A mix-design-stage sustainability analysis also found that the combined use of crushed sand and 30% fly ash reduced embodied carbon by about 28% and embodied energy by 25% to 26% relative to a reference concrete containing natural sand and no fly ash. Natural sand is increasingly scarce, while crushed sand is widely available because it is produced by crushing and screening rocks into particles smaller than 4.75 mm. The material is already widely used, but its irregular shapes, rough surfaces, flaky particles, uneven gradation, and potentially excessive fine powder can increase friction and water demand.

These characteristics can reduce flow and make segregation more likely when crushed sand replaces natural sand in high-fluidity concrete. The present study focused on crushed limestone sand, and its authors said that the optimized ranges would need verification for sands from other lithologies. The researchers addressed that gap with a six-factor, five-level L25 orthogonal experiment evaluating crushed-sand mortar.

The tested variables were the water-to-binder ratio, polycarboxylate water-reducer dosage, sand volume fraction, fly ash content, silica fume content, and rock-powder content. Researchers measured mortar rheology with a rotational rheometer, determined spread with the truncated-cone slump-flow test, and tested 28-day compressive and flexural strengths. Scanning electron microscopy was also used to examine how fly ash, silica fume, and rock powder affected the mortar matrix.

The experimental materials included washed and dried crushed limestone sand with a fineness modulus of 3.2, limestone gravel, ordinary Portland cement, Class F fly ash, silica fume, limestone powder, and a polycarboxylate-based water reducer. Range analysis identified different requirements for fluidity, rheological stability, and strength, making it necessary to select useful ranges rather than one universal mixture. The researchers recommended a sand volume fraction of 0.38–0.44, fly ash of 10%–40%, silica fume of 0%–4%, and crushed-sand rock powder of 0%–9%.

The water-to-binder ratio was expected to follow the target concrete strength, while the water-reducer dosage would be adjusted jointly with it to obtain the required flow. These limits were narrower than several values available from standards or earlier studies, but the authors cautioned that crushed sand from different parent rocks can differ in morphology, packing, and powder adsorption. The recommended ranges therefore require verification for granite, diabase, and other sands before they can be assumed to apply outside the tested limestone material.

The rheological measurements showed why the particle proportions mattered. More free water from a higher water-to-binder ratio lowered both initial yield shear stress and plastic viscosity, while additional water reducer reduced the stress needed to initiate flow and caused only a slight rise in viscosity. Sand fraction showed a different pattern: increasing it initially improved packing and lowered yield stress, but beyond a critical level, more contact between particles increased friction.

Fly ash produced a peak in slump-flow behavior near 30% because its spherical particles reduced friction at moderate contents; at higher contents, its large surface area increased water demand. Silica fume had the strongest adverse effect on fluidity, with mortar slump flow falling 36.3% as its content rose from 0% to 8%. These trends were observed under the study’s laboratory conditions rather than as universal responses for all cementitious systems.

Scanning electron micrographs supported the proposed particle-level explanation. A moderate amount of fly ash produced a more compact microstructure, whereas excessive fly ash was associated with pores and microcracks. Silica fume could adsorb substantial water at early ages because of its very fine particles and high surface area, potentially restricting hydration and reducing compactness.

Rock powder similarly helped fill voids at an appropriate content, but excess powder increased friction and reduced fluidity. These observations connect the characteristics of crushed sand to measurable mortar properties, including particle morphology, gradation, and fine-powder content, rather than treating all crushed sand as interchangeable. The researchers also fitted a piecewise relationship between mortar initial yield shear stress and slump flow, obtaining an R-squared value of 0.853.

Under the materials and test conditions used in the study, the relationship indicated that an initial yield shear stress no greater than 63.2 Pa corresponded to mortar slump flow of at least 250 mm. Five additional mixtures were then prepared to test the optimized ranges and the prediction. Their measured slump-flow values differed from predictions by 1% to 18%.

Two mixtures within the recommended range combined favorable flow, rheology, and mechanical properties. The other three deliberately moved outside one of those ranges: replacing 30% fly ash with 6% silica fume reduced measured slump flow by 58.8% and increased yield stress by a factor of 8.5; raising fly ash to 48% reduced slump flow slightly while increasing yield stress by 49% and plastic viscosity by 44.1%; and raising the sand volume fraction to 0.46 reduced slump flow by 69% and increased yield stress by a factor of 35.1. For concrete production, the mortar was treated as part of a two-phase suspension system containing mortar and coarse aggregate.

Some mortar fills the voids between aggregate particles, while an excess layer coats their surfaces. The design used a nominal mortar film thickness of 2.1 mm and recommended an optimized range of 1.9–2.3 mm. Increasing the film thickness provides greater spacing between coarse aggregate particles, reducing direct contact and interlocking.

After the mortar and aggregate are designed, the method calls for calculating their volume fractions from aggregate gradation, density, void ratio, and the selected film thickness. Because the calculation approximates aggregate particles as spheres with uniform coatings, the researchers stated that the film thickness may be adjusted to compensate for real aggregate morphology and mortar dispersion. Three concrete grades were produced from mortars with the same optimized sand fraction, fly ash content, and rock-powder content but different water-to-binder ratios and water-reducer dosages.

The resulting C30, C40, and C50 mixes achieved slump flows of 618, 660, and 705 mm, respectively. Their passing ability indices improved as the mortar’s initial yield shear stress declined, while segregation rates increased with rising yield stress. The 28-day compressive strengths were 44.98 MPa for C30, 54.76 MPa for C40, and 61.91 MPa for C50; flexural strengths were 3.81, 5.49, and 6.43 MPa, while splitting strengths were 4.56, 4.71, and 5.20 MPa.

The findings support the proposed physical model: once mortar film thickness separates the aggregate skeleton sufficiently, concrete flow is governed largely by the rheology of the mortar medium. The sustainability comparison was limited to raw materials and mix design rather than a full life-cycle assessment. It used published unit values for embodied carbon and energy and considered the materials in each mix, but it did not evaluate transport, construction, durability, demolition, recycling, or service life.

Within that boundary, the crushed-sand mixes with 30% fly ash produced 310.25, 346.50, and 379.11 kg CO2-eq per cubic meter for C30, C40, and C50 concrete, compared with 432.63, 482.92, and 527.09 kg CO2-eq per cubic meter for the natural-sand, zero-fly-ash reference. Their embodied energy was also lower: 1979.88, 2231.38, and 2516.78 MJ per cubic meter, compared with 2689.60, 3017.60, and 3366.00 MJ per cubic meter. The authors identified an unresolved need to quantify how plastic viscosity governs segregation resistance, while noting that the 63.2-Pa threshold and optimized ranges remain specific to the tested raw materials, laboratory conditions, and mix-design space.

The results therefore provide a laboratory-validated design framework, not a field trial or a general claim about every crushed-sand source.

Subject of Research: Laboratory optimization of crushed-limestone-sand mortar for high-fluidity concrete using rheological thresholds and film thickness.

Article Title: Optimization of crushed sand mortar for the preparation of high-fluidity concrete

Article References: Zhang, Y., Xiao, J., Zhen, Q., Zhou, Y., & He, X. (2026). Optimization of crushed sand mortar for the preparation of high-fluidity concrete. Case Studies in Construction Materials, 25, Article e06636. https://doi.org/10.1016/j.cscm.2026.e06636

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06636

Keywords: crushed limestone sand, high-fluidity concrete, mortar rheology, yield shear stress, fly ash, mix design, concrete workability, segregation resistance, embodied carbon, construction materials, Optimization, crushed

The problem the researchers set out to solve is a familiar one in climate accounting. Life cycle assessment, or LCA, is the standard tool for tallying the emissions embodied in a piece of infrastructure, from raw material extraction through manufacturing, construction, and eventual disposal. But conventional LCA is essentially static: it produces a snapshot of a single project at a single point in time. It cannot capture how infrastructure investment decisions, technological progress, and policy interventions interact over decades, nor how those interactions determine whether a sector locks itself into decades of avoidable emissions. Ports are particularly vulnerable to this carbon lock-in, because wharves and terminals built today will still be standing and operating long after mid-century climate deadlines have come and gone.

