Study of Particle Packing Theory

Particle packing deals with the problem of selecting appropriate sizes and proportions of particulate materials to obtain a compact mixture. The optimization of the packing-density of granular components of concrete has become an important factor in achieving improvements in the mechanical properties of conventional concrete. Granular components of concrete, i.e. aggregates and fillers occupy as high as 70 to 85% of the concrete volume. Therefore, controlling the granular mixture proportion will help in minimizing the volume of void space, thereby ensuring higher strength and better workability due to improved macro-mechanical properties. Further, with the same w/c ratio, a smaller amount of water and hence lesser cement paste is needed when the granular fraction is more densely packed, which in turn reduces the occurrence of the weak interface between the aggregate and the cement paste thus enhancing the strength and durability of the concrete. Since high-strength concrete mixes are made with a low w/c, they require a large amount of cement in the mixing process that may cause severe creep and drying shrinkage and other associated problems.