METHODS OF ANALYZING AND FACTORS INFLUENCING FRICTIONAL EFFECTS OF SUBBASES. FINAL REPORT

This final report for Research Project 459 reviews available information relating to the subbase frictional effect, especially an unpublished Portland Cement Association report for the Federal Highway Administration on cement stabilized subbases. Experimental results of push off tests on an unbound shell subbase layer underlying an in-service jointed reinforced concrete pavement are given and discussed. The report also lists and discusses the results of push off tests to find the effects of subbase depth and surface texture on the frictional resistance of an asphalt concrete pavement. Actual crack spacing values for continuously reinforced concrete pavements were then correlated to values predicted by the CRCP computer program in this report, using the subbase friction information found from this project study. Results of estimating subbase friction using the indirect tensile strength testing of subbase cores are shown and discussed, and implications of the subbase frictional effect on concrete pavements are presented. The report ends with a summary of conclusions and recommendations for future testing.