To bridge that gap, the team coupled the two approaches in what they call an LCA–SD framework. At the project level, they applied process-based life cycle assessment to real engineering schemes, drawing on a dataset of 214 construction designs from 39 Chinese coastal ports. The project-level results were then used to parameterize a national-scale system dynamics model of the port construction sector. System dynamics, a modeling technique that represents stocks, flows, and feedback loops, allowed the researchers to simulate how annual investment volumes, material emission factors, and policy stringency evolve together over time and shape long-term emission trajectories. Scenario and sensitivity analyses were then used to probe how the modeled emissions respond when key assumptions are varied.

The static findings are striking. Across the 214 engineering schemes, material manufacturing accounted for between 79.0 and 91.5 percent of total construction-stage carbon emissions. In other words, the vast majority of a port’s embodied carbon is released before a single pile is driven, in the kilns and blast furnaces that produce cement and steel. These two materials emerged as the dominant emission hotspots, and their relative importance depends on the structural type of the wharf. Piled wharves, which rest on driven or bored piles, are relatively steel-intensive, whereas gravity wharves, which rely on their own massive weight for stability, lean heavily on cement-based materials. That distinction matters for designers, because it means the decarbonization lever differs by structure: steel innovation for one class of wharf, low-carbon cement and concrete for another.

The dynamic modeling then translated these project-level insights into sector-wide trajectories. Under the baseline scenario, in which current trends in investment and technology continue without major policy acceleration, the study projects that sector-wide emissions from port infrastructure construction will peak between 2026 and 2028. That peak is not the finish line. What happens after the peak depends on how quickly low-carbon materials penetrate the market and how aggressively construction volumes are managed. The model shows that stronger intervention could pull the date of carbon neutrality forward by approximately 15 years, a dramatic shift for a sector whose assets are typically designed for lifespans of half a century or more.

Perhaps the most policy-relevant result comes from the sensitivity analysis. Within the tested range of plus or minus 10 percent, the annual emission trajectories proved more responsive to changes in investment volume than to changes in policy intensity. This is a counterintuitive finding with real-world implications. It suggests that the sheer scale of port construction activity, driven by demand for expanded capacity and new terminals, exerts a stronger pull on near-term emissions than the stringency of climate policies applied to each project. A modest swing in how much port infrastructure gets built moves the emissions needle more than a comparable tightening of per-project carbon rules. For planners, this means that managing the pace and volume of infrastructure expansion is not an optional complement to decarbonization policy; it is a central pillar of it.

The authors are careful to frame these results as requiring coordinated action rather than any single silver bullet. Their conclusions point to a portfolio of measures: accelerated deployment of low-carbon materials to attack the cement and steel hotspots, green procurement standards that reward suppliers with lower embodied carbon, design-stage carbon control that makes emissions a criterion when choosing between structural alternatives, and carbon offset mechanisms to neutralize the residual emissions that no material substitution can eliminate. Each of these levers addresses a different stage of the construction life cycle, and the modeling suggests they work best in combination.

The study’s empirical foundation gives it unusual weight. The 214 engineering schemes span a wide range of Chinese coastal port projects, and the carbon accounting draws on established national standards, including the Ministry of Transport’s quotas for maritime works and water transportation budgeting, the construction carbon emission calculation standards issued by China’s housing ministry, and the Chinese life cycle database maintained by IKE Environmental Technology. Emission factors for electricity were aligned with regional grid baselines published by China’s climate strategy authorities and with United Nations Framework Convention on Climate Change methodologies. This grounding in official quotas and databases means the results are not hypothetical modeling exercises but reflect the actual material intensities and construction practices of one of the world’s largest port-building programs.

The broader context makes the findings urgent. Global maritime trade continues to grow, and ports everywhere are expanding to accommodate larger vessels, automated terminals, and new energy supply chains. Every new berth adds tons of embodied carbon that cannot be recalled once the concrete is poured. The concept of carbon lock-in captures this inertia: infrastructure decisions made in the 2020s shape the emissions profile of the 2060s. By quantifying how much of a port’s construction carbon comes from materials, and by showing how investment volume and policy intensity interact dynamically, the study gives port authorities and regulators a quantitative basis for sequencing their decisions. Building less, building smarter, and building with cleaner materials are not competing strategies but complementary ones.

For the international audience watching China’s port sector, the framework itself may be as valuable as the specific numbers. The LCA–SD integration is transferable to other countries and other infrastructure classes, from highways to tunnels, wherever static carbon accounting has struggled to capture the dynamics of long-lived assets. As governments worldwide grapple with how to reconcile infrastructure ambitions with net-zero commitments, this study offers a template: measure the embodied carbon of real projects, feed those measurements into a dynamic sector model, and test how investment and policy levers shift the trajectory. The path to carbon-neutral ports, it turns out, is written in cement and steel, and the sooner planners read it, the more of the future they can still change.

Subject of Research: Integrated life cycle assessment and system dynamics modeling of carbon emissions from port infrastructure construction

Article Title: Decarbonizing port infrastructure: an integrated life cycle assessment–system dynamics framework for carbon neutrality pathways

Article References: Hou, D., Su, D., Shen, W., Zhao, A., Li, X., Meng, X., Ma, J., Pan, J., & Lin, A. (2026). Decarbonizing port infrastructure: an integrated life cycle assessment–system dynamics framework for carbon neutrality pathways. Clean Technologies and Environmental Policy, 28(11), Article 275. https://doi.org/10.1007/s10098-026-03610-9

Image Credits: AI Generated

DOI: 10.1007/s10098-026-03610-9

Keywords: port infrastructure, life cycle assessment, system dynamics, carbon neutrality, embodied carbon, cement, steel, carbon lock-in, green procurement, maritime transport, decarbonization, China

The methodological foundation of the study rests on two well-established traditions. Input-output analysis, first formulated by Wassily Leontief in the 1930s, captures the web of economic transactions linking every sector to every other: to produce one unit of output, a sector must consume inputs from others, each of which consumes inputs in turn, generating a cascade of indirect effects. By extending these tables with emissions coefficients, researchers can compute the total carbon dioxide released, directly and indirectly, whenever a sector produces goods for final consumption or export. Ecological network analysis, developed by ecologists such as Brian Fath and Robert Ulanowicz, adds a second layer of insight. Originally designed to study flows of energy and matter through ecosystems, it borrows concepts like control, dependency, and mutualism to ask not just how much carbon flows through an economy, but who dominates whom within the network of flows.

The researchers aggregated the economy into seven macro-sectors and computed pull and drive weights, network utility relationships, and control metrics across the entire regional system. Pull weights describe how strongly a sector draws carbon embodied in inputs from upstream suppliers, while drive weights measure how powerfully a sector pushes emissions downstream through its own demands. Network utility analysis assesses whether pairwise relationships between sectors are mutually beneficial or exploitative in flow terms, and control analysis identifies which sectors effectively govern the behavior of others. Together, these indicators transform a dense matrix of monetary transactions and emissions data into a structural map that resembles the hierarchy of a natural ecosystem, with producers, intermediaries, and apex consumers of carbon.

The results reveal a striking inefficiency at the heart of the region’s carbon metabolism. Rather than transmitting embodied emissions efficiently from primary producers to final consumers, ASEAN’s network structure allows intermediate sectors to absorb a significant portion of the carbon flowing through the system. In ecological terms, the metabolism is sluggish: carbon pools in the middle of the food web instead of passing cleanly through it. This stagnation matters for policy because it means that interventions aimed only at final consumers or only at raw producers would miss much of the region’s embedded emissions. The finding points instead toward intermediate manufacturing processes as critical leverage points where carbon can be either locked in or released, depending on the technologies and energy sources those sectors use.

At the top of the hierarchy, the study found that upstream primary sectors—agriculture, mining, and energy transformation—exert strong influence over everything downstream. These sectors act as the region’s primary producers in the ecological sense, anchoring the flow of embodied carbon that ultimately supports construction, manufacturing, and services. Their dominance means that decarbonization efforts targeting electricity generation and resource extraction would ripple through the entire network, whereas efforts confined to downstream sectors would struggle to propagate upstream. At the opposite end of the hierarchy, the construction sector emerged as the primary dependent sector, sitting at the bottom of the control hierarchy and drawing heavily on embodied carbon generated by others. Any building boom in the region, the analysis implies, transmits demand for carbon deep into the economy’s upstream foundations.

