Performance Engineering Research Articles

Drying Shrinkage Properties and Engineering Performance for Cement Mortar Containing Bamboo Biochar Powder (BCP)

Drying shrinkage, the reduction in volume as a material like cement mortar dries, can result in cracks and decreased durability. Bamboo biochar powder (BCP) serves as a substitute for cement in mortar, affecting its drying shrinkage characteristics. Research has shown that BCP in cement mortar can alleviate drying shrinkage by absorbing and retaining moisture. This study aims to assess the chemical and physical properties of BCP, determine the mechanical attributes of bamboo biochar mortar with varying percentages of cement replacement, and investigate the impact of BCP on mortar shrinkage in indoor and outdoor tropical conditions. BCP, derived from Gigantocholoa Abociliata species and sized at 75 µm, was used to replace cement rates of 0%, 5%, 10%, 15%, and 20%. Sixty cube samples (50x50x50mm) were employed for density, ultrasonic pulse velocity (upv), compressive strength, and water absorption tests. Additionally, thirty prism samples (100x100x400mm) were employed to assess drying shrinkage during outdoor and indoor exposure, spanning up to 150 days. The experimental data indicates a consistent trend as the percentage of cement replacement increases in the mortar mix, density, and compressive strength decrease, while UPV and water absorption increase. The lowest shrinkage strain was observed during indoor exposure with 5% cement replacement, attributed to BCP acting as a filler, creating strong bonding properties, and reducing shrinkage. Conversely, the highest strain was noted during outdoor exposure with 20% cement replacement, resulting from higher moisture loss. In summary, a 5% replacement of cement with BCP in mortar offers the most effective reduction in shrinkage strain.

Water retention characteristics and mechanical properties of vegetated biopolymer and biochar-reinforced sandy loam

Vegetation is a sustainable strategy for erosion control and slope stabilization, though its initial cultivation can be lengthy and potentially weaken soil structures. This study compared two bio-mediated ground improvement techniques, biopolymer and biochar, known for their supportive effects on vegetation growth. Additionally, a novel treatment combining biopolymer and biochar was examined for its potential in vegetated-engineering practices. Engineering performance was assessed through soil water characteristic curve, vegetation growth, direct shear testing, and rainfall simulation. The results revealed that biopolymer and biochar treatments enhanced soil water capacity but negatively impacted vegetation germination rates and shear strength of the reinforced soil, attributed to hydrogel formation and increased soil water content from irrigation. In comparison, soil reinforced with the combined method showed a promotion in the vegetation while maintaining the soil’s mechanical performance throughout the cultivation period and exhibited only minor reductions in the shear strength compared to other reinforced soils. Moreover, the new treatment showed improved soil erodibility under a majority of rainfall occasions, regardless of the vegetation coverage. This enhanced engineering performance by the new treatment is believed to be the polymerisation between the biopolymer hydrogel, biochar and soil particles.

Density gradient structure foams prepared by novel two-step foaming strategy: Performance, simulation and optimization

Functional gradient foam materials play a crucial role in meeting the diverse performance and functionality requirements of modern engineering. Density gradients enable the distribution of mechanical, dielectric, and optical properties within materials, exhibiting a gradient representation. However, creating density gradients within foams poses a significant challenge, especially for semi-crystalline polymers. The paper proposed a novel two-step foaming method for preparing polypropylene (PP) foams with density gradient structure (DGS). Initially, a pre-foaming process was conducted to prepare PP pre-foams with uniform structure (US) at low temperatures, followed by a secondary foaming process on partially saturated PP pre-foams to fabricate PP DGS foams. By adjusting the duration of partial saturation time, PP foams with various DGS can be achieved. Compared with the commonly used one-step foaming method and uniform foaming method in the literature, the DGS foams prepared by the two-step foaming method exhibit not only a significant enhancement in mechanical property but also achieve the lowest thermal conductivity, while maintaining comparable and outstanding sound insulation performance. Finally, a comprehensive evaluation model using COMSOL Multiphysics was developed for the DGS foams, providing insights for optimizing foam performance through process enhancements.

