Optimizing Aggregates to Reduce Cement in Concrete without Reducing Quality

Of the constituents of concrete, cement is the most expensive and has the largest carbon footprint. High cement content in concrete affects the durability of concrete. Shrinkage in concrete generally increases with increase in cement content; however, increasing the aggregate content provides more volume stability. Cement content can be reduced with the proper selection of aggregates and use of admixtures. Two approaches are considered: (a) optimizing aggregate gradation by varying aggregate and paste content and (b) replacing cement with mineral fillers (microfines). For each mixture, the high-range water-reducing admixture dosage was adjusted to maintain a constant slump (workability). The effects on slump, compressive strength, drying shrinkage, permeability, and abrasion were measured. Results show that both methods can be used to reduce cement content, maintain or improve performance, and reduce cost, with a more sustainable concrete as the end result.