Perhaps the most consequential finding is that ASEAN, taken as a whole, is a net exporter of embodied carbon to the rest of the world. The goods the region ships abroad carry more embedded emissions than the goods it imports, meaning that a substantial share of the carbon released within ASEAN’s borders is generated on behalf of foreign consumers. This asymmetry has long been recognized in global carbon accounting debates, but its implications have sharpened dramatically with the arrival of border carbon adjustment mechanisms. The European Union’s Carbon Border Adjustment Mechanism, and similar instruments under consideration in other jurisdictions, are designed to charge importers for the embedded carbon in goods arriving from regions with weaker climate policies. For export-oriented ASEAN economies, the study’s findings read as a warning: the region’s carbon-intensive export chains are directly exposed to emerging carbon regulations.

The vulnerability is structural rather than incidental. Because upstream energy transformation and primary sectors control much of the network’s carbon flows, and because intermediate sectors absorb rather than pass on emissions, exporters cannot easily demonstrate clean supply chains even if final assembly becomes more efficient. Border carbon adjustments do not distinguish between a factory that has decarbonized and one embedded in a carbon-intensive grid; they measure the carbon embodied in the product. As long as ASEAN’s electricity mix remains fossil-heavy and its industrial intermediates carbon-intensive, the region’s manufacturers will carry a hidden carbon tariff risk regardless of their own operational improvements. The authors argue that this is why targeted grid decarbonization must be a regional priority rather than a national afterthought.

The study’s prescriptions extend beyond clean power. The authors highlight circular economy strategies in advanced manufacturing as a second pillar, noting that closing material loops within industrial networks can reduce the pull of embodied carbon from upstream extractive sectors. ASEAN has already adopted a framework for circular economy, and the network analysis provides a quantitative rationale for targeting it at the intermediate sectors where carbon flows currently stagnate. The third pillar is governance: harmonized regional carbon accounting. If each ASEAN member measures embodied carbon differently, the region cannot present a coherent response to border adjustments, and firms face conflicting reporting requirements across markets. A common accounting standard would allow the region to negotiate from a position of shared evidence rather than fragmented estimates.

The analytical framework itself is part of the study’s significance. Ecological network analysis has been applied to urban metabolism in Beijing, energy systems in Guangdong, and circular economy performance at the city level, but comprehensive multi-regional applications spanning ASEAN have been scarce. By combining the Asian Development Bank’s multi-regional input-output tables with environmental extensions covering air emissions, the researchers demonstrate that the tools of ecosystem science can be scaled to an entire trade bloc. The approach also offers interpretability advantages over black-box optimization models: network metrics like control and utility produce statements about sectoral relationships that policymakers can examine, contest, and act upon, rather than opaque numerical prescriptions.

The broader lesson is that climate policy and trade policy are now inseparable, and that understanding an economy’s structure—not just its total emissions—determines its resilience in a carbon-regulated world. ASEAN’s position as a net embodied carbon exporter is not merely an accounting curiosity; it is a measure of how much of the region’s industrial future depends on rules being written elsewhere. The study’s metabolic metaphor ultimately delivers a practical message: a food web with bloated intermediaries and dominant primary producers responds slowly to change, and an economy shaped the same way will respond slowly to decarbonization. Reshaping those flows—through cleaner grids, circular manufacturing, and shared carbon accounting—offers the region a path to keep its export engines running as the global economy begins charging for every tonne of carbon embodied in the goods it buys.

Subject of Research: Embodied carbon flows in ASEAN economies analyzed with input-output and ecological network analysis

Article Title: Multi-regional ecological network analysis of ASEAN’s carbon metabolism

Article References: Gue, I. H. V., Teng, J. R. C., Li, M., & Tan, R. R. (2026). Multi-regional ecological network analysis of ASEAN’s carbon metabolism. Clean Technologies and Environmental Policy, 28(11), Article 272. https://doi.org/10.1007/s10098-026-03627-0

Image Credits: AI Generated

DOI: 10.1007/s10098-026-03627-0

Keywords: ASEAN, embodied carbon, ecological network analysis, multi-regional input-output, carbon border adjustment, carbon metabolism, supply chain emissions, grid decarbonization, circular economy, carbon accounting, global value chains, climate policy

The research, led by Yuanyuan Yang, Tengfei Xu, Tong Guo, Dapeng Mei, Bo-Tao Huang, and Tianyu Xie, focuses on steel fiber-reinforced concrete and ultra-high-performance concrete, two advanced materials prized for their exceptional toughness, tensile strength, and crack resistance. Unlike conventional concrete, whose carbon emissions are dominated by cement production, these fiber-reinforced composites introduce a second major emission source: the steel fibers themselves. Steel fibers are manufactured through an electric arc furnace short-process route followed by extensive wire drawing, and this production chain is extraordinarily electricity-hungry. Around 58.4 percent of the total energy consumed in making steel fibers is used during the wire drawing phase alone, which stretches hot-rolled wire down to fibers as thin as 0.15 millimeters.

That electricity dependence is what makes the new findings so striking. While the carbon emissions of cement are largely locked in by the chemistry of clinker calcination, a process that accounts for roughly 90 percent of cement’s footprint and is essentially independent of where it is made, the emissions of steel fibers swing wildly depending on the carbon intensity of the regional grid supplying the factory. Across the 31 provinces of mainland China, grid carbon emission factors range from 0.04 to 0.97 kilograms of carbon dioxide equivalent per kilowatt-hour, a nearly 24-fold difference. The consequence is dramatic: the carbon emission factor for a kilogram of steel fiber can range from 0.72 to 4.35 kilograms of carbon dioxide equivalent, purely because of where it was produced.

The study’s authors built a spatiotemporally explicit life cycle assessment framework that replaces the single, static national average emission factor used in most conventional carbon accounting with province-level and season-level values. They compiled provincial power generation mixes for 2022 and 2024, calculated fuel-specific emission factors for thermal power including upstream fuel emissions, accounted for inter-provincial electricity transfers and transmission losses, and then applied these refined factors to the cradle-to-gate emissions of concrete mixes spanning strength grades from C30 to C180. The results expose how badly national averages distort the picture. Using a unified national average overestimates emissions in clean-energy provinces by up to 177.5 percent while underestimating them by 25.5 percent in coal-dependent regions.

The geography of China’s power system explains the pattern. Southwestern provinces such as Yunnan, Sichuan, and Xizang, along with Qinghai in the northwest, draw more than 80 percent of their electricity from renewable sources, mostly hydropower, giving them grid emission factors as low as 0.04 kilograms of carbon dioxide equivalent per kilowatt-hour. At the other extreme, 21 provinces classified as thermal power-dominant, concentrated in North and Northeast China, average 0.83 kilograms per kilowatt-hour because of their heavy reliance on coal. The sensitivity analysis confirmed that for ordinary steel fiber-reinforced concrete, the grid emission factor and the steel fiber content are the two dominant parameters governing total emissions, with sensitivity coefficients of roughly 0.55 for C30 mixes, while transport distance barely registers at around 0.1.

The temporal dimension proved equally important. Because hydropower output surges during wet seasons and wind power fluctuates with the seasons, grid carbon intensity changes dramatically through the year. In Yunnan, hydropower’s share of generation climbed from 54.56 percent in the first quarter to 84.37 percent in the third, driving the provincial emission factor down from 0.35 to 0.13 kilograms of carbon dioxide equivalent per kilowatt-hour. In Hunan, the factor plunged from 0.67 to 0.42 in the second quarter as spring rains boosted hydropower. For a cubic meter of SFRC C30, that seasonal swing translated into emissions falling from 483.90 to 378.62 kilograms of carbon dioxide equivalent in Yunnan, a 21.76 percent reduction, simply by shifting production timing.

Perhaps the most provocative concept in the study is the carbon emission break-even distance, the transport distance at which shipping steel fiber from a clean-grid province produces less total carbon than manufacturing it locally in a coal-dependent one. Analyzing all 930 directional inter-provincial pairs, the researchers found that 87.5 percent of potentially beneficial routes could deliver calculated carbon savings, with 46.02 percent achieving at least 0.6 kilograms of carbon dioxide equivalent saved per kilogram of fiber. A case study made the counterintuitive logic vivid: for a Beijing project, sourcing fiber from neighboring Hebei, just 310 kilometers away, yields 4.15 kilograms of carbon dioxide equivalent per kilogram, while sourcing from Hubei, 1468 kilometers away, yields only 2.67, a 35.7 percent reduction despite nearly five times the transport distance. Grid carbon intensity, in other words, can outweigh distance as the decisive emission driver.

