FIELD AND LABORATORY STUDY OF THE EFFECTS OF WATER PUMPING BENEATH CONCRETE PAVEMENT SLABS. FINAL REPORT

Water pumping beneath concrete pavement slabs is considered to be a major cause of concrete pavement failure. The objectives of this work were to determine typical water pressures and velocities during pumping in the laboratory and the field and to determine the effects of pressure, velocity, thermal movement, and dynamic loading on erosion beneath the concrete slab. The location of the water pumping is between the bottom of the concrete pavement slab and the subbase. Laboratory tests indicated that high pressures beneath the second slab and suction pressures beneath the first slab induced water velocities opposite to the direction of vehicle motion. Field tests on I-10 in Florida revealed pressure differences as high as 10 psi which produced velocities up to 1 m/s in a direction opposite to vehicle motion. Water pumping was more severe at the corner of the second slab and under upward thermal curling. It was determined that water movement was not sufficient to cause subbase erosion. The daily expansion-contraction cycle was shown to be able to produce loose material at the rate of 35.5 gm/sq ft/1095 cycles which was estimated to produce 0.5 mm of faulting per year.