A Gaussian statistics-based unit-cell modeling method for the mechanical behavior prediction of 2.5D shallow straight-link-shaped woven composites

The shallow straight-link-shaped structure of 2.5D woven composites (2.5D-SSLS-WC) is a novel material with a wide range of promising applications, but the randomness of its internal structure has brought challenges to performance prediction and engineering design. The gap of existing unit-cell models in capturing the internal randomness of the 2.5D-SSLS-WC material limits the accurate prediction of properties and the optimization of engineering design. In this work, the modeling method for random unit-cell model based on Gaussian distribution is proposed for 2.5D-SSLS-WC structure considering random distribution property of weft yarns and extrusion effects between structural surfaces and internal yarns during the molding process, which can more effectively reflect the practical mesoscopic structure of the material, reveal the micro mechanical behavior inside materials and provide theoretical basis for material design and performance optimization. The mechanical property and damage evolution of the proposed model is predicted and analyzed using finite element (FE) analysis and progressive damage method. The maximum errors of equivalent stiffness and strength between prediction and experimental values are 6.7% and 2.3%, respectively. The results show that the proposed model has high prediction accuracy and can reasonably reflect the damage extension and ultimate failure mode of the material during the loading process, which verifies the rationality of the proposed unit-cell modeling strategy. The modeling method proposed in this paper provides a new perspective for the in-depth understanding and description of the microstructure and mechanical behavior of 2.5D-SSLS-WC materials, which is of significant theoretical and engineering value and can be extended to the modeling of other woven composites.

Study on the performance and mechanism of physicochemically modified asphalt based on spatial crosslinking by the crumb rubber and polyurethane precursor

ABSTRACT Crumb rubber (CR)-modified asphalt shows positive effects on engineering performance and environmental conservation. However, its limited compatibility with asphalt due to unstable interactions poses challenges for its application. The incorporation of polyurethane precursor-based reactive modifier (PRM) facilitates the establishment of a three-dimensional crosslinked network structure within the asphalt, thereby enhancing pavement performance and compatibility. In this study, a novel compound-modified asphalt (CPMA) was prepared with CR and PRM. The performance of CPMA was assessed using the Dynamic Shear Rheometer (DSR), Blend Beam Rheology (BBR) and storage stability tests. Microstructure and modification mechanism were revealed by Atomic Force Microscopy (AFM) and Fluorescence Microscopy (FM) analyses. The results show that CPMA produced using an optimized process has better high-temperature performance and fatigue life than CR-modified asphalt (CRMA) and PRM-modified asphalt (PMA). Polar molecules, such as asphaltenes and resins, are crosslinked by the PRM to form a three-dimensional network, which enhances the thermal storage stability of CPMA. Furthermore, the flexibility and resilience of CR mitigated the low-temperature hardening of PMA. Physicochemical compound modifications provide significant advantages in terms of performance enhancement and system stability and demonstrate the potential of CR and PRM to complement and enhance their respective applications.

High-volume recycled glass cementitious and geopolymer composites incorporating graphene oxide

This study presents the development of high-volume recycled glass construction materials using recycled glass aggregate (RGA) as a 100 % sand replacement, recycled glass powder (RGP) as 40 wt% of the binder, and 0.1 wt% graphene oxide (GO) as nano-reinforcement. The research investigates the individual and their combined effects on the engineering performance, reaction kinetics (using calorimetry, X-ray diffraction-XRD, Fourier Transform Infrared-FTIR and Thermogravimetric analysis-TGA), and microstructure (Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy-SEM/EDS) for both cementitious and geopolymer systems. The results indicate that while RGA reduces strength and exacerbates alkali-silica reaction (ASR), the presence of 40 wt% RGP significantly mitigates ASR despite a lower strength gain in both systems. Geopolymers exhibit significantly lower ASR expansion compared to cementitious matrices owing to their superior alkali-binding capacity and denser microstructure, which restricts water and alkali ion mobility. 0.1 wt% GO was found to accelerate geopolymerisation, enhancing the strength of geopolymer mixes, but it decreased compressive strength in cement-based mixes due to self-desiccation-induced micro-cracking under ambient curing condition. The study also highlights that cement and metasilicate, as well as slag, are the main contributors to cost and CO2 emissions in cementitious and geopolymer systems, respectively. Overall, geopolymers exhibit a significantly lower global warming potential (< 180 kg CO2-eq/m3) compared to cement-based mixes (> 365 kg CO2-eq/m3) with a comparable cost (190–230 AUD/m3). The results indicate the potential for sustainable construction applications using high volumes of recycled glass, incorporating over 70 % of the mixture by weight.

