The research team, led by Baowen Zhang and Md. Uzzal Hossain of Syracuse University alongside Minhajul Islam Aman and Paul Crovella, designed a family of concrete mixtures built around two supplementary cementitious materials, or SCMs. The first is ground glass powder, or GGP, milled from post-consumer glass bottles and processed by KLAW Industries in Binghamton, New York under the trade name Pantheon. The material is cleaned of organic and metallic contaminants and ground below 75 micrometers, fine enough to qualify as an ASTM-approved SCM that can be dropped directly into standard batching procedures. Chemically, it is classic soda-lime glass: about 74 percent silica, 15 percent sodium oxide, and 8.4 percent calcium oxide. The second ingredient is ground granulated blast-furnace slag, or GGBS, a glassy by-product of ironmaking that has long been prized for its latent hydraulic reactivity.

The chemistry of why these wastes work is elegant. In the highly alkaline pore solution of hydrating cement, the silica-rich glass powder undergoes pozzolanic reactions, consuming calcium hydroxide, a weak and soluble by-product of cement hydration, and converting it into additional calcium silicate hydrate gel, the glue that gives concrete its strength. GGBS contributes through its own slow hydraulic reaction while simultaneously lowering the heat of hydration and mitigating chloride ingress. The researchers blended these two materials in equal proportions, replacing Portland limestone cement at total substitution levels of 40, 50, 60, 70, and 80 percent, alongside a binary mix with 20 percent glass powder alone and a pure cement control. Total binder content was held constant at 390.5 kilograms per cubic meter, with water-to-binder ratios between 0.34 and 0.38, so that binder composition was the only variable.

The mechanical results tell a story of patience rewarded. Early on, the blended mixes lagged badly: at three days, the 20 percent glass powder mix was roughly 20 percent weaker than the control, and the 50 percent replacement mix was down 40 percent. Glass powder reacts slowly, and the diluted cement clinker produces less calcium hydroxide to feed the pozzolanic engine. But by 28 days the gap narrowed dramatically, and by 56 days something remarkable happened. The 70 percent replacement mix, BC-3, reached 62.8 megapascals, actually exceeding the control’s 59.8 megapascals, a five percent gain between 28 and 56 days compared with just six percent for pure cement. The 80 percent mix gained 23 percent over the same window. At extreme replacement levels, the slag hydration and glass pozzolanicity act synergistically, refining the pore structure and densifying the matrix long after the cement alone would have finished reacting.

Durability is where the blends truly shine. Surface resistivity, measured with a four-point Wenner probe according to AASHTO T-358, is a proxy for how easily chloride ions, the chief instigators of rebar corrosion, can migrate through concrete. The control mix measured 11.6 kilo-ohm-centimeters, placing it in the high chloride penetrability category. Every blended mix soared past that benchmark: the 60 percent mix hit 81.9, the 70 percent mix 124, and the 80 percent mix a remarkable 156 kilo-ohm-centimeters, a 1,251 percent increase that lands firmly in the very low penetrability class. All blends also suppressed the alkali-silica reaction, the insidious internal swelling that can crack concrete from within, staying well below the 0.10 percent expansion limit of ASTM C1567, while the control crept to 0.098 percent, dangerously close to the threshold. Drying shrinkage, meanwhile, dropped by 46 to 63 percent in the blended mixes relative to the cement-only control.

The environmental accounting is equally striking. Using a cradle-to-gate life cycle assessment aligned with ISO 14040 and 14044, with one cubic meter of concrete as the functional unit, the team quantified five impact categories using source-specific environmental product declaration data rather than generic industry averages, a methodological choice that better captures regional realities. Global warming potential fell from 371.67 kilograms of CO2-equivalent per cubic meter for the control to reductions of 16.4, 38.8, 46.5, 54.3, and 62.1 percent across the escalating blend levels. Eutrophication impacts tracked a similar downward path, and even acidification and smog formation declined, though the slag’s upstream processing burden slightly offset gains at the lowest blend level. Contribution analysis showed the Portland limestone cement share of carbon emissions falling from 86 percent in the control to 50 percent in the highest-replacement mix.

But raw numbers do not tell engineers which mix to pour. To answer that, the team deployed a multicriteria decision analysis using the simple additive weighting method, normalizing eight performance indicators, including slump, compressive and tensile strength, surface resistivity, setting time, CO2 emissions, alkali-silica expansion, and drying shrinkage, onto a common zero-to-one scale with equal weights. The verdict defied the intuitive assumption that maximum replacement wins. The 60 percent replacement mix, BC-2, took first place with a performance score of 0.755, thanks to the program’s best splitting tensile strength at 3.82 megapascals, strong durability, and solid carbon savings. The 70 percent mix ranked second at 0.745, and the 80 percent mix third at 0.715, penalized by an excessive 230-millimeter slump and the highest shrinkage among the blends. The control finished dead last at 0.661.

