Low Carbon Footprint Research Articles

Understanding the deterioration of hydration products in alkali-activated slag/Portland cement exposure to sulfate attack

The deterioration of different phases under sulfate attack is a critical durability problem for cementitious materials. Alkali-activated slag (AAS) is a kind of low carbon footprint cementitious material, whose hydration products are quite different from that of Portland cement (PC). The specific variations in the behavior of different hydration products under sulfate attack in PC and AAS have not been comprehensively explored. In this paper, a combination of BSE and EDS techniques was applied to investigate the change of various hydration products in PC and AAS before and after exposure to sulfate solutions. The results indicate that the unhydrated slag in AAS is more stable than the unhydrated C2S and C3S in PC paste after exposure to deionized water and sulfate solutions, and obvious substitution of Ca by Mg can be found for C2S and C3S after exposure to MgSO4 solution. In PC sample, the Ca/Si reduction of outer product after deterioration in different solutions is less significant than that of inner product, mainly due to the existing of Ca rich phases intermixed in Op. While in AAS, the change of Ca/Si in dark rims in different solutions is consistent with that of C-A-S-H presented in the matrix. After exposure to sulfate solutions, no significant sulfate rich area can be observed for AAS, which should mainly be attributed to the relatively slower formation of gypsum in AAS due to the absence of highly soluble calcium-rich phases like portlandite in PC.

Photocatalytic NOx removal and self-cleaning performance of polymeric carbon nitride functionalized alkali-activated slag composites

Alkali-activated slag (AAS) materials have been extensively investigated and employed for the photocatalytic coating incorporation due to their favorable binding property and low carbon emissions. However, the effects of photocatalysts on the microstructure and mechanical performance of AAS composites remain controversial, which have a significant impact on the durability of the photocatalytic composites in the real-life service environment. Herein, polymeric carbon nitride (PCN), as a metal-free photocatalyst, was mixed with AAS materials to prepare photocatalytic composites for nitrogen oxide (NOx) removal and surface self-cleaning. The PCN dosage effects on hydration products, microstructure, as well as mechanical and photocatalytic performances of the photocatalytic AAS composites were systematically studied. The results show that while hydration product formations are hindered by the PCN addition, its presence contributes to the carbonization of AAS composites. Additionally, due to the PCN microfiller effect, the microstructure of AAS composites is improved with the PCN addition, and the compressive strength of AAS composites becomes stronger as PCN dosage increases from 0 % to 6 %. The photocatalytic NOx removal and self-cleaning performances of PCN-added AAS composites are firstly increased and then decreased with the PCN addition. These findings provide the theoretical basis and technical support for PCN-added AAS composites application which satisfies the requirement for a sustainable and low carbon footprint future.

Develop a novel and multifunctional soy protein adhesive constructed by rosin acid emulsion and TiO2 organic-inorganic hybrid structure

Soy protein adhesives (SPI) exhibit broad prospects in substituting aldehyde-based resin due to the economic and environmental-friendly characteristics, but still face a challenge because of the dissatisfied bonding strength and terrible water resistance. Herein, prompted by organic-inorganic hierarchy, a multifunctional and novel soy protein adhesive (SPI-RAE-TiO2) consisting of rosin acid emulsion (RAE) and TiO2 nanoparticles (TiO2) were proposed. In comparison with original SPI, the dry and wet shear strengths of modified adhesive reached 2.01 and 1.21 MPa, respectively, which were increased by 130 % and 200 %. Furthermore, SPI-6RAE-0.5TiO2 was selected as the best proportion via the method of response surface methodology (RSM). What's more, SPI-6RAE-0.5TiO2 adhesive demonstrated prominent coating performance in both dry and wet surface conditions. Meanwhile, SPI-6RAE-0.5TiO2 adhesive possessed excellent mildew resistance and antibacterial ability with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), reflecting the antibacterial rates 97.71 % and 98.16 %, respectively. In addition, SPI-6RAE-0.5TiO2 adhesive also exhibited the outstanding green features such as the reduction of formaldehyde pollution and greenhouse effect through Life Cycle Assessment (LCA). Thus, this work provided a novel and functional approach to design multifunctional, superior-property and low-carbon footprint soy protein adhesive.

