INVESTIGATION OF CONCRETE PAVEMENT PUMPING /WITH DISCUSSION/

THIS PAPER DESCRIBED THE INVESTIGATION OF THE PUMPING AT TRANSVERSE JOINTS IN CONCRETE PAVEMENT SLABS ON A PROJECT 4.39 MILES IN LENGTH ON U.S. 52 IN SCIOTO COUNTY, OHIO. THE SOILS SURVEY MADE PRIOR TO GRADING OPERATIONS SHOWED THAT ON SOME SECTIONS THE PREDOMINATING SOIL WAS HIGH IN SILT CONTENT AND COULD BE CLASSIFIED IN THE A-4 GROUP. IT WAS CONSIDERED NECESSARY TO COVER THESE AREAS WITH SUITABLE GRANULAR MATERIAL TO A DEPTH OF 18 INCHES AND PROVIDE TILE DRAINAGE. THE PAVEMENT WAS BUILT WITHOUT REINFORCING OF LOAD TRANSFER DEVICES. OBSERVATIONS WERE MADE OF SLAB DEFLECTIONS UNDER MOVING LOADS. PUMPING WAS FOUND TO BE MUCH MORE EXTENSIVE AND SEVERE OVER THE AREAS WHERE NO GRANULAR MATERIAL WAS USED. ON THE PLAIN CONCRETE SECTION PUMPING WAS MORE SEVERE AT CONTRACTION JOINTS OF THE PREMOLDED TYPE. THE SEVERITY ON THE REINFORCED SECTION WAS ABOUT THE SAME FOR EXPANSION AND CONTRACTION JOINTS. ON THE PLAIN CONCRETE SLABS WITHOUT GRANULAR SUBBASE, 2 PERCENT OF THE EXPANSION JOINTS AND 52 PERCENT OF THE CONTRACTION JOINTS WERE PUMPING. ON THE PLAIN CONCRETE SLABS PLACED ON GRANULAR SUBBASE 1.5 PERCENT OF THE EXPANSION AND 16 PERCENT OF THE CONTRACTION JOINTS WERE PUMPING. ON THE REINFORCED SECTION, 71 PERCENT OF THE EXPANSION JOINTS AND 91 PERCENT OF THE CONTRACTION JOINTS WERE PUMPING. ON MOST OF THE WORK, THE GRADATION OF THE BACKFILL FOR THE TILE DRAINS WAS FROM THE 3/4-INCH TO NO. 4 SIZES. IT WAS OBSERVED THAT THESE DRAINS SILTED UP BADLY. THE CONCLUSIONS ARE: (1) A SUBBASE COMPOSED OF SUITABLE GRANULAR MATERIAL WILL APPRECIABLY REDUCE THE PUMPING AT JOINTS IN CONCRETE PAVEMENTS; (2) SMALL SIZE BACKFILL AGGREGATE WILL EXTEND THE USEFUL LIFE OF TILE DRAINS; AND (3) LOAD TRANSFER DEVICES PREVENT EXCESSIVE PERMANENT DEFORMATION AT THE JOINTS BETWEEN CONCRETE SLABS AFTER PUMPING STARTS. /AUTHOR/