The real-world industrial geography makes this opportunity even more tantalizing. A survey of China’s steel fiber manufacturers revealed that production capacity is heavily concentrated in northern and eastern provinces, with 890 registered manufacturers in Hebei alone, while clean-energy-rich Yunnan has just 16 and Sichuan only 7. The prevailing local-supply model thus locks the industry into relatively high-carbon supply chains. The authors frame their findings as a potential extension of China’s famous West-to-East Electricity Transmission strategy into a West-to-East Material Transfer concept, in which electricity-intensive materials are produced where the power is clean and shipped to where the demand is.

Seasonal scheduling offers an even simpler intervention. By reallocating 40 percent of quarterly production to the lowest-carbon quarter, a manufacturer in Yunnan could cut emissions by 6.02 percent and one in Hunan by 5.17 percent, with no equipment upgrades or capital investment. The researchers estimate that a single 100,000-ton steel fiber producer in Jiangsu shifting 15 percent of its output to the first quarter could avoid more than 1,000 tons of carbon dioxide equivalent annually. Scaled across China’s steel and other electricity-intensive material industries, the cumulative potential is substantial, though the authors caution these figures are calculated projections not yet validated in engineering practice.

The study also draws a crucial distinction between material types. Steel fiber-reinforced concrete, where fibers contribute 40 to 63 percent of emissions in lower grades, is genuinely energy-sensitive and benefits enormously from spatiotemporal optimization. Ultra-high-performance concrete, by contrast, is material-dominated: its enormous cement content, up to nearly 800 kilograms per cubic meter in the C180 mix, keeps its emissions comparatively grid-insensitive, so binder optimization matters more than location. Yet even UHPC holds a surprise when judged by the study’s carbon intensity index, which normalizes emissions by compressive strength. SFRC C80 achieved the lowest strength-adjusted carbon efficiency of all five mixes under every grid scenario, and UHPC C180 performed well despite its high absolute emissions, suggesting that high-strength concretes can be carbon-efficient when their mechanical performance is factored in. The researchers hope their high-resolution framework will push carbon accounting standards toward incorporating temporal adjustment factors and incentivize green electricity consumption, transforming carbon footprinting from a passive accounting exercise into an active tool for low-carbon supply chain design.

Subject of Research: Spatiotemporal variation in power grid carbon intensity and its effect on the embodied carbon of steel fiber-reinforced concrete in China

Article Title: Spatiotemporal variations in power grid carbon intensity and their impact on steel fiber-reinforced concrete emissions

Article References: Yang, Y., Xu, T., Guo, T., Mei, D., Huang, B.-T., & Xie, T. (2026). Spatiotemporal variations in power grid carbon intensity and their impact on steel fiber-reinforced concrete emissions. Case Studies in Construction Materials, 25, Article e06598. https://doi.org/10.1016/j.cscm.2026.e06598

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06598

Keywords: steel fiber-reinforced concrete, ultra-high-performance concrete, life cycle assessment, power grid carbon intensity, embodied carbon, China, cement emissions, hydropower, carbon accounting, supply chain optimization, seasonal electricity, decarbonization

The study, published in the journal Buildings, arrives at a moment when the UK housebuilding sector faces a double bind. Ministers have set ambitious annual construction targets intended to ease a chronic housing shortage, yet the built environment currently accounts for roughly a quarter of the nation’s carbon emissions, with the largest share embedded in the manufacture of steel, cement and concrete. Every traditional brick-and-block estate therefore carries a substantial hidden carbon bill, paid upfront in the form of greenhouse gases released before anyone even moves in. Straw bale construction inverts that equation: rather than emitting carbon, the material locks it away for the lifespan of the building.

The scale of the available resource is striking. The UK generates around 9.9 million tonnes of straw every year as a co-product of cereal farming, and the researchers found that only about 60 percent of the straw currently left in fields would be needed to supply enough material for up to 300,000 low-rise buildings annually. Even after accounting for fluctuations in crop yields and competing demands from other sectors, the analysis showed the country holds a consistent surplus of straw relative to what construction would require. In other words, material scarcity is simply not the problem.

Charlotte Taylor, a researcher in the Department of Architecture and Civil Engineering and the study’s lead author, emphasised just how ordinary straw is in British agriculture. Straw is an incredibly common resource in the UK, she noted, used as livestock bedding and feed, ploughed back into fields to improve the soil, and diverted to energy generation, horticulture and even mushroom cultivation. Yet despite being a renewable, low-carbon and historically important building material, very little of it ends up in walls: fewer than 20 new homes a year are currently built in the UK using straw as a construction material.

The carbon mathematics are compelling. According to the study, scaling up straw construction could cut emissions from building significantly while storing between 1.8 and 3.1 million tonnes of carbon dioxide every year, effectively turning new housing stock into a distributed carbon sink. Because straw is a co-product of grain production, the crop’s primary purpose and revenue remain intact; the stalks that would otherwise be baled for bedding or burned for energy instead become a higher-value commodity. That shift could also diversify farmers’ income streams, giving rural economies a stake in the low-carbon transition rather than leaving them on its sidelines.

The technical case for straw as a building material rests on more than carbon accounting. Straw bale walls can deliver exceptional thermal insulation, outperforming many conventional wall systems, which translates into lower heating demand over a building’s lifetime. In low-rise construction, straw can serve as a structural element as well as an insulating infill, and bale walls are known for good moisture regulation and indoor air quality, qualities increasingly valued as buildings become more airtight. Earlier studies have already highlighted straw’s promise as a high-performing, low-carbon building material; the Bath team’s contribution is to quantify whether the resource base exists to make a genuine dent in national housing and emissions targets. It does.

So why are so few straw houses being built? The researchers tested multiple scenarios for redirecting the UK’s straw supply into construction, including reallocating material from bioenergy and industrial uses, and growing more cereals on currently unused land. Diverting straw from other sectors would provide enough material for up to 300,000 low-rise buildings, while expanding cultivation on unused land could supply around 163,000 homes, with diversion from other industries required to close the gap to full housing targets. Supply, in every scenario examined, proved sufficient. The real obstacles, the study concludes, are systemic rather than material.

Those systemic barriers begin with the absence of established supply chains linking farms to building sites. Unlike brick or timber, straw does not arrive through mature distribution networks with predictable pricing, quality assurance and just-in-time delivery. The pool of specialised builders familiar with straw-based construction is limited, and uptake is slowed further because builders, lenders and insurers, wary of anything unconventional, seek to minimise the risk associated with alternative materials. A house that cannot easily be mortgaged or insured is a house that will not be built at scale, regardless of how well it performs.

Economics and logistics add further friction. Some straw construction methods remain less efficient than conventional techniques, raising costs in a sector where margins are thin and procurement is fiercely price-driven. Geographically, straw production is unevenly distributed across the UK, which complicates storage and transport and can make the material abundant in one region while scarce in another. These are solvable problems, but solving them requires coordination that no single farmer, builder or developer can supply alone.

The findings point toward a clear policy agenda. The researchers argue that straw offers the UK a genuine opportunity to cut construction emissions while accelerating homebuilding, but that realising this potential depends on coordinated policy support, clearer regulation and market incentives that reward low-carbon materials. Standards and certification pathways would give lenders and insurers the confidence to treat straw buildings as mainstream products rather than exotic experiments. Investment in supply chains, training and regional processing could convert a diffuse agricultural byproduct into a reliable industrial feedstock. If those pieces fall into place, the study suggests, the material that once housed the three little pigs could help house the nation, one carbon-storing bale at a time.

Subject of Research: Resource potential of straw construction for low-carbon UK housing

Article Title: Straw houses could help UK meet housing targets while cutting emissions

Article References: Straw houses could help UK meet housing targets while cutting emissions. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: straw bale construction, low-carbon building, UK housing targets, embodied carbon, University of Bath, agricultural co-products, carbon storage, sustainable construction, building materials, construction emissions, housing policy, renewable materials

Researchers from Loughborough University, the University of Sheffield, Newcastle University and Beijing University of Technology have built a deterministic workflow that reads an Industry Foundation Classes, or IFC, file directly and turns it into a complete material decision engine. IFC is the vendor-neutral exchange format maintained by buildingSMART, designed so that a model created in one authoring platform can be understood by another. Instead of treating that file as a mere snapshot for drawings and schedules, the prototype extracts component quantities and material assignments, runs automated data-quality checks, maps the results to a prototype material database, and then evaluates entire wall-floor-roof combinations for both embodied carbon and circularity. Because every step follows fixed rules, the same input file always produces the same output, a property the authors regard as essential for traceable design support.

