RIGID PAVEMENT PUMPING: (1) SUBBASE EROSION AND (2) ECONOMIC MODELING (SUBDRAINAGE, REHABILITATION, RIGID PAVEMENTS)

ADRIAAN JACOBUS VAN WIJK, Purdue University

Abstract

Pumping of rigid pavements is a major contributor to rigid pavement failure. Fines can be removed through pore water pressure buildup in the subbase or through surface erosion of subbase and shoulder materials. A number of studies have been conducted since the 1940s, and a number of remedies have been implemented, viz., granular, stabilized, open-graded, and lean concrete subbases. The effectiveness of these measures varied. Stabilized layers, although reducing pumping, do not eliminate pumping. Pumping in stabilized layers is caused primarily by surface erosion of these layers. The erosion of stabilized layers used in pavements and subject to service conditions in the pavement, have not been studied extensively. An extensive literature review was conducted to obtain information regarding pumping, with emphasis on designs to prevent pumping, the performance of different subbase materials, and tests used to simulate pumping. Three testing procedures were selected to be used to investigate and characterize the erosion of rigid pavement subbase and shoulder materials, viz., a brush test, a jetting test, and a rotational shear technique. The latter was designed and built especially for testing of subbase materials, and is an improvement on earlier models used by other researchers. Portland cement stabilized, asphalt stabilized, lean concrete, and unstabilized materials were tested in a statistically designed program. The rotational shear device gave the most useful results for stabilized materials. However, this device can not be used to test cohesionless materials. An effort was made to correlate the laboratory erosion results with the performance of the materials in the pavement. Guidelines are provided on the required material properties to minimize pumping due to surface erosion of subbase and shoulder materials. The feasibility of design and rehabilitation alternatives requires an economic analysis of the alternatives. A computer program (PEARDARP) was developed to evaluate the effect of rehabilitation and design alternatives on rigid pavement pumping and performance. The effects of different rehabilitation techniques on pavement distresses were quantified for inclusion in the program. An existing pumping prediction model was modified to include factors such as, drainage, climate, and subbase type.

Degree

Ph.D.

Subject Area

Civil engineering

COinS