new expression was included in a framework to predict soil water retention behaviour considering the aggregated structure and soil–root hydro-chemical interactions.

Experimental study of compression behavior and its correlation with the microstructure of a deep-water sediment

Understanding the volume change behavior of deep-water sediments is essential for the safety design of deep-water engineering structures. In this study, the volume change behaviors of marine sediments from the South China Sea were studied through oedometer and isotropic compression tests. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests have been conducted to investigate the microstructure evolution of two types of sediments under loads. The experimental results showed that the structural anisotropy of intact specimens is more pronounced in oedometer tests with the increase of stress, however, depolarization occurs in the isotropic consolidation test. The volume change after yield in the oedometer and isotropic consolidation tests comes from inter-aggregate pore variations associated with the adjustment of the soil fabric. The reconstituted specimen presents a more uniform distribution of pores than that of the intact specimen, and the macropores are more easily compressed for the reconstituted specimen than those of the intact specimen. With increasing stress, the oedometer compression and isotropic consolidation curves of intact specimens gradually approach those of the reconstituted specimen. The deformation mechanism under high stresses is that soil particles are reoriented and the variation of micropores.

3D Printing of Succulent‐Inspired Microneedle Array for Enhanced Tissue Adhesion and Controllable Drug Release

AbstractControllable and long‐term release remains a great challenge in current drug delivery systems. Benefiting from their efficient drug loading and painless administration, microneedles (MNs) have emerged as a promising platform for transdermal drug delivery, while they often fail to achieve long‐term tissue adhesion and controllable extended drug release. Here, 3D printing of an innovative MN patch is presented with succulent‐inspired responsive microstructures and light‐controllable long‐term release capability. The MN exhibits a reversible shrink‐swell volume change behavior in response to surrounding humidity, which enables sufficient mechanical strength for skin penetration under the shrinkage conditions and efficient long‐term adhesion when swollen in skin tissues. Moreover, the MN patch introduces a controllable long‐term drug release system, achieved through the integration of thiolated heparin (Hep‐SH) for sustained growth factor release and graphene oxide (GO) nanosheets for controlled drug release via near infrared (NIR) laser irradiation. The MN patches with growth factor loading have good biocompatibility and can promote the proliferation, migration, and proangiogenesis of endothelial cells is further demonstrated. Thus, it is believed that such flexible MN patches can be promising candidates for controllable long‐term transdermal drug delivery as well as other related tissue engineering applications.

Mitigation of soil frost heave with fungi

Frost heave and thaw weakening can impose engineering issues on cold region infrastructures, including pavements, slopes, pipes, foundations, and buildings. This study investigated the potential of fungi treatment to mitigate the frost susceptibility of soils. Fungi were grown with organic waste to develop fungal mycelium. Subsequently, it is introduced into the soil. A sensitivity study was conducted on the influence of fungi centration on soil behaviors. The volume change behaviors when subjected to freezing or thawing were monitored. The results indicated that both soil frost heave and thaw weakening were reduced significantly with fungi treatment. The mechanisms are investigated with the measurement of the soil water characteristic curves. The introduction of fungi treatment affected the SWCC and soil water affinity. These affect the moisture transport when soil is subjected to freezing/thawing. Subsequently, the volume changes were suppressed.

Volume change characteristic of compacted bentonite during hydration upon high suction change: Experimental study and constitutive simulation

The assessment and predicting of volume change characteristic in compacted bentonite during hydration upon high suction change are crucial considerations in the design and construction of geological repositories. However, the mechanism for volume change behavior of bentonite upon suction change path is not yet well understood. Existing elastoplastic models show some limitations for describing hydration deformation of compacted bentonite upon high suction change path. In this work, suction-controlled hydration deformation tests were conducted on compacted GMZ01 bentonite under constant vertical stresses. The various forms of void ratio-suction curves observed suggested that the swelling-collapse behavior during hydration was influenced by the over-consolidation ratio (OCR). Furthermore, it was observed that each hydration deformation curve (e-lns) exhibited a saturation suction value. When the suction decreased to the saturation suction, the bentonite reached a state where further hydration was no longer possible, resulting in the absence of additional swelling or collapse deformation. The unique relationship between saturation suction and stress applied, i.e. critical saturated state (CSS) curve was proved to existed, which dividing the stress space (s-p plane) into unsaturated and saturated zones. A model framework with the concept of CSS curve was introduced and the suction-induced volume change equation was determined based on the tests results. The simulation results of hydration deformation tests demonstrated excellent agreement with the experimental data. The test results in this work provide the important mechanical parameters for the design and construction of geological repositories. Meanwhile, the proposed model could describe volume change characteristic of compacted bentonite during hydration upon high suction change, showing great significance for the safety assessment of repositories.

