Pumping has been described as, "The process of ejecting the water-suspended subgrade soil from joints, cracks, and the edges of pavement caused by the deflection of the pavement slab under the action of traffic"(4)*. Obviously, the action is limited to rigid or semi-rigid pavements. Hence, the problem is largely concerned with soil and is almost entirely dependent upon properties of the subgrade. During the past five or six years pumping has become the most discussed if not the most important element of highway soils engineering largely because of the increase in heavily loaded vehicles resulting from wartime traffic requirements.

Report Date


Report Number

No. 16

Digital Object Identifier