The test bed was a buildingSMART reference IFC model, a deliberately ordinary assembly of walls, slabs and roofs. The extraction stage targeted eight elements. Seven of them carried enough material and quantity information to proceed into the calculation; one incomplete roof aggregate was excluded, and, crucially, the reason for that exclusion was recorded rather than silently dropped. The retained set comprised four walls, one floor slab and two roof slabs, a small but complete envelope that allowed the researchers to keep the entire decision space within reach of exact evaluation.

That decision space was constructed from six wall materials, five floor materials and five roof materials, producing 150 whole-building configurations. Each configuration was scored on two axes: cradle-to-gate embodied carbon, measured in kilograms of carbon dioxide equivalent, and a prototype Building Circularity Score that reflects how readily materials can be recovered and reused. All 150 combinations were then compared pairwise to identify Pareto-optimal solutions, the mathematical term for configurations in which neither objective can be improved without degrading the other. This is where multi-objective optimisation earns its keep, because it replaces a single ranked list with a map of genuine trade-offs.

The result was strikingly structured. Twelve of the 150 configurations proved non-dominated, and they split cleanly into two camps. Six low-carbon-oriented candidates were dominated by timber-roof systems, while the six circularity-oriented candidates all used aluminium roofs. Not a single configuration met the study’s balanced classification thresholds, meaning no option satisfied both objectives simultaneously at the levels the researchers defined. The contrast illustrates a practical feature of material choice that designers rarely see laid bare: the design space may contain distinct clusters rather than one obvious best answer, and choosing between clusters is a values question, not a calculation.

The roof emerged as the decisive lever in this reference case, and the numbers explain why. The two roof slabs alone accounted for 53.5 percent of the extracted material volume, so whatever sat above the walls shaped the whole-building result. In one paired comparison, swapping a timber roof for an aluminium roof raised embodied carbon from 591.8 to 21,706.5 kilograms of carbon dioxide equivalent, a more than thirtyfold increase, while lifting the circularity score from 0.712 to 0.865. The authors are careful to frame this as a case-specific observation rather than a general rule for buildings, but it demonstrates the kind of quantified, element-level insight the workflow is designed to surface before specifications harden.

On top of the calculation engine sits a controlled semantic query layer with twelve predefined query types. These can retrieve low-carbon or high-circularity options, identify which components drive a building’s material profile, compare Pareto candidates side by side, or explain why a particular option earned its score. Because the queries operate through fixed rules rather than free-form interpretation, reproducibility is guaranteed: the same data and the same query yield the same answer every time. The system can also package its results into structured prompt text suitable for downstream interpretation, though the study explicitly did not call or evaluate a large language model, keeping the pipeline fully deterministic end to end.

Sensitivity testing forms a substantial part of the paper’s argument that the reference-case findings are robust rather than artefacts of arbitrary modelling choices. The same twelve candidate scenarios survived five different weighting schemes applied to the circularity score. The classification of zero balanced, six low-carbon-oriented and six circularity-oriented candidates held across nine different threshold settings. Under uncertainty assumptions tested with 1,000 scenario-based Monte Carlo runs, every baseline candidate remained non-dominated in at least 83.2 percent of the runs. For a field where early-stage carbon estimates often wobble with every assumption, that level of stability is a meaningful claim.

Performance numbers come with an honest caveat. The full 150-configuration case completed in about 0.79 seconds, including roughly 0.023 seconds for the pairwise Pareto filtering, fast enough for interactive design sessions. However, runtime tests with larger synthetic sets showed that exhaustive pairwise comparison does not scale indefinitely; as the number of configurations grows combinatorially, the filtering step becomes a bottleneck. The authors note that much larger design spaces would require more efficient Pareto-search strategies, a recognised challenge in multi-objective optimisation that algorithms such as sorting-based filters have begun to address elsewhere.

The team is candid that the work is a proof of concept built on one reference IFC model and a prototype material database. It does not yet account for structural performance, fire resistance, moisture behaviour, cost, procurement realities, regulation, operational energy, or product-specific verified Environmental Product Declarations, all of which shape real material decisions. Testing across multiple authoring platforms and live projects will be needed before field deployment can be judged. Even so, the study makes a persuasive case that open BIM data can serve as far more than a visual or documentation layer. By keeping quantities, materials, carbon calculations, circularity scores and candidate explanations connected in one deterministic process, the workflow offers a traceable foundation for exploring early-stage trade-offs, exactly the phase of a project where decisions are cheapest to change and most consequential for the built environment’s carbon and material future.

Subject of Research: An open IFC-based BIM workflow for whole-building embodied carbon and circularity assessment

Article Title: Open BIM workflow links whole-building carbon and circularity decisions

Article References: Open BIM workflow links whole-building carbon and circularity decisions. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: BIM, IFC, embodied carbon, circularity, multi-objective optimisation, Pareto optimality, building materials, life cycle assessment, smart construction, decision support, buildingSMART, Monte Carlo analysis

The research, led by Jiazhen Sun and colleagues, tackles a class of materials known as low-cement concrete, or LCC. Instead of relying on ordinary Portland cement as the dominant binder, these mixes replace most of it with a carefully orchestrated blend of supplementary cementitious materials: ground granulated blast-furnace slag, fly ash, limestone powder, and iron tailing powder. The team designed four strength grades, from LC20 to LC50, in which cement content fell as low as 71.8 kilograms per cubic meter, compared with 359 kilograms in the reference mix. By weight, that means some of the mixes contained barely a fifth of the cement of conventional concrete, yet all met the compressive strength requirements of the corresponding Chinese standard grades at 28 days.

The chemistry behind this achievement is a story of staggered reactions. Slag, rich in calcium and already glassy in structure, activates early in the alkaline pore solution and begins forming calcium-aluminate-silicate-hydrate gel, the sticky glue of hardened concrete. Fly ash and iron tailing powder, which demand higher alkalinity before they react, hold back and then contribute steadily at middle and later ages. Limestone powder, largely inert, plays a physical role as a nucleation surface and microfiller while also reacting with aluminate phases to form carboaluminate compounds that add solid volume. The result is a binder system in which different components fire at different times, like relays in a long race, sustaining hydration for months.

A central worry with such extreme cement reduction is whether the pore solution stays alkaline enough to keep these secondary reactions running. The team measured pore-solution pH directly and found that even the leanest mix maintained a pH above 12.2 through 56 days of curing, with a minimum of 12.25. That is sufficient to depolymerize the glassy phases of slag and fly ash and keep the reaction engine turning. In fact, the pH of the low-cement pastes declined continuously with age, a sign that hydroxide ions were being actively consumed by ongoing secondary hydration rather than lost to a dying system.

The spectroscopic and thermal evidence told a consistent story. X-ray diffraction detected no portlandite, the crystalline calcium hydroxide that cement hydration normally produces in abundance, in the leanest mixes, and only weak traces in the higher grades. In the pure cement paste, portlandite content climbed from about 42 to 55 percent of the crystalline phases over two months. In the low-cement pastes, the trend reversed: calcium hydroxide was consumed almost as fast as it was made, dropping to between 0.71 and 1.62 percent by 56 days. Infrared spectroscopy showed the silicate band shifting toward higher wavenumbers, a fingerprint of increasingly polymerized, aluminum-bearing C-A-S-H gel. Thermogravimetric analysis, carefully corrected for the overlapping decomposition of iron tailing minerals and for limestone-derived carbonate, confirmed the same depletion.

The most eye-catching findings concerned the interfacial transition zone, the thin shell of paste surrounding each aggregate particle. In classical concrete science, this zone is the material’s Achilles heel. Because aggregate surfaces act like walls during casting, cement particles cannot pack densely against them, leaving a porous band, often tens of micrometers wide, enriched in weak, plate-like calcium hydroxide crystals. Cracks preferentially initiate and propagate here, and durability problems follow. Using backscattered electron imaging and a strip-based porosity profiling method, dividing the region next to the aggregate into fifteen strips ten micrometers apart, the researchers quantified this zone with unusual precision.

