Reducing global warming potential of concrete using particle packing theory and aggregate optimization

Concrete production alone, attributes to 8 – 9% of anthropogenic CO₂ emissions and 2 – 3% of annual energy demand, globally. Portland cement is the major contributor to CO₂ emissions, accounting for about 70% of total emissions from concrete production. Increasing the volume of aggregate through enhanced particle packing in concrete can reduce the amount of cement powder, thereby enabling the development of low-embodied-carbon concrete (LECC). However, the challenge resides in maintaining adequate performance. Here, we present a holistic particle packing and binary and ternary aggregate optimization approach (in baseline mixtures with various SCMs and w/b ratios) for ready-mix from concrete plants in the U.S. Northeast region to reduce the associated Global Warming Potential (GWP). Experimental and theoretical (modified-Toufar model) aggregate packing degree (PD) and power curves (PC) are considered for aggregate proportioning of concrete, with final aggregate selection constrained by workability considerations relevant to field implementation. An agreement between theoretical PD and experimental PD was found. Fresh and hardened properties of concrete with ternary optimized aggregates are compared against reproduced field mixtures without optimized aggregates, indicating adequate performance for normal-strength concrete. GWP and eco-efficiency metrics, including GWP normalized relative to compressive strength, were evaluated and decomposed to quantify the contributions from supplementary cementitious material (SCM) replacement, increased water-to-binder ratio, and aggregate optimization. These analyses enable assessment of the trade-off between compressive strength and environmental impact. While SCM incorporation and higher water-to-binder ratios reduce GWP, aggregate optimization provides an additional reduction, achieving up to 19.6% GWP reduction while maintaining normal-strength concrete performance.