{"id":54123,"date":"2026-11-15T10:17:00","date_gmt":"2026-11-15T15:17:00","guid":{"rendered":"https:\/\/www.ecoticias.com\/en\/?p=54123"},"modified":"2026-11-09T12:14:40","modified_gmt":"2026-11-09T17:14:40","slug":"china-could-pave-its-city-streets-with-recycled-steel-slag-and-cut-the-emissions-tied-to-those-roads-by-19-percent-and-the-catch-is-a-surface-that-keeps-traffic-off-for-a-week","status":"publish","type":"post","link":"https:\/\/www.ecoticias.com\/en\/china-could-pave-its-city-streets-with-recycled-steel-slag-and-cut-the-emissions-tied-to-those-roads-by-19-percent-and-the-catch-is-a-surface-that-keeps-traffic-off-for-a-week\/54123\/","title":{"rendered":"China could pave its city streets with recycled steel slag and cut the emissions tied to those roads by 19 percent, and the catch is a surface that keeps traffic off for a week"},"content":{"rendered":"\n

Paving China’s urban roads with recycled steel slag could cut the emissions tied to those roads by 19 percent. That projection comes from a modeling study published September 24, 2026, in Communications Earth & Environment<\/a>. Savings run from about 476 million to 1.92 billion U.S. tons (431 million to 1.74 billion metric tons) of carbon dioxide equivalent.<\/p>\n\n\n\n

The range depends on how much pavement gets replaced, from one-quarter to all of it. Those totals build up across a phased rollout plus two 15-year service cycles. These are projections from pavement data and computer models, with no national rollout behind them.<\/p>\n\n\n\n

Zhihan Zhang and Wei Huang of Southeast University in Nanjing share first authorship. Their 16-member team includes Carlo Ratti and Paolo Santi of the Senseable City Lab at MIT.<\/p>\n\n\n\n

Slag replaces every coarse stone<\/h2>\n\n\n\n

When steel is made, impurities separate from the molten metal and leave a stony residue called slag. A Federal Highway Administration guide<\/a> calls aggregate made from it “highly angular in shape.” The new paper says that shape and high strength suit it to paving.<\/p>\n\n\n\n

Aggregate makes up more than 90 percent of pavement materials, the authors note. China used about 15.1 billion U.S. tons (13.7 billion metric tons) of it in 2024, and registered quarries fell 11 percent from 2023. Elsewhere, desert-rich Saudi Arabia imports sand for concrete<\/a> because its own grains are too smooth.<\/p>\n\n\n\n

Under the tested recipe, slag replaces all of the natural coarse aggregate, compared with 60 percent in current slag asphalt. Epoxy resin goes into the binder, the sticky material holding the stones together. Road builders have also tried rubber-coated asphalt made from old tires<\/a>.<\/p>\n\n\n\n

The calculations use a surface layer about 1.6 inches (4 centimeters) thick. This is a recipe for the top of the pavement, then, and not for a road made wholly of waste.<\/p>\n\n\n\n

Fifteen years against six<\/h2>\n\n\n\n

Three binders went through the analysis, with 20, 35 and 50 percent epoxy. Fatigue tests and structural calculations gave assumed lives of 6, 15 and 20 years. Conventional pavement got 6.<\/p>\n\n\n\n

Of the three, the 35 percent blend offered the best balance. The 50 percent version lost ground on price. At 20 percent, the surface did not last long enough to deliver meaningful gains.<\/p>\n\n\n\n

Most of a road’s footprint comes from the vehicles driving on it. In the baseline scenarios, indirect effects during use made up 95.45 percent of emissions and 60.07 percent of costs. Fuel burned and pavement condition drove that share, because rougher roads raise fuel use.<\/p>\n\n\n\n

A week before traffic returns<\/h2>\n\n\n\n

Epoxy-modified asphalt costs roughly four to five times as much as the conventional kind, the paper reports. Over one service life, the slag mixture costs 189 to 365 percent more per square meter. Its carbon intensity runs 215 to 261 percent higher.<\/p>\n\n\n\n

Curing adds a second penalty. Conventional asphalt can reopen within a day, while the slag mixture needs seven days to reach full strength. Stop-and-go driving around each closure burns extra fuel.<\/p>\n\n\n\n

For that reason the authors write that “deployment strategy is as important as material performance.” In a Jiangsu Province test case, renovating expressways first delivered 2.87 to 6.05 percent more carbon savings than upgrading all road types in proportion. It also raised traffic delays by 33.8 percent over the baseline, about 259,900 extra hours a year.<\/p>\n\n\n\n

Provinces trading furnace waste<\/h2>\n\n\n\n

Beijing, Tibet and Hainan have no local slag production, so they would depend on shipments. Some provinces would need 10 to 15 years to reach full coverage alone. With outside slag, that drops to 1 to 5 years.<\/p>\n\n\n\n

Hauling the material adds about 5.6 million U.S. tons (5.06 million metric tons) of carbon dioxide equivalent. Net reductions from sharing reach about 659 million U.S. tons (597.63 million metric tons).<\/p>\n\n\n\n

Road density mattered more than steel output. Hebei produces a lot of slag, yet its sparse urban road network limits the net benefit. Added gains shrink once replacement passes 75 percent, as distribution burdens grow.<\/p>\n\n\n\n

Deaths avoided, with a warning<\/h2>\n\n\n\n

Emissions of PM2.5, the fine particles linked to heart and lung disease, fall by 13 percent in the model. The team estimated 31,802 to 128,980 avoided premature deaths over 30 years.<\/p>\n\n\n\n

According to the authors, those results “should be interpreted as indicative system-level outcomes rather than precise epidemiological predictions.” One paving project cannot be judged from them.<\/p>\n\n\n\n

Over 30 years, the paper projects a net economic return of 3.48 to 15.01 trillion yuan. Separately, it reports cost savings of 2.99 to 13.03 trillion yuan.<\/p>\n\n\n\n

Fatigue tests stand in for streets<\/h2>\n\n\n\n

Much of the gain depends on the assumed 15-year life, which rests on four-point bending tests and structural analysis. The model still schedules preventive maintenance every three years. Surfaces can also disappoint in service, as a Dutch solar cycle lane<\/a> showed.<\/p>\n\n\n\n

Slag has a known weakness, too. The federal guide warns that free lime and magnesium oxides can hydrate and change its volume by up to 10 percent or more. A 2025 laboratory study<\/a> sharing some of the same authors reported that more epoxy improved long-term volume stability and, through a stronger bond with the aggregate, limited moisture damage.<\/p>\n\n\n\n

On supply, the paper “does not model material production capacity, regional supply networks or competing industrial uses.” Its tonnages are technical requirements. They do not show that today’s market could meet national demand.<\/p>\n\n\n\n

The full study was published in Communications Earth & Environment<\/a>.<\/p>\n\n\n\n

Planners in India, Southeast Asia and parts of Africa could use the same framework, the authors suggest. Their absolute results would depend on local traffic, roads and materials.<\/p>\n\n\n\n

Photo: Wanderer777 \/ Wikimedia Commons, CC BY-SA 4.0<\/p>\n","protected":false},"excerpt":{"rendered":"

Paving China’s urban roads with recycled steel slag could cut the emissions tied to those roads by 19 percent. That … <\/p>\n

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