What they found upends the textbook picture. At three days, the interface of the low-cement concrete was indeed more porous than that of ordinary concrete, because the slow-starting supplementary materials had not yet produced enough hydration product to fill the voids left by the wall effect. But by 28 days the situation had inverted completely. The interfacial zone of the LC30 mix narrowed to roughly 60 micrometers, ten micrometers thinner than a pure cement paste control and thirty micrometers thinner than an ordinary C30 concrete. Its average porosity fell to about 4.7 percent, lower than the 6.2 percent of the surrounding matrix. The weak link had become a strengthened region, denser than the bulk paste it surrounds.

The mechanism is a triple play of packing, chemistry, and time. Fine, multisized supplementary particles pack more efficiently against the aggregate, softening the wall effect from the start. As secondary hydration proceeds, the moderate residual calcium hydroxide near the interface, rather than accumulating into weakening crystals, serves as a calcium reservoir and alkaline buffer that feeds the formation of additional C-A-S-H gel exactly where it is needed. Unreacted ultrafine particles lingering near the aggregate continue to hydrate under the low water-to-binder conditions, providing a sustained densification drive. Porosity profiles even revealed a subtle non-monotonic pattern in ordinary concrete, with porosity peaking a short distance from the aggregate surface, a signature of the wall effect that the low-cement system largely erased.

The macroscopic payoff showed up in long-term strength. Between 28 and 180 days, the low-cement mixes gained between 16.6 and 42.6 percent in compressive strength, with the leanest LC20 mix climbing from 32.6 to 46.5 megapascals. The ordinary reference concrete gained only 8.2 percent over the same period. Statistical analysis by two-way ANOVA with Holm-adjusted post hoc contrasts confirmed that every low-cement mix’s later-age gain was significantly greater than the reference, with p values ranging from below 0.001 to 0.029. The same calcium hydroxide that ordinary concrete leaves idle becomes, in this system, the fuel for months of continued gel formation, filling capillary pores in both the matrix and the interface.

The climate arithmetic is equally compelling. A cradle-to-gate assessment of embodied carbon showed the low-cement mixes cutting emissions by 44.7 to 68.8 percent relative to the conventional reference, with the leanest mix emitting just 101 kilograms of carbon dioxide equivalent per cubic meter against 324 for the control. For an industry under intense pressure to decarbonize, the message of this study is that cutting cement does not have to mean cutting performance. With the right blend of reactive and inert powders, staged hydration kinetics, and attention to particle packing, the concrete of the future may be both dramatically greener and, in its most vulnerable microstructural region, genuinely tougher than what it replaces.

Subject of Research: Microstructural evolution and interfacial transition zone densification in low-cement concrete with high volumes of supplementary cementitious materials

Article Title: Microstructural characteristics of low-cement concrete：From matrix to interfacial transition zone

Article References: Sun, J., Li, X., Chang, Z., Yang, C., Zhang, Q., Tang, Z., Han, Y., Miao, C., Wang, R., & Hu, Z. (2026). Microstructural characteristics of low-cement concrete：From matrix to interfacial transition zone. Case Studies in Construction Materials, 25, Article e06604. https://doi.org/10.1016/j.cscm.2026.e06604

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06604

Keywords: low-cement concrete, interfacial transition zone, supplementary cementitious materials, ground granulated blast-furnace slag, fly ash, limestone powder, iron tailing powder, C-A-S-H gel, calcium hydroxide, compressive strength, embodied carbon, sustainable construction

Researchers Anuoluwapo Sola Kolade, Damilola Oyewumi Oyejobi and Bolanle Deborah Ikotun assembled a database of 40 concrete mixes drawn from 20 peer-reviewed experimental studies published between 2016 and 2026, following a PRISMA-inspired screening procedure that began with 65 records. Twenty of the mixes relied on commercial sodium silicate activation, while twenty used activators synthesized from waste materials, most commonly waste glass powder and rice husk ash. The team deliberately distinguished between sole waste-derived activator systems, which eliminate commercial alkalis entirely, and hybrid systems that supplement the waste-derived activator with additional sodium hydroxide. Every mix was rebuilt from its published proportions into a harmonized cradle-to-gate life cycle inventory, using standardized environmental coefficients from the Inventory of Carbon and Energy database and process-specific literature, so that the environmental comparison rested on consistent assumptions rather than the heterogeneous reporting of the original studies.

The feedstocks at the heart of the analysis are abundant. The world generates an estimated 100 to 130 million tonnes of waste glass annually, while roughly 190 million tonnes of rice husks are produced each year, corresponding to a potential rice husk ash yield of 26 to 34 million tonnes. Both materials can contain more than 70 percent amorphous silica, the reactive ingredient needed to build soluble silicate activators. Two synthesis routes were compared: hydrothermal dissolution of the silica-rich waste in alkaline solution at 80 to 100 degrees Celsius, and thermochemical fusion, in which the waste is heated with solid alkalis at 150 to 650 degrees Celsius to form reactive solid silicate powders suitable for one-part, mix-and-go concretes. The thermochemical route proved especially attractive, since a standardized 500-degree-Celsius furnace cycle for two or three hours consumed only 0.072 to 0.108 megajoules per kilogram of product, roughly six times less energy than the hydrothermal coefficients adopted from the literature.

The mechanical verdict was strikingly even. Commercial-activated mixes averaged 41.56 megapascals of 28-day compressive strength across the pooled database, while the waste-derived systems averaged 39.44 megapascals, a difference the researchers’ statistical tests found insignificant, with a small effect size. Within the structural-grade class of 40 to 60 megapascals, the sole waste-derived systems actually outperformed both alternatives, averaging 52.87 megapascals against 50.32 for the commercial controls and 44.34 for the hybrids. The best waste-glass thermochemical formulations reached 59.12 megapascals, and several rice husk ash systems exceeded 55 megapascals, all without any heat curing. The authors attribute this performance to the higher slag contents these formulations carried, which supply calcium-rich phases that form dense C-(A)-S-H-type reaction products even at ambient temperature.

On carbon, the waste-derived systems delivered a decisive win. Average cradle-to-gate global warming potential fell from 173.42 kilograms of carbon dioxide equivalent per cubic metre for commercial activation to 114.82 for the waste-derived mixes, a reduction of about 34 percent that was statistically significant with a large effect size. The 95 percent confidence interval placed the true reduction between 19 and 49 percent. Sole waste-derived systems did best of all, averaging 103.50 kilograms of carbon dioxide equivalent per cubic metre, because hybrid systems still carry the burden of chlor-alkali sodium hydroxide production, an electrochemical process whose energy demand can exceed 20 megajoules per kilogram. Notably, the embodied energy picture was less flattering: waste-derived mixes actually consumed slightly more energy on average than the commercial controls, a difference that fell just short of statistical significance, reminding engineers that carbon savings and energy savings do not automatically travel together.

Contribution analysis made the reason unmistakable. Activator production dominated the environmental profile of every category, accounting for 82 percent of global warming potential in commercial systems and still 75 to 76 percent in the waste-derived ones, and for 65 to 73 percent of embodied energy. Precursors, particularly slag, formed the consistent secondary hotspot, while aggregates, water, superplasticizer and curing each contributed less than 13 percent individually. In other words, the lever that matters most in low-carbon alkali-activated concrete is not the aggregate supply or the mixing water but the chemistry of the activator itself, which is precisely where waste valorization intervenes.

The robustness of these conclusions was tested through sensitivity analyses that perturbed the most uncertain assumptions. Raising the environmental coefficients assigned to waste glass and rice husk ash by 20 percent shifted the sole waste-derived average by only about 2 percent and changed no rankings. Substituting an alternative, lower-impact inventory for commercial sodium silicate reduced the commercial systems’ average carbon footprint substantially, yet the waste-derived systems still held the lowest position. Cutting the hydrothermal processing energy by 20 percent likewise left the ordering intact. Formal t-tests at the 95 percent confidence level, with Welch’s correction applied where variances were unequal, supported the headline comparisons throughout.

