The effect of poor drainage on pavement structures studied under accelerated testing

Abstract

Most of the structural failures in road pavements are in one way or another associated with excess water trapped within the pavement structure owing to poor drainage. The combined effect of traffic loading and trapped water within the pavement is very destructive, particularly in the upper layers. The effect of excess porewater pressure (EPWP) was studied on several types of pavement strcutures with the aid of the South African Heavy Vehicle Simulator (HVS). The following pavement structures were tested, viz of bituminous base, cemented base, granular base and concrete base pavement structures. During the EPWP state, moisture-accelerated distress (MAD) of the pavement occurs. It was show that non-durable materials must be avoided, especially in the upper layers of the pavement structure. The measurement of permanent deformation on the surface of the pavement during HVS testing proved to be a relatively good indicator of behaviour during both dry and soaked conditions. In bituminous and concrete base structures durable subbases of adequate thickness and indispensable, whereas in cemented base and granular base structures it is essential to prevent surface water from entering through cracks in the relatively thin surfacing layers. This is accompanied by preventive maintenance and adequate drainage provision. Faulting and pumping on concrete pavement structures can also be limited by the use of durable subbase layers and concrete reinforcement to limit deflections.