The researchers then stress-tested their own ranking. Four alternative weighting scenarios, prioritizing mechanical performance, durability, environmental impact, or constructability, each crowned a different leader: BC-2 under mechanical weighting, BC-3 under durability, BC-4 under environmental priorities, and the 20 percent binary mix under constructability. A Monte Carlo analysis sampling 20,000 random weight vectors found BC-2 and BC-4 each ranked first in roughly a quarter of cases. Yet the broader conclusion held firm: the three high-replacement ternary mixes simultaneously outranked the control in 59 percent of sampled weightings, and individually in 60 to 83 percent, making them clearly preferable whenever durability or carbon reduction matters.

The practical implications are considerable. Slower setting times in the blends, with final set stretching from 350 minutes in the control to as long as 735 minutes, complicate construction scheduling but could prove advantageous in hot-weather concreting and mass pours where cold joints are a risk. The extended workability of high-replacement mixes may even allow formulators to reduce or eliminate high-range water reducers, cutting admixture costs. And because the glass powder derives from municipal recycling streams, the approach converts a landfill liability into structural strength, closing a circular loop at the scale of cities.

Caveats remain. The life cycle assessment excluded transportation of finished materials, and because glass powder and slag may travel farther than locally sourced cement, real-world sourcing could shift the environmental rankings. Long-term performance data on flexural strength, freeze-thaw cycling, and field exposure are still needed. But the core finding stands as a genuine milestone: concrete engineered with 60 to 80 percent waste-derived binder can match or beat conventional concrete on strength at later ages, dramatically outperform it on corrosion resistance and alkali-silira stability, and slash its carbon footprint by more than half. For an industry under intense pressure to decarbonize, the humble discarded glass bottle may turn out to be one of the most valuable materials of the coming decade.

Subject of Research: Sustainable concrete design using ground waste glass powder and blast-furnace slag as high-volume cement replacements

Article Title: Designing sustainable concrete to maximize the use of local waste materials: Mechanical, durability, and sustainability-based multicriteria analysis

Article References: Zhang, B., Aman, M. I., Crovella, P., & Hossain, M. U. (2026). Designing sustainable concrete to maximize the use of local waste materials: Mechanical, durability, and sustainability-based multicriteria analysis. Cleaner Engineering and Technology, 35, Article 101335. https://doi.org/10.1016/j.clet.2026.101335

Image Credits: AI Generated

DOI: 10.1016/j.clet.2026.101335

Keywords: sustainable concrete, ground glass powder, GGBS, cement replacement, carbon emissions, life cycle assessment, multicriteria analysis, durability, alkali-silica reaction, chloride resistance, supplementary cementitious materials, circular economy

The research team, led by Qiaoyun Wu, Zhifeng Xu, Xuyong Chen, and Shukai Cheng, set out to resolve a long-standing trade-off. Lightweight aggregate concrete reduces structural dead load, improves thermal insulation, and lowers seismic forces, which is why it appeals to builders of high-rises, long-span bridges, and coastal infrastructure. But lightweight aggregates are inherently weaker and more porous than natural sand and stone, so piling them into a mix eventually erodes mechanical performance. Earlier work on ultra-high-performance concrete showed that strength first rises and then falls as lightweight aggregate content increases, peaking at moderate replacement levels. The question was whether the superior chemistry of LC3 could compensate for higher doses of a weak, porous aggregate, and whether pre-soaking that aggregate could tip the balance further.

LC3 itself is one of the most promising low-carbon binders in cement science. It blends ordinary Portland cement with calcined clay and limestone powder, typically replacing 30 to 50 percent of the clinker. That substitution cuts carbon dioxide emissions by roughly 30 percent, from about 834 kilograms of CO2 per tonne of cement down to about 556 kilograms, while delivering 28-day strengths comparable to ordinary Portland cement. The magic lies in a synergistic reaction: aluminate species released by the calcined clay react with carbonate ions from the limestone to form carboaluminate hydrates, known as hemicarbonate and monocarbonate phases, alongside additional calcium-aluminosilicate gel. These phases fill pores, consume portlandite, and refine the microscopic architecture of the hardened paste.

