EVALUATION OF PERFORMANCE OF AN EXISTING CONCRETE PAVEMENT UNDER ACCELERATED LOAD APPLICATION

ACCELERATED LOAD TESTING WAS CONDUCTED TO DETERMINE THE RELATIVE EFFECTS ON A PARTICULAR CONCRETE PAVEMENT OF FOUR DIFFERENT AXLE LOADINGS -- TWO SINGLE AXLES AND TWO TANDUM AXLES. THE TEST PAVEMENT CONSISTED OF TWO 12-FT LANES EACH HAVING A NINE-SEVEN-NINE INCH CROSS-SECTION, BOTH REINFORCED WITH WIRE MESH. EXPANSION JOINTS WERE SPACED AT 120-FT INTERVALS WITH TWO INTERMEDIATE CONTRACTION JOINTS AT 40-FT SPACINGS. THE FOLLOWING METHODS WERE USED TO DETERMINE THE PERFORMANCE OF THE EXISTING CONCRETE PAVEMENT, BEFORE, DURING, AND AFTER RUNNING OF THE TEST TRAFFIC: SOIL SURVEY, PHYSICAL PROPERTIES OF THE CONCRETE, LOAD STRAINS AND DEFLECTIONS, TEMPERATURE WARPING STRESSES, SURFACE ROUGHNESS, AND SLAB SETTLEMENT. THE RESEARCH DEVELOPED INFORMATION OF: (1) LOAD-STRESS AND LOAD-DEFLECTION RELATIONS FOR SLABS ON GRANULAR SOIL WHERE NO PUMPING EXISTED AND FOR SLABS ON FINE-GRAINED SOIL PRIOR TO AND AFTER THE DEVELOPMENT OF PUMPING, (2) COMPARISON OF THE EFFECTS OF SINGLE- AND TANDEM-AXLE VEHICLES, (3) EFFECT OF SPEEDS AND TRANSVERSE PLACEMENT OF VEHICLES, LOAD TRANSFER, FAULTING, AND WARPING OF THE SLAB ON THE MAGNITUDE OF STRESS AND DEFLECTIONS CAUSED BY LOADS, AND (4) STRESSES RESULTING FROM UNRESTRAINED WARPING OF THE SLAB. THE MOST IMPORTANT WARPING STRESSES IN CONCRETE PAVEMENTS ARE THOSE CAUSED BY THE DAYTIME AND NIGHTTIME TEMPERATURE DIFFERENTIALS. RESTRAINED DAYTIME TEMPERATURE WARPING CAUSES TENSILE STRESSES IN THE BOTTOM OF THE SLAB, WHEREAS RESTRAINED NIGHTTIME WARPING CAUSES TENSILE STRESSES IN THE TOP OF THE SLAB. THE GREATEST SLAB SETTLEMENT WAS FOUND AT THE FREE- EDGE CORNERS OF THE SLABS AND THE LEAST SETTLEMENT WAS NOTED AT THE MIDPOINT OF THE SLAB ALONG THE LONGITUDINAL JOINT. THE EXTENT OF PUMPING VARIES WITH THE MAGNITUDE AND CHARACTER OF THE LOAD APPLIED. FOR SIMILAR TYPES OF SOILS, PUMPING DEVELOPED EARLIER AT EXPANSION JOINTS THAN AT CONTRACTION JOINTS.