Optimizing the Carbon Footprint of Performance-Engineered Concrete Mixtures

This paper describes a process to optimize concrete mixture proportions to meet specific performance criteria through the minimization of a user-defined objective function that considers material cost and CO2 cost. The performance criteria impose constraints in the form of required mechanical properties (e.g., compressive strength), microstructural parameters (e.g., porosity or calcium hydroxide content), transport properties (i.e., the formation factor), and durability predictions (e.g., time to corrosion initiation or time to critical saturation). A thermodynamics-based model is used to predict reaction products and these results are used to predict performance. A feasible region of mixture proportions satisfying these constraints is identified after varying the water-to-binder ratios, cement replacement levels using limestone or supplementary cementitious materials, and air contents. The objective function is minimized to identify the optimal mixture proportions that meet all constraints while minimizing the material cost and CO2 footprint.