Volume Change Behavior of Amended Expansive Soil Using Sugarcane Bagasse Ash-Based Geopolymer

Volume Change Behavior of Amended Expansive Soil Using Sugarcane Bagasse Ash-Based Geopolymer

The role of intrinsic soil properties in the compressive strength and volume change behavior of unstabilized earth mortars

Despite the growing interest in earthen construction, there is critical lack of reliable experimental data on the soil properties which mostly affect the engineering characteristics of the dried building material. Therefore, the main objective of this research was to explore the influence of some of these properties, namely clay fraction content, Specific Surface Area (SSA), Cation Exchange Capacity (CEC), chemical and mineralogical composition and various forms of iron and calcium carbonate on earth mortars. The initial trigger for this research was the extraordinary compressive strength of four earth mortars prepared with different soils. So, these four soils, along with seven others from previous research, were thoroughly examined using soil science techniques to investigate the link between soil properties and compressive strength and linear shrinkage of earth mortars. A relationship between the compressive strength to CEC ratio and dry density was found, highlighting the decisive role of clay activity as expressed by CEC, in earthen materials properties. According to linear regression and dominance analysis, the strongest correlation was exhibited by SSA followed by CEC, demonstrating that compressive strength is largely dependent on these two properties. Less strong correlation was found for clay fraction content, while poorly ordered/amorphous iron oxides were found to correlate with strength and shrinkage, but their contribution requires further research. Regarding the mineralogical properties, it was found that the mortars that achieved the highest strengths contained poorly crystalline smectite clays. Finally, even significant differences in soil chemical composition did not necessarily lead to different mortar properties.

Flow through and Volume Change Behavior of a Compacted Expansive Soil Amended with Natural Biopolymers

Natural biopolymers offer a sustainable alternative for improving soil behavior due to their inert nature, small dosage requirement, and applicability under ambient temperatures. This research evaluates the efficacy of natural biopolymers for ameliorating an expansive soil by using a 0.5% dosage of cationic chitosan, charge-neutral guar gum, and anionic xanthan gum during compaction. The results of laboratory investigations indicate that the flow through and volume change properties of the expansive soil were affected variably. The dual porosity, characterized by low air entry due to inter-aggregate pores (AEV1 of 4 kPa) and high air entry due to the clay matrix (AEV2 of 200 kPa) of the soil, was healed using chitosan and guar gum (AEV of 200 kPa) but was enhanced by the xanthan gum (AEV1 of 100 kPa and AEV2 of 200 kPa). The s-shaped swell–shrink path of the soil comprised structural (e from 1.23 to 1.11), normal (e from 1.11 to 0.6), and residual stages (e ranged from 0.6–0.43). This shape was converted into a j-shaped path through amendment using chitosan and guar gum, showing no structural volume change, with e from about 1.25 to 0.5, but was reverted to a more pronounced form by xanthan gum, with e from 1.5 to 1.32, 1.32 to 0.49, and 0.49 to 0.34 in the three stages, respectively. The consolidation behavior of the soil was largely unaffected by the addition of biopolymers such that the saturated hydraulic conductivity decreased from 10−9 m/s to 10−12 m/s over a void ratio decrease from 1.1 to 0.6. At a seating stress of 5 kPa, the swelling potential (7.8%) of the soil slightly decreased to 6.9% due to the addition of chitosan but increased to 9.4% and 12.2% with guar gum and xanthan gum, respectively. The use of chitosan and guar gum will allow the compaction of the investigated expansive soil on the dry side of optimum.

The volume change behavior of compacted GMZ bentonite: combined effects of temperature and suction

The volume change behavior of compacted GMZ bentonite: combined effects of temperature and suction

Evolution characteristics of fracture volume and acoustic emission entropy of monzogranite under cyclic loading

The volume evolution behavior of rock fissures and the characteristics of acoustic emission under cyclic loading are critical for rock stability analysis. To study the volume change behavior of monzogranite fissures and the characteristics of acoustic emission signals under cyclic loading, we selected samples of monzogranite at − 1600 m from a gold mine located in the Jiaodong Peninsula at a depth of − 1600 m and investigated the samples using triaxial cyclic loading—unloading tests and acoustic emission monitoring. As the volume change behavior of the monzogranite fissures and acoustic emission signals were monitored and recorded, the calculated fracture volume strain ratio coefficient and acoustic emission entropy value were proposed to describe the evolution process of fissures inside the rock. The research results showed that the volume strain ratio curve of the rock fractures exhibited a logarithmic variation characteristic during the cyclic loading and unloading, and the fracture volume strain ratio better reflected the relative scale of the internal fracture strain in the rock to the total volume strain. The acoustic emission entropy value reflected the crack evolution behavior during the loading and failure processes, which was a rapid decline in the initial stage of loading and a rapid upward trend in the failure stage. The observed “V”-shaped change in the acoustic emission entropy can be used as an early warning for rock failure. The research results can provide theoretical guidance for rock stability analysis.