Particle packing: an important concept for mix design of better compacted interfacial transition zone in cementitious composite systems

It is well known that the interfacial transition zone (ITZ) of concrete between aggregate and bulk paste often acts as a negative effect with respect to overall properties like strength and durability. To reduce the negative influence of ITZ, it was usually considered to add various pozzolan or mineral additions into concrete, such as granulated blast furnace slag (GBFS). These additions could incur both physical packing and affect the chemical hydration reaction. In this paper, the physical packing effect in ternary blended cementitious system was studied in more detail. The maximum packing density can be calculated by employing linear packing model (LPM), based on the discretization of particle size distribution (PSD). With various mix proportions of raw materials, the overall distribution of packing density was displayed. In order to show how the initial ITZ property was influenced by packing density, numerical modeling by means of random sequential addition (RSA) has also been conducted.