Micro-perforated plates constructions with approaching the theoretical limits of its sound absorption performance

Micro-perforated plates resonant absorbers have a considerable theoretical sound absorption bandwidth upper limit. Three types of MPPs with straight holes, including circular holes on thick plate, circular holes on thin plate, and slotted holes on thin plate, are investigated with approaching the theoretical limits of its sound absorption performance. It is demonstrated that thin plates are easy to obtain satisfactory sound absorption performance but hard to get high mechanical strength. Slotted holes are beneficial for extending the sound absorption bandwidth of MPP absorbers. MPPs with straight holes usually require a combination of thin plates, minute holes and high perforation ratios, which is practically difficult to apply on a large scale. Two other types of MPPs with variable cross-sectional holes, fabricated using the subtractive processing method and superposition processing method, are then proposed to achieve perfect sound absorption performance and good engineering feasibility.

Carbon sequestration in earth-based alkali-activated mortar: phase changes and performance after natural exposure

This research investigates the effect of carbon sequestration via accelerated carbon curing (ACC) in alkali-activated earth-based alkali-activated mortar (25S-AAM) on the long-term engineering performance, chemical bonding and microstructure. The addition of clay accelerates hydration kinetics and promotes the formation of more cross-linked calcium–(sodium) alumino silicate hydrates (N-A-S-H and C-(N)-A-S-H). This contributes to early strength and a 25% reduction in total shrinkage after 60 days. Although ACC promotes higher carbon sequestration and increases 1-d compressive strength by 13%, it leads to severe decalcification of 25S-AAM after 365 days of natural exposure, resulting in coarsening of the pore structure in the mesoporous size range of 10–100 nm. Due to a relatively low Ca/Si ratio, 25S-AAM is more adversely affected by natural carbonation during the 365-d exposure period than the control (without clay). In summary, ACC is not recommended for earth-based AAM products especially if they are applied for outdoor constructions.

ExaFEL: extreme-scale real-time data processing for X-ray free electron laser science

ExaFEL is an HPC-capable X-ray Free Electron Laser (XFEL) data analysis software suite for both Serial Femtosecond Crystallography (SFX) and Single Particle Imaging (SPI) developed in collaboration with the Linac Coherent Lightsource (LCLS), Lawrence Berkeley National Laboratory (LBNL) and Los Alamos National Laboratory. ExaFEL supports real-time data analysis via a cross-facility workflow spanning LCLS and HPC centers such as NERSC and OLCF. Our work therefore constitutes initial path-finding for the US Department of Energy's (DOE) Integrated Research Infrastructure (IRI) program. We present the ExaFEL team's 7 years of experience in developing real-time XFEL data analysis software for the DOE's exascale supercomputers. We present our experiences and lessons learned with the Perlmutter and Frontier supercomputers. Furthermore we outline essential data center services (and the implications for institutional policy) required for real-time data analysis. Finally we summarize our software and performance engineering approaches and our experiences with NERSC's Perlmutter and OLCF's Frontier systems. This work is intended to be a practical blueprint for similar efforts in integrating exascale compute resources into other cross-facility workflows.

Optimizing the effect of heat treatment on the mechanical properties (tensile Strength and hardness) of Hyphaene Thebaica nut; A machine learning and Taguchi approach

The demand for innovative and sustainable biomaterials in healthcare and biotechnology has fueled the need for advancements in its engineering performance. However, the limited properties of biomaterials without the integration of synthetic reinforcements or supports pose a challenge. Consequently, there is a growing necessity for the development of full cycle eco-friendly materials. This study focuses on enhancing the mechanical properties of Doum palm nuts through heat treatment for engineering applications. The research employs the Taguchi optimization technique and genetic algorithms to determine the optimal combination of heating temperature and holding time, aiming to achieve the highest tensile strength and hardness. The results showcase the effectiveness of the proposed approach, revealing the optimal tensile strength of 7.32 MPa at a treatment temperature of 50 °C and a holding time of 120 min. Similarly, the optimum hardness of 60.3 Hv is attained at a heat treatment temperature of 100 °C and a holding time of 120 min. The study further investigates chemical changes through Fourier transform infrared analysis and optical micrographs. Regression models for tensile strength and hardness are developed, and the global optimum is found using a genetic algorithm solver. The findings of this study demonstrate significant and remarkable improvements in the mechanical properties of biomaterials, highlighting their potential for demanding engineering applications. The optimized heat treatment parameters provide a path towards enhanced biomaterials performance and offer promising avenues for the development of tougher and more resilient materials. This research contributes to the field of biomaterials engineering, paving the way for the design and production of eco-friendly materials with superior mechanical properties, thus addressing the ongoing demand for innovative and sustainable solutions in various industries.