When strength was folded into the environmental accounting, the picture sharpened further. Strength-normalized carbon intensity averaged 3.23 kilograms of carbon dioxide equivalent per megapascal for waste-derived systems against 4.60 for the commercial controls, a significant difference with a moderate effect size. A composite sustainability index, which combines carbon and energy burdens per unit of strength, placed seven of the top ten most eco-efficient mixes in the waste-derived category, with the leading formulation achieving 50 megapascals at an index of just 2.23. Pareto analysis, which searches for mixes that no other formulation can beat on both strength and carbon simultaneously, identified three non-dominated systems, all of them sole waste-derived and all activated by thermochemically fused waste glass. One achieved 35 megapascals at a mere 51.52 kilograms of carbon dioxide equivalent per cubic metre, the lowest-carbon solution in the entire database, while another delivered 59.12 megapascals at 85.39.

Perhaps most consequential for real-world procurement, the researchers mapped their reconstructed carbon values onto the Low Carbon Concrete Group’s tiered embodied carbon classification, a framework increasingly used in infrastructure purchasing. Six of the eleven sole waste-derived formulations earned the top Market Beating rating, compared with only three of the twenty commercial mixes, and several waste-derived structural-grade concretes exceeded 50 megapascals while staying within that best band. The commercial systems, by contrast, spread across the ratings and included the only mixes classified in the worst band. The authors caution that these classifications were applied without regional adjustment for electricity mixes or supply chains, and that the cradle-to-gate boundary excludes transport, construction and end-of-life stages, so the results should be read as production-stage benchmarks rather than complete life cycle verdicts.

The path from laboratory promise to industrial deployment still runs through familiar obstacles: feedstock variability, contamination in waste glass streams, the regional dependence of rice husk ash quality, the need for dedicated thermal processing infrastructure, and the absence of the standards and mix-design frameworks that Portland cement enjoys. The study’s authors argue that future work should integrate durability indicators such as chloride migration and carbonation resistance into eco-efficiency assessments, standardize environmental reporting, and explore low-energy synthesis routes including mechanochemical processing. But the central message stands on firm quantitative ground: concrete that matches the strength of commercial formulations while cutting embodied carbon by roughly a third can be built on activators made from the glass bottles and rice husks the world already throws away, and the bottleneck to greener construction may be solved not by reinventing the binder but by reinventing its chemistry.

Subject of Research: Waste-derived alkaline activators for fly ash-slag alkali-activated concrete and their strength and life cycle environmental benchmarking

Article Title: Strength and environmental benchmarking of waste-derived activators in fly ash-slag alkali-activated concrete: A systematic and quantitative assessment

Article References: Kolade, A. S., Oyejobi, D. O., & Ikotun, B. D. (2026). Strength and environmental benchmarking of waste-derived activators in fly ash-slag alkali-activated concrete: A systematic and quantitative assessment. Case Studies in Construction Materials, 25, Article e06602. https://doi.org/10.1016/j.cscm.2026.e06602

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06602

Keywords: alkali-activated concrete, waste-derived activators, sodium silicate, waste glass powder, rice husk ash, fly ash, ground granulated blast furnace slag, life cycle assessment, global warming potential, embodied carbon, geopolymer, low-carbon procurement

The team’s starting point was the engineered cementitious composite, or ECC, a class of material designed to bend without shattering. Instead of failing with a single catastrophic crack, a well-designed ECC strain-hardens: once the matrix cracks, embedded fibres bridge the gap and the load keeps rising as a network of fine, tightly controlled microcracks spreads through the material. Polyethylene (PE) fibres are the stars of this show. Previous studies have reported tensile strain capacities of six to eight percent in PE-reinforced ECCs—hundreds of times the stretch of ordinary concrete—along with crack widths fine enough to keep water and corrosive agents out. But PE fibres are slippery and relatively compliant, which means they do little to raise the stress at which the very first crack forms.

That is where the hybrid strategy comes in. The researchers combined PE fibres with alkali-resistant (AR) glass fibres, which are stiffer, bond more strongly to the matrix, and are durable in the alkaline chemical environment of cement. The logic is complementary: glass fibres stiffen the composite and delay crack initiation, while PE fibres carry the load through the long post-cracking phase. Both fibre types were 12 millimetres long, with the glass fibres slightly thinner at 18 micrometres versus 24 micrometres for PE, and the glass fibres carrying more than 1000 megapascals of tensile strength against 3000 megapascals for PE. Crucially, the total fibre volume was held constant at two percent across all mixes, so any change in behaviour could be attributed purely to the ratio between the two fibre types.

The binder itself was chosen with the climate in mind. Rather than ordinary Portland cement, the mixes used a blend of 30 percent OPC, 20 percent reactive magnesium oxide and 50 percent ground granulated blast-furnace slag, a by-product of steelmaking. The high slag content slashes clinker consumption, while the reactive MgO promotes the formation of brucite and magnesium silicate hydrate phases that densify the matrix and improve strength retention. Water-to-binder and sand-to-binder ratios were fixed at 0.25 and 0.36. Five mixes were tested: an unreinforced control, a conventional 2 percent PE mix, and three hybrids in which 0.5, 0.75 and 1.0 percent of the PE was swapped for glass fibre.

The mechanical results reveal a clear trade-off. In compression, the plain control reached 71.90 megapascals, the highest of all mixes, thanks to its superior flow and compaction. Adding fibres reduced compressive strength modestly for the PE-only mix (67.31 megapascals, a 6.4 percent drop) but progressively more as glass content rose: 64.02, 60.11 and 54.47 megapascals for the three hybrids. The researchers attribute this to fibre agglomeration and trapped air, which increase porosity and weaken the fibre-matrix interface. Still, two of the three hybrids remained above the 55-megapascal threshold that American Concrete Institute guidelines use to define high-strength concrete.

In tension, the picture flipped. The unreinforced matrix cracked at about 3.1 megapascals and immediately failed, with a negligible strain capacity of 0.014 percent. Every fibre-reinforced mix, by contrast, satisfied the ECC ductility criterion of exceeding 0.5 percent tensile strain. The PE-only mix delivered the greatest stretch at 5.91 percent strain with a peak stress of 6.55 megapascals, but its first-cracking strength of 2.80 megapascals was the lowest among the fibre mixes. Replacing a quarter of the PE with glass fibre produced the most balanced tensile response: the 1.25P0.75G mix combined the highest first-cracking strength of 4.13 megapascals with a peak stress of 6.12 megapascals and a still-respectable 2.84 percent strain capacity. Beyond that ratio, ductility fell steadily, dropping to 2.08 percent when the fibres were split evenly.

Flexural testing told a similar story with a twist. The plain beam snapped at 2.99 megapascals after just 0.35 millimetres of deflection. All fibre mixes showed deflection-hardening, but the sweet spot was the 1.5P0.5G mix, which paired a first-cracking strength of 7.81 megapascals and a peak flexural stress of 13.78 megapascals with the largest ultimate deflection of any mix, 21.66 millimetres—actually exceeding the PE-only mix’s 19.95 millimetres. The small dose of glass fibre delayed crack localisation while the remaining PE fibres sustained large post-cracking deformation. Pushing glass content higher raised first-cracking resistance further, up to 10.68 megapascals in the 1P1G mix, but shrank deflection capacity to 14.82 millimetres, confirming that PE fibres are the indispensable ingredient for bending ductility.

Perhaps the most technically impressive part of the study is the imaging. X-ray micro-computed tomography is a powerful non-destructive tool, but PE fibres attenuate X-rays so weakly that they are nearly invisible against a cementitious matrix, which is why most micro-CT studies have focused on steel fibres. The researchers solved this with a dedicated workflow on a SkyScan 1273 scanner: 100 kilovolts, an aluminium filter, 2500-millisecond exposures and a voxel size of about 6 micrometres, followed by segmentation that combined grey-value thresholds with an aspect-ratio filter to pick out elongated PE-fibre-like features geometrically. The result was full three-dimensional maps of pores, glass fibres and PE fibres. These showed fibre clustering worsening as glass content increased, and detectable porosity climbing from 3.47 percent in the plain matrix to 5.71 percent in the 1P1G mix, with the pore-size distribution broadening toward larger voids. A Pearson correlation analysis reinforced the trends: glass fibre content correlated strongly and positively with porosity and flexural first-cracking strength, but negatively with compressive strength and flowability, while PE content tracked tensile strain capacity and deflection with correlation coefficients around 0.98 and 0.94.