Shale ceramsite, the second ingredient, is an expanded, sintered clay aggregate with an apparent density of 1720 kilograms per cubic meter and a water absorption capacity of 5.3 percent. Its porous interior can soak up water and release it later, a property the researchers exploited through internal curing. In the experiments, the ceramsite was either used dry or fully pre-wetted to its saturated surface-dry condition. The pre-wetting water was carefully subtracted from the mixing water so that every mixture shared the same effective water-to-binder ratio of 0.4, ensuring that any performance differences could be attributed to the internal reservoir effect rather than to extra free water. The sand-to-binder ratio was varied from 1.1 to 1.5, and the binder was held constant at 420 parts cement, 120 parts metakaolin, and 60 parts limestone powder per cubic meter.

The mechanical results were striking. All mixtures weighed in below 1700 kilograms per cubic meter when oven-dried, comfortably satisfying the lightweight mortar criterion of 2000 kilograms per cubic meter under EN 206-1. As expected, increasing the aggregate content reduced both density and strength. But the pre-wetted series consistently outperformed its dry-aggregate twin at 7 and 28 days, with the best formulation showing a 10.8 percent gain in 28-day compressive strength at the lowest aggregate ratio. Flexural strength told a subtler story: it fell by 25 to 35 percent as ceramsite content rose, a steeper decline than the 17 to 18 percent seen in compression. The porous particles act as preferential crack initiation sites under tension, while under compression the matrix can redistribute load around the softer inclusions. Pre-wetting strengthens the interfacial transition zone through enhanced local hydration but cannot fully erase the aggregate’s intrinsic weakness.

Perhaps the most commercially compelling number is specific strength, the ratio of compressive strength to density. Across a 36 percent increase in ceramsite dosage, the specific strength of both series remained remarkably stable, and the optimal pre-wetted mixes exceeded 50 megapascals with specific strengths above 0.03 megapascals per unit density. Conventional C50 concrete manages only 0.017 to 0.021, meaning the new material delivers roughly 1.7 to 2.0 times the strength per unit weight. That efficiency translates directly into slimmer columns, lighter foundations, and smaller seismic inertia forces, savings that compound across an entire structure.

Durability results were even more dramatic. In capillary water absorption tests, the pre-wetted mixes absorbed 64 to 67 percent less water over 150 hours than their dry-aggregate counterparts at identical aggregate ratios. Electric flux measurements, a standard proxy for chloride penetrability, told the same story: the pre-wetted mortars showed 59 to 80 percent lower flux, and the best mix registered below 100 coulombs, placing it in the very low permeability class, a level normally associated with high-performance concrete. For marine and coastal construction, where chloride-induced rebar corrosion is the dominant failure mode, that classification carries real practical weight.

The microstructural evidence explains why. X-ray diffraction revealed stronger hemicarbonate and monocarbonate peaks in the pre-wetted samples, confirming that the sustained internal water supply accelerates the signature LC3 reaction between metakaolin-derived aluminate and limestone carbonate. Thermogravimetric analysis quantified the shift: the best pre-wetted mix contained more carboaluminate hydrates and more calcium-aluminosilicate gel while consuming portlandite, converting a relatively inert crystalline byproduct into pore-filling binding phases. Non-evaporable water content, a proxy for hydration degree, was consistently higher in the pre-wetted series, and scanning electron microscopy showed fewer unhydrated clinker grains, fewer portlandite crystals, and a denser, crack-free matrix.

Mercury intrusion porosimetry completed the picture. The pre-wetted mortar with the lowest aggregate ratio achieved the highest gel pore fraction, 47.2 percent, and the lowest macroporosity, just 3.1 percent, with the pore size distribution shifting decisively toward fine capillary and gel pores. Because capillary water uptake is governed by large capillary pores while chloride migration depends on the connectivity of the whole network, this refinement suppresses both transport mechanisms simultaneously. The authors are careful to note that electric flux reflects pore solution chemistry as well as pore structure, and they recommend confirmation through long-term chloride migration and diffusion testing, along with studies of carbonation, freeze-thaw, and sulfate resistance.

The sustainability ledger is nuanced but favorable. Sintering ceramsite consumes about 0.534 gigajoules per tonne, nearly eight times the energy of natural sand, because the process requires kilns running at 1100 to 1250 degrees Celsius. Yet the aggregate can be made from industrial wastes such as fly ash and coal gangue, its lightness shrinks foundation and reinforcement demands, its insulating blocks cut building heating and cooling loads, and its low bulk density reduces transport emissions per cubic meter. Weighed over a full life cycle, the authors argue, these operational and structural savings outweigh the production penalty. Combined with LC3’s 30 percent carbon advantage at the binder stage, the system points toward a generation of lightweight, high-strength, chloride-resistant concrete suited to the decarbonized, resilient infrastructure the coming decades demand.