Optimizing engineering potential in sustainable structural concrete brick utilizing pond ash and unwashed recycled glass sand integration

The Australian construction sector faces a dual challenge of high demand for concrete bricks and the need for sustainable materials. This research investigates eco-friendly structural concrete brick formulations, incorporating pond ash and unwashed recycled glass sand. It aims to provide scientific evidence on their engineering performance as per AS/NZS 4455.1:2008 standard, thermal insulation, and fire resistance properties. Additionally, microstructural, chemical, and pore-structure analyses are carried out to gain insights into the reaction mechanisms and the evolution of their properties. Findings indicate that bricks with 15% pond ash and 20% unwashed glass sand meet structural requirements with compression strength of 29.63MPa at 28 days. Enhanced thermal insulation is observed due to the lower densities of pond ash and glass sand. After a 2-hour exposure to elevated temperatures, the unexposed surface of these bricks remains below 180°C, satisfying fire resistance criteria for wall elements. However, microstructure and chemistry analyses suggest lower compression and tensile strength comparable conventional bricks because of low reactivity of the pond ash and the smooth surface of the glass sand.

Enhancing Sustainable Subgrade Engineering Using Soil Tuff for Modifying Iron Tailings Sand: A Comprehensive Engineering Performance and Sustainability Analysis

Soil tuff, an industrial solid waste, can serve as a sustainable alternative to cement for modifying iron tailings sand (ITS). To substantiate this claim, the physical properties, durability and microstructure of soil tuff and cement-modified ITSs were analyzed at different modifier dosages, compaction degrees and maintenance ages, with a comprehensive comparison in the perspective of sustainable built environments. The results indicate that the physical properties of soil tuff-modified ITS (STM-ITS) were significantly enhanced in subgrade engineering applications compared with cement-modified ITS (CM-ITS). In addition, compared with CM-ITS, the hydration products of STM-ITS possessed a smaller amount of Ca(OH)2 and were cemented with surrounding binding products, which resulted in fewer cracks. STM-ITS featured a more stable C–S–H gel than CM-ITS due to a lower Ca/Si ratio, contributing to its higher corrosion resistance. Notably, a sustainability analysis demonstrated that incorporating STM-ITS has physical properties comparable to those of CM-ITS and can be obtained at a significantly lower cost, CO2 emission, and energy consumption. Therefore, this study highlights the potential of soil tuff as a promising eco-friendly option for subgrade engineering, promoting waste usage, improving built environments, and contributing to carbon-neutrality goals. These findings have significant implications for the construction industry and the pursuit of sustainable development.

Sedimentation-affected engineering performances and microstructures of a hybrid Portland-sulfate aluminate cement grout cast in long tubes

Material sedimentation may have non-negligible impacts on engineering properties of flowable cement grouts, and this issue cannot be addressed by in-lab tests on small size specimens. Herein, sedimentation tests were conducted to a high-strength hybrid Portland-sulfate aluminate cement (P-SAC) grout cast in 6-m-long tubes. Compressive strength and density of the P-SAC specimens at different depths were measured, and microstructures were assessed by X-ray computed tomography (XCT), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results showed that the hybrid P-SAC grout possessed the superior indices of flowability, expansion and compressive strength. The increasing rates of density and compressive strength to depth were 9.3 kg/m4 and 0.5 MPa/m, respectively. The shallow sites possessed a porous structure with 14.5 % more big pores (>1 mm). The pore structure followed fractal patterns, and the fractal dimensions increased slightly with depth. Our findings not only deepen the understandings in slurry sedimentation and the consequences of engineering properties, but also narrow the knowledge gaps between in-lab tests and in-situ applications for grouting construction.

