Assessment of carbon dioxide emissions from ready-mixed concrete production in different strength classes: A case study

Global warming, driven by the accumulation of greenhouse gases such as CO₂, poses significant environmental challenges. The construction sector is a major contributor to these emissions. Concrete, as one of the most widely used construction materials globally, plays a substantial role in the environmental impact of the industry, consuming vast natural resources and energy while generating considerable emissions. Cement, the primary binder in concrete, is the dominant source of its CO₂ footprint, primarily due to the high-temperature calcination of limestone during production. To evaluate these environmental impacts, Life Cycle Assessment (LCA) employed. This study utilized a 'cradle-to-gate' LCA approach to assess the CO₂ emissions associated with nine typical concrete mix designs produced by FAHAB Beton ready-mix concrete Company in Iran. The system boundary covered stages from raw material extraction to concrete production at the plant. A performance-based metric was established by defining the functional unit as the ratio of CO₂ emissions to the ۲۸-day compressive strength per unit volume (kg CO₂/MPa·m³). The results showed that cement was the largest contributor to CO₂ emissions across all mix designs. In self-consolidated concretes, superplasticizers also identified as significant contributors, second only to cement. Importantly, when analyzed using the functional unit, higher-strength concretes—despite having higher total emissions per cubic meter—exhibited lower CO₂ emissions per unit of strength, indicating higher environmental efficiency from a performance perspective. Given the widespread use of concrete in a developing country context such as Iran, incorporating both total emissions and performance-based environmental metrics is essential for advancing more sustainable concrete solutions.

Keywords:

Global Warming , CO۲ Emission , Life Cycle Assessment , Cradle-to-Gate , Functional Unit , Performance-based Environmental Metrics