Development & Validation of a Packed Bed Thermal Energy Storage Model

The rapid growth of economies and population around the world have exponentially increased the demand for energy. This demand has invoked increased annual global CO2 emissions and necessitated a transition to clean energy technologies. Reliable and affordable energy storage technologies are paramount for increasing renewable energy penetration onto the grid, supporting periods with reduced or no renewable energy generation. This project is aimed at developing a Thermal Energy Storage (TES) solution that can deliver heat to a heat engine for power production or to an industrial process for prolonged periods. TES long duration energy storage (LDES) presents many potential benefits, including 1) Low Cost 2) scalability 3) high energy density 4) low carbon footprint and 5) resiliency via ability to produce synchronous power (i.e., spinning turbomachinery). The broader objective of this project is to build, test, and model the TES concept at a 2 MWh scale to determine the economic and physics-based practicality of the system. The work presented here describes the first phase objectives of the project, including benchtop scale testing, model development, and Model Validation.

Utilization of dumped coal ash from power-plant landfills for carbon footprint reduction in sustainable pavement base construction

This study presents a novel methodology for repurposing dumped coal ash (DCA) from power plant landfills, aiming to reduce waste and lower carbon footprint of pavement base construction. Three DCAs were modified into two distinct particle groups through sieving: fine particles for cement replacement, evaluated against a ternary cementitious binder with fly ash (FA) and flue gas desulfurization gypsum (FG) using Response surface methodology (RSM), and coarse particles for aggregate treatment. The modified DCA mixes and conventional cement-treated base (CTB) mix were compared for environmental and economic benefits through cradle-to-gate life cycle assessment. The results indicate that replacing fine DCA optimized setting time and compressive strength based on its chemical composition, aligning with FA and FG in the RSM process. A 25 % cement replacement with fine DCA balanced the mechanical properties of the modified cement, while a 50 % replacement with coarse DCA effectively improved aggregate properties compared to natural crushed rock. Modified DCA enhanced pavement engineering properties, surpassing the strength and resilience benchmarks of CTB mix. Utilizing optimal modified DCA mixes could reduce carbon footprint and costs by approximately 40 % and 44 %, respectively. Hence, the outcomes highlight challenges and opportunities for modifying DCA for resource conservation and low-carbon transportation infrastructure.

Split injection timing optimization in ammonia/biodiesel powered by RCCI engine

Employing carbon-neutral (NH3) and low carbon footprint (biodiesel) fuels in Reactivity Controlled Compression Ignition (RCCI) engine mode is one possible method for minimizing carbon emissions in diesel engines. In this study, a Compression Ignition (CI) engine was customized to run in RCCI mode, employing High Reactive Fuel (HRF) as biodiesel and Low Reactive Fuel (LRF) as ammonia (NH3). Based on our earlier findings, the proportion of ammonia in premixing is fixed at 40 %. In the first phase, the primary injection timing of the algal biodiesel varied between 12 and 21°CA bTDC at a preset pre-injection timing of 46°CA bTDC. In the next phase, the pre-injection time varied between 46 and 54°CA bTDC, with the optimal main injection time being 18°CA. The result suggested that the optimal main and pre-injection at 18 and 58°CA bTDC increased the Cylinder Pressure (CP) by 30.1 %, and peak HRR and combustion phase angle were advanced. Brake Thermal Efficiency exhibited an 11 % enhancement, with Brake Specific Energy Consumption decreasing by 24.1 %. Nitrogen Oxide levels saw an increase of around 39.5 %. In contrast, reductions of 19.2 %, 23.5 %, 39.7 %, and 21.7 % were observed in Hydrocarbons, Carbon Monoxide, smoke emissions, and Exhaust Gas Temperature, respectively, compared to the single injection under full load conditions.