The sustainability accounting adds an honest caveat. The binder dominated the carbon footprint, with reactive MgO the largest single contributor, and fibres added further burden: embodied carbon rose from 0.864 tonnes of CO2-equivalent per cubic metre for the plain mix to 0.963 for the best hybrid, while primary energy climbed from 4.462 to 6.854 gigajoules per cubic metre, driven largely by the energy-intensive PE fibre. Even so, the 1.5P0.5G mix emerged as the best overall compromise, delivering high flexural strength, exceptional deflection capacity and acceptable compressive performance at a moderate environmental cost. For serviceability-critical elements such as thin façade panels, where crack control and deformation tolerance matter more than raw strength, hybrid PE-glass fibre reactive magnesia-slag composites offer a credible path toward low-clinker infrastructure that bends instead of breaking—and, thanks to the adapted micro-CT method, engineers can now see exactly what is happening inside.

Subject of Research: Hybrid polyethylene and glass fibre reinforcement of reactive magnesia-slag cementitious composites

Article Title: Effect of hybrid fibres on reactive magnesia-slag composites: mechanical behaviour, 3D microstructure by micro-CT and sustainability

Article References: Iqra, Soe, K., Yang, R. C., & Zhang, Y. (2026). Effect of hybrid fibres on reactive magnesia-slag composites: mechanical behaviour, 3D microstructure by micro-CT and sustainability. Case Studies in Construction Materials, 25, Article e06576. https://doi.org/10.1016/j.cscm.2026.e06576

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06576

Keywords: engineered cementitious composites, polyethylene fibres, alkali-resistant glass fibres, reactive magnesia, ground granulated blast-furnace slag, strain-hardening, micro-CT, porosity, flexural behaviour, embodied carbon, low-clinker binder, fibre dispersion

The study set out to answer a deceptively simple question: how does the science of building LCA actually handle resilience, the capacity of a structure to withstand hazards and recover its function afterward? Rios conducted a systematic review of 40 original LCA studies spanning four hazard types: heat, flood, wind, and seismic events. Each study was mapped against a diagnostic grid built from two established resilience frameworks. The first, from Bruneau and colleagues, describes resilience through four dimensions: robustness, the strength to withstand a shock; redundancy, the presence of substitutable systems; rapidity, the speed of restoration; and resourcefulness, the capacity to mobilize people and materials for recovery. The second, from Rehak and colleagues, divides the resilience timeline into four phases: preparation, system response, recovery, and adaptation.

The results of that mapping are strikingly lopsided. Nearly every study in the review clustered in a single cell of the grid: robustness during the preparation and recovery phases. In practice, this means researchers have become adept at asking how hazard-resistant design choices change the initial bill of materials, and at converting predicted damage into repair quantities that are added to the inventory as extra embodied carbon. Seismic studies, aided by the mature FEMA P-58 performance-based earthquake engineering pipeline, are the most internally consistent. Heat studies, powered by building energy simulation with future climate projections, form a second coherent camp. Flood studies are the most fragmented, with four distinct integration mechanisms, from depth-damage functions to insurance-based input-output conversion, coexisting without cross-fertilization. Wind studies, only three in total, borrow from both the seismic and insurance modeling traditions.

What the review found missing is more consequential than what it found present. The rapidity dimension appeared only as partial evidence in two seismic papers that treated time-to-repair as an output but never translated recovery duration into environmental flows. The redundancy and resourcefulness rows of the evidence map were entirely empty: no study modeled backup systems as a design variable, evaluated the environmental cost of built-in spare capacity, or asked what emissions would be avoided by systems that prevent damage escalation. The system response phase, the chaotic period during and immediately after a hazard when a building is operating below its functional threshold, was nearly absent across all hazard groups. In other words, the environmental cost of the disruption itself, the emergency fuel, the temporary shelter, the evacuation transport, falls outside every LCA system boundary in the reviewed literature.

The root of the problem, Rios argues, lies in the functional unit, the quantified description of service against which all environmental flows are normalized. In standard practice, that unit is static: one square meter of office space for fifty years, for example. This definition assumes the building delivers its service completely and continuously, an assumption that hazard exposure systematically violates. If a building loses functionality for six months after a flood, dividing its total life cycle impacts by the full fifty-year service life, as if those six months of failed delivery had never occurred, overstates its environmental efficiency and understates the cost of its fragility. The review found that not a single one of the 40 studies defined the functional unit in terms of sustained service delivery through disruption events.

To close this gap, the paper introduces a resilience-extended LCA framework, or RES-LCA, built on a reformulation of the functional unit as time-integrated functionality. Expressed mathematically as the sum over time of the functionality level Q multiplied by the duration of each time step, the new unit captures the cumulative service actually delivered over the building lifetime under all conditions, including disruption. When a building performs perfectly, the formulation reduces exactly to the conventional one. The difference appears only when service fails, which is precisely when resilience needs to be measured. Under this reformulation, the four resilience dimensions acquire distinct signatures in the functionality curve: robustness governs the magnitude of the initial drop, rapidity the slope of recovery, redundancy the residual service maintained during the disruption, and resourcefulness the shape and duration of the recovery trajectory.

The framework also extends the LCA inventory in two directions. A proposed system response module captures the environmental cost of compensatory services deployed while a building operates below functional threshold, flows that currently escape every assessment. An adaptation module captures the embodied impacts of post-event improvement works, embedding the bounce-forward logic in which a rebuilt building outperforms its pre-disaster baseline. Meanwhile, the often-optional Module D, normally limited to credits for reuse and recycling, is repositioned as a system-wide account of the avoided burdens generated by resilience investments. The approach builds on earlier work by Pizzol, who showed that representing resilience requires reformulating the functional unit and expanding the system boundary, and applies that insight within the existing EN 15978 modular structure that practitioners already use.

An illustrative example shows how the reformulation can flip conventional conclusions. Consider two identical residential buildings in a coastal flood zone, one at grade and one elevated on a concrete podium whose upfront embodied carbon is 30 percent higher. Both experience a single 100-year flood. The elevated building suffers no damage; the at-grade building spends two months nearly non-functional and four more months partially functional, requiring repairs and generating displacement-related emissions. Under conventional LCA, the elevated design appears environmentally preferable only if the avoided repair carbon exceeds the podium premium. Under RES-LCA, the compensatory service emissions of the disrupted building enter the calculation, and for a serious flood event, any non-zero displacement burden is enough to tip the balance toward the resilient design. The framework, in effect, makes the environmental value of resilience visible for the first time.

Perhaps the most provocative implication is what this means for the long-assumed trade-off between resilience and sustainability. The review confirms empirically that the tension is real in current practice: timber has the lowest embodied carbon but the highest flood vulnerability, green roofs reduce operational impacts but increase seismic repair flows, and passive cooling lowers energy use but raises overheating risk in extremes. Yet the study argues that this trade-off is, in part, an artifact of a measurement system that undercounts the environmental costs of service disruption. When environmental performance is defined in terms of service actually delivered, resilient buildings cease to look like costly deviations from efficiency and instead emerge as systems that deliver more reliable service per unit of environmental burden. Sustainability and resilience, long treated as competing agendas, become aligned.

The author acknowledges significant limitations. Data on compensatory service flows, phased recovery materials, and adaptation timelines are scarce and inconsistently reported, and no standardized method exists for quantifying building-level resourcefulness. The framework addresses only the technical dimension of resilience, leaving community-scale interdependencies and the social and organizational domains of the TOSE framework for future work, and the functionality trajectories it requires carry substantial uncertainty under a changing climate. Even so, the core message stands: as climate hazards intensify and billions in public infrastructure funding become tied to resilience criteria, the tools used to certify environmental performance must learn to count what happens when buildings fail. A green building that cannot keep its occupants sheltered through a disaster, the study suggests, is not as green as the spreadsheet claims.

Subject of Research: Integrating hazard resilience into building life cycle assessment through time-integrated functionality

Article Title: Resilience in building life cycle assessment: a critical review and framework for time-integrated functionality

Article References: Rios, F. C. (2026). Resilience in building life cycle assessment: a critical review and framework for time-integrated functionality. Journal of Industrial Ecology. https://doi.org/10.1007/s44498-026-00152-7

Image Credits: AI Generated

DOI: 10.1007/s44498-026-00152-7

Keywords: life cycle assessment, building resilience, embodied carbon, functional unit, seismic hazard, flood, heat waves, wind hazards, sustainability, climate adaptation, redundancy, EN 15978