Subject of Research: Internal curing and phase assembly in limestone calcined clay cement mortar with pre-wetted shale ceramsite

Article Title: Synergistic internal curing and phase assembly in limestone calcined clay cement mortar incorporating pre-wetted shale ceramsite: Mechanical properties, chloride resistance, and pore structure refinement

Article References: Wu, Q., Xu, Z., Chen, X., & Cheng, S. (2026). Synergistic internal curing and phase assembly in limestone calcined clay cement mortar incorporating pre-wetted shale ceramsite: Mechanical properties, chloride resistance, and pore structure refinement. Case Studies in Construction Materials, 25, Article e06607. https://doi.org/10.1016/j.cscm.2026.e06607

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06607

Keywords: limestone calcined clay cement, LC3, shale ceramsite, lightweight aggregate concrete, internal curing, chloride resistance, pore structure, carboaluminate hydrates, sustainable construction, compressive strength, capillary absorption, low-carbon cement

A research team led by Jinhyuk Baek, Yujin Son, Moonsu Kim, and Gibaek Lee at Yeungnam University and Gyeongkuk National University in the Republic of Korea has now reported a promising way out of this dilemma. Writing in the journal Advances in Industrial and Engineering Chemistry, they describe a ternary iron-molybdenum-cobalt oxide electrocatalyst, abbreviated Fe-CMO, that not only matches the activity of noble-metal benchmarks in alkaline water but also shrugs off the chloride ions that make seawater so hostile to conventional catalysts. Because seawater accounts for more than 97 percent of the water on Earth, a catalyst that can split it directly would remove one of the biggest resource constraints on green hydrogen production, freeing coastal regions and island nations from dependence on scarce freshwater supplies.

The problem with seawater is deceptively simple. Its roughly 0.5 molar concentration of chloride ions creates a competing reaction at the anode: instead of oxidizing water to oxygen, the electrode can oxidize chloride to chlorine or hypochlorous acid. This chlorine evolution reaction steals current, lowers efficiency, and generates corrosive byproducts that chew through catalyst surfaces. Most high-performing catalysts developed for alkaline freshwater electrolysis degrade rapidly when immersed in saline media, which is precisely why so many seawater-splitting studies report impressive initial numbers followed by disappointing stability. The Korean team’s strategy was to attack the chloride problem at the level of electronic structure, using two dopants with complementary roles rather than a single additive.

Synthesis began with a two-step hydrothermal process on a nickel foam substrate. In the first step, cobalt nitrate, urea, and ammonium fluoride were combined to grow urchin-like arrays of cobalt layered double hydroxide nanoneedles, with the urea and fluoride acting as structure-directing agents that produce a porous, radially aligned framework. The second hydrothermal step introduced sodium molybdate and iron nitrate, after which the sample was annealed first at 280 degrees Celsius and then at 450 degrees Celsius under a reducing 90:10 argon-hydrogen atmosphere. The sequence matters enormously. When the cobalt hydroxide precursor was annealed directly, or when iron alone was added, calcination caused the nanoneedles to coalesce into dense coral-reef-like structures, collapsing the surface area that electrocatalysis depends on. Molybdate ions, by contrast, transformed the nanoneedles into interconnected nanosheets, and the co-doped final product emerged as a well-defined three-dimensional nanoflower built from entangled nanosheet clusters that resist structural collapse during thermal treatment.

Microscopy and spectroscopy confirmed that the nanoflower is a genuine spinel cobalt oxide with the dopants incorporated at the lattice level rather than merely sitting on the surface. High-resolution transmission electron microscopy revealed lattice fringes of 0.25 and 0.29 nanometers corresponding to the (311) and (220) planes of spinel Co3O4, and elemental mapping showed a homogeneous distribution of cobalt, molybdenum, and iron throughout the material. X-ray photoelectron spectroscopy then delivered the most chemically interesting result: the coexistence of multiple oxidation states, including Mo4+, Mo5+, and Mo6+, alongside Co2+/Co3+ and Fe2+/Fe3+ redox couples. Critically, when the team annealed a comparison sample under argon alone, the Mo4+ signal vanished entirely, proving that the reducing atmosphere is essential for stabilizing the lower molybdenum valence that drives hydrogen evolution.

