SKID RESISTANCE STUDIES: AGGREGATE-SKID RESISTANCE RELATIONSHIP AS APPLIED TO PENNSYLVANIA AGGREGATES

The skid resistance studies are concerned with these problems: To what degree do the various aggregates tested contribute to the skid resistance properties of pavement? and what is the performance record of these aggregates when affected by traffic passes and seasonal changes? Research activities from 1960 to 1968 indicated skid resistance values on bituminous concrete pavements were governed primarily by coarse aggregate properties. In order to evaluate these aggregate parameters a series of test strips were planned and constructed in 1968-69 for periodic skid testing. The eleven test strips included a representative cross-section of the more than 340 sources producing aggregates for use in Pennsylvania. Petrographic analysis was made of the coarse aggregates used in the test strips and skid tests were conducted periodically at approximately one month intervals throughout the study. Analysis of all the data collected indicates that pavement skid resistance values in Pennsylvania go through an annual cycle roughly approximating a sine curve with low values usually occurring during last summer and early fall. The amplitude of the sine curve is dependent mainly upon the particular coarse aggregate characteristics in the pavement surface and the daily traffic volume. The petrographic properties of a coarse aggregate from a particular source within a type of rock can be related to its skid resistance performance under various traffic volumes.