ETHYLENE CONVERSION IN A BARRIER DISCHARGE: EXPERIMENT AND MODELING

The selective conversion of ethylene and its mixtures with argon and air in a barrier discharge has been studied. Plasma chemical transformation proceeds without the formation of polymer-like substances or products of deep oxidation to oxygen-containing compounds and various saturated and unsaturated hydrocarbons. Synthesis is carried out on a set-up with a gas-liquid reactor in the presence of water, which ensures the elimination of formed substances from the discharge area and prevents repeated exposure to barrier discharge plasma. The treatment of ethylene in a barrier discharge leads to the formation of saturated and unsaturated hydrocarbons C1–C5+ with a predominance of compounds with four carbon atoms in the molecule, the total content of which in the reaction products reaches 58.4 wt.%. The addition of argon to ethylene does not significantly affect the set and content of substances in the reaction products, an increase in ethylene conversion is observed, the maximum value of which reaches 58.9 wt.%. The treatment of a mixture of ethylene with air additives leads to the formation of hydroxyl and carboxyl compounds with a total content of ~29 wt.% in the products, and saturated and unsaturated hydrocarbons C1–C4 with a predominant acetylene content up to ~47 wt.%. The conversion of ethylene in one pass of the reaction mixture through the reactor under these conditions is 12.8 wt.%. When evaluating the energy losses of barrier discharge electrons in electron-molecular interactions during the conversion of ethylene, it was found that 78% of the energy of barrier discharge electrons is spent mainly on excitation of the electronic states of ethylene molecules, and argon additives can increase it to 86%. In the case of conversion of ethylene mixtures with air additives, it is shown that only ~14% of the discharge energy is spent on the excitation of the electronic states of the ethylene molecule, and the main amount (65%) is spent on the excitation of various different states of nitrogen molecules. The data obtained were used to develop a model of the chemical kinetics of ethylene conversion in a barrier discharge. The proposed model contains more than 280 reactions and is in good agreement with experimental data. As a result of the simulation, new data were obtained on the behavior of an ethylene molecule in a barrier discharge plasma with an average electron energy of 4-5 eV. The results obtained will be useful in the development of modern ethylene processing methods focused on the technological simplicity and compactness of the chemical process that meets the principles of "green chemistry" and low carbon footprint in the environment. For citation: Ryabov A.Yu., Kydryashov S.V. Ethylene conversion in a barrier discharge: experiment and modeling. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 6-14. DOI: 10.6060/ivkkt.20246708.12t.

Recombination Activity of Crystal Defects in Epitaxially Grown Silicon Wafers for Highly Efficient Solar Cells

Aiming for highly efficient solar cells based on wafers with a low carbon footprint, silicon (Si) EpiWafers are grown epitaxially on reusable, highly doped Si substrates with a stack of porous Si layers (PorSi) for detachment. A state‐of‐the‐art p‐type Si EpiWafer exhibiting a minority charge carrier lifetime of up to 2.2 ms detected at an excess charge carrier density of ≈1 × 1015 cm−3 by photoluminescence (PL) imaging is presented. This translates to a predicted solar cell efficiency of 25.6%, calculated by efficiency limiting bulk recombination analysis (ELBA), and corresponds to losses of less than 1%abs compared to the theoretical limit of the investigated solar cell concept. A detailed loss analysis shows that the major remaining quality limitations are structural defects, specifically stacking faults (SFs). Therefore, the recombination activity of isolated SFs in epitaxially grown reference (EpiRef) wafers on polished substrates without a PorSi is assessed by highly resolved μPL mappings. The recombination activity rises with the number of dislocations within an SF as demonstrated by a comparison to microscope images. When using highly doped substrates, as currently required for EpiWafer fabrication, EpiRef wafers show more SFs exhibiting additionally a higher number of dislocations than SFs in EpiRef wafers on moderately doped substrates.

