China steel-slag road model projects lower emissions over repeated resurfacing cycles

A study published on 24 September 2026 projects that steel-slag epoxy pavements could reduce emissions across China's urban roads if they last long enough to avoid repeated resurfacing. The national estimates are modelled outcomes, not measured results from a road-building programme. For cities weighing the material, the central question is whether longer service life would outweigh higher construction costs and a week-long curing period.

How the China road model estimates savings

The researchers combined road networks, traffic demand, pavement degradation and the availability of steelmaking slag in a model spanning 2030 to 2060. They assessed scenarios in which 25% to 100% of urban pavements are replaced. Steel slag, a by-product of steelmaking, takes the place of all natural coarse aggregate in the mixtures they tested; the asphalt binders contain 20%, 35% or 50% epoxy resin.

Across the replacement scenarios and assessment horizons, the study projects 431 million to 1,741 million tonnes less greenhouse-gas emissions and 303 million to 1,229 million kilograms less fine particulate matter, or PM2.5, emissions. It also models approximately 31,802 to 128,980 avoided premature deaths and net economic benefits of 3.48 trillion to 15.01 trillion yuan. Those health and economic figures are estimates derived from the model, not observed national outcomes.

Why the pavement's service life matters

The model's advantage comes from resurfacing less often. Fatigue tests and structural analysis underpin an assumed six-year service life for conventional pavement. The corresponding assumptions for the steel-slag designs are six years with 20% epoxy, 15 years with 35% and 20 years with 50%. A longer-lived road can spread its initial construction burden over more years and avoid some later renovation work.

The upfront cost and seven-day closure

The new mixtures carry a substantial initial penalty in the paper's comparison. For one service life, the authors report carbon intensity per square metre 215% to 261% higher than the conventional benchmark, PM2.5 intensity 230% to 315% higher and cost 189% to 365% higher. They estimate that epoxy-modified asphalt costs four to five times as much per unit as conventional asphalt. Repeated resurfacing is what allows the longer-lived designs to reverse those results in the wider model.

Construction also takes longer. The paper says conventional asphalt can reopen within one day, while its steel-slag epoxy mixture needs seven days of curing to reach full mechanical strength. The authors say the extended closure raises traffic-disruption emissions as congestion leads to repeated acceleration and braking. The available study text does not provide a separate numerical total for emissions caused by that curing-related traffic.

Road use is especially important to the model's result. In its baseline scenarios, the authors attribute 95.45% of emissions and 60.07% of costs to indirect effects during use, principally vehicle fuel consumption and pavement condition. That makes the result sensitive to how roads perform over time and how traffic changes, as well as to emissions from making and laying the pavement.

What other steel-slag research can establish

Steel slag does not deliver the same result in every asphalt mixture. A separate 2023 study by Xiaoqing Li and colleagues reported higher concentrations of volatile organic compounds and higher life-cycle greenhouse-gas emissions for the steel-slag asphalt it examined than for its natural-aggregate comparison. That study used a different formulation and scope, so its finding cannot be treated as a direct test of the new epoxy pavement or the China-wide model. It does show why the mixture and the boundaries of an emissions calculation matter.

What remains uncertain about deployment

The new model limits deployment according to technically suitable annual slag availability and permits transfers between provinces. It does not model production capacity, regional supply networks or competing industrial uses of the material. The authors also identify future traffic patterns, regional policy, material supply and long-term pavement performance as unresolved influences on the size of the projected benefits.

The study establishes a conditional case for longer-lasting pavement, rather than evidence that the proposed mixture has been laid across China's urban road network. Its largest climate, pollution, health and economic figures depend on the assumed service lives and deployment scenarios. Measuring how the mixture performs on roads over time would be necessary to assess how closely those projections match real resurfacing needs and traffic disruption.