Porosity assessment of granular mixtures intended for concrete using the fractal model of particle-size distribution

Abstract

Selecting an optimal granular mixture has always been a major concern for engineers and researchers in the field of building constructions and public works. Reducing the porosity of dry and/or wet granular mixtures remains a key factor in the field of concrete formulation. Worth noting is to improve durability while controlling the influence of porosity on the workability of wet granular mixtures. The present work aims primarily at estimating the porosity of dry granular mixtures and determining the optimal value of the fractal dimension (DF) for which the porosity is minimal. Granular mixtures, whose grains distribution was perfectly fractal, were developed for two different forms of grains aggregates, i.e. one range for a single rolled granular grain and six ranges for crushed granular grains. The porosity of the granular mixtures was determined using two setting (vibrated and/or non-vibrated) conditions and different vibration durations. The laboratory results enabled to develop an equation for the determination of the dry granular mixtures porosity of the crushed aggregates (CA) and rolled aggregates (RA), under the two above setting conditions. Minimum porosity of the dry granular mixtures was achieved for an optimal fractal dimension (DF) and an optimal vibration duration, respectively, close to 2.8 and 10 s.