Abstract:
THE DATA COLLECTED SHOW CONCLUSIVELY THAT THE REPEATED PASSAGE OF HEAVY AXLE LOADS IS THE PRIMARY ACTIVATING ELEMENT IN PUMPING AT JOINTS AND CRACKS IN CONCRETE PAVEMENTS. FREE WATER AND FINE-GRAINED SUBGRADE SOILS ARE THE OTHER CONTRIBUTING FACTORS. IN DUAL-LANE PAVEMENTS PRACTICALLY ALL OF THE PUMPING OCCURS IN THE OUTSIDE LANES WHICH ARE USED BY THE SLOWER, HEAVILY LOADED TRUCKS, WHILE LITTLE, IF ANY, PUMPING IS FOUND IN THE INNER LANES USED BY THE FASTER AND LIGHTER TRAFFIC. PUMPING OCCURS ON PAVEMENTS PLACED ON SUBGRADE SOILS THAT CONTAIN LESS THAN 55 PERCENT RETAINED ON THE NO. 270 SIEVE (0.05 MM), WHICH IS COMMONLY DESIGNATED AS SAND AND GRAVEL OR IN LOCATIONS WHERE GRANULAR SUBGRADES CONTAIN PLASTIC FINES AND THE TRUCK TRAFFIC IS EXCEPTIONALLY HEAVY. SUB-BASES COMPOSED OF GRANULAR MATERIALS PLACED OVER FINE-GRAINED OR PUMPING SOILS WILL PREVENT PUMPING. NO RELATION BETWEEN PAVEMENT AGE AND PUMPING HAS BEEN FOUND. THE DATA AVAILABLE SHOW THAT NEITHER CROSS SECTION NOR THICKNESS HAVE HAD ANY EFFECT ON PUMPING. IN ADDITION TO CORRECTING POOR DRAINAGE CONDITIONS, THE PROPER MAINTENANCE METHODS FOR PREVENTING AND CORRECTING THE PUMPING OF CONCRETE PAVEMENT SLABS INVOLVE TWO OR MORE OF THE FOLLOWING ACTIVITIES: (1) MUDJACKING, WITH SOIL-CEMENT- WATER MIXTURES OR CEMENT-WATER SLURRIES; (2) BITUMINOUS UNDERSEALING; (3) JOINT AND CRACK SEALING; (4) PATCHING FULL DEPTH WITH CONCRETE; (5) COVERING WITH BITUMINOUS SURFACING; (6) CONCRETE RESURFACING; (7) SHOULDER MAINTENANCE THAT WILL INSURE FAST RUN-OFF AND THUS AVOID THE PONDING OF WATER ALONG THE EDGES OF THE PAVEMENT. /AUTHOR/
Supplemental Notes:
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