Efficient mix design of alkali activated slag concretes based on packing fraction of ingredients and paste thickness

Many studies have been dedicated to the properties of alkali-activated slag concretes as a form of low-carbon high performance concrete, but less work has been focused on the application of mix design procedures to have a dense, durable and cost-efficient alkali-activated concrete. This study proposes a method for selecting the mix proportions of alkali-activated concretes based on the packing fraction of materials. The design method is based on the selection of the volumetric proportions of sand and coarse aggregate according to an ideal particle gradation curve. To validate this method, trial castings were carried out for concrete mixes containing alkali activated slag (AAS) with different paste contents to suggest the most cost-efficient concrete for different classes of workability and applications. Compaction and pore structure of these mixes studied by optical microscopy have shown that the design of AAS concretes based on the proposed method resulted in a dense and workable mix.