Predicting the Compressive Strength of Sustainable Portland Cement-Fly Ash Mortar Using Explainable Boosting Machine Learning Techniques.

Unconfined compressive strength (UCS) is a critical property for assessing the engineering performances of sustainable materials, such as cement-fly ash mortar (CFAM), in the design of construction engineering projects. The experimental determination of UCS is time-consuming and expensive. Therefore, the present study aims to model the UCS of CFAM with boosting machine learning methods. First, an extensive database consisting of 395 experimental data points derived from the literature was developed. Then, three typical boosting machine learning models were employed to model the UCS based on the database, including gradient boosting regressor (GBR), light gradient boosting machine (LGBM), and Ada-Boost regressor (ABR). Additionally, the importance of different input parameters was quantitatively analyzed using the SHapley Additive exPlanations (SHAP) approach. Finally, the best boosting machine learning model's prediction accuracy was compared to ten other commonly used machine learning models. The results indicate that the GBR model outperformed the LGBM and ABR models in predicting the UCS of the CFAM. The GBR model demonstrated significant accuracy, with no significant difference between the measured and predicted UCS values. The SHAP interpretations revealed that the curing time (T) was the most critical feature influencing the UCS values. At the same time, the chemical composition of the fly ash, particularly Al2O3, was more influential than the fly-ash dosage (FAD) or water-to-binder ratio (W/B) in determining the UCS values. Overall, this study demonstrates that SHAP boosting machine learning technology can be a useful tool for modeling and predicting UCS values of CFAM with good accuracy. It could also be helpful for CFAM design by saving time and costs on experimental tests.

Sustainability of Asphalt Mixtures Containing 50% RAP and Recycling Agents

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential “GWP”) for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures.

Green Hydrogen Production by Low-Temperature Membrane-Engineered Water Electrolyzers, and Regenerative Fuel Cells.

Green hydrogen (H2) is an essential component of global plans to reduce carbon emissions from hard-to-abate industries and heavy transport. However, challenges remain in the highly efficient H2 production from water electrolysis powered by renewable energies. The sluggish oxygen evolution restrains the H2 production from water splitting. Rational electrocatalyst designs for highly efficient H2 production and oxygen evolution are pivotal for water electrolysis. With the development of high-performance electrolyzers, the scale-up of H2 production to an industrial-level related activity can be achieved. This review summarizes recent advances in water electrolysis such as the proton exchange membrane water electrolyzer (PEMWE) and anion exchange membrane water electrolyzer (AEMWE). The critical challenges for PEMWE and AEMWE are the high cost of noble-metal catalysts and their durability, respectively. This review highlights the anode and cathode designs for improving the catalytic performance of electrocatalysts, the electrolyte and membrane engineering for membrane electrode assembly (MEA) optimizations, and stack systems for the most promising electrolyzers in water electrolysis. Besides, the advantages of integrating water electrolyzers, fuel cells (FC), and regenerative fuel cells (RFC) into the hydrogen ecosystem are introduced. Finally, the perspective of electrolyzer designs with superior performance is presented.

Analytical approach for vertical dynamic responses of stiffened deep cement mixing pile in unsaturated ground

Stiffened deep cement mixing (SDCM) piles present excellent engineering performance compared with conventional pipe piles and thus are often applied to the structure foundation in coastal soft-soil area. This study intends to explore the vertical dynamic behavior of a SDCM pile in unsaturated soil by developing an analytical approach. In the proposed approach, the SDCM pile divides into two parts. The first part is considered as a composite pile formed by a prestressed high-strength concrete (PHC) pipe pile and a cement mixing pile through high-strength bonding, and the second part formed by the PHC pipe pile and an unsaturated soil column. The closed-form solution for the dynamic impedance of the SDCM pile has been determined and then verified by contrasting with the existing solutions, where the dynamic impedance is mainly characterized by dynamic stiffness and dynamic damping at SDCM pile head in the vertical direction. Numerical discussions are finally implemented to analysis the dependence of physical parameters of cement mixing pile, PHC pipe pile, and unsaturated soil on the vertical dynamic impedance of SDCM pile. It can be concluded that increasing the depth, radius and elastic modulus of the cement mixing pile at relatively low load excitation frequencies is beneficial for enhancing the vertical vibration resistance of the SDCM pile, while the reverse is true at higher load excitation frequencies. Quantitatively, under relatively low load excitation frequencies, the reinforcement depth of the cement mixing pile should not exceed 2/3 of the length of the PHC pipe pile, while its elastic modulus should be 5 ‰ to 2 % of the elastic modulus of the PHC pipe pile.