Identifying a sustainable rice-based cropping system via on-farm evaluation of grain yield, carbon sequestration capacity and carbon footprints in Central China

ContextRice-based cropping system is a major anthropogenic source of direct greenhouse gases (GHG) emissions, agricultural inputs also produces numerous indirect GHG emissions and environmental problems. Identification of rice cropping systems with lower GHG emissions and higher grain yields is of great significance to ensure food security while minimizing agricultural carbon footprint (CF). ObjectiveThis study aimed to identify the optimal rice-based cropping system with lower greenhouse effects and comparable annual yield in central China. MethodsUsed life cycle assessment, a two-year field experiment was performed to evaluate the direct and indirect GHG emissions, CF, and carbon sequestration capacity in the six rice-based cropping systems widely used in central China, which consisted of fallow-early rice-late rice, rapeseed-early rice-late rice, fallow-ratoon rice, rapeseed-ratoon rice (RRaR), fallow-middle rice, and rapeseed-middle rice. ResultsThe results showed that compared with the three systems with fallow season, the three systems with rapeseed had lower annual CH4 emissions. The two systems with ratoon rice had lower annual indirect and direct GHG emissions than the two systems with double rice. The three systems with rapeseed had higher annual biomass, grain yields, and fixed carbon in biomass and significantly lower CF than the three systems with fallow season, and RRaR had the highest value of fixed carbon in biomass. The systems with ratoon rice had lower average CF than those systems with double rice. CH4 emissions from paddy fields were the primary source of total annual GHG and the main component of CF. Compared with the three systems with fallow season, the three systems with rapeseed had significantly higher annual carbon sequestration capacity based on net ecosystem production (NEP). Ratoon rice systems had higher average NEP than double- and middle-rice systems. RRaR had the lowest CF per unit yield and highest NEP among all the six systems. ConclusionsThe results indicated that appropriate rice-based cropping systems may alleviate the greenhouse effect via reducing GHG emissions and enhancing paddy NEP, RRaR could achieve relatively higher annual grain yield and carbon sequestration capacity as well as lower CF. SignificanceThis study highlight conversion of double rice and middle rice systems to RRaR may help improve grain yield and mitigate greenhouse effect. The findings may provide a theoretical basis for selection of sustainable development of rice based cropping systems in central China.

Recent Advances in Efficient Lutein-Loaded Zein-Based Solid Nano-Delivery Systems: Establishment, Structural Characterization, and Functional Properties.

Plant proteins have gained significant attention over animal proteins due to their low carbon footprint, balanced nutrition, and high sustainability. These attributes make plant protein nanocarriers promising for applications in drug delivery, nutraceuticals, functional foods, and other areas. Zein, a major by-product of corn starch processing, is inexpensive and widely available. Its unique self-assembly characteristics have led to its extensive use in various food and drug systems. Zein's functional tunability allows for excellent performance in loading and transporting bioactive substances. Lutein offers numerous bioactive functions, such as antioxidant and vision protection, but suffers from poor chemical stability and low bioavailability. Nano-embedding technology can construct various zein-loaded lutein nanodelivery systems to address these issues. This review provides an overview of recent advances in the construction of zein-loaded lutein nanosystems. It discusses the fundamental properties of these systems; systematically introduces preparation techniques, structural characterization, and functional properties; and analyzes and predicts the target-controlled release and bioaccessibility of zein-loaded lutein nanosystems. The interactions and synergistic effects between Zein and lutein in the nanocomplexes are examined to elucidate the formation mechanism and conformational relationship of zein-lutein nanoparticles. The physical and chemical properties of Zein are closely related to the molecular structure. Zein and its modified products can encapsulate and protect lutein through various methods, creating more stable and efficient zein-loaded lutein nanosystems. Additionally, embedding lutein in Zein and its derivatives enhances lutein's digestive stability, solubility, antioxidant properties, and overall bioavailability.

Sustainable local seismic culture in vernacular buildings of the Indian Himalayas: Field observations, knowledge dissemination, and recommendations

Vernacular buildings are the classic examples of sociocultural development, centuries of experience, and empirical knowledge gained from past earthquakes to construct climate-cum-earthquake resistant indigenous buildings in seismic-prone regions across the globe. Vernacular buildings are constructed using re-usable or re-cyclable materials with a low carbon footprint and are thus sustainable, and these buildings also follow local seismic culture in their building attributes. Elaborate field investigations are conducted in the Indian Himalayas to investigate the local seismic culture in prevalent vernacular building systems, namely, Kath-Kunni, Thathara, Taq, Dhajji-Dewari, Ikra, and Rammed-earth. Based on field observations, these building systems are rated to understand their relative merits/de-merits for earthquake-resiliency and construction sustainability attributes. Simple, ready-to-use sketches are developed to disseminate the construction process of vernacular buildings. Further, recommendations are made to overcome deficits and promote vernacular buildings for earthquake-resilient sustainable development in the Indian Himalayas.

