A recent study led by Martinez and colleagues evaluated three distinct recipes for Roman concrete, varying in slaked lime-to-pozzolan ratios of 1:2, 1:3, and 1:4. The researchers focused on the greenhouse gas and air emissions associated with each production stage, drawing insights from established Roman construction techniques. Historically, the Romans utilized oak and fir wood as fuel for their lime kilns, while labor for processes like loading, transportation, and mixing was provided by humans and animals, which were not included in the analysis.
The findings of the study challenged initial expectations. When comparing emissions per volume of concrete produced, Roman concrete demonstrated CO2 emissions that matched or occasionally exceeded those of modern concrete mixes. In contrast, Roman concrete was found to generate significantly lower levels of harmful air pollutants, such as nitrogen oxides and sulfur oxides, with reductions ranging from 11 percent to 98 percent depending on whether fossil fuels, biomass, or renewable energy sources were utilized (the latter showing the highest reductions).
Additionally, Roman concrete’s superior durability means it would require less frequent maintenance and replacement over time, potentially mitigating some of the negative environmental effects. However, the researchers note that direct comparisons are complicated by the fact that ancient Roman constructions did not incorporate steel reinforcements, which are a common feature in contemporary concrete. The corrosion of these steel bars primarily contributes to the deterioration of modern concrete structures.
“Surprisingly, integrating Roman concrete formulations with current technology may not lead to significant decreases in emissions or energy requirements,” stated Martinez. “Exploring biomass and other alternative fuels for kiln operations may offer a more effective pathway for decarbonizing modern cement production than simply adopting Roman concrete techniques.” Nevertheless, he emphasized the importance of learning from historical methods. “If we can blend their strategies with our modern innovations, we can work toward creating a more sustainable built environment.”
DOI: iScience, 2025. 10.1016/j.isci.2025.113052 (About DOIs).