17.2% Efficiency for Completely Non‐Fused Acceptor Organic Solar Cells Via Re‐Intermixing Strategy in D/A Stratified Active Layer

AbstractPursuing power conversion efficiency (PCE) is the priority of developing organic solar cells (OSCs) based on low‐cost completely non‐fused ring acceptors. Herein, a donor/acceptor re‐intermixing strategy to enhance the photon capturing process, based on a previously established well‐stratified active layer morphology is reported. By adding 20 wt% PTQ10 (polymer donor) into the acceptor's precursor, the device PCE is increased to 16.03% from 15.11% of the D18/A4T‐16 control system, which is attributed to the additional charge generation interface and suppressed bimolecular recombination. On the contrary, using the equal ratio of PM6 leads to significant efficiency loss, indicating the importance of considering vertical distribution from the perspective of thermodynamics. Moreover, a cutting‐edge level of 17.21% efficiency for completely non‐fused ring acceptor systems is realized by altering the active layer to PBQx‐TF/TBT‐26 and PTQ11, via the identical processing strategy. This work thus presents attractive device engineering and solar cell performance, as well as in‐depth vertical morphology understanding.

Financial Performance Measurement Using the Value Added Method to Determine the Effect on Stock Prices

One of the Indonesian government's policies since 2015 has been to increase development through its developed infrastructure, by increasing its budget for this sector from year to year. However, companies listed in the engineering and construction subsector on the Indonesian Stock Exchange, both state-owned enterprises and private companies, experienced losses so it could be said that their financial performance was poor. This study intends to evaluate the financial performance engineering and construction sub-sector companies using the Economic Value Added (EVA), Market Value Added (MVA), Refined Economic Value Added (REVA), Financial Value Added (FVA), and Shareholder Value Added (SVA) in 2018 – 2023 and determine their influence on stock prices. This type of research is quantitative descriptive research using E-Views 12 with a population 26 companies and a sample size 16 companies. Based on the results the calculations and analysis, it stated that EVA, MVA, REVA, FVA, SVA and stock prices engineering and construction companies, both state-owned and private, during the 2018 - 2023 period obtained an average of negative amounts. The research results show that the financial performance variables using value added have an influence on stock prices with influence of 74.57% while the rest is influenced by other variables not examined in this research. Partially only MVA and SVA have an influence on stock prices because based on the probability test using E-Views 12 it appears that only MVA and SVA produce results below the alpha. The suggestion for this research is that company management should pay attention to the company's financial performance, especially the MVA and SVA variables and further researcher can make comparative research between all value-added variables.

Novel chitosan-enhanced alkali-activated material for remediation of zinc-contaminated coastal mudflat sediment

Sustainable utilization and development for contaminated mudflat sites face dual challenges associated with contaminant enrichment and engineering diseases, impacting ecological quality and coastal construction. Commonly used cement has limitations in ensuring geo-environmental engineering performances for polluted sediments. This study investigates a solidification/stabilization approach using novel chitosan-enhanced alkali-activated material (CTS-AAM) to remediate highly concentrated zinc-contaminated sediments. Results exhibit that the compressive strength and water stability of sediments are remarkably improved by CTS-AAM, satisfying engineering service even under long-term immersion and zinc accumulation. Significant improvements dependent on curing period and CTS-AAM dosage also reflect in the resistance to deformation of remediated sediments, maintaining low-compressibility states due to the enhancement of structural yield stress. The leaching toxicity of remediated sediments meets Zn ≤ 5.0 mg/L, as zinc primarily distributes to the residual fraction associated with low mobility. The bidirectional enhancement of toxic sediment is attributed to the generation of hydrates with cementitious and pore-filling effects through hydration reactions. Simultaneously, chitosan with hydrated gels and ettringite collectively form gel networks and compact skeleton structures within sediments, as well as immobilize Zn through comprehensive physical encapsulation, chemical binding, and chelation. This study provides a feasible strategy for future projects involving remediation and utilization of mudflats.