Rigid Pavement Performance Influenced by Slab Strength and Thickness

EXISTING THEORIES FOR STRUCTURAL BEHAVIOR OF RIGID PAVEMENTS WERE EXAMINED IN VIEW OF THE LARGE AMOUNT OF CONTROLLED FIELD PERFORMANCE DATA COLLECTED DURING AN AASHO ROAD TEST. A SIGNIFICANT CONTRIBUTION WAS THE DEVELOPMENT OF A RELATIONSHIP BETWEEN TENSILE STRESS IN THE PAVEMENT SLAB CAUSED BY MOVING LOADS AND THE PERFORMANCE OF PORTLAND CEMENT CONCRETE PAVEMENT. THE FINDINGS SUPPORT MOST EXISTING THEORETICAL METHODS OF RIGID PAVEMENT DESIGN AND WILL BE OF PARTICULAR VALUE IN DESIGN OF PAVEMENTS FOR RAPIDLY INCREASING TRAFFIC, HEAVIER WHEEL LOADS, AND NEW OR MODIFIED CONSTRUCTION MATERIALS AND TECHNIQUES. THE EVIDENCE OF THE RELATIONSHIP BETWEEN TRAFFIC LOADINGS AND CONCRETE SLAB STRENGTH (BASED ON PAVEMENT SLABS 2.5 TO 11 INCHES THICK AND SINGLE-AXLE LOADINGS OF 6000-30,000 LB) IS STRONG ENOUGH SO THAT FURTHER CONFIRMATION IS NOT NEEDED, BUT THAT THE NEED FOR QUALITY CONTROL DURING CONSTRUCTION IS EMPHASIZED. EXAMINATION OF THE FINDINGS INDICATE: (1) SLAB THICKNESS SHOULD BE INCREASED AS THE FIFTH ROOT OF ANTICIPATED NUMBER OF LOAD APPLICATIONS; (2) PAVEMENT LIFE VARIES AS THE FOURTH POWER OF THE CONCRETE STRENGTH; (3) A CONSISTENT 20% OVERLOAD MAY REDUCE PAVEMENT LIFE TO 1/2, AND THE APPLICATION OF ONE DOUBLE LOAD IS EQUIVALENT TO 16 APPLICATIONS OF NORMAL LOAD; AND (4) THE ANALYSES FURNISH A BASIS FOR PREDICTION OF EFFECTS OF TANDEM-AXLE LOADS WITH DIFFERENT AXLE SPACING.