The division of labor among the three metals is what gives Fe-CMO its bifunctional character. Molybdenum6+ acts as an electron acceptor, pulling electrons from cobalt sites and continuously regenerating the Co2+/Co3+ redox pair that powers the oxygen evolution reaction. Molybdenum4+ plays the opposite role on the cathode side, serving as an electron reservoir that promotes the conversion of adsorbed hydrogen intermediates into molecular hydrogen at Mo-edge sites. Iron, present at a modest 1.31 atomic percent, modulates the local electronic environment around cobalt centers: the cobalt peaks in the XPS spectrum shift toward higher binding energies relative to the undoped material, indicating elevated positive charge on cobalt that favors the adsorption of anionic intermediates such as hydroxide. Raman spectroscopy corroborated this picture, with the A1g vibrational mode near 650 wavenumbers shifting leftward in the doped samples, a signature that iron substitution increases the covalency of the cobalt-oxygen bonds. The Fe2+/Fe3+ couple also provides local charge balance that keeps Mo4+ stable under operating conditions, preventing the electron reservoir from being irreversibly oxidized.

The electrochemical numbers are striking. In 1 molar potassium hydroxide, Fe-CMO required overpotentials of just 231 millivolts at 10 milliamperes per square centimeter and 289 millivolts at 50 milliamperes per square centimeter for oxygen evolution, comfortably beating commercial IrO2 and all undoped or singly doped controls. Its Tafel slope of 190 millivolts per decade was the lowest measured, and electrochemical impedance spectroscopy showed a charge transfer resistance of only 0.39 ohms, roughly one-eighth that of plain Co3O4. On the hydrogen side, the catalyst needed 153 millivolts at 50 milliamperes per square centimeter, nearly matching the commercial Pt/C benchmark at 129 millivolts, with a Tafel slope of 79 millivolts per decade characteristic of a Volmer-Heyrovsky pathway in which electrochemical desorption is rate-determining. The double-layer capacitance measurements told a structural story as well: Fe-CMO achieved 53 millifarads per square centimeter, compared with just 3 for the collapsed coral-like Co3O4, confirming that the molybdenum-guided nanosheet architecture preserves a far larger pool of accessible active sites.

When the electrolyte was switched to a mixture of 1 molar potassium hydroxide and real seawater collected from the East Sea at Najeong Beach in Gyeongju, the catalyst barely flinched. Oxygen evolution overpotentials of 238 millivolts at 10 and 289 millivolts at 50 milliamperes per square centimeter were essentially identical to the freshwater values, while hydrogen evolution required only 98 millivolts at 50 milliamperes per square centimeter, actually edging out Pt/C under the same conditions. In a two-electrode configuration pairing Fe-CMO against itself, the cell maintained nearly identical current-voltage characteristics in alkaline and seawater-mixed solutions, whereas undoped Co3O4 suffered severe degradation in the presence of chloride. Control experiments isolated the culprit and the cure: iron doping alone conferred little protection against chloride corrosion, but molybdenum incorporation dramatically improved stability, pointing to molybdenum’s ion-selective behavior and its ability to suppress chloride adsorption as the decisive factor.

Durability testing sealed the case. After 120 hours of continuous operation at an industrially relevant current density of 100 milliamperes per square centimeter in seawater-containing electrolyte, the cell voltage rose by only 19 millivolts, a performance loss of just 1.1 percent, while undoped Co3O4 lost 115 millivolts under far milder conditions. Post-mortem X-ray photoelectron spectroscopy of both electrodes revealed a fascinating asymmetric chemistry: on the anode side, molybdenum had partially oxidized from Mo4+ to Mo5+, cobalt’s metallic signal had disappeared into higher-valent states, and iron remained locked in the Fe3+ state, all consistent with productive oxygen evolution rather than parasitic chlorine chemistry. On the cathode side, reduced molybdenum and a healthy Co2+/Co3+ ratio were preserved, showing that each half of the cell maintains the valence environment its reaction requires. This reversible, reaction-specific redox adaptability is precisely what long-term seawater electrolysis demands, and it demonstrates that rational multimetal design, rather than exotic materials or prohibitively expensive noble metals, may be the key to unlocking the oceans as a hydrogen feedstock.

Subject of Research: Development of a chloride-resistant Fe-Mo co-doped Co3O4 electrocatalyst for hydrogen production via seawater electrolysis

Article Title: Robust Fe, Mo co-doped Co3O4 electrocatalyst with superior chloride resistance for efficient seawater electrolysis

Article References: Baek, J., Son, Y., Kim, M., & Lee, G. (2025). Robust Fe, Mo co-doped Co3O4 electrocatalyst with superior chloride resistance for efficient seawater electrolysis. Advances in Industrial and Engineering Chemistry, 1(1), Article 18. https://doi.org/10.1007/s44405-025-00018-9

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00018-9

Keywords: seawater electrolysis, green hydrogen, electrocatalyst, cobalt oxide, molybdenum doping, iron doping, oxygen evolution reaction, hydrogen evolution reaction, chloride resistance, spinel structure, bifunctional catalyst, water splitting