Machine learning-assisted wood materials: Applications and future prospects

Wood and wood-based materials, surpassing their conventional image as mere stems and branches of trees, have found extensive utilization in diverse industrial sectors due to their low carbon footprint. Nonetheless, maximizing wood utilization and advancing multifunctional wood materials face challenges due to resource-intensive conventional approaches. Integrating machine learning (ML) in wood mechanics has emerged as a promising avenue for deeper exploration of this remarkable material. By leveraging advanced computational techniques, researchers can delve into wood's intricate properties and behavior, unraveling the complex interactions between its chemical constituents, microstructures, and mechanical characteristics. Combined with imaging and sensor technologies, ML contributes to efficient, fast, and real-time health detection of wood materials. This review aims to illuminate the transformative impact of ML in unlocking the hidden potential of wood, fostering innovative applications, and facilitating sustainable engineering solutions. The basic workflow of ML and its typical applications in property prediction, defect detection, and optimized design of wood materials are discussed, thereby highlighting the challenges and the need for future research.

Mechanistic Implications of the Varying Susceptibility of PAHs to Pyro-Catalytic Treatment as a Function of Their Ionization Potential and Hydrophobicity.

Transition metal catalysts in soil constituents (e.g., clays) can significantly decrease the pyrolytic treatment temperature and energy requirements for efficient removal of polycyclic aromatic hydrocarbons (PAHs) and, thus, lead to more sustainable remediation of contaminated soils. However, the catalytic mechanism and its rate-limiting steps are not fully understood. Here, we show that PAHs with lower ionization potential (IP) are more easily removed by pyro-catalytic treatment when deposited onto Fe-enriched bentonite (1.8% wt. ion-exchanged content). We used four PAHs with decreasing IP: naphthalene > pyrene > benz(a)anthracene > benzo(g,h,i)perylene. Density functional theory (DFT) calculations showed that lower IP results in stronger PAH adsorption to Fe(III) sites and easier transfer of π-bond electrons from the aromatic ring to Fe(III) at the onset of pyrolysis. We postulate that the formation of aromatic radicals via this direct electron transfer (DET) mechanism is the initiation step of a cascade of aromatic polymerization reactions that eventually convert PAHs to a non-toxic and fertility-preserving char, as we demonstrated earlier. However, IP is inversely correlated with PAH hydrophobicity (log Kow), which may limit access to the Fe(III) catalytic sites (and thus DET) if it increases PAH sorption to soil OM. Thus, ensuring adequate contact between sorbed PAHs and the catalytic reaction centers represents an engineering challenge to achieve faster remediation with a lower carbon footprint via pyro-catalytic treatment.

Performance Characterization and Composition Design Using Machine Learning and Optimal Technology for Slag-Desulfurization Gypsum-Based Alkali-Activated Materials.

Fly ash-slag-based alkali-activated materials have excellent mechanical performance and a low carbon footprint, and they have emerged as a promising alternative to Portland cement. Therefore, replacing traditional Portland cement with slag-desulfurization gypsum-based alkali-activated materials will help to make better use of the waste, protect the environment, and improve the materials' performance. In order to better understand it and thus better use it in engineering, it needs to be characterized for performance and compositional design. This study developed a novel framework for performance characterization and composition design by combining Categorical Gradient Boosting (CatBoost), simplicial homology global optimization (SHGO), and laboratory tests. The CatBoost characterization model was evaluated and discussed based on SHapley Additive exPlanations (SHAPs) and a partial dependence plot (PDP). Through the proposed framework, the optimal composition of the slag-desulfurization gypsum-based alkali-activated materials with the maximum flexural strength and compressive strength at 1, 3, and 7 days is Ca(OH)2: 3.1%, fly ash: 2.6%, DG: 0.53%, alkali: 4.3%, modulus: 1.18, and W/G: 0.49. Compared with the material composition obtained from the traditional experiment, the actual flexural strength and compressive strength at 1, 3, and 7 days increased by 26.67%, 6.45%, 9.64%, 41.89%, 9.77%, and 7.18%, respectively. In addition, the results of the optimal composition obtained by laboratory tests are very close to the predictions of the developed framework, which shows that CatBoost characterizes the performance well based on test data. The developed framework provides a reasonable, scientific, and helpful way to characterize the performance and determine the optimal composition for civil materials.

