Simulation of air-void system in hardened concrete using a geometrical model

In this paper, a two-dimensional geometric model is developed to characterise the air-void system in hardened cement paste. This model consists of non-overlapping circular voids of different size classes randomly placed in the cementitious matrix of a specific size. The major output of this model is the distance of a specific void from its nearest neighbour (void–void spacing). The cumulative distribution function of the nearest void–void spacing fits well the Rosin–Rammler model, from which the probability distribution function is derived. The number and distribution of the voids is obtained from the chord length measurement based on the linear-traverse method. The effect of paste content and air-void saturation on the void spacing is investigated to illustrate gradual increase in void spacing with a higher paste content or the partial filling of air voids. This model is validated by the good correlation between the calculated spacing factor and the tensile strain capacity of concrete from length-change measurement.