Effect of fine particles on some characteristics of granular base courses

The paper presents the results of a scientific research program focused on determining the effect of the fine particles content in granular stone materials on particular properties of the unstabilized base course. Grain-size distribution of a granular system was within the defined limits, and the percentage of fine particles (< 0.02 mm in diameter) ranged from 0 to 10% by mass. Two types of fine particles were tested, those of stone and clay origin. The specimens were compacted using five energy levels. Used lab. equipment was in compliance with the requirements of German (DIN) and Swiss (SNV) standards. The following characteristics were tested: bearing capacity (CBR test) at optimum moisture content and after one freezing/thawing cycle permeability (coefficient of permeability k). The obtained results were statistically analyzed and graphically presented. The most important outputs are: (a) Bearing capacity within the research limits of 0 to 10% by mass, fine stone particles have positive effect and the bearing capacity increases, fine clay particles content not higher than 5% by mass is acceptable; for higher percentages, the bearing capacity decreases. (b) Permeability for fine stone particles content below 5% by mass permeability is still satisfactory; however, even a very small percentage of fine clay particles has an adverse impact on permeability. The conclusions are related to the tested materials and should be used as starting point for further investigation.