LABORATORY AND FIELD INVESTIGATION OF BITUMINOUS PAVEMENT AND AGGREGATE POLISHING

To investigate the field performance of aggregates, 11 test strips containing replicate sections of bituminous pavements used in Pennsylvania were designed and constructed by a joint industry-Pennsylvania Department of Transportation task force. In the investigation, 52 aggregate samples and 223 pavement cores of the test sections were polished in the laboratory by using various polishing methods and friction measurement techniques. Correlations between field and laboratory data were sought, and factors associated with skid-resistance variations were observation and investigated. Laboratory-field data correlations indicated that the general level of skid-resistance characteristics of surface aggregates may be determined in the laboratory and that the aggregates may be ranked similarly by both approaches. However, the correlations failed to produce regression equations that could with confidence, define specific mathematical relationships for predicting specific field skid numbers. A minimum field skid number occurred in the late summer and fall and correlated better with laboratory results than a mean skid number. The minimum number appears to stabilize after 2 years of pavement exposure to traffic, irrespective of the level of traffic. Higher average daily traffic produced a lower skid-resistance level, and one truck was equivalent to about 18 passenger cars in polishing effects. Cumulative traffic also caused reduction in the skid number until the surface stabilized; then the number leveled off. Temperature correction of the minimum skid number appears to have little or no effect on skid data analysis. Increase in the percentage of insoluble residue of carbonate aggregates indicated only possible increases in skid resistance, but no dependable quantitative correlation could be obtained from available tests.