Lognormal Simulation of Pore Size Distributions in Cementitious Materials

The pore size distributions in cement pastes and mortars, over the range of pore sizes determined by high-pressure mercury intrusion porosimetry (MIP), can be described in terms of a multimodal distribution by using lognormal simulation. The pore size distribution may be regarded as a mixture of lognormal distributions. Such a mixture is defined by a compound density function: p ( x ) =Σ f_i p ( x , μ _i , σ _i ), Σ f_i = 1, where x is the pore diameter, f_i , is the weighting factor of the i ^th lognormal subdistribution of pore sizes, p ( x , μ _i , σ _i ), and μ _i and σ _i are the location parameter and the shape parameter of the i ^th subdistribution, respectively. It may indicate that different origins and formation mechanisms exist for pores in different size ranges in cementitious materials. A graphical method is proposed to estimate the parameters for the compound distribution. Applications of this model to prediction of permeability are discussed.