Reinforcing steels in low-carbon mortars subjected to chloride attack and natural carbonation: Contradictory trends in passivation ability and corrosion resistance

After a 7-year exposure to simulated marine environments with chloride attack and natural carbonation, the passivation ability and corrosion resistance of carbon steel and 2304 duplex stainless steel in two types of low-carbon mortars, designed with alkali-activated slag and Bayer red mud, were investigated, which were compared with those observed in ordinary Portland cement (OPC) mortar. Although a reduced passivation ability was confirmed for steels in the low-carbon mortars, an improved corrosion resistance was highlighted after long-term exposure. Accordingly, the underlying mechanisms for the detrimental impacts and beneficial effects on the corrosion resistance of steels provided by these low-carbon mortars were discussed in terms of pore solution chemistry, pore structure as well as electrical resistivity, which will shed new lights on the design of novel cementitious materials with low carbon footprint and high corrosion protection.

Mechanized wet direct seeding for increased rice production efficiency and reduced carbon footprint

Crop establishment is one of the major rice production operations that strongly affects rice production, productivity, and environmental impacts. This research introduced a new technology and provided scientific evidence for the benefits of mechanized wet direct seeding (mDSR) of rice as compared with the other crop establishment practices commonly applied by farmers for wet direct seeded rice in Mekong River Delta in Vietnam, such as seeding in line using drum-seeder (dDSR) and broadcast seeding (bDSR). The experiment was implemented across two consecutive rice cropping seasons that are Winter-Spring season and Summer-Autumn season in 2020–2021. Treatments included (1–3) mDSR with seeding rates of 30, 50, and 70 kg ha− 1, (4) dDSR with 80 kg ha− 1 seed rate, and (5) bDSR as current farmer practice with seeding rate of 180 kg ha− 1. The fertilizer application was adjusted as per seeding rate with 80:40:30 kg ha− 1 N: P2O5: K2O with lower seed rate 30 and 50 kg ha− 1 in mDSR; 90:40:30 kg ha− 1 N: P2O5: K2O with medium seed rate of 70 to 80 kg ha− 1; and 115:55:40 kg ha− 1 N: P2O5: K2O with high seed rate of 180 kg ha− 1 in bDSR. Mechanized wet direct seeding rice with a lower seed rate of 30 to 70 kg ha− 1 and fertilizer rate by 22–30% reduced variation in seedling density by 40–80% and in yield by 0.1 to 0.3 t ha− 1 and had similar yield to bDSR. In consequence, N productivity was 27 and 32% higher in mDSR as compared to bDSR during the Winter-Spring season and Summer-Autumn seasons, respectively. The use of lower seed rate and fertilizer in mDSR also led to higher income and lower carbon footprint (GHGe per kg of paddy grains) of rice production than the currently used practices of bDSR. Net income of mDSR was comparable to that of dDSR and higher by 145–220 and 171–248 $US than that of bDSR in Winter-Spring season and Summer-Autumn, respectively. The carbon footprint of mDSR rice production compared to bDSR was lower by 22–25% and 12–20% during the Winter-Spring and Summer-Autumn seasons, respectively. Given the above benefits of farming efficiency, higher income, and low emission, mDSR would be a technology package that strongly supports sustainable rice cultivation transformation for the Mekong River Delta of Vietnam.

