AN EVALUATION OF THE RELATIVE STRENGTH OF FLEXIBLE PAVEMENT COMPONENTS

THE PRIMARY PURPOSE OF THIS STUDY WAS TO DETERMINE THE COEFFICIENTS OF RELATIVE STRENGTH FOR BASE AND SUBBASE MATERIALS COMMONLY USED IN SOUTH CAROLINA. THESE COEFFICIENTS ARE OF PRIMARY IMPORTANCE IN THIS STATE'S FLEXIBLE PAVEMENT DESIGN PROCEDURE WHICH IS BASED ON THE INTERIM GUIDE FOR THE DESIGN OF FLEXIBLE PAVEMENT STRUCTURES. IN THIS PROJECT, PROTOTYPE PAVEMENT MODELS WERE CONSTRUCTED IN 8 FT X 12 FT TEST PITS. THE SUBBASE MATERIALS TESTS WERE SAND-CLAY AND CEMENT MODIFIED SOIL WHILE THE BASE MATERIALS TESTED WERE BITUMINOUS STABILIZED MACADAM, TYPE 2 MACADAM (CRUSHED GRANITE-GNEISS) SAND- ASPHALT, SOIL STABILIZED AGGREGATE, FOSSILIFEROUS LIMESTONE, AND A CRUSHED LIMESTONE SIMILAR TO THAT USED IN THE AASHO ROAD TEST. THE AASHO LIMESTONE WAS TESTED FOR THE PURPOSE OF CORRELATING RESULTS WITH THE AASHO ROAD TEST. ALL PAVEMENT MODELS WERE SURFACED WITH A 3-INCH LAYER OF TYPE 1 ASPHALTIC CONCRETE. IT WAS FOUND THAT THE RELATIVE STRENGTH COEFFICIENT OF UNBOUND, GRANULAR BASE MATERIALS WHICH HAD NO CEMENTING CHARACTERISTICS DECREASED WITH INCREASING THICKNESS OF THE LAYER WHILE THE CEMENTED MATERIALS GENERALLY SHOWED AN INCREASE IN STRENGTH AS THE THICKNESS INCREASED. VARIATIONS WERE ALSO NOTED FOR REASONS OF ENVIRONMENT AND SUPPORT. THE RELATIVE STRENGTH VALUES FOR ALL BASE AND SUBBASE MATERIALS WERE INTERPOLATED FOR VARIOUS THICKNESSES AND APPLICATIONS AND THE VALUES RESPRESENTING THE BEST JUDGEMENT OF THE INVESTIGATORS WERE RECOMMENDED FOR DESIGN PURPOSES. THE RECOMMENDED VALUES ARE BASED ON ELASTIC DEFLECTION AND DO NOT CONSIDER RUTTING CAUSED BY DISPLACEMENT OR COMPACTION OF THE VARIOUS LAYERS UNDER TRAFFIC, OR DETERIORATION OF THE PAVEMENT DUE TO WEATHERING. /AUTHOR/