Abstract
The fractal distribution of the logitudinal primary surface cracks has shown the presence of secondary growth which yields longer cracks. To illustrate the secondary growth, a model which consists of two processes is considered ; one is the foregoing probability process for generation of the crack growth, and the subsequent growth process concerning the degree of growth : δ.Variations in distribution and integral functions and also in interval and cumulative frequencies for the secondary cracks and the residual primary cracks is given as a function of the dimensionless length, the ratio of crack length : L to the critical length : Lc at which the probability is assumed to be 1. Three data sets were analysed and calculated distributions for the grown secondary cracks and the residual primary cracks were in good accordance with those expected from the model. The correlation between Lc and δ suggested that there were two types of the growth process. One type showed the product of Lc and δ being constant in the range L = 1 to 2 m ; this type included data of the lower face of two slabs. The other showed δ being constant at about 2, regardless of Lc ; this type included data of the upper face.