Experimental study of bond behavior of geopolymer concrete under different curing condition using a pull-out test

Researchers recently have focused on geopolymer concrete as it has several advantages compared to traditional Portland cement, such as lower carbon footprint, high early strength, chemical resistance and long-lasting structural performance. This paper designed 192 pull-out specimens to investigate the influence of factors on the bond-slip behavior between geopolymer and steel bar such as curing condition (ambient and 80 °C for 7 hours), longitudinal rib angle, the position of longitudinal bar, bar diameter (12 mm and 24 mm), stirrup usage (with and without stirrup) and bond length (2d and 4d). The maximum bond strength, bond failure modes, and bond stress-slip relations were discussed. The test results showed that the longitudinal rib angle, and the position of rebar play a vital role in determining the bond strength as well as the bar diameter. In comparison with the specimens without the stirrup, the bond performance of specimens with stirrup increased more significantly, and this phenomenon became even more pronounced as the bar diameter increased. The stirrup usage in samples under ambient and heat cure increased the bond strength by an average of 45 % and %40, respectively. Moreover, it has been determined that the curing conditions have a significant effect on the bond performance, as especially the compressive and tensile strengths of the samples under heat cure improve. In samples exposed to both ambient and heat cure, doubling the bond length increased the bond strength by 70 %. Furthermore, increasing the bar diameter increased the bond strength of the samples exposed to ambient and heat curing by a maximum of 84 % and 79 %, respectively. The findings lay the groundwork for understanding the bond behavior of geopolymer, which is critical for the successful application of geopolymer-bonded rebar.

Towards 3D Pore Structure of Porous Gypsum Cement Pozzolan Ternary Binder by Micro-Computed Tomography

A sophisticated characterisation of a porous material structure has been challenging in material science. Three-dimensional (3D) structure analysis allows the evaluation of a material’s homogeneity, pore size distribution and pore wall properties. Micro-computed tomography (micro-CT) offers a non-destructive test method for material evaluation. This paper characterises a novel ternary binder’s porous structure using micro-CT. Gypsum–cement–pozzolan (GCP) ternary binders are low-carbon footprint binders. Both natural and industrial gypsum were evaluated as a major components of GCP binders. Porous GCP binder was obtained by a foaming admixture, and the bulk density of the material characterised ranged from 387 to 700 kg/m3. Micro-CT results indicate that pores in the range from 0.017 to 3.0 mm can be effectively detected and described for porous GCP binders. The GCP binder structure proved to be dominant by 0.1 to 0.2 mm micropores. For GCP binders produced with natural gypsum, macropores from 2.2 to 2.9 mm are formed, while GCP binders with phosphogypsum possess pores from 0.2 to 0.6 mm. Micro-CT proved to be an effective instrument for characterising the homogeneity and hierarchical pore structure of porous ternary binders.

Global Container Urbanism and Sustainable Urban Development

The crisis of urbanization, marked by rising property values, a lack of affordable housing, and chronic homelessness in cities, has fueled experiments with sustainable alternatives such as shipping container architecture. Shipping container homes are more cost-effective, energy-efficient, ecologically sustainable, versatile, have a lower carbon footprint, and are more durable than conventional construction methods. This study uses semi-structured interviews with container modular firms in selected cities to demonstrate the potential and challenges of construction innovation and the diffusion of container architecture in urban space. The findings call into question the fetishization of environmental friendliness and the allure of rational, mass-produced container homes as a solution to the urban housing crisis. Instead, the study draws attention to the paradox of sustainability, competition, and opposition from the traditional real estate market, regulations, and planning permitting systems, and the standardization-customization divergence of container urbanism.

Moving towards fully circular insect production: A focus on insect-derived biowastes

Over the last decade, commercialization of insects for food and feed has been exponentially increasing. Insect protein is emerging as a sustainable livestock feed and human food alternative due to its low land and carbon footprint. The principles of insect industry are deeply embedded in the core values of sustainability and circular economy. Black soldier fly (BSF) is the crown jewel of insect industry and is one of the most commercially farmed insects. However, this steadfast growth is accompanied by generation of insect based biowaste such as dead flies and pupae exuviae. This will be a major waste fraction from this industry. This study discusses the valorization potential of this waste into chitin (which finds application in cosmetics, bioplastics, and pesticides, among other industries), biogas, fertilizer, and biochar. There is need to conduct more explorative research on value proposition of insect based biowaste to ensure that this industry can comply fully with circular economy and sustainability principles.